mirror of
https://github.com/warpdotdev/warp.git
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8752 lines
277 KiB
Rust
8752 lines
277 KiB
Rust
//! Traits, helpers, and type definitions for core I/O functionality.
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//!
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//! The `std::io` module contains a number of common things you'll need
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//! when doing input and output. The most core part of this module is
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//! the [`Read`] and [`Write`] traits, which provide the
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//! most general interface for reading and writing input and output.
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//!
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//! ## Read and Write
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//!
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//! Because they are traits, [`Read`] and [`Write`] are implemented by a number
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//! of other types, and you can implement them for your types too. As such,
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//! you'll see a few different types of I/O throughout the documentation in
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//! this module: [`File`]s, [`TcpStream`]s, and sometimes even [`Vec<T>`]s. For
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//! example, [`Read`] adds a [`read`][`Read::read`] method, which we can use on
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//! [`File`]s:
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//!
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//! ```no_run
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//! use std::io;
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//! use std::io::prelude::*;
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//! use std::fs::File;
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//!
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//! fn main() -> io::Result<()> {
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//! let mut f = File::open("foo.txt")?;
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//! let mut buffer = [0; 10];
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//!
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//! // read up to 10 bytes
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//! let n = f.read(&mut buffer)?;
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//!
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//! println!("The bytes: {:?}", &buffer[..n]);
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//! Ok(())
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//! }
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//! ```
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//!
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//! [`Read`] and [`Write`] are so important, implementors of the two traits have a
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//! nickname: readers and writers. So you'll sometimes see 'a reader' instead
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//! of 'a type that implements the [`Read`] trait'. Much easier!
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//!
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//! ## Seek and BufRead
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//!
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//! Beyond that, there are two important traits that are provided: [`Seek`]
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//! and [`BufRead`]. Both of these build on top of a reader to control
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//! how the reading happens. [`Seek`] lets you control where the next byte is
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//! coming from:
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//!
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//! ```no_run
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//! use std::io;
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//! use std::io::prelude::*;
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//! use std::io::SeekFrom;
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//! use std::fs::File;
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//!
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//! fn main() -> io::Result<()> {
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//! let mut f = File::open("foo.txt")?;
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//! let mut buffer = [0; 10];
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//!
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//! // skip to the last 10 bytes of the file
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//! f.seek(SeekFrom::End(-10))?;
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//!
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//! // read up to 10 bytes
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//! let n = f.read(&mut buffer)?;
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//!
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//! println!("The bytes: {:?}", &buffer[..n]);
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//! Ok(())
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//! }
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//! ```
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//!
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//! [`BufRead`] uses an internal buffer to provide a number of other ways to read, but
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//! to show it off, we'll need to talk about buffers in general. Keep reading!
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//!
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//! ## BufReader and BufWriter
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//!
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//! Byte-based interfaces are unwieldy and can be inefficient, as we'd need to be
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//! making near-constant calls to the operating system. To help with this,
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//! `std::io` comes with two structs, [`BufReader`] and [`BufWriter`], which wrap
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//! readers and writers. The wrapper uses a buffer, reducing the number of
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//! calls and providing nicer methods for accessing exactly what you want.
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//!
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//! For example, [`BufReader`] works with the [`BufRead`] trait to add extra
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//! methods to any reader:
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//!
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//! ```no_run
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//! use std::io;
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//! use std::io::prelude::*;
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//! use std::io::BufReader;
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//! use std::fs::File;
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//!
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//! fn main() -> io::Result<()> {
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//! let f = File::open("foo.txt")?;
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//! let mut reader = BufReader::new(f);
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//! let mut buffer = String::new();
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//!
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//! // read a line into buffer
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//! reader.read_line(&mut buffer)?;
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//!
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//! println!("{buffer}");
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//! Ok(())
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//! }
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//! ```
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//!
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//! [`BufWriter`] doesn't add any new ways of writing; it just buffers every call
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//! to [`write`][`Write::write`]:
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//!
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//! ```no_run
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//! use std::io;
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//! use std::io::prelude::*;
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//! use std::io::BufWriter;
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//! use std::fs::File;
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//!
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//! fn main() -> io::Result<()> {
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//! let f = File::create("foo.txt")?;
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//! {
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//! let mut writer = BufWriter::new(f);
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//!
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//! // write a byte to the buffer
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//! writer.write(&[42])?;
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//!
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//! } // the buffer is flushed once writer goes out of scope
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//!
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//! Ok(())
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//! }
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//! ```
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//!
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//! ## Standard input and output
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//!
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//! A very common source of input is standard input:
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//!
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//! ```no_run
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//! use std::io;
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//!
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//! fn main() -> io::Result<()> {
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//! let mut input = String::new();
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//!
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//! io::stdin().read_line(&mut input)?;
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//!
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//! println!("You typed: {}", input.trim());
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//! Ok(())
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//! }
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//! ```
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//!
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//! Note that you cannot use the [`?` operator] in functions that do not return
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//! a [`Result<T, E>`][`Result`]. Instead, you can call [`.unwrap()`]
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//! or `match` on the return value to catch any possible errors:
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//!
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//! ```no_run
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//! use std::io;
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//!
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//! let mut input = String::new();
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//!
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//! io::stdin().read_line(&mut input).unwrap();
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//! ```
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//!
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//! And a very common source of output is standard output:
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//!
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//! ```no_run
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//! use std::io;
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//! use std::io::prelude::*;
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//!
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//! fn main() -> io::Result<()> {
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//! io::stdout().write(&[42])?;
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//! Ok(())
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//! }
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//! ```
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//!
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//! Of course, using [`io::stdout`] directly is less common than something like
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//! [`println!`].
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//!
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//! ## Iterator types
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//!
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//! A large number of the structures provided by `std::io` are for various
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//! ways of iterating over I/O. For example, [`Lines`] is used to split over
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//! lines:
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//!
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//! ```no_run
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//! use std::io;
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//! use std::io::prelude::*;
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//! use std::io::BufReader;
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//! use std::fs::File;
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//!
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//! fn main() -> io::Result<()> {
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//! let f = File::open("foo.txt")?;
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//! let reader = BufReader::new(f);
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//!
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//! for line in reader.lines() {
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//! println!("{}", line?);
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//! }
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//! Ok(())
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//! }
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//! ```
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//!
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//! ## Functions
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//!
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//! There are a number of [functions][functions-list] that offer access to various
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//! features. For example, we can use three of these functions to copy everything
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//! from standard input to standard output:
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//!
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//! ```no_run
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//! use std::io;
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//!
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//! fn main() -> io::Result<()> {
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//! io::copy(&mut io::stdin(), &mut io::stdout())?;
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//! Ok(())
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//! }
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//! ```
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//!
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//! [functions-list]: #functions-1
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//!
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//! ## io::Result
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//!
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//! Last, but certainly not least, is [`io::Result`]. This type is used
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//! as the return type of many `std::io` functions that can cause an error, and
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//! can be returned from your own functions as well. Many of the examples in this
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//! module use the [`?` operator]:
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//!
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//! ```
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//! use std::io;
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//!
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//! fn read_input() -> io::Result<()> {
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//! let mut input = String::new();
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//!
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//! io::stdin().read_line(&mut input)?;
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//!
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//! println!("You typed: {}", input.trim());
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//!
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//! Ok(())
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//! }
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//! ```
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//!
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//! The return type of `read_input()`, [`io::Result<()>`][`io::Result`], is a very
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//! common type for functions which don't have a 'real' return value, but do want to
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//! return errors if they happen. In this case, the only purpose of this function is
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//! to read the line and print it, so we use `()`.
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//!
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//! ## Platform-specific behavior
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//!
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//! Many I/O functions throughout the standard library are documented to indicate
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//! what various library or syscalls they are delegated to. This is done to help
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//! applications both understand what's happening under the hood as well as investigate
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//! any possibly unclear semantics. Note, however, that this is informative, not a binding
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//! contract. The implementation of many of these functions are subject to change over
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//! time and may call fewer or more syscalls/library functions.
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//!
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//! ## I/O Safety
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//!
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//! Rust follows an I/O safety discipline that is comparable to its memory safety discipline. This
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//! means that file descriptors can be *exclusively owned*. (Here, "file descriptor" is meant to
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//! subsume similar concepts that exist across a wide range of operating systems even if they might
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//! use a different name, such as "handle".) An exclusively owned file descriptor is one that no
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//! other code is allowed to access in any way, but the owner is allowed to access and even close
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//! it any time. A type that owns its file descriptor should usually close it in its `drop`
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//! function. Types like [`File`] own their file descriptor. Similarly, file descriptors
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//! can be *borrowed*, granting the temporary right to perform operations on this file descriptor.
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//! This indicates that the file descriptor will not be closed for the lifetime of the borrow, but
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//! it does *not* imply any right to close this file descriptor, since it will likely be owned by
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//! someone else.
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//!
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//! The platform-specific parts of the Rust standard library expose types that reflect these
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//! concepts, see [`os::unix`] and [`os::windows`].
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//!
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//! To uphold I/O safety, it is crucial that no code acts on file descriptors it does not own or
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//! borrow, and no code closes file descriptors it does not own. In other words, a safe function
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//! that takes a regular integer, treats it as a file descriptor, and acts on it, is *unsound*.
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//!
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//! Not upholding I/O safety and acting on a file descriptor without proof of ownership can lead to
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//! misbehavior and even Undefined Behavior in code that relies on ownership of its file
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//! descriptors: a closed file descriptor could be re-allocated, so the original owner of that file
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//! descriptor is now working on the wrong file. Some code might even rely on fully encapsulating
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//! its file descriptors with no operations being performed by any other part of the program.
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//!
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//! Note that exclusive ownership of a file descriptor does *not* imply exclusive ownership of the
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//! underlying kernel object that the file descriptor references (also called "open file description" on
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//! some operating systems). File descriptors basically work like [`Arc`]: when you receive an owned
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//! file descriptor, you cannot know whether there are any other file descriptors that reference the
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//! same kernel object. However, when you create a new kernel object, you know that you are holding
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//! the only reference to it. Just be careful not to lend it to anyone, since they can obtain a
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//! clone and then you can no longer know what the reference count is! In that sense, [`OwnedFd`] is
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//! like `Arc` and [`BorrowedFd<'a>`] is like `&'a Arc` (and similar for the Windows types). In
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//! particular, given a `BorrowedFd<'a>`, you are not allowed to close the file descriptor -- just
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//! like how, given a `&'a Arc`, you are not allowed to decrement the reference count and
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//! potentially free the underlying object. There is no equivalent to `Box` for file descriptors in
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//! the standard library (that would be a type that guarantees that the reference count is `1`),
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//! however, it would be possible for a crate to define a type with those semantics.
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//!
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//! [`File`]: crate::fs::File
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//! [`TcpStream`]: crate::net::TcpStream
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//! [`io::stdout`]: stdout
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//! [`io::Result`]: self::Result
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//! [`?` operator]: ../../book/appendix-02-operators.html
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//! [`Result`]: crate::result::Result
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//! [`.unwrap()`]: crate::result::Result::unwrap
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//! [`os::unix`]: ../os/unix/io/index.html
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//! [`os::windows`]: ../os/windows/io/index.html
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//! [`OwnedFd`]: ../os/fd/struct.OwnedFd.html
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//! [`BorrowedFd<'a>`]: ../os/fd/struct.BorrowedFd.html
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//! [`Arc`]: crate::sync::Arc
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#![stable(feature = "rust1", since = "1.0.0")]
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#[cfg(test)]
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mod tests;
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use crate::cmp;
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use crate::fmt;
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use crate::mem::take;
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use crate::ops::{Deref, DerefMut};
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use crate::slice;
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use crate::str;
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use crate::sys;
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use core::slice::memchr;
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#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
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pub use self::buffered::WriterPanicked;
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#[unstable(feature = "raw_os_error_ty", issue = "107792")]
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pub use self::error::RawOsError;
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pub(crate) use self::stdio::attempt_print_to_stderr;
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#[stable(feature = "is_terminal", since = "1.70.0")]
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pub use self::stdio::IsTerminal;
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#[unstable(feature = "print_internals", issue = "none")]
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#[doc(hidden)]
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pub use self::stdio::{_eprint, _print};
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#[unstable(feature = "internal_output_capture", issue = "none")]
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#[doc(no_inline, hidden)]
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pub use self::stdio::{set_output_capture, try_set_output_capture};
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use self::{
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buffered::{BufReader, BufWriter, IntoInnerError, LineWriter},
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copy::copy,
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cursor::Cursor,
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error::{Error, ErrorKind, Result},
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stdio::{stderr, stdin, stdout, Stderr, StderrLock, Stdin, StdinLock, Stdout, StdoutLock},
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util::{empty, repeat, sink, Empty, Repeat, Sink},
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};
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#[unstable(feature = "read_buf", issue = "78485")]
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pub use core::io::{BorrowedBuf, BorrowedCursor};
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pub(crate) use error::const_io_error;
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||
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mod buffered;
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pub(crate) mod copy;
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mod cursor;
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mod error;
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mod impls;
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pub mod prelude;
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mod stdio;
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mod util;
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const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
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pub(crate) use stdio::cleanup;
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struct Guard<'a> {
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buf: &'a mut Vec<u8>,
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len: usize,
|
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}
|
||
|
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impl Drop for Guard<'_> {
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||
fn drop(&mut self) {
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||
unsafe {
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self.buf.set_len(self.len);
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||
}
|
||
}
|
||
}
|
||
|
||
// Several `read_to_string` and `read_line` methods in the standard library will
|
||
// append data into a `String` buffer, but we need to be pretty careful when
|
||
// doing this. The implementation will just call `.as_mut_vec()` and then
|
||
// delegate to a byte-oriented reading method, but we must ensure that when
|
||
// returning we never leave `buf` in a state such that it contains invalid UTF-8
|
||
// in its bounds.
|
||
//
|
||
// To this end, we use an RAII guard (to protect against panics) which updates
|
||
// the length of the string when it is dropped. This guard initially truncates
|
||
// the string to the prior length and only after we've validated that the
|
||
// new contents are valid UTF-8 do we allow it to set a longer length.
|
||
//
|
||
// The unsafety in this function is twofold:
|
||
//
|
||
// 1. We're looking at the raw bytes of `buf`, so we take on the burden of UTF-8
|
||
// checks.
|
||
// 2. We're passing a raw buffer to the function `f`, and it is expected that
|
||
// the function only *appends* bytes to the buffer. We'll get undefined
|
||
// behavior if existing bytes are overwritten to have non-UTF-8 data.
|
||
pub(crate) unsafe fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize>
|
||
where
|
||
F: FnOnce(&mut Vec<u8>) -> Result<usize>,
|
||
{
|
||
let mut g = Guard { len: buf.len(), buf: buf.as_mut_vec() };
|
||
let ret = f(g.buf);
|
||
|
||
// SAFETY: the caller promises to only append data to `buf`
|
||
let appended = g.buf.get_unchecked(g.len..);
|
||
if str::from_utf8(appended).is_err() {
|
||
ret.and_then(|_| Err(Error::INVALID_UTF8))
|
||
} else {
|
||
g.len = g.buf.len();
|
||
ret
|
||
}
|
||
}
|
||
|
||
// Here we must serve many masters with conflicting goals:
|
||
//
|
||
// - avoid allocating unless necessary
|
||
// - avoid overallocating if we know the exact size (#89165)
|
||
// - avoid passing large buffers to readers that always initialize the free capacity if they perform short reads (#23815, #23820)
|
||
// - pass large buffers to readers that do not initialize the spare capacity. this can amortize per-call overheads
|
||
// - and finally pass not-too-small and not-too-large buffers to Windows read APIs because they manage to suffer from both problems
|
||
// at the same time, i.e. small reads suffer from syscall overhead, all reads incur initialization cost
|
||
// proportional to buffer size (#110650)
|
||
//
|
||
pub(crate) fn default_read_to_end<R: Read + ?Sized>(
|
||
r: &mut R,
|
||
buf: &mut Vec<u8>,
|
||
size_hint: Option<usize>,
|
||
) -> Result<usize> {
|
||
let start_len = buf.len();
|
||
let start_cap = buf.capacity();
|
||
// Optionally limit the maximum bytes read on each iteration.
|
||
// This adds an arbitrary fiddle factor to allow for more data than we expect.
|
||
let mut max_read_size = size_hint
|
||
.and_then(|s| s.checked_add(1024)?.checked_next_multiple_of(DEFAULT_BUF_SIZE))
|
||
.unwrap_or(DEFAULT_BUF_SIZE);
|
||
|
||
let mut initialized = 0; // Extra initialized bytes from previous loop iteration
|
||
|
||
const PROBE_SIZE: usize = 32;
|
||
|
||
fn small_probe_read<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize> {
|
||
let mut probe = [0u8; PROBE_SIZE];
|
||
|
||
loop {
|
||
match r.read(&mut probe) {
|
||
Ok(n) => {
|
||
// there is no way to recover from allocation failure here
|
||
// because the data has already been read.
|
||
buf.extend_from_slice(&probe[..n]);
|
||
return Ok(n);
|
||
}
|
||
Err(ref e) if e.is_interrupted() => continue,
|
||
Err(e) => return Err(e),
|
||
}
|
||
}
|
||
}
|
||
|
||
// avoid inflating empty/small vecs before we have determined that there's anything to read
|
||
if (size_hint.is_none() || size_hint == Some(0)) && buf.capacity() - buf.len() < PROBE_SIZE {
|
||
let read = small_probe_read(r, buf)?;
|
||
|
||
if read == 0 {
|
||
return Ok(0);
|
||
}
|
||
}
|
||
|
||
loop {
|
||
if buf.len() == buf.capacity() && buf.capacity() == start_cap {
|
||
// The buffer might be an exact fit. Let's read into a probe buffer
|
||
// and see if it returns `Ok(0)`. If so, we've avoided an
|
||
// unnecessary doubling of the capacity. But if not, append the
|
||
// probe buffer to the primary buffer and let its capacity grow.
|
||
let read = small_probe_read(r, buf)?;
|
||
|
||
if read == 0 {
|
||
return Ok(buf.len() - start_len);
|
||
}
|
||
}
|
||
|
||
if buf.len() == buf.capacity() {
|
||
// buf is full, need more space
|
||
buf.try_reserve(PROBE_SIZE)?;
|
||
}
|
||
|
||
let mut spare = buf.spare_capacity_mut();
|
||
let buf_len = cmp::min(spare.len(), max_read_size);
|
||
spare = &mut spare[..buf_len];
|
||
let mut read_buf: BorrowedBuf<'_> = spare.into();
|
||
|
||
// SAFETY: These bytes were initialized but not filled in the previous loop
|
||
unsafe {
|
||
read_buf.set_init(initialized);
|
||
}
|
||
|
||
let mut cursor = read_buf.unfilled();
|
||
loop {
|
||
match r.read_buf(cursor.reborrow()) {
|
||
Ok(()) => break,
|
||
Err(e) if e.is_interrupted() => continue,
|
||
Err(e) => return Err(e),
|
||
}
|
||
}
|
||
|
||
let unfilled_but_initialized = cursor.init_ref().len();
|
||
let bytes_read = cursor.written();
|
||
let was_fully_initialized = read_buf.init_len() == buf_len;
|
||
|
||
if bytes_read == 0 {
|
||
return Ok(buf.len() - start_len);
|
||
}
|
||
|
||
// store how much was initialized but not filled
|
||
initialized = unfilled_but_initialized;
|
||
|
||
// SAFETY: BorrowedBuf's invariants mean this much memory is initialized.
|
||
unsafe {
|
||
let new_len = bytes_read + buf.len();
|
||
buf.set_len(new_len);
|
||
}
|
||
|
||
// Use heuristics to determine the max read size if no initial size hint was provided
|
||
if size_hint.is_none() {
|
||
// The reader is returning short reads but it doesn't call ensure_init().
|
||
// In that case we no longer need to restrict read sizes to avoid
|
||
// initialization costs.
|
||
if !was_fully_initialized {
|
||
max_read_size = usize::MAX;
|
||
}
|
||
|
||
// we have passed a larger buffer than previously and the
|
||
// reader still hasn't returned a short read
|
||
if buf_len >= max_read_size && bytes_read == buf_len {
|
||
max_read_size = max_read_size.saturating_mul(2);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
pub(crate) fn default_read_to_string<R: Read + ?Sized>(
|
||
r: &mut R,
|
||
buf: &mut String,
|
||
size_hint: Option<usize>,
|
||
) -> Result<usize> {
|
||
// Note that we do *not* call `r.read_to_end()` here. We are passing
|
||
// `&mut Vec<u8>` (the raw contents of `buf`) into the `read_to_end`
|
||
// method to fill it up. An arbitrary implementation could overwrite the
|
||
// entire contents of the vector, not just append to it (which is what
|
||
// we are expecting).
|
||
//
|
||
// To prevent extraneously checking the UTF-8-ness of the entire buffer
|
||
// we pass it to our hardcoded `default_read_to_end` implementation which
|
||
// we know is guaranteed to only read data into the end of the buffer.
|
||
unsafe { append_to_string(buf, |b| default_read_to_end(r, b, size_hint)) }
|
||
}
|
||
|
||
pub(crate) fn default_read_vectored<F>(read: F, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>
|
||
where
|
||
F: FnOnce(&mut [u8]) -> Result<usize>,
|
||
{
|
||
let buf = bufs.iter_mut().find(|b| !b.is_empty()).map_or(&mut [][..], |b| &mut **b);
|
||
read(buf)
|
||
}
|
||
|
||
pub(crate) fn default_write_vectored<F>(write: F, bufs: &[IoSlice<'_>]) -> Result<usize>
|
||
where
|
||
F: FnOnce(&[u8]) -> Result<usize>,
|
||
{
|
||
let buf = bufs.iter().find(|b| !b.is_empty()).map_or(&[][..], |b| &**b);
|
||
write(buf)
|
||
}
|
||
|
||
pub(crate) fn default_read_exact<R: Read + ?Sized>(this: &mut R, mut buf: &mut [u8]) -> Result<()> {
|
||
while !buf.is_empty() {
|
||
match this.read(buf) {
|
||
Ok(0) => break,
|
||
Ok(n) => {
|
||
buf = &mut buf[n..];
|
||
}
|
||
Err(ref e) if e.is_interrupted() => {}
|
||
Err(e) => return Err(e),
|
||
}
|
||
}
|
||
if !buf.is_empty() { Err(Error::READ_EXACT_EOF) } else { Ok(()) }
|
||
}
|
||
|
||
pub(crate) fn default_read_buf<F>(read: F, mut cursor: BorrowedCursor<'_>) -> Result<()>
|
||
where
|
||
F: FnOnce(&mut [u8]) -> Result<usize>,
|
||
{
|
||
let n = read(cursor.ensure_init().init_mut())?;
|
||
cursor.advance(n);
|
||
Ok(())
|
||
}
|
||
|
||
pub(crate) fn default_read_buf_exact<R: Read + ?Sized>(
|
||
this: &mut R,
|
||
mut cursor: BorrowedCursor<'_>,
|
||
) -> Result<()> {
|
||
while cursor.capacity() > 0 {
|
||
let prev_written = cursor.written();
|
||
match this.read_buf(cursor.reborrow()) {
|
||
Ok(()) => {}
|
||
Err(e) if e.is_interrupted() => continue,
|
||
Err(e) => return Err(e),
|
||
}
|
||
|
||
if cursor.written() == prev_written {
|
||
return Err(Error::READ_EXACT_EOF);
|
||
}
|
||
}
|
||
|
||
Ok(())
|
||
}
|
||
|
||
/// The `Read` trait allows for reading bytes from a source.
|
||
///
|
||
/// Implementors of the `Read` trait are called 'readers'.
|
||
///
|
||
/// Readers are defined by one required method, [`read()`]. Each call to [`read()`]
|
||
/// will attempt to pull bytes from this source into a provided buffer. A
|
||
/// number of other methods are implemented in terms of [`read()`], giving
|
||
/// implementors a number of ways to read bytes while only needing to implement
|
||
/// a single method.
|
||
///
|
||
/// Readers are intended to be composable with one another. Many implementors
|
||
/// throughout [`std::io`] take and provide types which implement the `Read`
|
||
/// trait.
|
||
///
|
||
/// Please note that each call to [`read()`] may involve a system call, and
|
||
/// therefore, using something that implements [`BufRead`], such as
|
||
/// [`BufReader`], will be more efficient.
|
||
///
|
||
/// Repeated calls to the reader use the same cursor, so for example
|
||
/// calling `read_to_end` twice on a [`File`] will only return the file's
|
||
/// contents once. It's recommended to first call `rewind()` in that case.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// let mut buffer = [0; 10];
|
||
///
|
||
/// // read up to 10 bytes
|
||
/// f.read(&mut buffer)?;
|
||
///
|
||
/// let mut buffer = Vec::new();
|
||
/// // read the whole file
|
||
/// f.read_to_end(&mut buffer)?;
|
||
///
|
||
/// // read into a String, so that you don't need to do the conversion.
|
||
/// let mut buffer = String::new();
|
||
/// f.read_to_string(&mut buffer)?;
|
||
///
|
||
/// // and more! See the other methods for more details.
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// Read from [`&str`] because [`&[u8]`][prim@slice] implements `Read`:
|
||
///
|
||
/// ```no_run
|
||
/// # use std::io;
|
||
/// use std::io::prelude::*;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut b = "This string will be read".as_bytes();
|
||
/// let mut buffer = [0; 10];
|
||
///
|
||
/// // read up to 10 bytes
|
||
/// b.read(&mut buffer)?;
|
||
///
|
||
/// // etc... it works exactly as a File does!
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [`read()`]: Read::read
|
||
/// [`&str`]: prim@str
|
||
/// [`std::io`]: self
|
||
/// [`File`]: crate::fs::File
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[doc(notable_trait)]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "IoRead")]
|
||
pub trait Read {
|
||
/// Pull some bytes from this source into the specified buffer, returning
|
||
/// how many bytes were read.
|
||
///
|
||
/// This function does not provide any guarantees about whether it blocks
|
||
/// waiting for data, but if an object needs to block for a read and cannot,
|
||
/// it will typically signal this via an [`Err`] return value.
|
||
///
|
||
/// If the return value of this method is [`Ok(n)`], then implementations must
|
||
/// guarantee that `0 <= n <= buf.len()`. A nonzero `n` value indicates
|
||
/// that the buffer `buf` has been filled in with `n` bytes of data from this
|
||
/// source. If `n` is `0`, then it can indicate one of two scenarios:
|
||
///
|
||
/// 1. This reader has reached its "end of file" and will likely no longer
|
||
/// be able to produce bytes. Note that this does not mean that the
|
||
/// reader will *always* no longer be able to produce bytes. As an example,
|
||
/// on Linux, this method will call the `recv` syscall for a [`TcpStream`],
|
||
/// where returning zero indicates the connection was shut down correctly. While
|
||
/// for [`File`], it is possible to reach the end of file and get zero as result,
|
||
/// but if more data is appended to the file, future calls to `read` will return
|
||
/// more data.
|
||
/// 2. The buffer specified was 0 bytes in length.
|
||
///
|
||
/// It is not an error if the returned value `n` is smaller than the buffer size,
|
||
/// even when the reader is not at the end of the stream yet.
|
||
/// This may happen for example because fewer bytes are actually available right now
|
||
/// (e. g. being close to end-of-file) or because read() was interrupted by a signal.
|
||
///
|
||
/// As this trait is safe to implement, callers in unsafe code cannot rely on
|
||
/// `n <= buf.len()` for safety.
|
||
/// Extra care needs to be taken when `unsafe` functions are used to access the read bytes.
|
||
/// Callers have to ensure that no unchecked out-of-bounds accesses are possible even if
|
||
/// `n > buf.len()`.
|
||
///
|
||
/// *Implementations* of this method can make no assumptions about the contents of `buf` when
|
||
/// this function is called. It is recommended that implementations only write data to `buf`
|
||
/// instead of reading its contents.
|
||
///
|
||
/// Correspondingly, however, *callers* of this method in unsafe code must not assume
|
||
/// any guarantees about how the implementation uses `buf`. The trait is safe to implement,
|
||
/// so it is possible that the code that's supposed to write to the buffer might also read
|
||
/// from it. It is your responsibility to make sure that `buf` is initialized
|
||
/// before calling `read`. Calling `read` with an uninitialized `buf` (of the kind one
|
||
/// obtains via [`MaybeUninit<T>`]) is not safe, and can lead to undefined behavior.
|
||
///
|
||
/// [`MaybeUninit<T>`]: crate::mem::MaybeUninit
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If this function encounters any form of I/O or other error, an error
|
||
/// variant will be returned. If an error is returned then it must be
|
||
/// guaranteed that no bytes were read.
|
||
///
|
||
/// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the read
|
||
/// operation should be retried if there is nothing else to do.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`Ok(n)`]: Ok
|
||
/// [`File`]: crate::fs::File
|
||
/// [`TcpStream`]: crate::net::TcpStream
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// let mut buffer = [0; 10];
|
||
///
|
||
/// // read up to 10 bytes
|
||
/// let n = f.read(&mut buffer[..])?;
|
||
///
|
||
/// println!("The bytes: {:?}", &buffer[..n]);
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
|
||
|
||
/// Like `read`, except that it reads into a slice of buffers.
|
||
///
|
||
/// Data is copied to fill each buffer in order, with the final buffer
|
||
/// written to possibly being only partially filled. This method must
|
||
/// behave equivalently to a single call to `read` with concatenated
|
||
/// buffers.
|
||
///
|
||
/// The default implementation calls `read` with either the first nonempty
|
||
/// buffer provided, or an empty one if none exists.
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> {
|
||
default_read_vectored(|b| self.read(b), bufs)
|
||
}
|
||
|
||
/// Determines if this `Read`er has an efficient `read_vectored`
|
||
/// implementation.
|
||
///
|
||
/// If a `Read`er does not override the default `read_vectored`
|
||
/// implementation, code using it may want to avoid the method all together
|
||
/// and coalesce writes into a single buffer for higher performance.
|
||
///
|
||
/// The default implementation returns `false`.
|
||
#[unstable(feature = "can_vector", issue = "69941")]
|
||
fn is_read_vectored(&self) -> bool {
|
||
false
|
||
}
|
||
|
||
/// Read all bytes until EOF in this source, placing them into `buf`.
|
||
///
|
||
/// All bytes read from this source will be appended to the specified buffer
|
||
/// `buf`. This function will continuously call [`read()`] to append more data to
|
||
/// `buf` until [`read()`] returns either [`Ok(0)`] or an error of
|
||
/// non-[`ErrorKind::Interrupted`] kind.
|
||
///
|
||
/// If successful, this function will return the total number of bytes read.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If this function encounters an error of the kind
|
||
/// [`ErrorKind::Interrupted`] then the error is ignored and the operation
|
||
/// will continue.
|
||
///
|
||
/// If any other read error is encountered then this function immediately
|
||
/// returns. Any bytes which have already been read will be appended to
|
||
/// `buf`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`read()`]: Read::read
|
||
/// [`Ok(0)`]: Ok
|
||
/// [`File`]: crate::fs::File
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// let mut buffer = Vec::new();
|
||
///
|
||
/// // read the whole file
|
||
/// f.read_to_end(&mut buffer)?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// (See also the [`std::fs::read`] convenience function for reading from a
|
||
/// file.)
|
||
///
|
||
/// [`std::fs::read`]: crate::fs::read
|
||
///
|
||
/// ## Implementing `read_to_end`
|
||
///
|
||
/// When implementing the `io::Read` trait, it is recommended to allocate
|
||
/// memory using [`Vec::try_reserve`]. However, this behavior is not guaranteed
|
||
/// by all implementations, and `read_to_end` may not handle out-of-memory
|
||
/// situations gracefully.
|
||
///
|
||
/// ```no_run
|
||
/// # use std::io::{self, BufRead};
|
||
/// # struct Example { example_datasource: io::Empty } impl Example {
|
||
/// # fn get_some_data_for_the_example(&self) -> &'static [u8] { &[] }
|
||
/// fn read_to_end(&mut self, dest_vec: &mut Vec<u8>) -> io::Result<usize> {
|
||
/// let initial_vec_len = dest_vec.len();
|
||
/// loop {
|
||
/// let src_buf = self.example_datasource.fill_buf()?;
|
||
/// if src_buf.is_empty() {
|
||
/// break;
|
||
/// }
|
||
/// dest_vec.try_reserve(src_buf.len())?;
|
||
/// dest_vec.extend_from_slice(src_buf);
|
||
///
|
||
/// // Any irreversible side effects should happen after `try_reserve` succeeds,
|
||
/// // to avoid losing data on allocation error.
|
||
/// let read = src_buf.len();
|
||
/// self.example_datasource.consume(read);
|
||
/// }
|
||
/// Ok(dest_vec.len() - initial_vec_len)
|
||
/// }
|
||
/// # }
|
||
/// ```
|
||
///
|
||
/// [`Vec::try_reserve`]: crate::vec::Vec::try_reserve
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
|
||
default_read_to_end(self, buf, None)
|
||
}
|
||
|
||
/// Read all bytes until EOF in this source, appending them to `buf`.
|
||
///
|
||
/// If successful, this function returns the number of bytes which were read
|
||
/// and appended to `buf`.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the data in this stream is *not* valid UTF-8 then an error is
|
||
/// returned and `buf` is unchanged.
|
||
///
|
||
/// See [`read_to_end`] for other error semantics.
|
||
///
|
||
/// [`read_to_end`]: Read::read_to_end
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`File`]: crate::fs::File
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// let mut buffer = String::new();
|
||
///
|
||
/// f.read_to_string(&mut buffer)?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// (See also the [`std::fs::read_to_string`] convenience function for
|
||
/// reading from a file.)
|
||
///
|
||
/// [`std::fs::read_to_string`]: crate::fs::read_to_string
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn read_to_string(&mut self, buf: &mut String) -> Result<usize> {
|
||
default_read_to_string(self, buf, None)
|
||
}
|
||
|
||
/// Read the exact number of bytes required to fill `buf`.
|
||
///
|
||
/// This function reads as many bytes as necessary to completely fill the
|
||
/// specified buffer `buf`.
|
||
///
|
||
/// *Implementations* of this method can make no assumptions about the contents of `buf` when
|
||
/// this function is called. It is recommended that implementations only write data to `buf`
|
||
/// instead of reading its contents. The documentation on [`read`] has a more detailed
|
||
/// explanation of this subject.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If this function encounters an error of the kind
|
||
/// [`ErrorKind::Interrupted`] then the error is ignored and the operation
|
||
/// will continue.
|
||
///
|
||
/// If this function encounters an "end of file" before completely filling
|
||
/// the buffer, it returns an error of the kind [`ErrorKind::UnexpectedEof`].
|
||
/// The contents of `buf` are unspecified in this case.
|
||
///
|
||
/// If any other read error is encountered then this function immediately
|
||
/// returns. The contents of `buf` are unspecified in this case.
|
||
///
|
||
/// If this function returns an error, it is unspecified how many bytes it
|
||
/// has read, but it will never read more than would be necessary to
|
||
/// completely fill the buffer.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`read`]: Read::read
|
||
/// [`File`]: crate::fs::File
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// let mut buffer = [0; 10];
|
||
///
|
||
/// // read exactly 10 bytes
|
||
/// f.read_exact(&mut buffer)?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "read_exact", since = "1.6.0")]
|
||
fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
|
||
default_read_exact(self, buf)
|
||
}
|
||
|
||
/// Pull some bytes from this source into the specified buffer.
|
||
///
|
||
/// This is equivalent to the [`read`](Read::read) method, except that it is passed a [`BorrowedCursor`] rather than `[u8]` to allow use
|
||
/// with uninitialized buffers. The new data will be appended to any existing contents of `buf`.
|
||
///
|
||
/// The default implementation delegates to `read`.
|
||
#[unstable(feature = "read_buf", issue = "78485")]
|
||
fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()> {
|
||
default_read_buf(|b| self.read(b), buf)
|
||
}
|
||
|
||
/// Read the exact number of bytes required to fill `cursor`.
|
||
///
|
||
/// This is similar to the [`read_exact`](Read::read_exact) method, except
|
||
/// that it is passed a [`BorrowedCursor`] rather than `[u8]` to allow use
|
||
/// with uninitialized buffers.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If this function encounters an error of the kind [`ErrorKind::Interrupted`]
|
||
/// then the error is ignored and the operation will continue.
|
||
///
|
||
/// If this function encounters an "end of file" before completely filling
|
||
/// the buffer, it returns an error of the kind [`ErrorKind::UnexpectedEof`].
|
||
///
|
||
/// If any other read error is encountered then this function immediately
|
||
/// returns.
|
||
///
|
||
/// If this function returns an error, all bytes read will be appended to `cursor`.
|
||
#[unstable(feature = "read_buf", issue = "78485")]
|
||
fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()> {
|
||
default_read_buf_exact(self, cursor)
|
||
}
|
||
|
||
/// Creates a "by reference" adaptor for this instance of `Read`.
|
||
///
|
||
/// The returned adapter also implements `Read` and will simply borrow this
|
||
/// current reader.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`File`]: crate::fs::File
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::Read;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// let mut buffer = Vec::new();
|
||
/// let mut other_buffer = Vec::new();
|
||
///
|
||
/// {
|
||
/// let reference = f.by_ref();
|
||
///
|
||
/// // read at most 5 bytes
|
||
/// reference.take(5).read_to_end(&mut buffer)?;
|
||
///
|
||
/// } // drop our &mut reference so we can use f again
|
||
///
|
||
/// // original file still usable, read the rest
|
||
/// f.read_to_end(&mut other_buffer)?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn by_ref(&mut self) -> &mut Self
|
||
where
|
||
Self: Sized,
|
||
{
|
||
self
|
||
}
|
||
|
||
/// Transforms this `Read` instance to an [`Iterator`] over its bytes.
|
||
///
|
||
/// The returned type implements [`Iterator`] where the [`Item`] is
|
||
/// <code>[Result]<[u8], [io::Error]></code>.
|
||
/// The yielded item is [`Ok`] if a byte was successfully read and [`Err`]
|
||
/// otherwise. EOF is mapped to returning [`None`] from this iterator.
|
||
///
|
||
/// The default implementation calls `read` for each byte,
|
||
/// which can be very inefficient for data that's not in memory,
|
||
/// such as [`File`]. Consider using a [`BufReader`] in such cases.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`Item`]: Iterator::Item
|
||
/// [`File`]: crate::fs::File "fs::File"
|
||
/// [Result]: crate::result::Result "Result"
|
||
/// [io::Error]: self::Error "io::Error"
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::io::BufReader;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let f = BufReader::new(File::open("foo.txt")?);
|
||
///
|
||
/// for byte in f.bytes() {
|
||
/// println!("{}", byte.unwrap());
|
||
/// }
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn bytes(self) -> Bytes<Self>
|
||
where
|
||
Self: Sized,
|
||
{
|
||
Bytes { inner: self }
|
||
}
|
||
|
||
/// Creates an adapter which will chain this stream with another.
|
||
///
|
||
/// The returned `Read` instance will first read all bytes from this object
|
||
/// until EOF is encountered. Afterwards the output is equivalent to the
|
||
/// output of `next`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`File`]: crate::fs::File
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let f1 = File::open("foo.txt")?;
|
||
/// let f2 = File::open("bar.txt")?;
|
||
///
|
||
/// let mut handle = f1.chain(f2);
|
||
/// let mut buffer = String::new();
|
||
///
|
||
/// // read the value into a String. We could use any Read method here,
|
||
/// // this is just one example.
|
||
/// handle.read_to_string(&mut buffer)?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn chain<R: Read>(self, next: R) -> Chain<Self, R>
|
||
where
|
||
Self: Sized,
|
||
{
|
||
Chain { first: self, second: next, done_first: false }
|
||
}
|
||
|
||
/// Creates an adapter which will read at most `limit` bytes from it.
|
||
///
|
||
/// This function returns a new instance of `Read` which will read at most
|
||
/// `limit` bytes, after which it will always return EOF ([`Ok(0)`]). Any
|
||
/// read errors will not count towards the number of bytes read and future
|
||
/// calls to [`read()`] may succeed.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Read`:
|
||
///
|
||
/// [`File`]: crate::fs::File
|
||
/// [`Ok(0)`]: Ok
|
||
/// [`read()`]: Read::read
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let f = File::open("foo.txt")?;
|
||
/// let mut buffer = [0; 5];
|
||
///
|
||
/// // read at most five bytes
|
||
/// let mut handle = f.take(5);
|
||
///
|
||
/// handle.read(&mut buffer)?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn take(self, limit: u64) -> Take<Self>
|
||
where
|
||
Self: Sized,
|
||
{
|
||
Take { inner: self, limit }
|
||
}
|
||
}
|
||
|
||
/// Read all bytes from a [reader][Read] into a new [`String`].
|
||
///
|
||
/// This is a convenience function for [`Read::read_to_string`]. Using this
|
||
/// function avoids having to create a variable first and provides more type
|
||
/// safety since you can only get the buffer out if there were no errors. (If you
|
||
/// use [`Read::read_to_string`] you have to remember to check whether the read
|
||
/// succeeded because otherwise your buffer will be empty or only partially full.)
|
||
///
|
||
/// # Performance
|
||
///
|
||
/// The downside of this function's increased ease of use and type safety is
|
||
/// that it gives you less control over performance. For example, you can't
|
||
/// pre-allocate memory like you can using [`String::with_capacity`] and
|
||
/// [`Read::read_to_string`]. Also, you can't re-use the buffer if an error
|
||
/// occurs while reading.
|
||
///
|
||
/// In many cases, this function's performance will be adequate and the ease of use
|
||
/// and type safety tradeoffs will be worth it. However, there are cases where you
|
||
/// need more control over performance, and in those cases you should definitely use
|
||
/// [`Read::read_to_string`] directly.
|
||
///
|
||
/// Note that in some special cases, such as when reading files, this function will
|
||
/// pre-allocate memory based on the size of the input it is reading. In those
|
||
/// cases, the performance should be as good as if you had used
|
||
/// [`Read::read_to_string`] with a manually pre-allocated buffer.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function forces you to handle errors because the output (the `String`)
|
||
/// is wrapped in a [`Result`]. See [`Read::read_to_string`] for the errors
|
||
/// that can occur. If any error occurs, you will get an [`Err`], so you
|
||
/// don't have to worry about your buffer being empty or partially full.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// # use std::io;
|
||
/// fn main() -> io::Result<()> {
|
||
/// let stdin = io::read_to_string(io::stdin())?;
|
||
/// println!("Stdin was:");
|
||
/// println!("{stdin}");
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "io_read_to_string", since = "1.65.0")]
|
||
pub fn read_to_string<R: Read>(mut reader: R) -> Result<String> {
|
||
let mut buf = String::new();
|
||
reader.read_to_string(&mut buf)?;
|
||
Ok(buf)
|
||
}
|
||
|
||
/// A buffer type used with `Read::read_vectored`.
|
||
///
|
||
/// It is semantically a wrapper around an `&mut [u8]`, but is guaranteed to be
|
||
/// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on
|
||
/// Windows.
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
#[repr(transparent)]
|
||
pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>);
|
||
|
||
#[stable(feature = "iovec_send_sync", since = "1.44.0")]
|
||
unsafe impl<'a> Send for IoSliceMut<'a> {}
|
||
|
||
#[stable(feature = "iovec_send_sync", since = "1.44.0")]
|
||
unsafe impl<'a> Sync for IoSliceMut<'a> {}
|
||
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
impl<'a> fmt::Debug for IoSliceMut<'a> {
|
||
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(self.0.as_slice(), fmt)
|
||
}
|
||
}
|
||
|
||
impl<'a> IoSliceMut<'a> {
|
||
/// Creates a new `IoSliceMut` wrapping a byte slice.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics on Windows if the slice is larger than 4GB.
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
#[inline]
|
||
pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
|
||
IoSliceMut(sys::io::IoSliceMut::new(buf))
|
||
}
|
||
|
||
/// Advance the internal cursor of the slice.
|
||
///
|
||
/// Also see [`IoSliceMut::advance_slices`] to advance the cursors of
|
||
/// multiple buffers.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics when trying to advance beyond the end of the slice.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(io_slice_advance)]
|
||
///
|
||
/// use std::io::IoSliceMut;
|
||
/// use std::ops::Deref;
|
||
///
|
||
/// let mut data = [1; 8];
|
||
/// let mut buf = IoSliceMut::new(&mut data);
|
||
///
|
||
/// // Mark 3 bytes as read.
|
||
/// buf.advance(3);
|
||
/// assert_eq!(buf.deref(), [1; 5].as_ref());
|
||
/// ```
|
||
#[unstable(feature = "io_slice_advance", issue = "62726")]
|
||
#[inline]
|
||
pub fn advance(&mut self, n: usize) {
|
||
self.0.advance(n)
|
||
}
|
||
|
||
/// Advance a slice of slices.
|
||
///
|
||
/// Shrinks the slice to remove any `IoSliceMut`s that are fully advanced over.
|
||
/// If the cursor ends up in the middle of an `IoSliceMut`, it is modified
|
||
/// to start at that cursor.
|
||
///
|
||
/// For example, if we have a slice of two 8-byte `IoSliceMut`s, and we advance by 10 bytes,
|
||
/// the result will only include the second `IoSliceMut`, advanced by 2 bytes.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics when trying to advance beyond the end of the slices.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(io_slice_advance)]
|
||
///
|
||
/// use std::io::IoSliceMut;
|
||
/// use std::ops::Deref;
|
||
///
|
||
/// let mut buf1 = [1; 8];
|
||
/// let mut buf2 = [2; 16];
|
||
/// let mut buf3 = [3; 8];
|
||
/// let mut bufs = &mut [
|
||
/// IoSliceMut::new(&mut buf1),
|
||
/// IoSliceMut::new(&mut buf2),
|
||
/// IoSliceMut::new(&mut buf3),
|
||
/// ][..];
|
||
///
|
||
/// // Mark 10 bytes as read.
|
||
/// IoSliceMut::advance_slices(&mut bufs, 10);
|
||
/// assert_eq!(bufs[0].deref(), [2; 14].as_ref());
|
||
/// assert_eq!(bufs[1].deref(), [3; 8].as_ref());
|
||
/// ```
|
||
#[unstable(feature = "io_slice_advance", issue = "62726")]
|
||
#[inline]
|
||
pub fn advance_slices(bufs: &mut &mut [IoSliceMut<'a>], n: usize) {
|
||
// Number of buffers to remove.
|
||
let mut remove = 0;
|
||
// Remaining length before reaching n.
|
||
let mut left = n;
|
||
for buf in bufs.iter() {
|
||
if let Some(remainder) = left.checked_sub(buf.len()) {
|
||
left = remainder;
|
||
remove += 1;
|
||
} else {
|
||
break;
|
||
}
|
||
}
|
||
|
||
*bufs = &mut take(bufs)[remove..];
|
||
if bufs.is_empty() {
|
||
assert!(left == 0, "advancing io slices beyond their length");
|
||
} else {
|
||
bufs[0].advance(left);
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
impl<'a> Deref for IoSliceMut<'a> {
|
||
type Target = [u8];
|
||
|
||
#[inline]
|
||
fn deref(&self) -> &[u8] {
|
||
self.0.as_slice()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
impl<'a> DerefMut for IoSliceMut<'a> {
|
||
#[inline]
|
||
fn deref_mut(&mut self) -> &mut [u8] {
|
||
self.0.as_mut_slice()
|
||
}
|
||
}
|
||
|
||
/// A buffer type used with `Write::write_vectored`.
|
||
///
|
||
/// It is semantically a wrapper around a `&[u8]`, but is guaranteed to be
|
||
/// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on
|
||
/// Windows.
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
#[derive(Copy, Clone)]
|
||
#[repr(transparent)]
|
||
pub struct IoSlice<'a>(sys::io::IoSlice<'a>);
|
||
|
||
#[stable(feature = "iovec_send_sync", since = "1.44.0")]
|
||
unsafe impl<'a> Send for IoSlice<'a> {}
|
||
|
||
#[stable(feature = "iovec_send_sync", since = "1.44.0")]
|
||
unsafe impl<'a> Sync for IoSlice<'a> {}
|
||
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
impl<'a> fmt::Debug for IoSlice<'a> {
|
||
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(self.0.as_slice(), fmt)
|
||
}
|
||
}
|
||
|
||
impl<'a> IoSlice<'a> {
|
||
/// Creates a new `IoSlice` wrapping a byte slice.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics on Windows if the slice is larger than 4GB.
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
#[must_use]
|
||
#[inline]
|
||
pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
|
||
IoSlice(sys::io::IoSlice::new(buf))
|
||
}
|
||
|
||
/// Advance the internal cursor of the slice.
|
||
///
|
||
/// Also see [`IoSlice::advance_slices`] to advance the cursors of multiple
|
||
/// buffers.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics when trying to advance beyond the end of the slice.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(io_slice_advance)]
|
||
///
|
||
/// use std::io::IoSlice;
|
||
/// use std::ops::Deref;
|
||
///
|
||
/// let data = [1; 8];
|
||
/// let mut buf = IoSlice::new(&data);
|
||
///
|
||
/// // Mark 3 bytes as read.
|
||
/// buf.advance(3);
|
||
/// assert_eq!(buf.deref(), [1; 5].as_ref());
|
||
/// ```
|
||
#[unstable(feature = "io_slice_advance", issue = "62726")]
|
||
#[inline]
|
||
pub fn advance(&mut self, n: usize) {
|
||
self.0.advance(n)
|
||
}
|
||
|
||
/// Advance a slice of slices.
|
||
///
|
||
/// Shrinks the slice to remove any `IoSlice`s that are fully advanced over.
|
||
/// If the cursor ends up in the middle of an `IoSlice`, it is modified
|
||
/// to start at that cursor.
|
||
///
|
||
/// For example, if we have a slice of two 8-byte `IoSlice`s, and we advance by 10 bytes,
|
||
/// the result will only include the second `IoSlice`, advanced by 2 bytes.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics when trying to advance beyond the end of the slices.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(io_slice_advance)]
|
||
///
|
||
/// use std::io::IoSlice;
|
||
/// use std::ops::Deref;
|
||
///
|
||
/// let buf1 = [1; 8];
|
||
/// let buf2 = [2; 16];
|
||
/// let buf3 = [3; 8];
|
||
/// let mut bufs = &mut [
|
||
/// IoSlice::new(&buf1),
|
||
/// IoSlice::new(&buf2),
|
||
/// IoSlice::new(&buf3),
|
||
/// ][..];
|
||
///
|
||
/// // Mark 10 bytes as written.
|
||
/// IoSlice::advance_slices(&mut bufs, 10);
|
||
/// assert_eq!(bufs[0].deref(), [2; 14].as_ref());
|
||
/// assert_eq!(bufs[1].deref(), [3; 8].as_ref());
|
||
#[unstable(feature = "io_slice_advance", issue = "62726")]
|
||
#[inline]
|
||
pub fn advance_slices(bufs: &mut &mut [IoSlice<'a>], n: usize) {
|
||
// Number of buffers to remove.
|
||
let mut remove = 0;
|
||
// Remaining length before reaching n. This prevents overflow
|
||
// that could happen if the length of slices in `bufs` were instead
|
||
// accumulated. Those slice may be aliased and, if they are large
|
||
// enough, their added length may overflow a `usize`.
|
||
let mut left = n;
|
||
for buf in bufs.iter() {
|
||
if let Some(remainder) = left.checked_sub(buf.len()) {
|
||
left = remainder;
|
||
remove += 1;
|
||
} else {
|
||
break;
|
||
}
|
||
}
|
||
|
||
*bufs = &mut take(bufs)[remove..];
|
||
if bufs.is_empty() {
|
||
assert!(left == 0, "advancing io slices beyond their length");
|
||
} else {
|
||
bufs[0].advance(left);
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
impl<'a> Deref for IoSlice<'a> {
|
||
type Target = [u8];
|
||
|
||
#[inline]
|
||
fn deref(&self) -> &[u8] {
|
||
self.0.as_slice()
|
||
}
|
||
}
|
||
|
||
/// A trait for objects which are byte-oriented sinks.
|
||
///
|
||
/// Implementors of the `Write` trait are sometimes called 'writers'.
|
||
///
|
||
/// Writers are defined by two required methods, [`write`] and [`flush`]:
|
||
///
|
||
/// * The [`write`] method will attempt to write some data into the object,
|
||
/// returning how many bytes were successfully written.
|
||
///
|
||
/// * The [`flush`] method is useful for adapters and explicit buffers
|
||
/// themselves for ensuring that all buffered data has been pushed out to the
|
||
/// 'true sink'.
|
||
///
|
||
/// Writers are intended to be composable with one another. Many implementors
|
||
/// throughout [`std::io`] take and provide types which implement the `Write`
|
||
/// trait.
|
||
///
|
||
/// [`write`]: Write::write
|
||
/// [`flush`]: Write::flush
|
||
/// [`std::io`]: self
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let data = b"some bytes";
|
||
///
|
||
/// let mut pos = 0;
|
||
/// let mut buffer = File::create("foo.txt")?;
|
||
///
|
||
/// while pos < data.len() {
|
||
/// let bytes_written = buffer.write(&data[pos..])?;
|
||
/// pos += bytes_written;
|
||
/// }
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// The trait also provides convenience methods like [`write_all`], which calls
|
||
/// `write` in a loop until its entire input has been written.
|
||
///
|
||
/// [`write_all`]: Write::write_all
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[doc(notable_trait)]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "IoWrite")]
|
||
pub trait Write {
|
||
/// Write a buffer into this writer, returning how many bytes were written.
|
||
///
|
||
/// This function will attempt to write the entire contents of `buf`, but
|
||
/// the entire write might not succeed, or the write may also generate an
|
||
/// error. Typically, a call to `write` represents one attempt to write to
|
||
/// any wrapped object.
|
||
///
|
||
/// Calls to `write` are not guaranteed to block waiting for data to be
|
||
/// written, and a write which would otherwise block can be indicated through
|
||
/// an [`Err`] variant.
|
||
///
|
||
/// If this method consumed `n > 0` bytes of `buf` it must return [`Ok(n)`].
|
||
/// If the return value is `Ok(n)` then `n` must satisfy `n <= buf.len()`.
|
||
/// A return value of `Ok(0)` typically means that the underlying object is
|
||
/// no longer able to accept bytes and will likely not be able to in the
|
||
/// future as well, or that the buffer provided is empty.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Each call to `write` may generate an I/O error indicating that the
|
||
/// operation could not be completed. If an error is returned then no bytes
|
||
/// in the buffer were written to this writer.
|
||
///
|
||
/// It is **not** considered an error if the entire buffer could not be
|
||
/// written to this writer.
|
||
///
|
||
/// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the
|
||
/// write operation should be retried if there is nothing else to do.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let mut buffer = File::create("foo.txt")?;
|
||
///
|
||
/// // Writes some prefix of the byte string, not necessarily all of it.
|
||
/// buffer.write(b"some bytes")?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [`Ok(n)`]: Ok
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn write(&mut self, buf: &[u8]) -> Result<usize>;
|
||
|
||
/// Like [`write`], except that it writes from a slice of buffers.
|
||
///
|
||
/// Data is copied from each buffer in order, with the final buffer
|
||
/// read from possibly being only partially consumed. This method must
|
||
/// behave as a call to [`write`] with the buffers concatenated would.
|
||
///
|
||
/// The default implementation calls [`write`] with either the first nonempty
|
||
/// buffer provided, or an empty one if none exists.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::IoSlice;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let data1 = [1; 8];
|
||
/// let data2 = [15; 8];
|
||
/// let io_slice1 = IoSlice::new(&data1);
|
||
/// let io_slice2 = IoSlice::new(&data2);
|
||
///
|
||
/// let mut buffer = File::create("foo.txt")?;
|
||
///
|
||
/// // Writes some prefix of the byte string, not necessarily all of it.
|
||
/// buffer.write_vectored(&[io_slice1, io_slice2])?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [`write`]: Write::write
|
||
#[stable(feature = "iovec", since = "1.36.0")]
|
||
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> {
|
||
default_write_vectored(|b| self.write(b), bufs)
|
||
}
|
||
|
||
/// Determines if this `Write`r has an efficient [`write_vectored`]
|
||
/// implementation.
|
||
///
|
||
/// If a `Write`r does not override the default [`write_vectored`]
|
||
/// implementation, code using it may want to avoid the method all together
|
||
/// and coalesce writes into a single buffer for higher performance.
|
||
///
|
||
/// The default implementation returns `false`.
|
||
///
|
||
/// [`write_vectored`]: Write::write_vectored
|
||
#[unstable(feature = "can_vector", issue = "69941")]
|
||
fn is_write_vectored(&self) -> bool {
|
||
false
|
||
}
|
||
|
||
/// Flush this output stream, ensuring that all intermediately buffered
|
||
/// contents reach their destination.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// It is considered an error if not all bytes could be written due to
|
||
/// I/O errors or EOF being reached.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::prelude::*;
|
||
/// use std::io::BufWriter;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let mut buffer = BufWriter::new(File::create("foo.txt")?);
|
||
///
|
||
/// buffer.write_all(b"some bytes")?;
|
||
/// buffer.flush()?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn flush(&mut self) -> Result<()>;
|
||
|
||
/// Attempts to write an entire buffer into this writer.
|
||
///
|
||
/// This method will continuously call [`write`] until there is no more data
|
||
/// to be written or an error of non-[`ErrorKind::Interrupted`] kind is
|
||
/// returned. This method will not return until the entire buffer has been
|
||
/// successfully written or such an error occurs. The first error that is
|
||
/// not of [`ErrorKind::Interrupted`] kind generated from this method will be
|
||
/// returned.
|
||
///
|
||
/// If the buffer contains no data, this will never call [`write`].
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function will return the first error of
|
||
/// non-[`ErrorKind::Interrupted`] kind that [`write`] returns.
|
||
///
|
||
/// [`write`]: Write::write
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let mut buffer = File::create("foo.txt")?;
|
||
///
|
||
/// buffer.write_all(b"some bytes")?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
|
||
while !buf.is_empty() {
|
||
match self.write(buf) {
|
||
Ok(0) => {
|
||
return Err(Error::WRITE_ALL_EOF);
|
||
}
|
||
Ok(n) => buf = &buf[n..],
|
||
Err(ref e) if e.is_interrupted() => {}
|
||
Err(e) => return Err(e),
|
||
}
|
||
}
|
||
Ok(())
|
||
}
|
||
|
||
/// Attempts to write multiple buffers into this writer.
|
||
///
|
||
/// This method will continuously call [`write_vectored`] until there is no
|
||
/// more data to be written or an error of non-[`ErrorKind::Interrupted`]
|
||
/// kind is returned. This method will not return until all buffers have
|
||
/// been successfully written or such an error occurs. The first error that
|
||
/// is not of [`ErrorKind::Interrupted`] kind generated from this method
|
||
/// will be returned.
|
||
///
|
||
/// If the buffer contains no data, this will never call [`write_vectored`].
|
||
///
|
||
/// # Notes
|
||
///
|
||
/// Unlike [`write_vectored`], this takes a *mutable* reference to
|
||
/// a slice of [`IoSlice`]s, not an immutable one. That's because we need to
|
||
/// modify the slice to keep track of the bytes already written.
|
||
///
|
||
/// Once this function returns, the contents of `bufs` are unspecified, as
|
||
/// this depends on how many calls to [`write_vectored`] were necessary. It is
|
||
/// best to understand this function as taking ownership of `bufs` and to
|
||
/// not use `bufs` afterwards. The underlying buffers, to which the
|
||
/// [`IoSlice`]s point (but not the [`IoSlice`]s themselves), are unchanged and
|
||
/// can be reused.
|
||
///
|
||
/// [`write_vectored`]: Write::write_vectored
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(write_all_vectored)]
|
||
/// # fn main() -> std::io::Result<()> {
|
||
///
|
||
/// use std::io::{Write, IoSlice};
|
||
///
|
||
/// let mut writer = Vec::new();
|
||
/// let bufs = &mut [
|
||
/// IoSlice::new(&[1]),
|
||
/// IoSlice::new(&[2, 3]),
|
||
/// IoSlice::new(&[4, 5, 6]),
|
||
/// ];
|
||
///
|
||
/// writer.write_all_vectored(bufs)?;
|
||
/// // Note: the contents of `bufs` is now undefined, see the Notes section.
|
||
///
|
||
/// assert_eq!(writer, &[1, 2, 3, 4, 5, 6]);
|
||
/// # Ok(()) }
|
||
/// ```
|
||
#[unstable(feature = "write_all_vectored", issue = "70436")]
|
||
fn write_all_vectored(&mut self, mut bufs: &mut [IoSlice<'_>]) -> Result<()> {
|
||
// Guarantee that bufs is empty if it contains no data,
|
||
// to avoid calling write_vectored if there is no data to be written.
|
||
IoSlice::advance_slices(&mut bufs, 0);
|
||
while !bufs.is_empty() {
|
||
match self.write_vectored(bufs) {
|
||
Ok(0) => {
|
||
return Err(Error::WRITE_ALL_EOF);
|
||
}
|
||
Ok(n) => IoSlice::advance_slices(&mut bufs, n),
|
||
Err(ref e) if e.is_interrupted() => {}
|
||
Err(e) => return Err(e),
|
||
}
|
||
}
|
||
Ok(())
|
||
}
|
||
|
||
/// Writes a formatted string into this writer, returning any error
|
||
/// encountered.
|
||
///
|
||
/// This method is primarily used to interface with the
|
||
/// [`format_args!()`] macro, and it is rare that this should
|
||
/// explicitly be called. The [`write!()`] macro should be favored to
|
||
/// invoke this method instead.
|
||
///
|
||
/// This function internally uses the [`write_all`] method on
|
||
/// this trait and hence will continuously write data so long as no errors
|
||
/// are received. This also means that partial writes are not indicated in
|
||
/// this signature.
|
||
///
|
||
/// [`write_all`]: Write::write_all
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function will return any I/O error reported while formatting.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let mut buffer = File::create("foo.txt")?;
|
||
///
|
||
/// // this call
|
||
/// write!(buffer, "{:.*}", 2, 1.234567)?;
|
||
/// // turns into this:
|
||
/// buffer.write_fmt(format_args!("{:.*}", 2, 1.234567))?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> Result<()> {
|
||
// Create a shim which translates a Write to a fmt::Write and saves
|
||
// off I/O errors. instead of discarding them
|
||
struct Adapter<'a, T: ?Sized + 'a> {
|
||
inner: &'a mut T,
|
||
error: Result<()>,
|
||
}
|
||
|
||
impl<T: Write + ?Sized> fmt::Write for Adapter<'_, T> {
|
||
fn write_str(&mut self, s: &str) -> fmt::Result {
|
||
match self.inner.write_all(s.as_bytes()) {
|
||
Ok(()) => Ok(()),
|
||
Err(e) => {
|
||
self.error = Err(e);
|
||
Err(fmt::Error)
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
let mut output = Adapter { inner: self, error: Ok(()) };
|
||
match fmt::write(&mut output, fmt) {
|
||
Ok(()) => Ok(()),
|
||
Err(..) => {
|
||
// check if the error came from the underlying `Write` or not
|
||
if output.error.is_err() {
|
||
output.error
|
||
} else {
|
||
Err(error::const_io_error!(ErrorKind::Uncategorized, "formatter error"))
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Creates a "by reference" adapter for this instance of `Write`.
|
||
///
|
||
/// The returned adapter also implements `Write` and will simply borrow this
|
||
/// current writer.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::Write;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> std::io::Result<()> {
|
||
/// let mut buffer = File::create("foo.txt")?;
|
||
///
|
||
/// let reference = buffer.by_ref();
|
||
///
|
||
/// // we can use reference just like our original buffer
|
||
/// reference.write_all(b"some bytes")?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn by_ref(&mut self) -> &mut Self
|
||
where
|
||
Self: Sized,
|
||
{
|
||
self
|
||
}
|
||
}
|
||
|
||
/// The `Seek` trait provides a cursor which can be moved within a stream of
|
||
/// bytes.
|
||
///
|
||
/// The stream typically has a fixed size, allowing seeking relative to either
|
||
/// end or the current offset.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`File`]s implement `Seek`:
|
||
///
|
||
/// [`File`]: crate::fs::File
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
/// use std::io::SeekFrom;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
///
|
||
/// // move the cursor 42 bytes from the start of the file
|
||
/// f.seek(SeekFrom::Start(42))?;
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "IoSeek")]
|
||
pub trait Seek {
|
||
/// Seek to an offset, in bytes, in a stream.
|
||
///
|
||
/// A seek beyond the end of a stream is allowed, but behavior is defined
|
||
/// by the implementation.
|
||
///
|
||
/// If the seek operation completed successfully,
|
||
/// this method returns the new position from the start of the stream.
|
||
/// That position can be used later with [`SeekFrom::Start`].
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Seeking can fail, for example because it might involve flushing a buffer.
|
||
///
|
||
/// Seeking to a negative offset is considered an error.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
|
||
|
||
/// Rewind to the beginning of a stream.
|
||
///
|
||
/// This is a convenience method, equivalent to `seek(SeekFrom::Start(0))`.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Rewinding can fail, for example because it might involve flushing a buffer.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::{Read, Seek, Write};
|
||
/// use std::fs::OpenOptions;
|
||
///
|
||
/// let mut f = OpenOptions::new()
|
||
/// .write(true)
|
||
/// .read(true)
|
||
/// .create(true)
|
||
/// .open("foo.txt").unwrap();
|
||
///
|
||
/// let hello = "Hello!\n";
|
||
/// write!(f, "{hello}").unwrap();
|
||
/// f.rewind().unwrap();
|
||
///
|
||
/// let mut buf = String::new();
|
||
/// f.read_to_string(&mut buf).unwrap();
|
||
/// assert_eq!(&buf, hello);
|
||
/// ```
|
||
#[stable(feature = "seek_rewind", since = "1.55.0")]
|
||
fn rewind(&mut self) -> Result<()> {
|
||
self.seek(SeekFrom::Start(0))?;
|
||
Ok(())
|
||
}
|
||
|
||
/// Returns the length of this stream (in bytes).
|
||
///
|
||
/// This method is implemented using up to three seek operations. If this
|
||
/// method returns successfully, the seek position is unchanged (i.e. the
|
||
/// position before calling this method is the same as afterwards).
|
||
/// However, if this method returns an error, the seek position is
|
||
/// unspecified.
|
||
///
|
||
/// If you need to obtain the length of *many* streams and you don't care
|
||
/// about the seek position afterwards, you can reduce the number of seek
|
||
/// operations by simply calling `seek(SeekFrom::End(0))` and using its
|
||
/// return value (it is also the stream length).
|
||
///
|
||
/// Note that length of a stream can change over time (for example, when
|
||
/// data is appended to a file). So calling this method multiple times does
|
||
/// not necessarily return the same length each time.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```no_run
|
||
/// #![feature(seek_stream_len)]
|
||
/// use std::{
|
||
/// io::{self, Seek},
|
||
/// fs::File,
|
||
/// };
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
///
|
||
/// let len = f.stream_len()?;
|
||
/// println!("The file is currently {len} bytes long");
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[unstable(feature = "seek_stream_len", issue = "59359")]
|
||
fn stream_len(&mut self) -> Result<u64> {
|
||
let old_pos = self.stream_position()?;
|
||
let len = self.seek(SeekFrom::End(0))?;
|
||
|
||
// Avoid seeking a third time when we were already at the end of the
|
||
// stream. The branch is usually way cheaper than a seek operation.
|
||
if old_pos != len {
|
||
self.seek(SeekFrom::Start(old_pos))?;
|
||
}
|
||
|
||
Ok(len)
|
||
}
|
||
|
||
/// Returns the current seek position from the start of the stream.
|
||
///
|
||
/// This is equivalent to `self.seek(SeekFrom::Current(0))`.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```no_run
|
||
/// use std::{
|
||
/// io::{self, BufRead, BufReader, Seek},
|
||
/// fs::File,
|
||
/// };
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = BufReader::new(File::open("foo.txt")?);
|
||
///
|
||
/// let before = f.stream_position()?;
|
||
/// f.read_line(&mut String::new())?;
|
||
/// let after = f.stream_position()?;
|
||
///
|
||
/// println!("The first line was {} bytes long", after - before);
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "seek_convenience", since = "1.51.0")]
|
||
fn stream_position(&mut self) -> Result<u64> {
|
||
self.seek(SeekFrom::Current(0))
|
||
}
|
||
|
||
/// Seeks relative to the current position.
|
||
///
|
||
/// This is equivalent to `self.seek(SeekFrom::Current(offset))` but
|
||
/// doesn't return the new position which can allow some implementations
|
||
/// such as [`BufReader`] to perform more efficient seeks.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```no_run
|
||
/// #![feature(seek_seek_relative)]
|
||
/// use std::{
|
||
/// io::{self, Seek},
|
||
/// fs::File,
|
||
/// };
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut f = File::open("foo.txt")?;
|
||
/// f.seek_relative(10)?;
|
||
/// assert_eq!(f.stream_position()?, 10);
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [`BufReader`]: crate::io::BufReader
|
||
#[unstable(feature = "seek_seek_relative", issue = "117374")]
|
||
fn seek_relative(&mut self, offset: i64) -> Result<()> {
|
||
self.seek(SeekFrom::Current(offset))?;
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
/// Enumeration of possible methods to seek within an I/O object.
|
||
///
|
||
/// It is used by the [`Seek`] trait.
|
||
#[derive(Copy, PartialEq, Eq, Clone, Debug)]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub enum SeekFrom {
|
||
/// Sets the offset to the provided number of bytes.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
Start(#[stable(feature = "rust1", since = "1.0.0")] u64),
|
||
|
||
/// Sets the offset to the size of this object plus the specified number of
|
||
/// bytes.
|
||
///
|
||
/// It is possible to seek beyond the end of an object, but it's an error to
|
||
/// seek before byte 0.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
End(#[stable(feature = "rust1", since = "1.0.0")] i64),
|
||
|
||
/// Sets the offset to the current position plus the specified number of
|
||
/// bytes.
|
||
///
|
||
/// It is possible to seek beyond the end of an object, but it's an error to
|
||
/// seek before byte 0.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
Current(#[stable(feature = "rust1", since = "1.0.0")] i64),
|
||
}
|
||
|
||
fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>) -> Result<usize> {
|
||
let mut read = 0;
|
||
loop {
|
||
let (done, used) = {
|
||
let available = match r.fill_buf() {
|
||
Ok(n) => n,
|
||
Err(ref e) if e.is_interrupted() => continue,
|
||
Err(e) => return Err(e),
|
||
};
|
||
match memchr::memchr(delim, available) {
|
||
Some(i) => {
|
||
buf.extend_from_slice(&available[..=i]);
|
||
(true, i + 1)
|
||
}
|
||
None => {
|
||
buf.extend_from_slice(available);
|
||
(false, available.len())
|
||
}
|
||
}
|
||
};
|
||
r.consume(used);
|
||
read += used;
|
||
if done || used == 0 {
|
||
return Ok(read);
|
||
}
|
||
}
|
||
}
|
||
|
||
fn skip_until<R: BufRead + ?Sized>(r: &mut R, delim: u8) -> Result<usize> {
|
||
let mut read = 0;
|
||
loop {
|
||
let (done, used) = {
|
||
let available = match r.fill_buf() {
|
||
Ok(n) => n,
|
||
Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
|
||
Err(e) => return Err(e),
|
||
};
|
||
match memchr::memchr(delim, available) {
|
||
Some(i) => (true, i + 1),
|
||
None => (false, available.len()),
|
||
}
|
||
};
|
||
r.consume(used);
|
||
read += used;
|
||
if done || used == 0 {
|
||
return Ok(read);
|
||
}
|
||
}
|
||
}
|
||
|
||
/// A `BufRead` is a type of `Read`er which has an internal buffer, allowing it
|
||
/// to perform extra ways of reading.
|
||
///
|
||
/// For example, reading line-by-line is inefficient without using a buffer, so
|
||
/// if you want to read by line, you'll need `BufRead`, which includes a
|
||
/// [`read_line`] method as well as a [`lines`] iterator.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// A locked standard input implements `BufRead`:
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
///
|
||
/// let stdin = io::stdin();
|
||
/// for line in stdin.lock().lines() {
|
||
/// println!("{}", line.unwrap());
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// If you have something that implements [`Read`], you can use the [`BufReader`
|
||
/// type][`BufReader`] to turn it into a `BufRead`.
|
||
///
|
||
/// For example, [`File`] implements [`Read`], but not `BufRead`.
|
||
/// [`BufReader`] to the rescue!
|
||
///
|
||
/// [`File`]: crate::fs::File
|
||
/// [`read_line`]: BufRead::read_line
|
||
/// [`lines`]: BufRead::lines
|
||
///
|
||
/// ```no_run
|
||
/// use std::io::{self, BufReader};
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let f = File::open("foo.txt")?;
|
||
/// let f = BufReader::new(f);
|
||
///
|
||
/// for line in f.lines() {
|
||
/// println!("{}", line.unwrap());
|
||
/// }
|
||
///
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait BufRead: Read {
|
||
/// Returns the contents of the internal buffer, filling it with more data
|
||
/// from the inner reader if it is empty.
|
||
///
|
||
/// This function is a lower-level call. It needs to be paired with the
|
||
/// [`consume`] method to function properly. When calling this
|
||
/// method, none of the contents will be "read" in the sense that later
|
||
/// calling `read` may return the same contents. As such, [`consume`] must
|
||
/// be called with the number of bytes that are consumed from this buffer to
|
||
/// ensure that the bytes are never returned twice.
|
||
///
|
||
/// [`consume`]: BufRead::consume
|
||
///
|
||
/// An empty buffer returned indicates that the stream has reached EOF.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function will return an I/O error if the underlying reader was
|
||
/// read, but returned an error.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// A locked standard input implements `BufRead`:
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
///
|
||
/// let stdin = io::stdin();
|
||
/// let mut stdin = stdin.lock();
|
||
///
|
||
/// let buffer = stdin.fill_buf().unwrap();
|
||
///
|
||
/// // work with buffer
|
||
/// println!("{buffer:?}");
|
||
///
|
||
/// // ensure the bytes we worked with aren't returned again later
|
||
/// let length = buffer.len();
|
||
/// stdin.consume(length);
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fill_buf(&mut self) -> Result<&[u8]>;
|
||
|
||
/// Tells this buffer that `amt` bytes have been consumed from the buffer,
|
||
/// so they should no longer be returned in calls to `read`.
|
||
///
|
||
/// This function is a lower-level call. It needs to be paired with the
|
||
/// [`fill_buf`] method to function properly. This function does
|
||
/// not perform any I/O, it simply informs this object that some amount of
|
||
/// its buffer, returned from [`fill_buf`], has been consumed and should
|
||
/// no longer be returned. As such, this function may do odd things if
|
||
/// [`fill_buf`] isn't called before calling it.
|
||
///
|
||
/// The `amt` must be `<=` the number of bytes in the buffer returned by
|
||
/// [`fill_buf`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Since `consume()` is meant to be used with [`fill_buf`],
|
||
/// that method's example includes an example of `consume()`.
|
||
///
|
||
/// [`fill_buf`]: BufRead::fill_buf
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn consume(&mut self, amt: usize);
|
||
|
||
/// Check if the underlying `Read` has any data left to be read.
|
||
///
|
||
/// This function may fill the buffer to check for data,
|
||
/// so this functions returns `Result<bool>`, not `bool`.
|
||
///
|
||
/// Default implementation calls `fill_buf` and checks that
|
||
/// returned slice is empty (which means that there is no data left,
|
||
/// since EOF is reached).
|
||
///
|
||
/// Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(buf_read_has_data_left)]
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
///
|
||
/// let stdin = io::stdin();
|
||
/// let mut stdin = stdin.lock();
|
||
///
|
||
/// while stdin.has_data_left().unwrap() {
|
||
/// let mut line = String::new();
|
||
/// stdin.read_line(&mut line).unwrap();
|
||
/// // work with line
|
||
/// println!("{line:?}");
|
||
/// }
|
||
/// ```
|
||
#[unstable(feature = "buf_read_has_data_left", reason = "recently added", issue = "86423")]
|
||
fn has_data_left(&mut self) -> Result<bool> {
|
||
self.fill_buf().map(|b| !b.is_empty())
|
||
}
|
||
|
||
/// Read all bytes into `buf` until the delimiter `byte` or EOF is reached.
|
||
///
|
||
/// This function will read bytes from the underlying stream until the
|
||
/// delimiter or EOF is found. Once found, all bytes up to, and including,
|
||
/// the delimiter (if found) will be appended to `buf`.
|
||
///
|
||
/// If successful, this function will return the total number of bytes read.
|
||
///
|
||
/// This function is blocking and should be used carefully: it is possible for
|
||
/// an attacker to continuously send bytes without ever sending the delimiter
|
||
/// or EOF.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function will ignore all instances of [`ErrorKind::Interrupted`] and
|
||
/// will otherwise return any errors returned by [`fill_buf`].
|
||
///
|
||
/// If an I/O error is encountered then all bytes read so far will be
|
||
/// present in `buf` and its length will have been adjusted appropriately.
|
||
///
|
||
/// [`fill_buf`]: BufRead::fill_buf
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In
|
||
/// this example, we use [`Cursor`] to read all the bytes in a byte slice
|
||
/// in hyphen delimited segments:
|
||
///
|
||
/// ```
|
||
/// use std::io::{self, BufRead};
|
||
///
|
||
/// let mut cursor = io::Cursor::new(b"lorem-ipsum");
|
||
/// let mut buf = vec![];
|
||
///
|
||
/// // cursor is at 'l'
|
||
/// let num_bytes = cursor.read_until(b'-', &mut buf)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 6);
|
||
/// assert_eq!(buf, b"lorem-");
|
||
/// buf.clear();
|
||
///
|
||
/// // cursor is at 'i'
|
||
/// let num_bytes = cursor.read_until(b'-', &mut buf)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 5);
|
||
/// assert_eq!(buf, b"ipsum");
|
||
/// buf.clear();
|
||
///
|
||
/// // cursor is at EOF
|
||
/// let num_bytes = cursor.read_until(b'-', &mut buf)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 0);
|
||
/// assert_eq!(buf, b"");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> {
|
||
read_until(self, byte, buf)
|
||
}
|
||
|
||
/// Skip all bytes until the delimiter `byte` or EOF is reached.
|
||
///
|
||
/// This function will read (and discard) bytes from the underlying stream until the
|
||
/// delimiter or EOF is found.
|
||
///
|
||
/// If successful, this function will return the total number of bytes read,
|
||
/// including the delimiter byte.
|
||
///
|
||
/// This is useful for efficiently skipping data such as NUL-terminated strings
|
||
/// in binary file formats without buffering.
|
||
///
|
||
/// This function is blocking and should be used carefully: it is possible for
|
||
/// an attacker to continuously send bytes without ever sending the delimiter
|
||
/// or EOF.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function will ignore all instances of [`ErrorKind::Interrupted`] and
|
||
/// will otherwise return any errors returned by [`fill_buf`].
|
||
///
|
||
/// If an I/O error is encountered then all bytes read so far will be
|
||
/// present in `buf` and its length will have been adjusted appropriately.
|
||
///
|
||
/// [`fill_buf`]: BufRead::fill_buf
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In
|
||
/// this example, we use [`Cursor`] to read some NUL-terminated information
|
||
/// about Ferris from a binary string, skipping the fun fact:
|
||
///
|
||
/// ```
|
||
/// #![feature(bufread_skip_until)]
|
||
///
|
||
/// use std::io::{self, BufRead};
|
||
///
|
||
/// let mut cursor = io::Cursor::new(b"Ferris\0Likes long walks on the beach\0Crustacean\0");
|
||
///
|
||
/// // read name
|
||
/// let mut name = Vec::new();
|
||
/// let num_bytes = cursor.read_until(b'\0', &mut name)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 7);
|
||
/// assert_eq!(name, b"Ferris\0");
|
||
///
|
||
/// // skip fun fact
|
||
/// let num_bytes = cursor.skip_until(b'\0')
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 30);
|
||
///
|
||
/// // read animal type
|
||
/// let mut animal = Vec::new();
|
||
/// let num_bytes = cursor.read_until(b'\0', &mut animal)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 11);
|
||
/// assert_eq!(animal, b"Crustacean\0");
|
||
/// ```
|
||
#[unstable(feature = "bufread_skip_until", issue = "111735")]
|
||
fn skip_until(&mut self, byte: u8) -> Result<usize> {
|
||
skip_until(self, byte)
|
||
}
|
||
|
||
/// Read all bytes until a newline (the `0xA` byte) is reached, and append
|
||
/// them to the provided `String` buffer.
|
||
///
|
||
/// Previous content of the buffer will be preserved. To avoid appending to
|
||
/// the buffer, you need to [`clear`] it first.
|
||
///
|
||
/// This function will read bytes from the underlying stream until the
|
||
/// newline delimiter (the `0xA` byte) or EOF is found. Once found, all bytes
|
||
/// up to, and including, the delimiter (if found) will be appended to
|
||
/// `buf`.
|
||
///
|
||
/// If successful, this function will return the total number of bytes read.
|
||
///
|
||
/// If this function returns [`Ok(0)`], the stream has reached EOF.
|
||
///
|
||
/// This function is blocking and should be used carefully: it is possible for
|
||
/// an attacker to continuously send bytes without ever sending a newline
|
||
/// or EOF. You can use [`take`] to limit the maximum number of bytes read.
|
||
///
|
||
/// [`Ok(0)`]: Ok
|
||
/// [`clear`]: String::clear
|
||
/// [`take`]: crate::io::Read::take
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// This function has the same error semantics as [`read_until`] and will
|
||
/// also return an error if the read bytes are not valid UTF-8. If an I/O
|
||
/// error is encountered then `buf` may contain some bytes already read in
|
||
/// the event that all data read so far was valid UTF-8.
|
||
///
|
||
/// [`read_until`]: BufRead::read_until
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In
|
||
/// this example, we use [`Cursor`] to read all the lines in a byte slice:
|
||
///
|
||
/// ```
|
||
/// use std::io::{self, BufRead};
|
||
///
|
||
/// let mut cursor = io::Cursor::new(b"foo\nbar");
|
||
/// let mut buf = String::new();
|
||
///
|
||
/// // cursor is at 'f'
|
||
/// let num_bytes = cursor.read_line(&mut buf)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 4);
|
||
/// assert_eq!(buf, "foo\n");
|
||
/// buf.clear();
|
||
///
|
||
/// // cursor is at 'b'
|
||
/// let num_bytes = cursor.read_line(&mut buf)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 3);
|
||
/// assert_eq!(buf, "bar");
|
||
/// buf.clear();
|
||
///
|
||
/// // cursor is at EOF
|
||
/// let num_bytes = cursor.read_line(&mut buf)
|
||
/// .expect("reading from cursor won't fail");
|
||
/// assert_eq!(num_bytes, 0);
|
||
/// assert_eq!(buf, "");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn read_line(&mut self, buf: &mut String) -> Result<usize> {
|
||
// Note that we are not calling the `.read_until` method here, but
|
||
// rather our hardcoded implementation. For more details as to why, see
|
||
// the comments in `read_to_end`.
|
||
unsafe { append_to_string(buf, |b| read_until(self, b'\n', b)) }
|
||
}
|
||
|
||
/// Returns an iterator over the contents of this reader split on the byte
|
||
/// `byte`.
|
||
///
|
||
/// The iterator returned from this function will return instances of
|
||
/// <code>[io::Result]<[Vec]\<u8>></code>. Each vector returned will *not* have
|
||
/// the delimiter byte at the end.
|
||
///
|
||
/// This function will yield errors whenever [`read_until`] would have
|
||
/// also yielded an error.
|
||
///
|
||
/// [io::Result]: self::Result "io::Result"
|
||
/// [`read_until`]: BufRead::read_until
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In
|
||
/// this example, we use [`Cursor`] to iterate over all hyphen delimited
|
||
/// segments in a byte slice
|
||
///
|
||
/// ```
|
||
/// use std::io::{self, BufRead};
|
||
///
|
||
/// let cursor = io::Cursor::new(b"lorem-ipsum-dolor");
|
||
///
|
||
/// let mut split_iter = cursor.split(b'-').map(|l| l.unwrap());
|
||
/// assert_eq!(split_iter.next(), Some(b"lorem".to_vec()));
|
||
/// assert_eq!(split_iter.next(), Some(b"ipsum".to_vec()));
|
||
/// assert_eq!(split_iter.next(), Some(b"dolor".to_vec()));
|
||
/// assert_eq!(split_iter.next(), None);
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn split(self, byte: u8) -> Split<Self>
|
||
where
|
||
Self: Sized,
|
||
{
|
||
Split { buf: self, delim: byte }
|
||
}
|
||
|
||
/// Returns an iterator over the lines of this reader.
|
||
///
|
||
/// The iterator returned from this function will yield instances of
|
||
/// <code>[io::Result]<[String]></code>. Each string returned will *not* have a newline
|
||
/// byte (the `0xA` byte) or `CRLF` (`0xD`, `0xA` bytes) at the end.
|
||
///
|
||
/// [io::Result]: self::Result "io::Result"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In
|
||
/// this example, we use [`Cursor`] to iterate over all the lines in a byte
|
||
/// slice.
|
||
///
|
||
/// ```
|
||
/// use std::io::{self, BufRead};
|
||
///
|
||
/// let cursor = io::Cursor::new(b"lorem\nipsum\r\ndolor");
|
||
///
|
||
/// let mut lines_iter = cursor.lines().map(|l| l.unwrap());
|
||
/// assert_eq!(lines_iter.next(), Some(String::from("lorem")));
|
||
/// assert_eq!(lines_iter.next(), Some(String::from("ipsum")));
|
||
/// assert_eq!(lines_iter.next(), Some(String::from("dolor")));
|
||
/// assert_eq!(lines_iter.next(), None);
|
||
/// ```
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Each line of the iterator has the same error semantics as [`BufRead::read_line`].
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn lines(self) -> Lines<Self>
|
||
where
|
||
Self: Sized,
|
||
{
|
||
Lines { buf: self }
|
||
}
|
||
}
|
||
|
||
/// Adapter to chain together two readers.
|
||
///
|
||
/// This struct is generally created by calling [`chain`] on a reader.
|
||
/// Please see the documentation of [`chain`] for more details.
|
||
///
|
||
/// [`chain`]: Read::chain
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
pub struct Chain<T, U> {
|
||
first: T,
|
||
second: U,
|
||
done_first: bool,
|
||
}
|
||
|
||
impl<T, U> Chain<T, U> {
|
||
/// Consumes the `Chain`, returning the wrapped readers.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut foo_file = File::open("foo.txt")?;
|
||
/// let mut bar_file = File::open("bar.txt")?;
|
||
///
|
||
/// let chain = foo_file.chain(bar_file);
|
||
/// let (foo_file, bar_file) = chain.into_inner();
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "more_io_inner_methods", since = "1.20.0")]
|
||
pub fn into_inner(self) -> (T, U) {
|
||
(self.first, self.second)
|
||
}
|
||
|
||
/// Gets references to the underlying readers in this `Chain`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut foo_file = File::open("foo.txt")?;
|
||
/// let mut bar_file = File::open("bar.txt")?;
|
||
///
|
||
/// let chain = foo_file.chain(bar_file);
|
||
/// let (foo_file, bar_file) = chain.get_ref();
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "more_io_inner_methods", since = "1.20.0")]
|
||
pub fn get_ref(&self) -> (&T, &U) {
|
||
(&self.first, &self.second)
|
||
}
|
||
|
||
/// Gets mutable references to the underlying readers in this `Chain`.
|
||
///
|
||
/// Care should be taken to avoid modifying the internal I/O state of the
|
||
/// underlying readers as doing so may corrupt the internal state of this
|
||
/// `Chain`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut foo_file = File::open("foo.txt")?;
|
||
/// let mut bar_file = File::open("bar.txt")?;
|
||
///
|
||
/// let mut chain = foo_file.chain(bar_file);
|
||
/// let (foo_file, bar_file) = chain.get_mut();
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "more_io_inner_methods", since = "1.20.0")]
|
||
pub fn get_mut(&mut self) -> (&mut T, &mut U) {
|
||
(&mut self.first, &mut self.second)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Read, U: Read> Read for Chain<T, U> {
|
||
fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
|
||
if !self.done_first {
|
||
match self.first.read(buf)? {
|
||
0 if !buf.is_empty() => self.done_first = true,
|
||
n => return Ok(n),
|
||
}
|
||
}
|
||
self.second.read(buf)
|
||
}
|
||
|
||
fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> {
|
||
if !self.done_first {
|
||
match self.first.read_vectored(bufs)? {
|
||
0 if bufs.iter().any(|b| !b.is_empty()) => self.done_first = true,
|
||
n => return Ok(n),
|
||
}
|
||
}
|
||
self.second.read_vectored(bufs)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_read_vectored(&self) -> bool {
|
||
self.first.is_read_vectored() || self.second.is_read_vectored()
|
||
}
|
||
|
||
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
|
||
let mut read = 0;
|
||
if !self.done_first {
|
||
read += self.first.read_to_end(buf)?;
|
||
self.done_first = true;
|
||
}
|
||
read += self.second.read_to_end(buf)?;
|
||
Ok(read)
|
||
}
|
||
|
||
// We don't override `read_to_string` here because an UTF-8 sequence could
|
||
// be split between the two parts of the chain
|
||
|
||
fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> Result<()> {
|
||
if buf.capacity() == 0 {
|
||
return Ok(());
|
||
}
|
||
|
||
if !self.done_first {
|
||
let old_len = buf.written();
|
||
self.first.read_buf(buf.reborrow())?;
|
||
|
||
if buf.written() != old_len {
|
||
return Ok(());
|
||
} else {
|
||
self.done_first = true;
|
||
}
|
||
}
|
||
self.second.read_buf(buf)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "chain_bufread", since = "1.9.0")]
|
||
impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
|
||
fn fill_buf(&mut self) -> Result<&[u8]> {
|
||
if !self.done_first {
|
||
match self.first.fill_buf()? {
|
||
buf if buf.is_empty() => self.done_first = true,
|
||
buf => return Ok(buf),
|
||
}
|
||
}
|
||
self.second.fill_buf()
|
||
}
|
||
|
||
fn consume(&mut self, amt: usize) {
|
||
if !self.done_first { self.first.consume(amt) } else { self.second.consume(amt) }
|
||
}
|
||
|
||
fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> {
|
||
let mut read = 0;
|
||
if !self.done_first {
|
||
let n = self.first.read_until(byte, buf)?;
|
||
read += n;
|
||
|
||
match buf.last() {
|
||
Some(b) if *b == byte && n != 0 => return Ok(read),
|
||
_ => self.done_first = true,
|
||
}
|
||
}
|
||
read += self.second.read_until(byte, buf)?;
|
||
Ok(read)
|
||
}
|
||
|
||
// We don't override `read_line` here because an UTF-8 sequence could be
|
||
// split between the two parts of the chain
|
||
}
|
||
|
||
impl<T, U> SizeHint for Chain<T, U> {
|
||
#[inline]
|
||
fn lower_bound(&self) -> usize {
|
||
SizeHint::lower_bound(&self.first) + SizeHint::lower_bound(&self.second)
|
||
}
|
||
|
||
#[inline]
|
||
fn upper_bound(&self) -> Option<usize> {
|
||
match (SizeHint::upper_bound(&self.first), SizeHint::upper_bound(&self.second)) {
|
||
(Some(first), Some(second)) => first.checked_add(second),
|
||
_ => None,
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Reader adapter which limits the bytes read from an underlying reader.
|
||
///
|
||
/// This struct is generally created by calling [`take`] on a reader.
|
||
/// Please see the documentation of [`take`] for more details.
|
||
///
|
||
/// [`take`]: Read::take
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
pub struct Take<T> {
|
||
inner: T,
|
||
limit: u64,
|
||
}
|
||
|
||
impl<T> Take<T> {
|
||
/// Returns the number of bytes that can be read before this instance will
|
||
/// return EOF.
|
||
///
|
||
/// # Note
|
||
///
|
||
/// This instance may reach `EOF` after reading fewer bytes than indicated by
|
||
/// this method if the underlying [`Read`] instance reaches EOF.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let f = File::open("foo.txt")?;
|
||
///
|
||
/// // read at most five bytes
|
||
/// let handle = f.take(5);
|
||
///
|
||
/// println!("limit: {}", handle.limit());
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn limit(&self) -> u64 {
|
||
self.limit
|
||
}
|
||
|
||
/// Sets the number of bytes that can be read before this instance will
|
||
/// return EOF. This is the same as constructing a new `Take` instance, so
|
||
/// the amount of bytes read and the previous limit value don't matter when
|
||
/// calling this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let f = File::open("foo.txt")?;
|
||
///
|
||
/// // read at most five bytes
|
||
/// let mut handle = f.take(5);
|
||
/// handle.set_limit(10);
|
||
///
|
||
/// assert_eq!(handle.limit(), 10);
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "take_set_limit", since = "1.27.0")]
|
||
pub fn set_limit(&mut self, limit: u64) {
|
||
self.limit = limit;
|
||
}
|
||
|
||
/// Consumes the `Take`, returning the wrapped reader.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut file = File::open("foo.txt")?;
|
||
///
|
||
/// let mut buffer = [0; 5];
|
||
/// let mut handle = file.take(5);
|
||
/// handle.read(&mut buffer)?;
|
||
///
|
||
/// let file = handle.into_inner();
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "io_take_into_inner", since = "1.15.0")]
|
||
pub fn into_inner(self) -> T {
|
||
self.inner
|
||
}
|
||
|
||
/// Gets a reference to the underlying reader.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut file = File::open("foo.txt")?;
|
||
///
|
||
/// let mut buffer = [0; 5];
|
||
/// let mut handle = file.take(5);
|
||
/// handle.read(&mut buffer)?;
|
||
///
|
||
/// let file = handle.get_ref();
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "more_io_inner_methods", since = "1.20.0")]
|
||
pub fn get_ref(&self) -> &T {
|
||
&self.inner
|
||
}
|
||
|
||
/// Gets a mutable reference to the underlying reader.
|
||
///
|
||
/// Care should be taken to avoid modifying the internal I/O state of the
|
||
/// underlying reader as doing so may corrupt the internal limit of this
|
||
/// `Take`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```no_run
|
||
/// use std::io;
|
||
/// use std::io::prelude::*;
|
||
/// use std::fs::File;
|
||
///
|
||
/// fn main() -> io::Result<()> {
|
||
/// let mut file = File::open("foo.txt")?;
|
||
///
|
||
/// let mut buffer = [0; 5];
|
||
/// let mut handle = file.take(5);
|
||
/// handle.read(&mut buffer)?;
|
||
///
|
||
/// let file = handle.get_mut();
|
||
/// Ok(())
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "more_io_inner_methods", since = "1.20.0")]
|
||
pub fn get_mut(&mut self) -> &mut T {
|
||
&mut self.inner
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Read> Read for Take<T> {
|
||
fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
|
||
// Don't call into inner reader at all at EOF because it may still block
|
||
if self.limit == 0 {
|
||
return Ok(0);
|
||
}
|
||
|
||
let max = cmp::min(buf.len() as u64, self.limit) as usize;
|
||
let n = self.inner.read(&mut buf[..max])?;
|
||
assert!(n as u64 <= self.limit, "number of read bytes exceeds limit");
|
||
self.limit -= n as u64;
|
||
Ok(n)
|
||
}
|
||
|
||
fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> Result<()> {
|
||
// Don't call into inner reader at all at EOF because it may still block
|
||
if self.limit == 0 {
|
||
return Ok(());
|
||
}
|
||
|
||
if self.limit <= buf.capacity() as u64 {
|
||
// if we just use an as cast to convert, limit may wrap around on a 32 bit target
|
||
let limit = cmp::min(self.limit, usize::MAX as u64) as usize;
|
||
|
||
let extra_init = cmp::min(limit as usize, buf.init_ref().len());
|
||
|
||
// SAFETY: no uninit data is written to ibuf
|
||
let ibuf = unsafe { &mut buf.as_mut()[..limit] };
|
||
|
||
let mut sliced_buf: BorrowedBuf<'_> = ibuf.into();
|
||
|
||
// SAFETY: extra_init bytes of ibuf are known to be initialized
|
||
unsafe {
|
||
sliced_buf.set_init(extra_init);
|
||
}
|
||
|
||
let mut cursor = sliced_buf.unfilled();
|
||
self.inner.read_buf(cursor.reborrow())?;
|
||
|
||
let new_init = cursor.init_ref().len();
|
||
let filled = sliced_buf.len();
|
||
|
||
// cursor / sliced_buf / ibuf must drop here
|
||
|
||
unsafe {
|
||
// SAFETY: filled bytes have been filled and therefore initialized
|
||
buf.advance_unchecked(filled);
|
||
// SAFETY: new_init bytes of buf's unfilled buffer have been initialized
|
||
buf.set_init(new_init);
|
||
}
|
||
|
||
self.limit -= filled as u64;
|
||
} else {
|
||
let written = buf.written();
|
||
self.inner.read_buf(buf.reborrow())?;
|
||
self.limit -= (buf.written() - written) as u64;
|
||
}
|
||
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: BufRead> BufRead for Take<T> {
|
||
fn fill_buf(&mut self) -> Result<&[u8]> {
|
||
// Don't call into inner reader at all at EOF because it may still block
|
||
if self.limit == 0 {
|
||
return Ok(&[]);
|
||
}
|
||
|
||
let buf = self.inner.fill_buf()?;
|
||
let cap = cmp::min(buf.len() as u64, self.limit) as usize;
|
||
Ok(&buf[..cap])
|
||
}
|
||
|
||
fn consume(&mut self, amt: usize) {
|
||
// Don't let callers reset the limit by passing an overlarge value
|
||
let amt = cmp::min(amt as u64, self.limit) as usize;
|
||
self.limit -= amt as u64;
|
||
self.inner.consume(amt);
|
||
}
|
||
}
|
||
|
||
impl<T> SizeHint for Take<T> {
|
||
#[inline]
|
||
fn lower_bound(&self) -> usize {
|
||
cmp::min(SizeHint::lower_bound(&self.inner) as u64, self.limit) as usize
|
||
}
|
||
|
||
#[inline]
|
||
fn upper_bound(&self) -> Option<usize> {
|
||
match SizeHint::upper_bound(&self.inner) {
|
||
Some(upper_bound) => Some(cmp::min(upper_bound as u64, self.limit) as usize),
|
||
None => self.limit.try_into().ok(),
|
||
}
|
||
}
|
||
}
|
||
|
||
/// An iterator over `u8` values of a reader.
|
||
///
|
||
/// This struct is generally created by calling [`bytes`] on a reader.
|
||
/// Please see the documentation of [`bytes`] for more details.
|
||
///
|
||
/// [`bytes`]: Read::bytes
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
pub struct Bytes<R> {
|
||
inner: R,
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<R: Read> Iterator for Bytes<R> {
|
||
type Item = Result<u8>;
|
||
|
||
// Not `#[inline]`. This function gets inlined even without it, but having
|
||
// the inline annotation can result in worse code generation. See #116785.
|
||
fn next(&mut self) -> Option<Result<u8>> {
|
||
SpecReadByte::spec_read_byte(&mut self.inner)
|
||
}
|
||
|
||
#[inline]
|
||
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
SizeHint::size_hint(&self.inner)
|
||
}
|
||
}
|
||
|
||
/// For the specialization of `Bytes::next`.
|
||
trait SpecReadByte {
|
||
fn spec_read_byte(&mut self) -> Option<Result<u8>>;
|
||
}
|
||
|
||
impl<R> SpecReadByte for R
|
||
where
|
||
Self: Read,
|
||
{
|
||
#[inline]
|
||
default fn spec_read_byte(&mut self) -> Option<Result<u8>> {
|
||
inlined_slow_read_byte(self)
|
||
}
|
||
}
|
||
|
||
/// Read a single byte in a slow, generic way. This is used by the default
|
||
/// `spec_read_byte`.
|
||
#[inline]
|
||
fn inlined_slow_read_byte<R: Read>(reader: &mut R) -> Option<Result<u8>> {
|
||
let mut byte = 0;
|
||
loop {
|
||
return match reader.read(slice::from_mut(&mut byte)) {
|
||
Ok(0) => None,
|
||
Ok(..) => Some(Ok(byte)),
|
||
Err(ref e) if e.is_interrupted() => continue,
|
||
Err(e) => Some(Err(e)),
|
||
};
|
||
}
|
||
}
|
||
|
||
// Used by `BufReader::spec_read_byte`, for which the `inline(ever)` is
|
||
// important.
|
||
#[inline(never)]
|
||
fn uninlined_slow_read_byte<R: Read>(reader: &mut R) -> Option<Result<u8>> {
|
||
inlined_slow_read_byte(reader)
|
||
}
|
||
|
||
trait SizeHint {
|
||
fn lower_bound(&self) -> usize;
|
||
|
||
fn upper_bound(&self) -> Option<usize>;
|
||
|
||
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
(self.lower_bound(), self.upper_bound())
|
||
}
|
||
}
|
||
|
||
impl<T: ?Sized> SizeHint for T {
|
||
#[inline]
|
||
default fn lower_bound(&self) -> usize {
|
||
0
|
||
}
|
||
|
||
#[inline]
|
||
default fn upper_bound(&self) -> Option<usize> {
|
||
None
|
||
}
|
||
}
|
||
|
||
impl<T> SizeHint for &mut T {
|
||
#[inline]
|
||
fn lower_bound(&self) -> usize {
|
||
SizeHint::lower_bound(*self)
|
||
}
|
||
|
||
#[inline]
|
||
fn upper_bound(&self) -> Option<usize> {
|
||
SizeHint::upper_bound(*self)
|
||
}
|
||
}
|
||
|
||
impl<T> SizeHint for Box<T> {
|
||
#[inline]
|
||
fn lower_bound(&self) -> usize {
|
||
SizeHint::lower_bound(&**self)
|
||
}
|
||
|
||
#[inline]
|
||
fn upper_bound(&self) -> Option<usize> {
|
||
SizeHint::upper_bound(&**self)
|
||
}
|
||
}
|
||
|
||
impl SizeHint for &[u8] {
|
||
#[inline]
|
||
fn lower_bound(&self) -> usize {
|
||
self.len()
|
||
}
|
||
|
||
#[inline]
|
||
fn upper_bound(&self) -> Option<usize> {
|
||
Some(self.len())
|
||
}
|
||
}
|
||
|
||
/// An iterator over the contents of an instance of `BufRead` split on a
|
||
/// particular byte.
|
||
///
|
||
/// This struct is generally created by calling [`split`] on a `BufRead`.
|
||
/// Please see the documentation of [`split`] for more details.
|
||
///
|
||
/// [`split`]: BufRead::split
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
pub struct Split<B> {
|
||
buf: B,
|
||
delim: u8,
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<B: BufRead> Iterator for Split<B> {
|
||
type Item = Result<Vec<u8>>;
|
||
|
||
fn next(&mut self) -> Option<Result<Vec<u8>>> {
|
||
let mut buf = Vec::new();
|
||
match self.buf.read_until(self.delim, &mut buf) {
|
||
Ok(0) => None,
|
||
Ok(_n) => {
|
||
if buf[buf.len() - 1] == self.delim {
|
||
buf.pop();
|
||
}
|
||
Some(Ok(buf))
|
||
}
|
||
Err(e) => Some(Err(e)),
|
||
}
|
||
}
|
||
}
|
||
|
||
/// An iterator over the lines of an instance of `BufRead`.
|
||
///
|
||
/// This struct is generally created by calling [`lines`] on a `BufRead`.
|
||
/// Please see the documentation of [`lines`] for more details.
|
||
///
|
||
/// [`lines`]: BufRead::lines
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "IoLines")]
|
||
pub struct Lines<B> {
|
||
buf: B,
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<B: BufRead> Iterator for Lines<B> {
|
||
type Item = Result<String>;
|
||
|
||
fn next(&mut self) -> Option<Result<String>> {
|
||
let mut buf = String::new();
|
||
match self.buf.read_line(&mut buf) {
|
||
Ok(0) => None,
|
||
Ok(_n) => {
|
||
if buf.ends_with('\n') {
|
||
buf.pop();
|
||
if buf.ends_with('\r') {
|
||
buf.pop();
|
||
}
|
||
}
|
||
Some(Ok(buf))
|
||
}
|
||
Err(e) => Some(Err(e)),
|
||
}
|
||
}
|
||
}
|
||
|
||
//! The `Box<T>` type for heap allocation.
|
||
//!
|
||
//! [`Box<T>`], casually referred to as a 'box', provides the simplest form of
|
||
//! heap allocation in Rust. Boxes provide ownership for this allocation, and
|
||
//! drop their contents when they go out of scope. Boxes also ensure that they
|
||
//! never allocate more than `isize::MAX` bytes.
|
||
//!
|
||
//! # Examples
|
||
//!
|
||
//! Move a value from the stack to the heap by creating a [`Box`]:
|
||
//!
|
||
//! ```
|
||
//! let val: u8 = 5;
|
||
//! let boxed: Box<u8> = Box::new(val);
|
||
//! ```
|
||
//!
|
||
//! Move a value from a [`Box`] back to the stack by [dereferencing]:
|
||
//!
|
||
//! ```
|
||
//! let boxed: Box<u8> = Box::new(5);
|
||
//! let val: u8 = *boxed;
|
||
//! ```
|
||
//!
|
||
//! Creating a recursive data structure:
|
||
//!
|
||
//! ```
|
||
//! ##[allow(dead_code)]
|
||
//! #[derive(Debug)]
|
||
//! enum List<T> {
|
||
//! Cons(T, Box<List<T>>),
|
||
//! Nil,
|
||
//! }
|
||
//!
|
||
//! let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
|
||
//! println!("{list:?}");
|
||
//! ```
|
||
//!
|
||
//! This will print `Cons(1, Cons(2, Nil))`.
|
||
//!
|
||
//! Recursive structures must be boxed, because if the definition of `Cons`
|
||
//! looked like this:
|
||
//!
|
||
//! ```compile_fail,E0072
|
||
//! # enum List<T> {
|
||
//! Cons(T, List<T>),
|
||
//! # }
|
||
//! ```
|
||
//!
|
||
//! It wouldn't work. This is because the size of a `List` depends on how many
|
||
//! elements are in the list, and so we don't know how much memory to allocate
|
||
//! for a `Cons`. By introducing a [`Box<T>`], which has a defined size, we know how
|
||
//! big `Cons` needs to be.
|
||
//!
|
||
//! # Memory layout
|
||
//!
|
||
//! For non-zero-sized values, a [`Box`] will use the [`Global`] allocator for
|
||
//! its allocation. It is valid to convert both ways between a [`Box`] and a
|
||
//! raw pointer allocated with the [`Global`] allocator, given that the
|
||
//! [`Layout`] used with the allocator is correct for the type. More precisely,
|
||
//! a `value: *mut T` that has been allocated with the [`Global`] allocator
|
||
//! with `Layout::for_value(&*value)` may be converted into a box using
|
||
//! [`Box::<T>::from_raw(value)`]. Conversely, the memory backing a `value: *mut
|
||
//! T` obtained from [`Box::<T>::into_raw`] may be deallocated using the
|
||
//! [`Global`] allocator with [`Layout::for_value(&*value)`].
|
||
//!
|
||
//! For zero-sized values, the `Box` pointer still has to be [valid] for reads
|
||
//! and writes and sufficiently aligned. In particular, casting any aligned
|
||
//! non-zero integer literal to a raw pointer produces a valid pointer, but a
|
||
//! pointer pointing into previously allocated memory that since got freed is
|
||
//! not valid. The recommended way to build a Box to a ZST if `Box::new` cannot
|
||
//! be used is to use [`ptr::NonNull::dangling`].
|
||
//!
|
||
//! So long as `T: Sized`, a `Box<T>` is guaranteed to be represented
|
||
//! as a single pointer and is also ABI-compatible with C pointers
|
||
//! (i.e. the C type `T*`). This means that if you have extern "C"
|
||
//! Rust functions that will be called from C, you can define those
|
||
//! Rust functions using `Box<T>` types, and use `T*` as corresponding
|
||
//! type on the C side. As an example, consider this C header which
|
||
//! declares functions that create and destroy some kind of `Foo`
|
||
//! value:
|
||
//!
|
||
//! ```c
|
||
//! /* C header */
|
||
//!
|
||
//! /* Returns ownership to the caller */
|
||
//! struct Foo* foo_new(void);
|
||
//!
|
||
//! /* Takes ownership from the caller; no-op when invoked with null */
|
||
//! void foo_delete(struct Foo*);
|
||
//! ```
|
||
//!
|
||
//! These two functions might be implemented in Rust as follows. Here, the
|
||
//! `struct Foo*` type from C is translated to `Box<Foo>`, which captures
|
||
//! the ownership constraints. Note also that the nullable argument to
|
||
//! `foo_delete` is represented in Rust as `Option<Box<Foo>>`, since `Box<Foo>`
|
||
//! cannot be null.
|
||
//!
|
||
//! ```
|
||
//! #[repr(C)]
|
||
//! pub struct Foo;
|
||
//!
|
||
//! #[no_mangle]
|
||
//! pub extern "C-unwind" fn foo_new() -> Box<Foo> {
|
||
//! Box::new(Foo)
|
||
//! }
|
||
//!
|
||
//! #[no_mangle]
|
||
//! pub extern "C-unwind" fn foo_delete(_: Option<Box<Foo>>) {}
|
||
//! ```
|
||
//!
|
||
//! Even though `Box<T>` has the same representation and C ABI as a C pointer,
|
||
//! this does not mean that you can convert an arbitrary `T*` into a `Box<T>`
|
||
//! and expect things to work. `Box<T>` values will always be fully aligned,
|
||
//! non-null pointers. Moreover, the destructor for `Box<T>` will attempt to
|
||
//! free the value with the global allocator. In general, the best practice
|
||
//! is to only use `Box<T>` for pointers that originated from the global
|
||
//! allocator.
|
||
//!
|
||
//! **Important.** At least at present, you should avoid using
|
||
//! `Box<T>` types for functions that are defined in C but invoked
|
||
//! from Rust. In those cases, you should directly mirror the C types
|
||
//! as closely as possible. Using types like `Box<T>` where the C
|
||
//! definition is just using `T*` can lead to undefined behavior, as
|
||
//! described in [rust-lang/unsafe-code-guidelines#198][ucg#198].
|
||
//!
|
||
//! # Considerations for unsafe code
|
||
//!
|
||
//! **Warning: This section is not normative and is subject to change, possibly
|
||
//! being relaxed in the future! It is a simplified summary of the rules
|
||
//! currently implemented in the compiler.**
|
||
//!
|
||
//! The aliasing rules for `Box<T>` are the same as for `&mut T`. `Box<T>`
|
||
//! asserts uniqueness over its content. Using raw pointers derived from a box
|
||
//! after that box has been mutated through, moved or borrowed as `&mut T`
|
||
//! is not allowed. For more guidance on working with box from unsafe code, see
|
||
//! [rust-lang/unsafe-code-guidelines#326][ucg#326].
|
||
//!
|
||
//!
|
||
//! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198
|
||
//! [ucg#326]: https://github.com/rust-lang/unsafe-code-guidelines/issues/326
|
||
//! [dereferencing]: core::ops::Deref
|
||
//! [`Box::<T>::from_raw(value)`]: Box::from_raw
|
||
//! [`Global`]: crate::alloc::Global
|
||
//! [`Layout`]: crate::alloc::Layout
|
||
//! [`Layout::for_value(&*value)`]: crate::alloc::Layout::for_value
|
||
//! [valid]: ptr#safety
|
||
|
||
#![stable(feature = "rust1", since = "1.0.0")]
|
||
|
||
use core::any::Any;
|
||
use core::async_iter::AsyncIterator;
|
||
use core::borrow;
|
||
use core::cmp::Ordering;
|
||
use core::error::Error;
|
||
use core::fmt;
|
||
use core::future::Future;
|
||
use core::hash::{Hash, Hasher};
|
||
use core::iter::FusedIterator;
|
||
use core::marker::Tuple;
|
||
use core::marker::Unsize;
|
||
use core::mem::{self, SizedTypeProperties};
|
||
use core::ops::{AsyncFn, AsyncFnMut, AsyncFnOnce};
|
||
use core::ops::{
|
||
CoerceUnsized, Coroutine, CoroutineState, Deref, DerefMut, DerefPure, DispatchFromDyn, Receiver,
|
||
};
|
||
use core::pin::Pin;
|
||
use core::ptr::{self, addr_of_mut, NonNull, Unique};
|
||
use core::task::{Context, Poll};
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::alloc::{handle_alloc_error, WriteCloneIntoRaw};
|
||
use crate::alloc::{AllocError, Allocator, Global, Layout};
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::borrow::Cow;
|
||
use crate::raw_vec::RawVec;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::str::from_boxed_utf8_unchecked;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::string::String;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::vec::Vec;
|
||
|
||
#[unstable(feature = "thin_box", issue = "92791")]
|
||
pub use thin::ThinBox;
|
||
|
||
mod thin;
|
||
|
||
/// A pointer type that uniquely owns a heap allocation of type `T`.
|
||
///
|
||
/// See the [module-level documentation](../../std/boxed/index.html) for more.
|
||
#[lang = "owned_box"]
|
||
#[fundamental]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
// The declaration of the `Box` struct must be kept in sync with the
|
||
// compiler or ICEs will happen.
|
||
pub struct Box<
|
||
T: ?Sized,
|
||
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
|
||
>(Unique<T>, A);
|
||
|
||
impl<T> Box<T> {
|
||
/// Allocates memory on the heap and then places `x` into it.
|
||
///
|
||
/// This doesn't actually allocate if `T` is zero-sized.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let five = Box::new(5);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline(always)]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[must_use]
|
||
#[rustc_diagnostic_item = "box_new"]
|
||
pub fn new(x: T) -> Self {
|
||
#[rustc_box]
|
||
Box::new(x)
|
||
}
|
||
|
||
/// Constructs a new box with uninitialized contents.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let mut five = Box::<u32>::new_uninit();
|
||
///
|
||
/// let five = unsafe {
|
||
/// // Deferred initialization:
|
||
/// five.as_mut_ptr().write(5);
|
||
///
|
||
/// five.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*five, 5)
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
#[inline]
|
||
pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
|
||
Self::new_uninit_in(Global)
|
||
}
|
||
|
||
/// Constructs a new `Box` with uninitialized contents, with the memory
|
||
/// being filled with `0` bytes.
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let zero = Box::<u32>::new_zeroed();
|
||
/// let zero = unsafe { zero.assume_init() };
|
||
///
|
||
/// assert_eq!(*zero, 0)
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
pub fn new_zeroed() -> Box<mem::MaybeUninit<T>> {
|
||
Self::new_zeroed_in(Global)
|
||
}
|
||
|
||
/// Constructs a new `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then
|
||
/// `x` will be pinned in memory and unable to be moved.
|
||
///
|
||
/// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin(x)`
|
||
/// does the same as <code>[Box::into_pin]\([Box::new]\(x))</code>. Consider using
|
||
/// [`into_pin`](Box::into_pin) if you already have a `Box<T>`, or if you want to
|
||
/// construct a (pinned) `Box` in a different way than with [`Box::new`].
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "pin", since = "1.33.0")]
|
||
#[must_use]
|
||
#[inline(always)]
|
||
pub fn pin(x: T) -> Pin<Box<T>> {
|
||
Box::new(x).into()
|
||
}
|
||
|
||
/// Allocates memory on the heap then places `x` into it,
|
||
/// returning an error if the allocation fails
|
||
///
|
||
/// This doesn't actually allocate if `T` is zero-sized.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// let five = Box::try_new(5)?;
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[inline]
|
||
pub fn try_new(x: T) -> Result<Self, AllocError> {
|
||
Self::try_new_in(x, Global)
|
||
}
|
||
|
||
/// Constructs a new box with uninitialized contents on the heap,
|
||
/// returning an error if the allocation fails
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// let mut five = Box::<u32>::try_new_uninit()?;
|
||
///
|
||
/// let five = unsafe {
|
||
/// // Deferred initialization:
|
||
/// five.as_mut_ptr().write(5);
|
||
///
|
||
/// five.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*five, 5);
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[inline]
|
||
pub fn try_new_uninit() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
|
||
Box::try_new_uninit_in(Global)
|
||
}
|
||
|
||
/// Constructs a new `Box` with uninitialized contents, with the memory
|
||
/// being filled with `0` bytes on the heap
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// let zero = Box::<u32>::try_new_zeroed()?;
|
||
/// let zero = unsafe { zero.assume_init() };
|
||
///
|
||
/// assert_eq!(*zero, 0);
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[inline]
|
||
pub fn try_new_zeroed() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
|
||
Box::try_new_zeroed_in(Global)
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Box<T, A> {
|
||
/// Allocates memory in the given allocator then places `x` into it.
|
||
///
|
||
/// This doesn't actually allocate if `T` is zero-sized.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let five = Box::new_in(5, System);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[must_use]
|
||
#[inline]
|
||
pub fn new_in(x: T, alloc: A) -> Self
|
||
where
|
||
A: Allocator,
|
||
{
|
||
let mut boxed = Self::new_uninit_in(alloc);
|
||
unsafe {
|
||
boxed.as_mut_ptr().write(x);
|
||
boxed.assume_init()
|
||
}
|
||
}
|
||
|
||
/// Allocates memory in the given allocator then places `x` into it,
|
||
/// returning an error if the allocation fails
|
||
///
|
||
/// This doesn't actually allocate if `T` is zero-sized.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let five = Box::try_new_in(5, System)?;
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[inline]
|
||
pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError>
|
||
where
|
||
A: Allocator,
|
||
{
|
||
let mut boxed = Self::try_new_uninit_in(alloc)?;
|
||
unsafe {
|
||
boxed.as_mut_ptr().write(x);
|
||
Ok(boxed.assume_init())
|
||
}
|
||
}
|
||
|
||
/// Constructs a new box with uninitialized contents in the provided allocator.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let mut five = Box::<u32, _>::new_uninit_in(System);
|
||
///
|
||
/// let five = unsafe {
|
||
/// // Deferred initialization:
|
||
/// five.as_mut_ptr().write(5);
|
||
///
|
||
/// five.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*five, 5)
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[must_use]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
|
||
where
|
||
A: Allocator,
|
||
{
|
||
let layout = Layout::new::<mem::MaybeUninit<T>>();
|
||
// NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
|
||
// That would make code size bigger.
|
||
match Box::try_new_uninit_in(alloc) {
|
||
Ok(m) => m,
|
||
Err(_) => handle_alloc_error(layout),
|
||
}
|
||
}
|
||
|
||
/// Constructs a new box with uninitialized contents in the provided allocator,
|
||
/// returning an error if the allocation fails
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let mut five = Box::<u32, _>::try_new_uninit_in(System)?;
|
||
///
|
||
/// let five = unsafe {
|
||
/// // Deferred initialization:
|
||
/// five.as_mut_ptr().write(5);
|
||
///
|
||
/// five.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*five, 5);
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
pub fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
|
||
where
|
||
A: Allocator,
|
||
{
|
||
let ptr = if T::IS_ZST {
|
||
NonNull::dangling()
|
||
} else {
|
||
let layout = Layout::new::<mem::MaybeUninit<T>>();
|
||
alloc.allocate(layout)?.cast()
|
||
};
|
||
unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
|
||
}
|
||
|
||
/// Constructs a new `Box` with uninitialized contents, with the memory
|
||
/// being filled with `0` bytes in the provided allocator.
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let zero = Box::<u32, _>::new_zeroed_in(System);
|
||
/// let zero = unsafe { zero.assume_init() };
|
||
///
|
||
/// assert_eq!(*zero, 0)
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
|
||
where
|
||
A: Allocator,
|
||
{
|
||
let layout = Layout::new::<mem::MaybeUninit<T>>();
|
||
// NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
|
||
// That would make code size bigger.
|
||
match Box::try_new_zeroed_in(alloc) {
|
||
Ok(m) => m,
|
||
Err(_) => handle_alloc_error(layout),
|
||
}
|
||
}
|
||
|
||
/// Constructs a new `Box` with uninitialized contents, with the memory
|
||
/// being filled with `0` bytes in the provided allocator,
|
||
/// returning an error if the allocation fails,
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let zero = Box::<u32, _>::try_new_zeroed_in(System)?;
|
||
/// let zero = unsafe { zero.assume_init() };
|
||
///
|
||
/// assert_eq!(*zero, 0);
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
pub fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
|
||
where
|
||
A: Allocator,
|
||
{
|
||
let ptr = if T::IS_ZST {
|
||
NonNull::dangling()
|
||
} else {
|
||
let layout = Layout::new::<mem::MaybeUninit<T>>();
|
||
alloc.allocate_zeroed(layout)?.cast()
|
||
};
|
||
unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
|
||
}
|
||
|
||
/// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement [`Unpin`], then
|
||
/// `x` will be pinned in memory and unable to be moved.
|
||
///
|
||
/// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin_in(x, alloc)`
|
||
/// does the same as <code>[Box::into_pin]\([Box::new_in]\(x, alloc))</code>. Consider using
|
||
/// [`into_pin`](Box::into_pin) if you already have a `Box<T, A>`, or if you want to
|
||
/// construct a (pinned) `Box` in a different way than with [`Box::new_in`].
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[must_use]
|
||
#[inline(always)]
|
||
pub fn pin_in(x: T, alloc: A) -> Pin<Self>
|
||
where
|
||
A: 'static + Allocator,
|
||
{
|
||
Self::into_pin(Self::new_in(x, alloc))
|
||
}
|
||
|
||
/// Converts a `Box<T>` into a `Box<[T]>`
|
||
///
|
||
/// This conversion does not allocate on the heap and happens in place.
|
||
#[unstable(feature = "box_into_boxed_slice", issue = "71582")]
|
||
pub fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
|
||
let (raw, alloc) = Box::into_raw_with_allocator(boxed);
|
||
unsafe { Box::from_raw_in(raw as *mut [T; 1], alloc) }
|
||
}
|
||
|
||
/// Consumes the `Box`, returning the wrapped value.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(box_into_inner)]
|
||
///
|
||
/// let c = Box::new(5);
|
||
///
|
||
/// assert_eq!(Box::into_inner(c), 5);
|
||
/// ```
|
||
#[unstable(feature = "box_into_inner", issue = "80437")]
|
||
#[inline]
|
||
pub fn into_inner(boxed: Self) -> T {
|
||
*boxed
|
||
}
|
||
}
|
||
|
||
impl<T> Box<[T]> {
|
||
/// Constructs a new boxed slice with uninitialized contents.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let mut values = Box::<[u32]>::new_uninit_slice(3);
|
||
///
|
||
/// let values = unsafe {
|
||
/// // Deferred initialization:
|
||
/// values[0].as_mut_ptr().write(1);
|
||
/// values[1].as_mut_ptr().write(2);
|
||
/// values[2].as_mut_ptr().write(3);
|
||
///
|
||
/// values.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*values, [1, 2, 3])
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
|
||
unsafe { RawVec::with_capacity(len).into_box(len) }
|
||
}
|
||
|
||
/// Constructs a new boxed slice with uninitialized contents, with the memory
|
||
/// being filled with `0` bytes.
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let values = Box::<[u32]>::new_zeroed_slice(3);
|
||
/// let values = unsafe { values.assume_init() };
|
||
///
|
||
/// assert_eq!(*values, [0, 0, 0])
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
pub fn new_zeroed_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
|
||
unsafe { RawVec::with_capacity_zeroed(len).into_box(len) }
|
||
}
|
||
|
||
/// Constructs a new boxed slice with uninitialized contents. Returns an error if
|
||
/// the allocation fails
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// let mut values = Box::<[u32]>::try_new_uninit_slice(3)?;
|
||
/// let values = unsafe {
|
||
/// // Deferred initialization:
|
||
/// values[0].as_mut_ptr().write(1);
|
||
/// values[1].as_mut_ptr().write(2);
|
||
/// values[2].as_mut_ptr().write(3);
|
||
/// values.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*values, [1, 2, 3]);
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[inline]
|
||
pub fn try_new_uninit_slice(len: usize) -> Result<Box<[mem::MaybeUninit<T>]>, AllocError> {
|
||
let ptr = if T::IS_ZST || len == 0 {
|
||
NonNull::dangling()
|
||
} else {
|
||
let layout = match Layout::array::<mem::MaybeUninit<T>>(len) {
|
||
Ok(l) => l,
|
||
Err(_) => return Err(AllocError),
|
||
};
|
||
Global.allocate(layout)?.cast()
|
||
};
|
||
unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
|
||
}
|
||
|
||
/// Constructs a new boxed slice with uninitialized contents, with the memory
|
||
/// being filled with `0` bytes. Returns an error if the allocation fails
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// let values = Box::<[u32]>::try_new_zeroed_slice(3)?;
|
||
/// let values = unsafe { values.assume_init() };
|
||
///
|
||
/// assert_eq!(*values, [0, 0, 0]);
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[inline]
|
||
pub fn try_new_zeroed_slice(len: usize) -> Result<Box<[mem::MaybeUninit<T>]>, AllocError> {
|
||
let ptr = if T::IS_ZST || len == 0 {
|
||
NonNull::dangling()
|
||
} else {
|
||
let layout = match Layout::array::<mem::MaybeUninit<T>>(len) {
|
||
Ok(l) => l,
|
||
Err(_) => return Err(AllocError),
|
||
};
|
||
Global.allocate_zeroed(layout)?.cast()
|
||
};
|
||
unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Box<[T], A> {
|
||
/// Constructs a new boxed slice with uninitialized contents in the provided allocator.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);
|
||
///
|
||
/// let values = unsafe {
|
||
/// // Deferred initialization:
|
||
/// values[0].as_mut_ptr().write(1);
|
||
/// values[1].as_mut_ptr().write(2);
|
||
/// values[2].as_mut_ptr().write(3);
|
||
///
|
||
/// values.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*values, [1, 2, 3])
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
|
||
unsafe { RawVec::with_capacity_in(len, alloc).into_box(len) }
|
||
}
|
||
|
||
/// Constructs a new boxed slice with uninitialized contents in the provided allocator,
|
||
/// with the memory being filled with `0` bytes.
|
||
///
|
||
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
||
/// of this method.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, new_uninit)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let values = Box::<[u32], _>::new_zeroed_slice_in(3, System);
|
||
/// let values = unsafe { values.assume_init() };
|
||
///
|
||
/// assert_eq!(*values, [0, 0, 0])
|
||
/// ```
|
||
///
|
||
/// [zeroed]: mem::MaybeUninit::zeroed
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[must_use]
|
||
pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
|
||
unsafe { RawVec::with_capacity_zeroed_in(len, alloc).into_box(len) }
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
|
||
/// Converts to `Box<T, A>`.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// As with [`MaybeUninit::assume_init`],
|
||
/// it is up to the caller to guarantee that the value
|
||
/// really is in an initialized state.
|
||
/// Calling this when the content is not yet fully initialized
|
||
/// causes immediate undefined behavior.
|
||
///
|
||
/// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let mut five = Box::<u32>::new_uninit();
|
||
///
|
||
/// let five: Box<u32> = unsafe {
|
||
/// // Deferred initialization:
|
||
/// five.as_mut_ptr().write(5);
|
||
///
|
||
/// five.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*five, 5)
|
||
/// ```
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[inline]
|
||
pub unsafe fn assume_init(self) -> Box<T, A> {
|
||
let (raw, alloc) = Box::into_raw_with_allocator(self);
|
||
unsafe { Box::from_raw_in(raw as *mut T, alloc) }
|
||
}
|
||
|
||
/// Writes the value and converts to `Box<T, A>`.
|
||
///
|
||
/// This method converts the box similarly to [`Box::assume_init`] but
|
||
/// writes `value` into it before conversion thus guaranteeing safety.
|
||
/// In some scenarios use of this method may improve performance because
|
||
/// the compiler may be able to optimize copying from stack.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let big_box = Box::<[usize; 1024]>::new_uninit();
|
||
///
|
||
/// let mut array = [0; 1024];
|
||
/// for (i, place) in array.iter_mut().enumerate() {
|
||
/// *place = i;
|
||
/// }
|
||
///
|
||
/// // The optimizer may be able to elide this copy, so previous code writes
|
||
/// // to heap directly.
|
||
/// let big_box = Box::write(big_box, array);
|
||
///
|
||
/// for (i, x) in big_box.iter().enumerate() {
|
||
/// assert_eq!(*x, i);
|
||
/// }
|
||
/// ```
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[inline]
|
||
pub fn write(mut boxed: Self, value: T) -> Box<T, A> {
|
||
unsafe {
|
||
(*boxed).write(value);
|
||
boxed.assume_init()
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Box<[mem::MaybeUninit<T>], A> {
|
||
/// Converts to `Box<[T], A>`.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// As with [`MaybeUninit::assume_init`],
|
||
/// it is up to the caller to guarantee that the values
|
||
/// really are in an initialized state.
|
||
/// Calling this when the content is not yet fully initialized
|
||
/// causes immediate undefined behavior.
|
||
///
|
||
/// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(new_uninit)]
|
||
///
|
||
/// let mut values = Box::<[u32]>::new_uninit_slice(3);
|
||
///
|
||
/// let values = unsafe {
|
||
/// // Deferred initialization:
|
||
/// values[0].as_mut_ptr().write(1);
|
||
/// values[1].as_mut_ptr().write(2);
|
||
/// values[2].as_mut_ptr().write(3);
|
||
///
|
||
/// values.assume_init()
|
||
/// };
|
||
///
|
||
/// assert_eq!(*values, [1, 2, 3])
|
||
/// ```
|
||
#[unstable(feature = "new_uninit", issue = "63291")]
|
||
#[inline]
|
||
pub unsafe fn assume_init(self) -> Box<[T], A> {
|
||
let (raw, alloc) = Box::into_raw_with_allocator(self);
|
||
unsafe { Box::from_raw_in(raw as *mut [T], alloc) }
|
||
}
|
||
}
|
||
|
||
impl<T: ?Sized> Box<T> {
|
||
/// Constructs a box from a raw pointer.
|
||
///
|
||
/// After calling this function, the raw pointer is owned by the
|
||
/// resulting `Box`. Specifically, the `Box` destructor will call
|
||
/// the destructor of `T` and free the allocated memory. For this
|
||
/// to be safe, the memory must have been allocated in accordance
|
||
/// with the [memory layout] used by `Box` .
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This function is unsafe because improper use may lead to
|
||
/// memory problems. For example, a double-free may occur if the
|
||
/// function is called twice on the same raw pointer.
|
||
///
|
||
/// The safety conditions are described in the [memory layout] section.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Recreate a `Box` which was previously converted to a raw pointer
|
||
/// using [`Box::into_raw`]:
|
||
/// ```
|
||
/// let x = Box::new(5);
|
||
/// let ptr = Box::into_raw(x);
|
||
/// let x = unsafe { Box::from_raw(ptr) };
|
||
/// ```
|
||
/// Manually create a `Box` from scratch by using the global allocator:
|
||
/// ```
|
||
/// use std::alloc::{alloc, Layout};
|
||
///
|
||
/// unsafe {
|
||
/// let ptr = alloc(Layout::new::<i32>()) as *mut i32;
|
||
/// // In general .write is required to avoid attempting to destruct
|
||
/// // the (uninitialized) previous contents of `ptr`, though for this
|
||
/// // simple example `*ptr = 5` would have worked as well.
|
||
/// ptr.write(5);
|
||
/// let x = Box::from_raw(ptr);
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [memory layout]: self#memory-layout
|
||
/// [`Layout`]: crate::Layout
|
||
#[stable(feature = "box_raw", since = "1.4.0")]
|
||
#[inline]
|
||
#[must_use = "call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`"]
|
||
pub unsafe fn from_raw(raw: *mut T) -> Self {
|
||
unsafe { Self::from_raw_in(raw, Global) }
|
||
}
|
||
}
|
||
|
||
impl<T: ?Sized, A: Allocator> Box<T, A> {
|
||
/// Constructs a box from a raw pointer in the given allocator.
|
||
///
|
||
/// After calling this function, the raw pointer is owned by the
|
||
/// resulting `Box`. Specifically, the `Box` destructor will call
|
||
/// the destructor of `T` and free the allocated memory. For this
|
||
/// to be safe, the memory must have been allocated in accordance
|
||
/// with the [memory layout] used by `Box` .
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This function is unsafe because improper use may lead to
|
||
/// memory problems. For example, a double-free may occur if the
|
||
/// function is called twice on the same raw pointer.
|
||
///
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Recreate a `Box` which was previously converted to a raw pointer
|
||
/// using [`Box::into_raw_with_allocator`]:
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let x = Box::new_in(5, System);
|
||
/// let (ptr, alloc) = Box::into_raw_with_allocator(x);
|
||
/// let x = unsafe { Box::from_raw_in(ptr, alloc) };
|
||
/// ```
|
||
/// Manually create a `Box` from scratch by using the system allocator:
|
||
/// ```
|
||
/// #![feature(allocator_api, slice_ptr_get)]
|
||
///
|
||
/// use std::alloc::{Allocator, Layout, System};
|
||
///
|
||
/// unsafe {
|
||
/// let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
|
||
/// // In general .write is required to avoid attempting to destruct
|
||
/// // the (uninitialized) previous contents of `ptr`, though for this
|
||
/// // simple example `*ptr = 5` would have worked as well.
|
||
/// ptr.write(5);
|
||
/// let x = Box::from_raw_in(ptr, System);
|
||
/// }
|
||
/// # Ok::<(), std::alloc::AllocError>(())
|
||
/// ```
|
||
///
|
||
/// [memory layout]: self#memory-layout
|
||
/// [`Layout`]: crate::Layout
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
||
#[inline]
|
||
pub const unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self {
|
||
Box(unsafe { Unique::new_unchecked(raw) }, alloc)
|
||
}
|
||
|
||
/// Consumes the `Box`, returning a wrapped raw pointer.
|
||
///
|
||
/// The pointer will be properly aligned and non-null.
|
||
///
|
||
/// After calling this function, the caller is responsible for the
|
||
/// memory previously managed by the `Box`. In particular, the
|
||
/// caller should properly destroy `T` and release the memory, taking
|
||
/// into account the [memory layout] used by `Box`. The easiest way to
|
||
/// do this is to convert the raw pointer back into a `Box` with the
|
||
/// [`Box::from_raw`] function, allowing the `Box` destructor to perform
|
||
/// the cleanup.
|
||
///
|
||
/// Note: this is an associated function, which means that you have
|
||
/// to call it as `Box::into_raw(b)` instead of `b.into_raw()`. This
|
||
/// is so that there is no conflict with a method on the inner type.
|
||
///
|
||
/// # Examples
|
||
/// Converting the raw pointer back into a `Box` with [`Box::from_raw`]
|
||
/// for automatic cleanup:
|
||
/// ```
|
||
/// let x = Box::new(String::from("Hello"));
|
||
/// let ptr = Box::into_raw(x);
|
||
/// let x = unsafe { Box::from_raw(ptr) };
|
||
/// ```
|
||
/// Manual cleanup by explicitly running the destructor and deallocating
|
||
/// the memory:
|
||
/// ```
|
||
/// use std::alloc::{dealloc, Layout};
|
||
/// use std::ptr;
|
||
///
|
||
/// let x = Box::new(String::from("Hello"));
|
||
/// let ptr = Box::into_raw(x);
|
||
/// unsafe {
|
||
/// ptr::drop_in_place(ptr);
|
||
/// dealloc(ptr as *mut u8, Layout::new::<String>());
|
||
/// }
|
||
/// ```
|
||
/// Note: This is equivalent to the following:
|
||
/// ```
|
||
/// let x = Box::new(String::from("Hello"));
|
||
/// let ptr = Box::into_raw(x);
|
||
/// unsafe {
|
||
/// drop(Box::from_raw(ptr));
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [memory layout]: self#memory-layout
|
||
#[stable(feature = "box_raw", since = "1.4.0")]
|
||
#[inline]
|
||
pub fn into_raw(b: Self) -> *mut T {
|
||
// Make sure Miri realizes that we transition from a noalias pointer to a raw pointer here.
|
||
unsafe { addr_of_mut!(*&mut *Self::into_raw_with_allocator(b).0) }
|
||
}
|
||
|
||
/// Consumes the `Box`, returning a wrapped raw pointer and the allocator.
|
||
///
|
||
/// The pointer will be properly aligned and non-null.
|
||
///
|
||
/// After calling this function, the caller is responsible for the
|
||
/// memory previously managed by the `Box`. In particular, the
|
||
/// caller should properly destroy `T` and release the memory, taking
|
||
/// into account the [memory layout] used by `Box`. The easiest way to
|
||
/// do this is to convert the raw pointer back into a `Box` with the
|
||
/// [`Box::from_raw_in`] function, allowing the `Box` destructor to perform
|
||
/// the cleanup.
|
||
///
|
||
/// Note: this is an associated function, which means that you have
|
||
/// to call it as `Box::into_raw_with_allocator(b)` instead of `b.into_raw_with_allocator()`. This
|
||
/// is so that there is no conflict with a method on the inner type.
|
||
///
|
||
/// # Examples
|
||
/// Converting the raw pointer back into a `Box` with [`Box::from_raw_in`]
|
||
/// for automatic cleanup:
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let x = Box::new_in(String::from("Hello"), System);
|
||
/// let (ptr, alloc) = Box::into_raw_with_allocator(x);
|
||
/// let x = unsafe { Box::from_raw_in(ptr, alloc) };
|
||
/// ```
|
||
/// Manual cleanup by explicitly running the destructor and deallocating
|
||
/// the memory:
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::{Allocator, Layout, System};
|
||
/// use std::ptr::{self, NonNull};
|
||
///
|
||
/// let x = Box::new_in(String::from("Hello"), System);
|
||
/// let (ptr, alloc) = Box::into_raw_with_allocator(x);
|
||
/// unsafe {
|
||
/// ptr::drop_in_place(ptr);
|
||
/// let non_null = NonNull::new_unchecked(ptr);
|
||
/// alloc.deallocate(non_null.cast(), Layout::new::<String>());
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [memory layout]: self#memory-layout
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[inline]
|
||
pub fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
|
||
let mut b = mem::ManuallyDrop::new(b);
|
||
// We carefully get the raw pointer out in a way that Miri's aliasing model understands what
|
||
// is happening: using the primitive "deref" of `Box`. In case `A` is *not* `Global`, we
|
||
// want *no* aliasing requirements here!
|
||
// In case `A` *is* `Global`, this does not quite have the right behavior; `into_raw`
|
||
// works around that.
|
||
let ptr = addr_of_mut!(**b);
|
||
let alloc = unsafe { ptr::read(&b.1) };
|
||
(ptr, alloc)
|
||
}
|
||
|
||
#[unstable(
|
||
feature = "ptr_internals",
|
||
issue = "none",
|
||
reason = "use `Box::leak(b).into()` or `Unique::from(Box::leak(b))` instead"
|
||
)]
|
||
#[inline]
|
||
#[doc(hidden)]
|
||
pub fn into_unique(b: Self) -> (Unique<T>, A) {
|
||
let (ptr, alloc) = Box::into_raw_with_allocator(b);
|
||
unsafe { (Unique::from(&mut *ptr), alloc) }
|
||
}
|
||
|
||
/// Returns a reference to the underlying allocator.
|
||
///
|
||
/// Note: this is an associated function, which means that you have
|
||
/// to call it as `Box::allocator(&b)` instead of `b.allocator()`. This
|
||
/// is so that there is no conflict with a method on the inner type.
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
||
#[inline]
|
||
pub const fn allocator(b: &Self) -> &A {
|
||
&b.1
|
||
}
|
||
|
||
/// Consumes and leaks the `Box`, returning a mutable reference,
|
||
/// `&'a mut T`. Note that the type `T` must outlive the chosen lifetime
|
||
/// `'a`. If the type has only static references, or none at all, then this
|
||
/// may be chosen to be `'static`.
|
||
///
|
||
/// This function is mainly useful for data that lives for the remainder of
|
||
/// the program's life. Dropping the returned reference will cause a memory
|
||
/// leak. If this is not acceptable, the reference should first be wrapped
|
||
/// with the [`Box::from_raw`] function producing a `Box`. This `Box` can
|
||
/// then be dropped which will properly destroy `T` and release the
|
||
/// allocated memory.
|
||
///
|
||
/// Note: this is an associated function, which means that you have
|
||
/// to call it as `Box::leak(b)` instead of `b.leak()`. This
|
||
/// is so that there is no conflict with a method on the inner type.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Simple usage:
|
||
///
|
||
/// ```
|
||
/// let x = Box::new(41);
|
||
/// let static_ref: &'static mut usize = Box::leak(x);
|
||
/// *static_ref += 1;
|
||
/// assert_eq!(*static_ref, 42);
|
||
/// ```
|
||
///
|
||
/// Unsized data:
|
||
///
|
||
/// ```
|
||
/// let x = vec![1, 2, 3].into_boxed_slice();
|
||
/// let static_ref = Box::leak(x);
|
||
/// static_ref[0] = 4;
|
||
/// assert_eq!(*static_ref, [4, 2, 3]);
|
||
/// ```
|
||
#[stable(feature = "box_leak", since = "1.26.0")]
|
||
#[inline]
|
||
pub fn leak<'a>(b: Self) -> &'a mut T
|
||
where
|
||
A: 'a,
|
||
{
|
||
unsafe { &mut *Box::into_raw(b) }
|
||
}
|
||
|
||
/// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then
|
||
/// `*boxed` will be pinned in memory and unable to be moved.
|
||
///
|
||
/// This conversion does not allocate on the heap and happens in place.
|
||
///
|
||
/// This is also available via [`From`].
|
||
///
|
||
/// Constructing and pinning a `Box` with <code>Box::into_pin([Box::new]\(x))</code>
|
||
/// can also be written more concisely using <code>[Box::pin]\(x)</code>.
|
||
/// This `into_pin` method is useful if you already have a `Box<T>`, or you are
|
||
/// constructing a (pinned) `Box` in a different way than with [`Box::new`].
|
||
///
|
||
/// # Notes
|
||
///
|
||
/// It's not recommended that crates add an impl like `From<Box<T>> for Pin<T>`,
|
||
/// as it'll introduce an ambiguity when calling `Pin::from`.
|
||
/// A demonstration of such a poor impl is shown below.
|
||
///
|
||
/// ```compile_fail
|
||
/// # use std::pin::Pin;
|
||
/// struct Foo; // A type defined in this crate.
|
||
/// impl From<Box<()>> for Pin<Foo> {
|
||
/// fn from(_: Box<()>) -> Pin<Foo> {
|
||
/// Pin::new(Foo)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let foo = Box::new(());
|
||
/// let bar = Pin::from(foo);
|
||
/// ```
|
||
#[stable(feature = "box_into_pin", since = "1.63.0")]
|
||
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
||
pub const fn into_pin(boxed: Self) -> Pin<Self>
|
||
where
|
||
A: 'static,
|
||
{
|
||
// It's not possible to move or replace the insides of a `Pin<Box<T>>`
|
||
// when `T: !Unpin`, so it's safe to pin it directly without any
|
||
// additional requirements.
|
||
unsafe { Pin::new_unchecked(boxed) }
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> {
|
||
#[inline]
|
||
fn drop(&mut self) {
|
||
// the T in the Box is dropped by the compiler before the destructor is run
|
||
|
||
let ptr = self.0;
|
||
|
||
unsafe {
|
||
let layout = Layout::for_value_raw(ptr.as_ptr());
|
||
if layout.size() != 0 {
|
||
self.1.deallocate(From::from(ptr.cast()), layout);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Default> Default for Box<T> {
|
||
/// Creates a `Box<T>`, with the `Default` value for T.
|
||
#[inline]
|
||
fn default() -> Self {
|
||
Box::new(T::default())
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T> Default for Box<[T]> {
|
||
#[inline]
|
||
fn default() -> Self {
|
||
let ptr: Unique<[T]> = Unique::<[T; 0]>::dangling();
|
||
Box(ptr, Global)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "default_box_extra", since = "1.17.0")]
|
||
impl Default for Box<str> {
|
||
#[inline]
|
||
fn default() -> Self {
|
||
// SAFETY: This is the same as `Unique::cast<U>` but with an unsized `U = str`.
|
||
let ptr: Unique<str> = unsafe {
|
||
let bytes: Unique<[u8]> = Unique::<[u8; 0]>::dangling();
|
||
Unique::new_unchecked(bytes.as_ptr() as *mut str)
|
||
};
|
||
Box(ptr, Global)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A> {
|
||
/// Returns a new box with a `clone()` of this box's contents.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let x = Box::new(5);
|
||
/// let y = x.clone();
|
||
///
|
||
/// // The value is the same
|
||
/// assert_eq!(x, y);
|
||
///
|
||
/// // But they are unique objects
|
||
/// assert_ne!(&*x as *const i32, &*y as *const i32);
|
||
/// ```
|
||
#[inline]
|
||
fn clone(&self) -> Self {
|
||
// Pre-allocate memory to allow writing the cloned value directly.
|
||
let mut boxed = Self::new_uninit_in(self.1.clone());
|
||
unsafe {
|
||
(**self).write_clone_into_raw(boxed.as_mut_ptr());
|
||
boxed.assume_init()
|
||
}
|
||
}
|
||
|
||
/// Copies `source`'s contents into `self` without creating a new allocation.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let x = Box::new(5);
|
||
/// let mut y = Box::new(10);
|
||
/// let yp: *const i32 = &*y;
|
||
///
|
||
/// y.clone_from(&x);
|
||
///
|
||
/// // The value is the same
|
||
/// assert_eq!(x, y);
|
||
///
|
||
/// // And no allocation occurred
|
||
/// assert_eq!(yp, &*y);
|
||
/// ```
|
||
#[inline]
|
||
fn clone_from(&mut self, source: &Self) {
|
||
(**self).clone_from(&(**source));
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_slice_clone", since = "1.3.0")]
|
||
impl Clone for Box<str> {
|
||
fn clone(&self) -> Self {
|
||
// this makes a copy of the data
|
||
let buf: Box<[u8]> = self.as_bytes().into();
|
||
unsafe { from_boxed_utf8_unchecked(buf) }
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + PartialEq, A: Allocator> PartialEq for Box<T, A> {
|
||
#[inline]
|
||
fn eq(&self, other: &Self) -> bool {
|
||
PartialEq::eq(&**self, &**other)
|
||
}
|
||
#[inline]
|
||
fn ne(&self, other: &Self) -> bool {
|
||
PartialEq::ne(&**self, &**other)
|
||
}
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for Box<T, A> {
|
||
#[inline]
|
||
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
|
||
PartialOrd::partial_cmp(&**self, &**other)
|
||
}
|
||
#[inline]
|
||
fn lt(&self, other: &Self) -> bool {
|
||
PartialOrd::lt(&**self, &**other)
|
||
}
|
||
#[inline]
|
||
fn le(&self, other: &Self) -> bool {
|
||
PartialOrd::le(&**self, &**other)
|
||
}
|
||
#[inline]
|
||
fn ge(&self, other: &Self) -> bool {
|
||
PartialOrd::ge(&**self, &**other)
|
||
}
|
||
#[inline]
|
||
fn gt(&self, other: &Self) -> bool {
|
||
PartialOrd::gt(&**self, &**other)
|
||
}
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A> {
|
||
#[inline]
|
||
fn cmp(&self, other: &Self) -> Ordering {
|
||
Ord::cmp(&**self, &**other)
|
||
}
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + Eq, A: Allocator> Eq for Box<T, A> {}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + Hash, A: Allocator> Hash for Box<T, A> {
|
||
fn hash<H: Hasher>(&self, state: &mut H) {
|
||
(**self).hash(state);
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "indirect_hasher_impl", since = "1.22.0")]
|
||
impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A> {
|
||
fn finish(&self) -> u64 {
|
||
(**self).finish()
|
||
}
|
||
fn write(&mut self, bytes: &[u8]) {
|
||
(**self).write(bytes)
|
||
}
|
||
fn write_u8(&mut self, i: u8) {
|
||
(**self).write_u8(i)
|
||
}
|
||
fn write_u16(&mut self, i: u16) {
|
||
(**self).write_u16(i)
|
||
}
|
||
fn write_u32(&mut self, i: u32) {
|
||
(**self).write_u32(i)
|
||
}
|
||
fn write_u64(&mut self, i: u64) {
|
||
(**self).write_u64(i)
|
||
}
|
||
fn write_u128(&mut self, i: u128) {
|
||
(**self).write_u128(i)
|
||
}
|
||
fn write_usize(&mut self, i: usize) {
|
||
(**self).write_usize(i)
|
||
}
|
||
fn write_i8(&mut self, i: i8) {
|
||
(**self).write_i8(i)
|
||
}
|
||
fn write_i16(&mut self, i: i16) {
|
||
(**self).write_i16(i)
|
||
}
|
||
fn write_i32(&mut self, i: i32) {
|
||
(**self).write_i32(i)
|
||
}
|
||
fn write_i64(&mut self, i: i64) {
|
||
(**self).write_i64(i)
|
||
}
|
||
fn write_i128(&mut self, i: i128) {
|
||
(**self).write_i128(i)
|
||
}
|
||
fn write_isize(&mut self, i: isize) {
|
||
(**self).write_isize(i)
|
||
}
|
||
fn write_length_prefix(&mut self, len: usize) {
|
||
(**self).write_length_prefix(len)
|
||
}
|
||
fn write_str(&mut self, s: &str) {
|
||
(**self).write_str(s)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_for_ptrs", since = "1.6.0")]
|
||
impl<T> From<T> for Box<T> {
|
||
/// Converts a `T` into a `Box<T>`
|
||
///
|
||
/// The conversion allocates on the heap and moves `t`
|
||
/// from the stack into it.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// let x = 5;
|
||
/// let boxed = Box::new(5);
|
||
///
|
||
/// assert_eq!(Box::from(x), boxed);
|
||
/// ```
|
||
fn from(t: T) -> Self {
|
||
Box::new(t)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "pin", since = "1.33.0")]
|
||
impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>>
|
||
where
|
||
A: 'static,
|
||
{
|
||
/// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then
|
||
/// `*boxed` will be pinned in memory and unable to be moved.
|
||
///
|
||
/// This conversion does not allocate on the heap and happens in place.
|
||
///
|
||
/// This is also available via [`Box::into_pin`].
|
||
///
|
||
/// Constructing and pinning a `Box` with <code><Pin<Box\<T>>>::from([Box::new]\(x))</code>
|
||
/// can also be written more concisely using <code>[Box::pin]\(x)</code>.
|
||
/// This `From` implementation is useful if you already have a `Box<T>`, or you are
|
||
/// constructing a (pinned) `Box` in a different way than with [`Box::new`].
|
||
fn from(boxed: Box<T, A>) -> Self {
|
||
Box::into_pin(boxed)
|
||
}
|
||
}
|
||
|
||
/// Specialization trait used for `From<&[T]>`.
|
||
#[cfg(not(no_global_oom_handling))]
|
||
trait BoxFromSlice<T> {
|
||
fn from_slice(slice: &[T]) -> Self;
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl<T: Clone> BoxFromSlice<T> for Box<[T]> {
|
||
#[inline]
|
||
default fn from_slice(slice: &[T]) -> Self {
|
||
slice.to_vec().into_boxed_slice()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl<T: Copy> BoxFromSlice<T> for Box<[T]> {
|
||
#[inline]
|
||
fn from_slice(slice: &[T]) -> Self {
|
||
let len = slice.len();
|
||
let buf = RawVec::with_capacity(len);
|
||
unsafe {
|
||
ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
|
||
buf.into_box(slice.len()).assume_init()
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_slice", since = "1.17.0")]
|
||
impl<T: Clone> From<&[T]> for Box<[T]> {
|
||
/// Converts a `&[T]` into a `Box<[T]>`
|
||
///
|
||
/// This conversion allocates on the heap
|
||
/// and performs a copy of `slice` and its contents.
|
||
///
|
||
/// # Examples
|
||
/// ```rust
|
||
/// // create a &[u8] which will be used to create a Box<[u8]>
|
||
/// let slice: &[u8] = &[104, 101, 108, 108, 111];
|
||
/// let boxed_slice: Box<[u8]> = Box::from(slice);
|
||
///
|
||
/// println!("{boxed_slice:?}");
|
||
/// ```
|
||
#[inline]
|
||
fn from(slice: &[T]) -> Box<[T]> {
|
||
<Self as BoxFromSlice<T>>::from_slice(slice)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_cow", since = "1.45.0")]
|
||
impl<T: Clone> From<Cow<'_, [T]>> for Box<[T]> {
|
||
/// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
|
||
///
|
||
/// When `cow` is the `Cow::Borrowed` variant, this
|
||
/// conversion allocates on the heap and copies the
|
||
/// underlying slice. Otherwise, it will try to reuse the owned
|
||
/// `Vec`'s allocation.
|
||
#[inline]
|
||
fn from(cow: Cow<'_, [T]>) -> Box<[T]> {
|
||
match cow {
|
||
Cow::Borrowed(slice) => Box::from(slice),
|
||
Cow::Owned(slice) => Box::from(slice),
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_slice", since = "1.17.0")]
|
||
impl From<&str> for Box<str> {
|
||
/// Converts a `&str` into a `Box<str>`
|
||
///
|
||
/// This conversion allocates on the heap
|
||
/// and performs a copy of `s`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// let boxed: Box<str> = Box::from("hello");
|
||
/// println!("{boxed}");
|
||
/// ```
|
||
#[inline]
|
||
fn from(s: &str) -> Box<str> {
|
||
unsafe { from_boxed_utf8_unchecked(Box::from(s.as_bytes())) }
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_cow", since = "1.45.0")]
|
||
impl From<Cow<'_, str>> for Box<str> {
|
||
/// Converts a `Cow<'_, str>` into a `Box<str>`
|
||
///
|
||
/// When `cow` is the `Cow::Borrowed` variant, this
|
||
/// conversion allocates on the heap and copies the
|
||
/// underlying `str`. Otherwise, it will try to reuse the owned
|
||
/// `String`'s allocation.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::borrow::Cow;
|
||
///
|
||
/// let unboxed = Cow::Borrowed("hello");
|
||
/// let boxed: Box<str> = Box::from(unboxed);
|
||
/// println!("{boxed}");
|
||
/// ```
|
||
///
|
||
/// ```rust
|
||
/// # use std::borrow::Cow;
|
||
/// let unboxed = Cow::Owned("hello".to_string());
|
||
/// let boxed: Box<str> = Box::from(unboxed);
|
||
/// println!("{boxed}");
|
||
/// ```
|
||
#[inline]
|
||
fn from(cow: Cow<'_, str>) -> Box<str> {
|
||
match cow {
|
||
Cow::Borrowed(s) => Box::from(s),
|
||
Cow::Owned(s) => Box::from(s),
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "boxed_str_conv", since = "1.19.0")]
|
||
impl<A: Allocator> From<Box<str, A>> for Box<[u8], A> {
|
||
/// Converts a `Box<str>` into a `Box<[u8]>`
|
||
///
|
||
/// This conversion does not allocate on the heap and happens in place.
|
||
///
|
||
/// # Examples
|
||
/// ```rust
|
||
/// // create a Box<str> which will be used to create a Box<[u8]>
|
||
/// let boxed: Box<str> = Box::from("hello");
|
||
/// let boxed_str: Box<[u8]> = Box::from(boxed);
|
||
///
|
||
/// // create a &[u8] which will be used to create a Box<[u8]>
|
||
/// let slice: &[u8] = &[104, 101, 108, 108, 111];
|
||
/// let boxed_slice = Box::from(slice);
|
||
///
|
||
/// assert_eq!(boxed_slice, boxed_str);
|
||
/// ```
|
||
#[inline]
|
||
fn from(s: Box<str, A>) -> Self {
|
||
let (raw, alloc) = Box::into_raw_with_allocator(s);
|
||
unsafe { Box::from_raw_in(raw as *mut [u8], alloc) }
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_array", since = "1.45.0")]
|
||
impl<T, const N: usize> From<[T; N]> for Box<[T]> {
|
||
/// Converts a `[T; N]` into a `Box<[T]>`
|
||
///
|
||
/// This conversion moves the array to newly heap-allocated memory.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// let boxed: Box<[u8]> = Box::from([4, 2]);
|
||
/// println!("{boxed:?}");
|
||
/// ```
|
||
fn from(array: [T; N]) -> Box<[T]> {
|
||
Box::new(array)
|
||
}
|
||
}
|
||
|
||
/// Casts a boxed slice to a boxed array.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// `boxed_slice.len()` must be exactly `N`.
|
||
unsafe fn boxed_slice_as_array_unchecked<T, A: Allocator, const N: usize>(
|
||
boxed_slice: Box<[T], A>,
|
||
) -> Box<[T; N], A> {
|
||
debug_assert_eq!(boxed_slice.len(), N);
|
||
|
||
let (ptr, alloc) = Box::into_raw_with_allocator(boxed_slice);
|
||
// SAFETY: Pointer and allocator came from an existing box,
|
||
// and our safety condition requires that the length is exactly `N`
|
||
unsafe { Box::from_raw_in(ptr as *mut [T; N], alloc) }
|
||
}
|
||
|
||
#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
|
||
impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> {
|
||
type Error = Box<[T]>;
|
||
|
||
/// Attempts to convert a `Box<[T]>` into a `Box<[T; N]>`.
|
||
///
|
||
/// The conversion occurs in-place and does not require a
|
||
/// new memory allocation.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Returns the old `Box<[T]>` in the `Err` variant if
|
||
/// `boxed_slice.len()` does not equal `N`.
|
||
fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error> {
|
||
if boxed_slice.len() == N {
|
||
Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) })
|
||
} else {
|
||
Err(boxed_slice)
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "boxed_array_try_from_vec", since = "1.66.0")]
|
||
impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]> {
|
||
type Error = Vec<T>;
|
||
|
||
/// Attempts to convert a `Vec<T>` into a `Box<[T; N]>`.
|
||
///
|
||
/// Like [`Vec::into_boxed_slice`], this is in-place if `vec.capacity() == N`,
|
||
/// but will require a reallocation otherwise.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Returns the original `Vec<T>` in the `Err` variant if
|
||
/// `boxed_slice.len()` does not equal `N`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// This can be used with [`vec!`] to create an array on the heap:
|
||
///
|
||
/// ```
|
||
/// let state: Box<[f32; 100]> = vec![1.0; 100].try_into().unwrap();
|
||
/// assert_eq!(state.len(), 100);
|
||
/// ```
|
||
fn try_from(vec: Vec<T>) -> Result<Self, Self::Error> {
|
||
if vec.len() == N {
|
||
let boxed_slice = vec.into_boxed_slice();
|
||
Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) })
|
||
} else {
|
||
Err(vec)
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<A: Allocator> Box<dyn Any, A> {
|
||
/// Attempt to downcast the box to a concrete type.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::any::Any;
|
||
///
|
||
/// fn print_if_string(value: Box<dyn Any>) {
|
||
/// if let Ok(string) = value.downcast::<String>() {
|
||
/// println!("String ({}): {}", string.len(), string);
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let my_string = "Hello World".to_string();
|
||
/// print_if_string(Box::new(my_string));
|
||
/// print_if_string(Box::new(0i8));
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
|
||
if self.is::<T>() { unsafe { Ok(self.downcast_unchecked::<T>()) } } else { Err(self) }
|
||
}
|
||
|
||
/// Downcasts the box to a concrete type.
|
||
///
|
||
/// For a safe alternative see [`downcast`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(downcast_unchecked)]
|
||
///
|
||
/// use std::any::Any;
|
||
///
|
||
/// let x: Box<dyn Any> = Box::new(1_usize);
|
||
///
|
||
/// unsafe {
|
||
/// assert_eq!(*x.downcast_unchecked::<usize>(), 1);
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// The contained value must be of type `T`. Calling this method
|
||
/// with the incorrect type is *undefined behavior*.
|
||
///
|
||
/// [`downcast`]: Self::downcast
|
||
#[inline]
|
||
#[unstable(feature = "downcast_unchecked", issue = "90850")]
|
||
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A> {
|
||
debug_assert!(self.is::<T>());
|
||
unsafe {
|
||
let (raw, alloc): (*mut dyn Any, _) = Box::into_raw_with_allocator(self);
|
||
Box::from_raw_in(raw as *mut T, alloc)
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<A: Allocator> Box<dyn Any + Send, A> {
|
||
/// Attempt to downcast the box to a concrete type.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::any::Any;
|
||
///
|
||
/// fn print_if_string(value: Box<dyn Any + Send>) {
|
||
/// if let Ok(string) = value.downcast::<String>() {
|
||
/// println!("String ({}): {}", string.len(), string);
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let my_string = "Hello World".to_string();
|
||
/// print_if_string(Box::new(my_string));
|
||
/// print_if_string(Box::new(0i8));
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
|
||
if self.is::<T>() { unsafe { Ok(self.downcast_unchecked::<T>()) } } else { Err(self) }
|
||
}
|
||
|
||
/// Downcasts the box to a concrete type.
|
||
///
|
||
/// For a safe alternative see [`downcast`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(downcast_unchecked)]
|
||
///
|
||
/// use std::any::Any;
|
||
///
|
||
/// let x: Box<dyn Any + Send> = Box::new(1_usize);
|
||
///
|
||
/// unsafe {
|
||
/// assert_eq!(*x.downcast_unchecked::<usize>(), 1);
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// The contained value must be of type `T`. Calling this method
|
||
/// with the incorrect type is *undefined behavior*.
|
||
///
|
||
/// [`downcast`]: Self::downcast
|
||
#[inline]
|
||
#[unstable(feature = "downcast_unchecked", issue = "90850")]
|
||
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A> {
|
||
debug_assert!(self.is::<T>());
|
||
unsafe {
|
||
let (raw, alloc): (*mut (dyn Any + Send), _) = Box::into_raw_with_allocator(self);
|
||
Box::from_raw_in(raw as *mut T, alloc)
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<A: Allocator> Box<dyn Any + Send + Sync, A> {
|
||
/// Attempt to downcast the box to a concrete type.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::any::Any;
|
||
///
|
||
/// fn print_if_string(value: Box<dyn Any + Send + Sync>) {
|
||
/// if let Ok(string) = value.downcast::<String>() {
|
||
/// println!("String ({}): {}", string.len(), string);
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let my_string = "Hello World".to_string();
|
||
/// print_if_string(Box::new(my_string));
|
||
/// print_if_string(Box::new(0i8));
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "box_send_sync_any_downcast", since = "1.51.0")]
|
||
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
|
||
if self.is::<T>() { unsafe { Ok(self.downcast_unchecked::<T>()) } } else { Err(self) }
|
||
}
|
||
|
||
/// Downcasts the box to a concrete type.
|
||
///
|
||
/// For a safe alternative see [`downcast`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(downcast_unchecked)]
|
||
///
|
||
/// use std::any::Any;
|
||
///
|
||
/// let x: Box<dyn Any + Send + Sync> = Box::new(1_usize);
|
||
///
|
||
/// unsafe {
|
||
/// assert_eq!(*x.downcast_unchecked::<usize>(), 1);
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// The contained value must be of type `T`. Calling this method
|
||
/// with the incorrect type is *undefined behavior*.
|
||
///
|
||
/// [`downcast`]: Self::downcast
|
||
#[inline]
|
||
#[unstable(feature = "downcast_unchecked", issue = "90850")]
|
||
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A> {
|
||
debug_assert!(self.is::<T>());
|
||
unsafe {
|
||
let (raw, alloc): (*mut (dyn Any + Send + Sync), _) =
|
||
Box::into_raw_with_allocator(self);
|
||
Box::from_raw_in(raw as *mut T, alloc)
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: fmt::Display + ?Sized, A: Allocator> fmt::Display for Box<T, A> {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: fmt::Debug + ?Sized, A: Allocator> fmt::Debug for Box<T, A> {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized, A: Allocator> fmt::Pointer for Box<T, A> {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
// It's not possible to extract the inner Uniq directly from the Box,
|
||
// instead we cast it to a *const which aliases the Unique
|
||
let ptr: *const T = &**self;
|
||
fmt::Pointer::fmt(&ptr, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized, A: Allocator> Deref for Box<T, A> {
|
||
type Target = T;
|
||
|
||
fn deref(&self) -> &T {
|
||
&**self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized, A: Allocator> DerefMut for Box<T, A> {
|
||
fn deref_mut(&mut self) -> &mut T {
|
||
&mut **self
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "deref_pure_trait", issue = "87121")]
|
||
unsafe impl<T: ?Sized, A: Allocator> DerefPure for Box<T, A> {}
|
||
|
||
#[unstable(feature = "receiver_trait", issue = "none")]
|
||
impl<T: ?Sized, A: Allocator> Receiver for Box<T, A> {}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> {
|
||
type Item = I::Item;
|
||
fn next(&mut self) -> Option<I::Item> {
|
||
(**self).next()
|
||
}
|
||
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
(**self).size_hint()
|
||
}
|
||
fn nth(&mut self, n: usize) -> Option<I::Item> {
|
||
(**self).nth(n)
|
||
}
|
||
fn last(self) -> Option<I::Item> {
|
||
BoxIter::last(self)
|
||
}
|
||
}
|
||
|
||
trait BoxIter {
|
||
type Item;
|
||
fn last(self) -> Option<Self::Item>;
|
||
}
|
||
|
||
impl<I: Iterator + ?Sized, A: Allocator> BoxIter for Box<I, A> {
|
||
type Item = I::Item;
|
||
default fn last(self) -> Option<I::Item> {
|
||
#[inline]
|
||
fn some<T>(_: Option<T>, x: T) -> Option<T> {
|
||
Some(x)
|
||
}
|
||
|
||
self.fold(None, some)
|
||
}
|
||
}
|
||
|
||
/// Specialization for sized `I`s that uses `I`s implementation of `last()`
|
||
/// instead of the default.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I: Iterator, A: Allocator> BoxIter for Box<I, A> {
|
||
fn last(self) -> Option<I::Item> {
|
||
(*self).last()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A> {
|
||
fn next_back(&mut self) -> Option<I::Item> {
|
||
(**self).next_back()
|
||
}
|
||
fn nth_back(&mut self, n: usize) -> Option<I::Item> {
|
||
(**self).nth_back(n)
|
||
}
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A> {
|
||
fn len(&self) -> usize {
|
||
(**self).len()
|
||
}
|
||
fn is_empty(&self) -> bool {
|
||
(**self).is_empty()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "fused", since = "1.26.0")]
|
||
impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A> {}
|
||
|
||
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
|
||
impl<Args: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
|
||
type Output = <F as FnOnce<Args>>::Output;
|
||
|
||
extern "rust-call" fn call_once(self, args: Args) -> Self::Output {
|
||
<F as FnOnce<Args>>::call_once(*self, args)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
|
||
impl<Args: Tuple, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
|
||
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
|
||
<F as FnMut<Args>>::call_mut(self, args)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
|
||
impl<Args: Tuple, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
|
||
extern "rust-call" fn call(&self, args: Args) -> Self::Output {
|
||
<F as Fn<Args>>::call(self, args)
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "async_fn_traits", issue = "none")]
|
||
impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args> for Box<F, A> {
|
||
type Output = F::Output;
|
||
type CallOnceFuture = F::CallOnceFuture;
|
||
|
||
extern "rust-call" fn async_call_once(self, args: Args) -> Self::CallOnceFuture {
|
||
F::async_call_once(*self, args)
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "async_fn_traits", issue = "none")]
|
||
impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> for Box<F, A> {
|
||
type CallRefFuture<'a> = F::CallRefFuture<'a> where Self: 'a;
|
||
|
||
extern "rust-call" fn async_call_mut(&mut self, args: Args) -> Self::CallRefFuture<'_> {
|
||
F::async_call_mut(self, args)
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "async_fn_traits", issue = "none")]
|
||
impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box<F, A> {
|
||
extern "rust-call" fn async_call(&self, args: Args) -> Self::CallRefFuture<'_> {
|
||
F::async_call(self, args)
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "coerce_unsized", issue = "18598")]
|
||
impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}
|
||
|
||
// It is quite crucial that we only allow the `Global` allocator here.
|
||
// Handling arbitrary custom allocators (which can affect the `Box` layout heavily!)
|
||
// would need a lot of codegen and interpreter adjustments.
|
||
#[unstable(feature = "dispatch_from_dyn", issue = "none")]
|
||
impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T, Global> {}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "boxed_slice_from_iter", since = "1.32.0")]
|
||
impl<I> FromIterator<I> for Box<[I]> {
|
||
fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
|
||
iter.into_iter().collect::<Vec<_>>().into_boxed_slice()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_slice_clone", since = "1.3.0")]
|
||
impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A> {
|
||
fn clone(&self) -> Self {
|
||
let alloc = Box::allocator(self).clone();
|
||
self.to_vec_in(alloc).into_boxed_slice()
|
||
}
|
||
|
||
/// Copies `source`'s contents into `self` without creating a new allocation,
|
||
/// so long as the two are of the same length.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let x = Box::new([5, 6, 7]);
|
||
/// let mut y = Box::new([8, 9, 10]);
|
||
/// let yp: *const [i32] = &*y;
|
||
///
|
||
/// y.clone_from(&x);
|
||
///
|
||
/// // The value is the same
|
||
/// assert_eq!(x, y);
|
||
///
|
||
/// // And no allocation occurred
|
||
/// assert_eq!(yp, &*y);
|
||
/// ```
|
||
fn clone_from(&mut self, source: &Self) {
|
||
if self.len() == source.len() {
|
||
self.clone_from_slice(&source);
|
||
} else {
|
||
*self = source.clone();
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "box_borrow", since = "1.1.0")]
|
||
impl<T: ?Sized, A: Allocator> borrow::Borrow<T> for Box<T, A> {
|
||
fn borrow(&self) -> &T {
|
||
&**self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "box_borrow", since = "1.1.0")]
|
||
impl<T: ?Sized, A: Allocator> borrow::BorrowMut<T> for Box<T, A> {
|
||
fn borrow_mut(&mut self) -> &mut T {
|
||
&mut **self
|
||
}
|
||
}
|
||
|
||
#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
|
||
impl<T: ?Sized, A: Allocator> AsRef<T> for Box<T, A> {
|
||
fn as_ref(&self) -> &T {
|
||
&**self
|
||
}
|
||
}
|
||
|
||
#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
|
||
impl<T: ?Sized, A: Allocator> AsMut<T> for Box<T, A> {
|
||
fn as_mut(&mut self) -> &mut T {
|
||
&mut **self
|
||
}
|
||
}
|
||
|
||
/* Nota bene
|
||
*
|
||
* We could have chosen not to add this impl, and instead have written a
|
||
* function of Pin<Box<T>> to Pin<T>. Such a function would not be sound,
|
||
* because Box<T> implements Unpin even when T does not, as a result of
|
||
* this impl.
|
||
*
|
||
* We chose this API instead of the alternative for a few reasons:
|
||
* - Logically, it is helpful to understand pinning in regard to the
|
||
* memory region being pointed to. For this reason none of the
|
||
* standard library pointer types support projecting through a pin
|
||
* (Box<T> is the only pointer type in std for which this would be
|
||
* safe.)
|
||
* - It is in practice very useful to have Box<T> be unconditionally
|
||
* Unpin because of trait objects, for which the structural auto
|
||
* trait functionality does not apply (e.g., Box<dyn Foo> would
|
||
* otherwise not be Unpin).
|
||
*
|
||
* Another type with the same semantics as Box but only a conditional
|
||
* implementation of `Unpin` (where `T: Unpin`) would be valid/safe, and
|
||
* could have a method to project a Pin<T> from it.
|
||
*/
|
||
#[stable(feature = "pin", since = "1.33.0")]
|
||
impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> {}
|
||
|
||
#[unstable(feature = "coroutine_trait", issue = "43122")]
|
||
impl<G: ?Sized + Coroutine<R> + Unpin, R, A: Allocator> Coroutine<R> for Box<G, A> {
|
||
type Yield = G::Yield;
|
||
type Return = G::Return;
|
||
|
||
fn resume(mut self: Pin<&mut Self>, arg: R) -> CoroutineState<Self::Yield, Self::Return> {
|
||
G::resume(Pin::new(&mut *self), arg)
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "coroutine_trait", issue = "43122")]
|
||
impl<G: ?Sized + Coroutine<R>, R, A: Allocator> Coroutine<R> for Pin<Box<G, A>>
|
||
where
|
||
A: 'static,
|
||
{
|
||
type Yield = G::Yield;
|
||
type Return = G::Return;
|
||
|
||
fn resume(mut self: Pin<&mut Self>, arg: R) -> CoroutineState<Self::Yield, Self::Return> {
|
||
G::resume((*self).as_mut(), arg)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "futures_api", since = "1.36.0")]
|
||
impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> {
|
||
type Output = F::Output;
|
||
|
||
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
|
||
F::poll(Pin::new(&mut *self), cx)
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "async_iterator", issue = "79024")]
|
||
impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S> {
|
||
type Item = S::Item;
|
||
|
||
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
|
||
Pin::new(&mut **self).poll_next(cx)
|
||
}
|
||
|
||
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
(**self).size_hint()
|
||
}
|
||
}
|
||
|
||
impl dyn Error {
|
||
#[inline]
|
||
#[stable(feature = "error_downcast", since = "1.3.0")]
|
||
#[rustc_allow_incoherent_impl]
|
||
/// Attempts to downcast the box to a concrete type.
|
||
pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> {
|
||
if self.is::<T>() {
|
||
unsafe {
|
||
let raw: *mut dyn Error = Box::into_raw(self);
|
||
Ok(Box::from_raw(raw as *mut T))
|
||
}
|
||
} else {
|
||
Err(self)
|
||
}
|
||
}
|
||
}
|
||
|
||
impl dyn Error + Send {
|
||
#[inline]
|
||
#[stable(feature = "error_downcast", since = "1.3.0")]
|
||
#[rustc_allow_incoherent_impl]
|
||
/// Attempts to downcast the box to a concrete type.
|
||
pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error + Send>> {
|
||
let err: Box<dyn Error> = self;
|
||
<dyn Error>::downcast(err).map_err(|s| unsafe {
|
||
// Reapply the `Send` marker.
|
||
Box::from_raw(Box::into_raw(s) as *mut (dyn Error + Send))
|
||
})
|
||
}
|
||
}
|
||
|
||
impl dyn Error + Send + Sync {
|
||
#[inline]
|
||
#[stable(feature = "error_downcast", since = "1.3.0")]
|
||
#[rustc_allow_incoherent_impl]
|
||
/// Attempts to downcast the box to a concrete type.
|
||
pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Self>> {
|
||
let err: Box<dyn Error> = self;
|
||
<dyn Error>::downcast(err).map_err(|s| unsafe {
|
||
// Reapply the `Send + Sync` marker.
|
||
Box::from_raw(Box::into_raw(s) as *mut (dyn Error + Send + Sync))
|
||
})
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
|
||
/// Converts a type of [`Error`] into a box of dyn [`Error`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::fmt;
|
||
/// use std::mem;
|
||
///
|
||
/// #[derive(Debug)]
|
||
/// struct AnError;
|
||
///
|
||
/// impl fmt::Display for AnError {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// write!(f, "An error")
|
||
/// }
|
||
/// }
|
||
///
|
||
/// impl Error for AnError {}
|
||
///
|
||
/// let an_error = AnError;
|
||
/// assert!(0 == mem::size_of_val(&an_error));
|
||
/// let a_boxed_error = Box::<dyn Error>::from(an_error);
|
||
/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
fn from(err: E) -> Box<dyn Error + 'a> {
|
||
Box::new(err)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> {
|
||
/// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of
|
||
/// dyn [`Error`] + [`Send`] + [`Sync`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::fmt;
|
||
/// use std::mem;
|
||
///
|
||
/// #[derive(Debug)]
|
||
/// struct AnError;
|
||
///
|
||
/// impl fmt::Display for AnError {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// write!(f, "An error")
|
||
/// }
|
||
/// }
|
||
///
|
||
/// impl Error for AnError {}
|
||
///
|
||
/// unsafe impl Send for AnError {}
|
||
///
|
||
/// unsafe impl Sync for AnError {}
|
||
///
|
||
/// let an_error = AnError;
|
||
/// assert!(0 == mem::size_of_val(&an_error));
|
||
/// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
|
||
/// assert!(
|
||
/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> {
|
||
Box::new(err)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a> {
|
||
/// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::mem;
|
||
///
|
||
/// let a_string_error = "a string error".to_string();
|
||
/// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
|
||
/// assert!(
|
||
/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
#[inline]
|
||
fn from(err: String) -> Box<dyn Error + Send + Sync + 'a> {
|
||
struct StringError(String);
|
||
|
||
impl Error for StringError {
|
||
#[allow(deprecated)]
|
||
fn description(&self) -> &str {
|
||
&self.0
|
||
}
|
||
}
|
||
|
||
impl fmt::Display for StringError {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt(&self.0, f)
|
||
}
|
||
}
|
||
|
||
// Purposefully skip printing "StringError(..)"
|
||
impl fmt::Debug for StringError {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(&self.0, f)
|
||
}
|
||
}
|
||
|
||
Box::new(StringError(err))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_box_error", since = "1.6.0")]
|
||
impl<'a> From<String> for Box<dyn Error + 'a> {
|
||
/// Converts a [`String`] into a box of dyn [`Error`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::mem;
|
||
///
|
||
/// let a_string_error = "a string error".to_string();
|
||
/// let a_boxed_error = Box::<dyn Error>::from(a_string_error);
|
||
/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
fn from(str_err: String) -> Box<dyn Error + 'a> {
|
||
let err1: Box<dyn Error + Send + Sync> = From::from(str_err);
|
||
let err2: Box<dyn Error> = err1;
|
||
err2
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> {
|
||
/// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
|
||
///
|
||
/// [`str`]: prim@str
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::mem;
|
||
///
|
||
/// let a_str_error = "a str error";
|
||
/// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error);
|
||
/// assert!(
|
||
/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
#[inline]
|
||
fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> {
|
||
From::from(String::from(err))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_box_error", since = "1.6.0")]
|
||
impl<'a> From<&str> for Box<dyn Error + 'a> {
|
||
/// Converts a [`str`] into a box of dyn [`Error`].
|
||
///
|
||
/// [`str`]: prim@str
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::mem;
|
||
///
|
||
/// let a_str_error = "a str error";
|
||
/// let a_boxed_error = Box::<dyn Error>::from(a_str_error);
|
||
/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
fn from(err: &str) -> Box<dyn Error + 'a> {
|
||
From::from(String::from(err))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_box_error", since = "1.22.0")]
|
||
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
|
||
/// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::mem;
|
||
/// use std::borrow::Cow;
|
||
///
|
||
/// let a_cow_str_error = Cow::from("a str error");
|
||
/// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error);
|
||
/// assert!(
|
||
/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> {
|
||
From::from(String::from(err))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_box_error", since = "1.22.0")]
|
||
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a> {
|
||
/// Converts a [`Cow`] into a box of dyn [`Error`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::error::Error;
|
||
/// use std::mem;
|
||
/// use std::borrow::Cow;
|
||
///
|
||
/// let a_cow_str_error = Cow::from("a str error");
|
||
/// let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error);
|
||
/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
|
||
/// ```
|
||
fn from(err: Cow<'b, str>) -> Box<dyn Error + 'a> {
|
||
From::from(String::from(err))
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "box_error", since = "1.8.0")]
|
||
impl<T: core::error::Error> core::error::Error for Box<T> {
|
||
#[allow(deprecated, deprecated_in_future)]
|
||
fn description(&self) -> &str {
|
||
core::error::Error::description(&**self)
|
||
}
|
||
|
||
#[allow(deprecated)]
|
||
fn cause(&self) -> Option<&dyn core::error::Error> {
|
||
core::error::Error::cause(&**self)
|
||
}
|
||
|
||
fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
|
||
core::error::Error::source(&**self)
|
||
}
|
||
|
||
fn provide<'b>(&'b self, request: &mut core::error::Request<'b>) {
|
||
core::error::Error::provide(&**self, request);
|
||
}
|
||
}
|
||
|
||
//! A UTF-8–encoded, growable string.
|
||
//!
|
||
//! This module contains the [`String`] type, the [`ToString`] trait for
|
||
//! converting to strings, and several error types that may result from
|
||
//! working with [`String`]s.
|
||
//!
|
||
//! # Examples
|
||
//!
|
||
//! There are multiple ways to create a new [`String`] from a string literal:
|
||
//!
|
||
//! ```
|
||
//! let s = "Hello".to_string();
|
||
//!
|
||
//! let s = String::from("world");
|
||
//! let s: String = "also this".into();
|
||
//! ```
|
||
//!
|
||
//! You can create a new [`String`] from an existing one by concatenating with
|
||
//! `+`:
|
||
//!
|
||
//! ```
|
||
//! let s = "Hello".to_string();
|
||
//!
|
||
//! let message = s + " world!";
|
||
//! ```
|
||
//!
|
||
//! If you have a vector of valid UTF-8 bytes, you can make a [`String`] out of
|
||
//! it. You can do the reverse too.
|
||
//!
|
||
//! ```
|
||
//! let sparkle_heart = vec![240, 159, 146, 150];
|
||
//!
|
||
//! // We know these bytes are valid, so we'll use `unwrap()`.
|
||
//! let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
|
||
//!
|
||
//! assert_eq!("💖", sparkle_heart);
|
||
//!
|
||
//! let bytes = sparkle_heart.into_bytes();
|
||
//!
|
||
//! assert_eq!(bytes, [240, 159, 146, 150]);
|
||
//! ```
|
||
|
||
#![stable(feature = "rust1", since = "1.0.0")]
|
||
|
||
use core::error::Error;
|
||
use core::fmt;
|
||
use core::hash;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::iter::from_fn;
|
||
use core::iter::FusedIterator;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::ops::Add;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::ops::AddAssign;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::ops::Bound::{Excluded, Included, Unbounded};
|
||
use core::ops::{self, Range, RangeBounds};
|
||
use core::ptr;
|
||
use core::slice;
|
||
use core::str::pattern::Pattern;
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::borrow::{Cow, ToOwned};
|
||
use crate::boxed::Box;
|
||
use crate::collections::TryReserveError;
|
||
use crate::str::{self, from_utf8_unchecked_mut, Chars, Utf8Error};
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::str::{from_boxed_utf8_unchecked, FromStr};
|
||
use crate::vec::Vec;
|
||
|
||
/// A UTF-8–encoded, growable string.
|
||
///
|
||
/// `String` is the most common string type. It has ownership over the contents
|
||
/// of the string, stored in a heap-allocated buffer (see [Representation](#representation)).
|
||
/// It is closely related to its borrowed counterpart, the primitive [`str`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// You can create a `String` from [a literal string][`&str`] with [`String::from`]:
|
||
///
|
||
/// [`String::from`]: From::from
|
||
///
|
||
/// ```
|
||
/// let hello = String::from("Hello, world!");
|
||
/// ```
|
||
///
|
||
/// You can append a [`char`] to a `String` with the [`push`] method, and
|
||
/// append a [`&str`] with the [`push_str`] method:
|
||
///
|
||
/// ```
|
||
/// let mut hello = String::from("Hello, ");
|
||
///
|
||
/// hello.push('w');
|
||
/// hello.push_str("orld!");
|
||
/// ```
|
||
///
|
||
/// [`push`]: String::push
|
||
/// [`push_str`]: String::push_str
|
||
///
|
||
/// If you have a vector of UTF-8 bytes, you can create a `String` from it with
|
||
/// the [`from_utf8`] method:
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// // We know these bytes are valid, so we'll use `unwrap()`.
|
||
/// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
///
|
||
/// # UTF-8
|
||
///
|
||
/// `String`s are always valid UTF-8. If you need a non-UTF-8 string, consider
|
||
/// [`OsString`]. It is similar, but without the UTF-8 constraint. Because UTF-8
|
||
/// is a variable width encoding, `String`s are typically smaller than an array of
|
||
/// the same `chars`:
|
||
///
|
||
/// ```
|
||
/// use std::mem;
|
||
///
|
||
/// // `s` is ASCII which represents each `char` as one byte
|
||
/// let s = "hello";
|
||
/// assert_eq!(s.len(), 5);
|
||
///
|
||
/// // A `char` array with the same contents would be longer because
|
||
/// // every `char` is four bytes
|
||
/// let s = ['h', 'e', 'l', 'l', 'o'];
|
||
/// let size: usize = s.into_iter().map(|c| mem::size_of_val(&c)).sum();
|
||
/// assert_eq!(size, 20);
|
||
///
|
||
/// // However, for non-ASCII strings, the difference will be smaller
|
||
/// // and sometimes they are the same
|
||
/// let s = "💖💖💖💖💖";
|
||
/// assert_eq!(s.len(), 20);
|
||
///
|
||
/// let s = ['💖', '💖', '💖', '💖', '💖'];
|
||
/// let size: usize = s.into_iter().map(|c| mem::size_of_val(&c)).sum();
|
||
/// assert_eq!(size, 20);
|
||
/// ```
|
||
///
|
||
/// This raises interesting questions as to how `s[i]` should work.
|
||
/// What should `i` be here? Several options include byte indices and
|
||
/// `char` indices but, because of UTF-8 encoding, only byte indices
|
||
/// would provide constant time indexing. Getting the `i`th `char`, for
|
||
/// example, is available using [`chars`]:
|
||
///
|
||
/// ```
|
||
/// let s = "hello";
|
||
/// let third_character = s.chars().nth(2);
|
||
/// assert_eq!(third_character, Some('l'));
|
||
///
|
||
/// let s = "💖💖💖💖💖";
|
||
/// let third_character = s.chars().nth(2);
|
||
/// assert_eq!(third_character, Some('💖'));
|
||
/// ```
|
||
///
|
||
/// Next, what should `s[i]` return? Because indexing returns a reference
|
||
/// to underlying data it could be `&u8`, `&[u8]`, or something else similar.
|
||
/// Since we're only providing one index, `&u8` makes the most sense but that
|
||
/// might not be what the user expects and can be explicitly achieved with
|
||
/// [`as_bytes()`]:
|
||
///
|
||
/// ```
|
||
/// // The first byte is 104 - the byte value of `'h'`
|
||
/// let s = "hello";
|
||
/// assert_eq!(s.as_bytes()[0], 104);
|
||
/// // or
|
||
/// assert_eq!(s.as_bytes()[0], b'h');
|
||
///
|
||
/// // The first byte is 240 which isn't obviously useful
|
||
/// let s = "💖💖💖💖💖";
|
||
/// assert_eq!(s.as_bytes()[0], 240);
|
||
/// ```
|
||
///
|
||
/// Due to these ambiguities/restrictions, indexing with a `usize` is simply
|
||
/// forbidden:
|
||
///
|
||
/// ```compile_fail,E0277
|
||
/// let s = "hello";
|
||
///
|
||
/// // The following will not compile!
|
||
/// println!("The first letter of s is {}", s[0]);
|
||
/// ```
|
||
///
|
||
/// It is more clear, however, how `&s[i..j]` should work (that is,
|
||
/// indexing with a range). It should accept byte indices (to be constant-time)
|
||
/// and return a `&str` which is UTF-8 encoded. This is also called "string slicing".
|
||
/// Note this will panic if the byte indices provided are not character
|
||
/// boundaries - see [`is_char_boundary`] for more details. See the implementations
|
||
/// for [`SliceIndex<str>`] for more details on string slicing. For a non-panicking
|
||
/// version of string slicing, see [`get`].
|
||
///
|
||
/// [`OsString`]: ../../std/ffi/struct.OsString.html "ffi::OsString"
|
||
/// [`SliceIndex<str>`]: core::slice::SliceIndex
|
||
/// [`as_bytes()`]: str::as_bytes
|
||
/// [`get`]: str::get
|
||
/// [`is_char_boundary`]: str::is_char_boundary
|
||
///
|
||
/// The [`bytes`] and [`chars`] methods return iterators over the bytes and
|
||
/// codepoints of the string, respectively. To iterate over codepoints along
|
||
/// with byte indices, use [`char_indices`].
|
||
///
|
||
/// [`bytes`]: str::bytes
|
||
/// [`chars`]: str::chars
|
||
/// [`char_indices`]: str::char_indices
|
||
///
|
||
/// # Deref
|
||
///
|
||
/// `String` implements <code>[Deref]<Target = [str]></code>, and so inherits all of [`str`]'s
|
||
/// methods. In addition, this means that you can pass a `String` to a
|
||
/// function which takes a [`&str`] by using an ampersand (`&`):
|
||
///
|
||
/// ```
|
||
/// fn takes_str(s: &str) { }
|
||
///
|
||
/// let s = String::from("Hello");
|
||
///
|
||
/// takes_str(&s);
|
||
/// ```
|
||
///
|
||
/// This will create a [`&str`] from the `String` and pass it in. This
|
||
/// conversion is very inexpensive, and so generally, functions will accept
|
||
/// [`&str`]s as arguments unless they need a `String` for some specific
|
||
/// reason.
|
||
///
|
||
/// In certain cases Rust doesn't have enough information to make this
|
||
/// conversion, known as [`Deref`] coercion. In the following example a string
|
||
/// slice [`&'a str`][`&str`] implements the trait `TraitExample`, and the function
|
||
/// `example_func` takes anything that implements the trait. In this case Rust
|
||
/// would need to make two implicit conversions, which Rust doesn't have the
|
||
/// means to do. For that reason, the following example will not compile.
|
||
///
|
||
/// ```compile_fail,E0277
|
||
/// trait TraitExample {}
|
||
///
|
||
/// impl<'a> TraitExample for &'a str {}
|
||
///
|
||
/// fn example_func<A: TraitExample>(example_arg: A) {}
|
||
///
|
||
/// let example_string = String::from("example_string");
|
||
/// example_func(&example_string);
|
||
/// ```
|
||
///
|
||
/// There are two options that would work instead. The first would be to
|
||
/// change the line `example_func(&example_string);` to
|
||
/// `example_func(example_string.as_str());`, using the method [`as_str()`]
|
||
/// to explicitly extract the string slice containing the string. The second
|
||
/// way changes `example_func(&example_string);` to
|
||
/// `example_func(&*example_string);`. In this case we are dereferencing a
|
||
/// `String` to a [`str`], then referencing the [`str`] back to
|
||
/// [`&str`]. The second way is more idiomatic, however both work to do the
|
||
/// conversion explicitly rather than relying on the implicit conversion.
|
||
///
|
||
/// # Representation
|
||
///
|
||
/// A `String` is made up of three components: a pointer to some bytes, a
|
||
/// length, and a capacity. The pointer points to the internal buffer which `String`
|
||
/// uses to store its data. The length is the number of bytes currently stored
|
||
/// in the buffer, and the capacity is the size of the buffer in bytes. As such,
|
||
/// the length will always be less than or equal to the capacity.
|
||
///
|
||
/// This buffer is always stored on the heap.
|
||
///
|
||
/// You can look at these with the [`as_ptr`], [`len`], and [`capacity`]
|
||
/// methods:
|
||
///
|
||
/// ```
|
||
/// use std::mem;
|
||
///
|
||
/// let story = String::from("Once upon a time...");
|
||
///
|
||
// FIXME Update this when vec_into_raw_parts is stabilized
|
||
/// // Prevent automatically dropping the String's data
|
||
/// let mut story = mem::ManuallyDrop::new(story);
|
||
///
|
||
/// let ptr = story.as_mut_ptr();
|
||
/// let len = story.len();
|
||
/// let capacity = story.capacity();
|
||
///
|
||
/// // story has nineteen bytes
|
||
/// assert_eq!(19, len);
|
||
///
|
||
/// // We can re-build a String out of ptr, len, and capacity. This is all
|
||
/// // unsafe because we are responsible for making sure the components are
|
||
/// // valid:
|
||
/// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ;
|
||
///
|
||
/// assert_eq!(String::from("Once upon a time..."), s);
|
||
/// ```
|
||
///
|
||
/// [`as_ptr`]: str::as_ptr
|
||
/// [`len`]: String::len
|
||
/// [`capacity`]: String::capacity
|
||
///
|
||
/// If a `String` has enough capacity, adding elements to it will not
|
||
/// re-allocate. For example, consider this program:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::new();
|
||
///
|
||
/// println!("{}", s.capacity());
|
||
///
|
||
/// for _ in 0..5 {
|
||
/// s.push_str("hello");
|
||
/// println!("{}", s.capacity());
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// This will output the following:
|
||
///
|
||
/// ```text
|
||
/// 0
|
||
/// 8
|
||
/// 16
|
||
/// 16
|
||
/// 32
|
||
/// 32
|
||
/// ```
|
||
///
|
||
/// At first, we have no memory allocated at all, but as we append to the
|
||
/// string, it increases its capacity appropriately. If we instead use the
|
||
/// [`with_capacity`] method to allocate the correct capacity initially:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(25);
|
||
///
|
||
/// println!("{}", s.capacity());
|
||
///
|
||
/// for _ in 0..5 {
|
||
/// s.push_str("hello");
|
||
/// println!("{}", s.capacity());
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [`with_capacity`]: String::with_capacity
|
||
///
|
||
/// We end up with a different output:
|
||
///
|
||
/// ```text
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// ```
|
||
///
|
||
/// Here, there's no need to allocate more memory inside the loop.
|
||
///
|
||
/// [str]: prim@str "str"
|
||
/// [`str`]: prim@str "str"
|
||
/// [`&str`]: prim@str "&str"
|
||
/// [Deref]: core::ops::Deref "ops::Deref"
|
||
/// [`Deref`]: core::ops::Deref "ops::Deref"
|
||
/// [`as_str()`]: String::as_str
|
||
#[derive(PartialEq, PartialOrd, Eq, Ord)]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(test), lang = "String")]
|
||
pub struct String {
|
||
vec: Vec<u8>,
|
||
}
|
||
|
||
/// A possible error value when converting a `String` from a UTF-8 byte vector.
|
||
///
|
||
/// This type is the error type for the [`from_utf8`] method on [`String`]. It
|
||
/// is designed in such a way to carefully avoid reallocations: the
|
||
/// [`into_bytes`] method will give back the byte vector that was used in the
|
||
/// conversion attempt.
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
/// [`into_bytes`]: FromUtf8Error::into_bytes
|
||
///
|
||
/// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
|
||
/// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
|
||
/// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error`
|
||
/// through the [`utf8_error`] method.
|
||
///
|
||
/// [`Utf8Error`]: str::Utf8Error "std::str::Utf8Error"
|
||
/// [`std::str`]: core::str "std::str"
|
||
/// [`&str`]: prim@str "&str"
|
||
/// [`utf8_error`]: FromUtf8Error::utf8_error
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let value = String::from_utf8(bytes);
|
||
///
|
||
/// assert!(value.is_err());
|
||
/// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(no_global_oom_handling), derive(Clone))]
|
||
#[derive(Debug, PartialEq, Eq)]
|
||
pub struct FromUtf8Error {
|
||
bytes: Vec<u8>,
|
||
error: Utf8Error,
|
||
}
|
||
|
||
/// A possible error value when converting a `String` from a UTF-16 byte slice.
|
||
///
|
||
/// This type is the error type for the [`from_utf16`] method on [`String`].
|
||
///
|
||
/// [`from_utf16`]: String::from_utf16
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0xD800, 0x0069, 0x0063];
|
||
///
|
||
/// assert!(String::from_utf16(v).is_err());
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
pub struct FromUtf16Error(());
|
||
|
||
impl String {
|
||
/// Creates a new empty `String`.
|
||
///
|
||
/// Given that the `String` is empty, this will not allocate any initial
|
||
/// buffer. While that means that this initial operation is very
|
||
/// inexpensive, it may cause excessive allocation later when you add
|
||
/// data. If you have an idea of how much data the `String` will hold,
|
||
/// consider the [`with_capacity`] method to prevent excessive
|
||
/// re-allocation.
|
||
///
|
||
/// [`with_capacity`]: String::with_capacity
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::new();
|
||
/// ```
|
||
#[inline]
|
||
#[rustc_const_stable(feature = "const_string_new", since = "1.39.0")]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[must_use]
|
||
pub const fn new() -> String {
|
||
String { vec: Vec::new() }
|
||
}
|
||
|
||
/// Creates a new empty `String` with at least the specified capacity.
|
||
///
|
||
/// `String`s have an internal buffer to hold their data. The capacity is
|
||
/// the length of that buffer, and can be queried with the [`capacity`]
|
||
/// method. This method creates an empty `String`, but one with an initial
|
||
/// buffer that can hold at least `capacity` bytes. This is useful when you
|
||
/// may be appending a bunch of data to the `String`, reducing the number of
|
||
/// reallocations it needs to do.
|
||
///
|
||
/// [`capacity`]: String::capacity
|
||
///
|
||
/// If the given capacity is `0`, no allocation will occur, and this method
|
||
/// is identical to the [`new`] method.
|
||
///
|
||
/// [`new`]: String::new
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(10);
|
||
///
|
||
/// // The String contains no chars, even though it has capacity for more
|
||
/// assert_eq!(s.len(), 0);
|
||
///
|
||
/// // These are all done without reallocating...
|
||
/// let cap = s.capacity();
|
||
/// for _ in 0..10 {
|
||
/// s.push('a');
|
||
/// }
|
||
///
|
||
/// assert_eq!(s.capacity(), cap);
|
||
///
|
||
/// // ...but this may make the string reallocate
|
||
/// s.push('a');
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[must_use]
|
||
pub fn with_capacity(capacity: usize) -> String {
|
||
String { vec: Vec::with_capacity(capacity) }
|
||
}
|
||
|
||
/// Creates a new empty `String` with at least the specified capacity.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Returns [`Err`] if the capacity exceeds `isize::MAX` bytes,
|
||
/// or if the memory allocator reports failure.
|
||
///
|
||
#[inline]
|
||
#[unstable(feature = "try_with_capacity", issue = "91913")]
|
||
pub fn try_with_capacity(capacity: usize) -> Result<String, TryReserveError> {
|
||
Ok(String { vec: Vec::try_with_capacity(capacity)? })
|
||
}
|
||
|
||
// HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
|
||
// required for this method definition, is not available. Since we don't
|
||
// require this method for testing purposes, I'll just stub it
|
||
// NB see the slice::hack module in slice.rs for more information
|
||
#[inline]
|
||
#[cfg(test)]
|
||
pub fn from_str(_: &str) -> String {
|
||
panic!("not available with cfg(test)");
|
||
}
|
||
|
||
/// Converts a vector of bytes to a `String`.
|
||
///
|
||
/// A string ([`String`]) is made of bytes ([`u8`]), and a vector of bytes
|
||
/// ([`Vec<u8>`]) is made of bytes, so this function converts between the
|
||
/// two. Not all byte slices are valid `String`s, however: `String`
|
||
/// requires that it is valid UTF-8. `from_utf8()` checks to ensure that
|
||
/// the bytes are valid UTF-8, and then does the conversion.
|
||
///
|
||
/// If you are sure that the byte slice is valid UTF-8, and you don't want
|
||
/// to incur the overhead of the validity check, there is an unsafe version
|
||
/// of this function, [`from_utf8_unchecked`], which has the same behavior
|
||
/// but skips the check.
|
||
///
|
||
/// This method will take care to not copy the vector, for efficiency's
|
||
/// sake.
|
||
///
|
||
/// If you need a [`&str`] instead of a `String`, consider
|
||
/// [`str::from_utf8`].
|
||
///
|
||
/// The inverse of this method is [`into_bytes`].
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Returns [`Err`] if the slice is not UTF-8 with a description as to why the
|
||
/// provided bytes are not UTF-8. The vector you moved in is also included.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// // We know these bytes are valid, so we'll use `unwrap()`.
|
||
/// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
///
|
||
/// Incorrect bytes:
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let sparkle_heart = vec![0, 159, 146, 150];
|
||
///
|
||
/// assert!(String::from_utf8(sparkle_heart).is_err());
|
||
/// ```
|
||
///
|
||
/// See the docs for [`FromUtf8Error`] for more details on what you can do
|
||
/// with this error.
|
||
///
|
||
/// [`from_utf8_unchecked`]: String::from_utf8_unchecked
|
||
/// [`Vec<u8>`]: crate::vec::Vec "Vec"
|
||
/// [`&str`]: prim@str "&str"
|
||
/// [`into_bytes`]: String::into_bytes
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> {
|
||
match str::from_utf8(&vec) {
|
||
Ok(..) => Ok(String { vec }),
|
||
Err(e) => Err(FromUtf8Error { bytes: vec, error: e }),
|
||
}
|
||
}
|
||
|
||
/// Converts a slice of bytes to a string, including invalid characters.
|
||
///
|
||
/// Strings are made of bytes ([`u8`]), and a slice of bytes
|
||
/// ([`&[u8]`][byteslice]) is made of bytes, so this function converts
|
||
/// between the two. Not all byte slices are valid strings, however: strings
|
||
/// are required to be valid UTF-8. During this conversion,
|
||
/// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with
|
||
/// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: <20>
|
||
///
|
||
/// [byteslice]: prim@slice
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// If you are sure that the byte slice is valid UTF-8, and you don't want
|
||
/// to incur the overhead of the conversion, there is an unsafe version
|
||
/// of this function, [`from_utf8_unchecked`], which has the same behavior
|
||
/// but skips the checks.
|
||
///
|
||
/// [`from_utf8_unchecked`]: String::from_utf8_unchecked
|
||
///
|
||
/// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid
|
||
/// UTF-8, then we need to insert the replacement characters, which will
|
||
/// change the size of the string, and hence, require a `String`. But if
|
||
/// it's already valid UTF-8, we don't need a new allocation. This return
|
||
/// type allows us to handle both cases.
|
||
///
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart);
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
///
|
||
/// Incorrect bytes:
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes
|
||
/// let input = b"Hello \xF0\x90\x80World";
|
||
/// let output = String::from_utf8_lossy(input);
|
||
///
|
||
/// assert_eq!("Hello <20>World", output);
|
||
/// ```
|
||
#[must_use]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> {
|
||
let mut iter = v.utf8_chunks();
|
||
|
||
let first_valid = if let Some(chunk) = iter.next() {
|
||
let valid = chunk.valid();
|
||
if chunk.invalid().is_empty() {
|
||
debug_assert_eq!(valid.len(), v.len());
|
||
return Cow::Borrowed(valid);
|
||
}
|
||
valid
|
||
} else {
|
||
return Cow::Borrowed("");
|
||
};
|
||
|
||
const REPLACEMENT: &str = "\u{FFFD}";
|
||
|
||
let mut res = String::with_capacity(v.len());
|
||
res.push_str(first_valid);
|
||
res.push_str(REPLACEMENT);
|
||
|
||
for chunk in iter {
|
||
res.push_str(chunk.valid());
|
||
if !chunk.invalid().is_empty() {
|
||
res.push_str(REPLACEMENT);
|
||
}
|
||
}
|
||
|
||
Cow::Owned(res)
|
||
}
|
||
|
||
/// Decode a UTF-16–encoded vector `v` into a `String`, returning [`Err`]
|
||
/// if `v` contains any invalid data.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // 𝄞music
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0x0073, 0x0069, 0x0063];
|
||
/// assert_eq!(String::from("𝄞music"),
|
||
/// String::from_utf16(v).unwrap());
|
||
///
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0xD800, 0x0069, 0x0063];
|
||
/// assert!(String::from_utf16(v).is_err());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> {
|
||
// This isn't done via collect::<Result<_, _>>() for performance reasons.
|
||
// FIXME: the function can be simplified again when #48994 is closed.
|
||
let mut ret = String::with_capacity(v.len());
|
||
for c in char::decode_utf16(v.iter().cloned()) {
|
||
if let Ok(c) = c {
|
||
ret.push(c);
|
||
} else {
|
||
return Err(FromUtf16Error(()));
|
||
}
|
||
}
|
||
Ok(ret)
|
||
}
|
||
|
||
/// Decode a UTF-16–encoded slice `v` into a `String`, replacing
|
||
/// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
|
||
///
|
||
/// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
|
||
/// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8
|
||
/// conversion requires a memory allocation.
|
||
///
|
||
/// [`from_utf8_lossy`]: String::from_utf8_lossy
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // 𝄞mus<invalid>ic<invalid>
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0x0073, 0xDD1E, 0x0069, 0x0063,
|
||
/// 0xD834];
|
||
///
|
||
/// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
|
||
/// String::from_utf16_lossy(v));
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[must_use]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf16_lossy(v: &[u16]) -> String {
|
||
char::decode_utf16(v.iter().cloned())
|
||
.map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
|
||
.collect()
|
||
}
|
||
|
||
/// Decode a UTF-16LE–encoded vector `v` into a `String`, returning [`Err`]
|
||
/// if `v` contains any invalid data.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞music
|
||
/// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
|
||
/// 0x73, 0x00, 0x69, 0x00, 0x63, 0x00];
|
||
/// assert_eq!(String::from("𝄞music"),
|
||
/// String::from_utf16le(v).unwrap());
|
||
///
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
|
||
/// 0x00, 0xD8, 0x69, 0x00, 0x63, 0x00];
|
||
/// assert!(String::from_utf16le(v).is_err());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16le(v: &[u8]) -> Result<String, FromUtf16Error> {
|
||
if v.len() % 2 != 0 {
|
||
return Err(FromUtf16Error(()));
|
||
}
|
||
match (cfg!(target_endian = "little"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16(v),
|
||
_ => char::decode_utf16(v.array_chunks::<2>().copied().map(u16::from_le_bytes))
|
||
.collect::<Result<_, _>>()
|
||
.map_err(|_| FromUtf16Error(())),
|
||
}
|
||
}
|
||
|
||
/// Decode a UTF-16LE–encoded slice `v` into a `String`, replacing
|
||
/// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
|
||
///
|
||
/// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
|
||
/// `from_utf16le_lossy` returns a `String` since the UTF-16 to UTF-8
|
||
/// conversion requires a memory allocation.
|
||
///
|
||
/// [`from_utf8_lossy`]: String::from_utf8_lossy
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞mus<invalid>ic<invalid>
|
||
/// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
|
||
/// 0x73, 0x00, 0x1E, 0xDD, 0x69, 0x00, 0x63, 0x00,
|
||
/// 0x34, 0xD8];
|
||
///
|
||
/// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
|
||
/// String::from_utf16le_lossy(v));
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16le_lossy(v: &[u8]) -> String {
|
||
match (cfg!(target_endian = "little"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16_lossy(v),
|
||
(true, ([], v, [_remainder])) => Self::from_utf16_lossy(v) + "\u{FFFD}",
|
||
_ => {
|
||
let mut iter = v.array_chunks::<2>();
|
||
let string = char::decode_utf16(iter.by_ref().copied().map(u16::from_le_bytes))
|
||
.map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
|
||
.collect();
|
||
if iter.remainder().is_empty() { string } else { string + "\u{FFFD}" }
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Decode a UTF-16BE–encoded vector `v` into a `String`, returning [`Err`]
|
||
/// if `v` contains any invalid data.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞music
|
||
/// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
|
||
/// 0x00, 0x73, 0x00, 0x69, 0x00, 0x63];
|
||
/// assert_eq!(String::from("𝄞music"),
|
||
/// String::from_utf16be(v).unwrap());
|
||
///
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
|
||
/// 0xD8, 0x00, 0x00, 0x69, 0x00, 0x63];
|
||
/// assert!(String::from_utf16be(v).is_err());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16be(v: &[u8]) -> Result<String, FromUtf16Error> {
|
||
if v.len() % 2 != 0 {
|
||
return Err(FromUtf16Error(()));
|
||
}
|
||
match (cfg!(target_endian = "big"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16(v),
|
||
_ => char::decode_utf16(v.array_chunks::<2>().copied().map(u16::from_be_bytes))
|
||
.collect::<Result<_, _>>()
|
||
.map_err(|_| FromUtf16Error(())),
|
||
}
|
||
}
|
||
|
||
/// Decode a UTF-16BE–encoded slice `v` into a `String`, replacing
|
||
/// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
|
||
///
|
||
/// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
|
||
/// `from_utf16le_lossy` returns a `String` since the UTF-16 to UTF-8
|
||
/// conversion requires a memory allocation.
|
||
///
|
||
/// [`from_utf8_lossy`]: String::from_utf8_lossy
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞mus<invalid>ic<invalid>
|
||
/// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
|
||
/// 0x00, 0x73, 0xDD, 0x1E, 0x00, 0x69, 0x00, 0x63,
|
||
/// 0xD8, 0x34];
|
||
///
|
||
/// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
|
||
/// String::from_utf16be_lossy(v));
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16be_lossy(v: &[u8]) -> String {
|
||
match (cfg!(target_endian = "big"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16_lossy(v),
|
||
(true, ([], v, [_remainder])) => Self::from_utf16_lossy(v) + "\u{FFFD}",
|
||
_ => {
|
||
let mut iter = v.array_chunks::<2>();
|
||
let string = char::decode_utf16(iter.by_ref().copied().map(u16::from_be_bytes))
|
||
.map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
|
||
.collect();
|
||
if iter.remainder().is_empty() { string } else { string + "\u{FFFD}" }
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Decomposes a `String` into its raw components: `(pointer, length, capacity)`.
|
||
///
|
||
/// Returns the raw pointer to the underlying data, the length of
|
||
/// the string (in bytes), and the allocated capacity of the data
|
||
/// (in bytes). These are the same arguments in the same order as
|
||
/// the arguments to [`from_raw_parts`].
|
||
///
|
||
/// After calling this function, the caller is responsible for the
|
||
/// memory previously managed by the `String`. The only way to do
|
||
/// this is to convert the raw pointer, length, and capacity back
|
||
/// into a `String` with the [`from_raw_parts`] function, allowing
|
||
/// the destructor to perform the cleanup.
|
||
///
|
||
/// [`from_raw_parts`]: String::from_raw_parts
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(vec_into_raw_parts)]
|
||
/// let s = String::from("hello");
|
||
///
|
||
/// let (ptr, len, cap) = s.into_raw_parts();
|
||
///
|
||
/// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) };
|
||
/// assert_eq!(rebuilt, "hello");
|
||
/// ```
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
|
||
pub fn into_raw_parts(self) -> (*mut u8, usize, usize) {
|
||
self.vec.into_raw_parts()
|
||
}
|
||
|
||
/// Creates a new `String` from a pointer, a length and a capacity.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This is highly unsafe, due to the number of invariants that aren't
|
||
/// checked:
|
||
///
|
||
/// * The memory at `buf` needs to have been previously allocated by the
|
||
/// same allocator the standard library uses, with a required alignment of exactly 1.
|
||
/// * `length` needs to be less than or equal to `capacity`.
|
||
/// * `capacity` needs to be the correct value.
|
||
/// * The first `length` bytes at `buf` need to be valid UTF-8.
|
||
///
|
||
/// Violating these may cause problems like corrupting the allocator's
|
||
/// internal data structures. For example, it is normally **not** safe to
|
||
/// build a `String` from a pointer to a C `char` array containing UTF-8
|
||
/// _unless_ you are certain that array was originally allocated by the
|
||
/// Rust standard library's allocator.
|
||
///
|
||
/// The ownership of `buf` is effectively transferred to the
|
||
/// `String` which may then deallocate, reallocate or change the
|
||
/// contents of memory pointed to by the pointer at will. Ensure
|
||
/// that nothing else uses the pointer after calling this
|
||
/// function.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::mem;
|
||
///
|
||
/// unsafe {
|
||
/// let s = String::from("hello");
|
||
///
|
||
// FIXME Update this when vec_into_raw_parts is stabilized
|
||
/// // Prevent automatically dropping the String's data
|
||
/// let mut s = mem::ManuallyDrop::new(s);
|
||
///
|
||
/// let ptr = s.as_mut_ptr();
|
||
/// let len = s.len();
|
||
/// let capacity = s.capacity();
|
||
///
|
||
/// let s = String::from_raw_parts(ptr, len, capacity);
|
||
///
|
||
/// assert_eq!(String::from("hello"), s);
|
||
/// }
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String {
|
||
unsafe { String { vec: Vec::from_raw_parts(buf, length, capacity) } }
|
||
}
|
||
|
||
/// Converts a vector of bytes to a `String` without checking that the
|
||
/// string contains valid UTF-8.
|
||
///
|
||
/// See the safe version, [`from_utf8`], for more details.
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This function is unsafe because it does not check that the bytes passed
|
||
/// to it are valid UTF-8. If this constraint is violated, it may cause
|
||
/// memory unsafety issues with future users of the `String`, as the rest of
|
||
/// the standard library assumes that `String`s are valid UTF-8.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// let sparkle_heart = unsafe {
|
||
/// String::from_utf8_unchecked(sparkle_heart)
|
||
/// };
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String {
|
||
String { vec: bytes }
|
||
}
|
||
|
||
/// Converts a `String` into a byte vector.
|
||
///
|
||
/// This consumes the `String`, so we do not need to copy its contents.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("hello");
|
||
/// let bytes = s.into_bytes();
|
||
///
|
||
/// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn into_bytes(self) -> Vec<u8> {
|
||
self.vec
|
||
}
|
||
|
||
/// Extracts a string slice containing the entire `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("foo");
|
||
///
|
||
/// assert_eq!("foo", s.as_str());
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "string_as_str", since = "1.7.0")]
|
||
pub fn as_str(&self) -> &str {
|
||
self
|
||
}
|
||
|
||
/// Converts a `String` into a mutable string slice.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foobar");
|
||
/// let s_mut_str = s.as_mut_str();
|
||
///
|
||
/// s_mut_str.make_ascii_uppercase();
|
||
///
|
||
/// assert_eq!("FOOBAR", s_mut_str);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "string_as_str", since = "1.7.0")]
|
||
pub fn as_mut_str(&mut self) -> &mut str {
|
||
self
|
||
}
|
||
|
||
/// Appends a given string slice onto the end of this `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.push_str("bar");
|
||
///
|
||
/// assert_eq!("foobar", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("append", "push")]
|
||
pub fn push_str(&mut self, string: &str) {
|
||
self.vec.extend_from_slice(string.as_bytes())
|
||
}
|
||
|
||
/// Copies elements from `src` range to the end of the string.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the starting point or end point do not lie on a [`char`]
|
||
/// boundary, or if they're out of bounds.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(string_extend_from_within)]
|
||
/// let mut string = String::from("abcde");
|
||
///
|
||
/// string.extend_from_within(2..);
|
||
/// assert_eq!(string, "abcdecde");
|
||
///
|
||
/// string.extend_from_within(..2);
|
||
/// assert_eq!(string, "abcdecdeab");
|
||
///
|
||
/// string.extend_from_within(4..8);
|
||
/// assert_eq!(string, "abcdecdeabecde");
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "string_extend_from_within", issue = "103806")]
|
||
pub fn extend_from_within<R>(&mut self, src: R)
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
let src @ Range { start, end } = slice::range(src, ..self.len());
|
||
|
||
assert!(self.is_char_boundary(start));
|
||
assert!(self.is_char_boundary(end));
|
||
|
||
self.vec.extend_from_within(src);
|
||
}
|
||
|
||
/// Returns this `String`'s capacity, in bytes.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::with_capacity(10);
|
||
///
|
||
/// assert!(s.capacity() >= 10);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn capacity(&self) -> usize {
|
||
self.vec.capacity()
|
||
}
|
||
|
||
/// Reserves capacity for at least `additional` bytes more than the
|
||
/// current length. The allocator may reserve more space to speculatively
|
||
/// avoid frequent allocations. After calling `reserve`,
|
||
/// capacity will be greater than or equal to `self.len() + additional`.
|
||
/// Does nothing if capacity is already sufficient.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity overflows [`usize`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::new();
|
||
///
|
||
/// s.reserve(10);
|
||
///
|
||
/// assert!(s.capacity() >= 10);
|
||
/// ```
|
||
///
|
||
/// This might not actually increase the capacity:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(10);
|
||
/// s.push('a');
|
||
/// s.push('b');
|
||
///
|
||
/// // s now has a length of 2 and a capacity of at least 10
|
||
/// let capacity = s.capacity();
|
||
/// assert_eq!(2, s.len());
|
||
/// assert!(capacity >= 10);
|
||
///
|
||
/// // Since we already have at least an extra 8 capacity, calling this...
|
||
/// s.reserve(8);
|
||
///
|
||
/// // ... doesn't actually increase.
|
||
/// assert_eq!(capacity, s.capacity());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn reserve(&mut self, additional: usize) {
|
||
self.vec.reserve(additional)
|
||
}
|
||
|
||
/// Reserves the minimum capacity for at least `additional` bytes more than
|
||
/// the current length. Unlike [`reserve`], this will not
|
||
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
||
/// After calling `reserve_exact`, capacity will be greater than or equal to
|
||
/// `self.len() + additional`. Does nothing if the capacity is already
|
||
/// sufficient.
|
||
///
|
||
/// [`reserve`]: String::reserve
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity overflows [`usize`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::new();
|
||
///
|
||
/// s.reserve_exact(10);
|
||
///
|
||
/// assert!(s.capacity() >= 10);
|
||
/// ```
|
||
///
|
||
/// This might not actually increase the capacity:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(10);
|
||
/// s.push('a');
|
||
/// s.push('b');
|
||
///
|
||
/// // s now has a length of 2 and a capacity of at least 10
|
||
/// let capacity = s.capacity();
|
||
/// assert_eq!(2, s.len());
|
||
/// assert!(capacity >= 10);
|
||
///
|
||
/// // Since we already have at least an extra 8 capacity, calling this...
|
||
/// s.reserve_exact(8);
|
||
///
|
||
/// // ... doesn't actually increase.
|
||
/// assert_eq!(capacity, s.capacity());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn reserve_exact(&mut self, additional: usize) {
|
||
self.vec.reserve_exact(additional)
|
||
}
|
||
|
||
/// Tries to reserve capacity for at least `additional` bytes more than the
|
||
/// current length. The allocator may reserve more space to speculatively
|
||
/// avoid frequent allocations. After calling `try_reserve`, capacity will be
|
||
/// greater than or equal to `self.len() + additional` if it returns
|
||
/// `Ok(())`. Does nothing if capacity is already sufficient. This method
|
||
/// preserves the contents even if an error occurs.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the capacity overflows, or the allocator reports a failure, then an error
|
||
/// is returned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::collections::TryReserveError;
|
||
///
|
||
/// fn process_data(data: &str) -> Result<String, TryReserveError> {
|
||
/// let mut output = String::new();
|
||
///
|
||
/// // Pre-reserve the memory, exiting if we can't
|
||
/// output.try_reserve(data.len())?;
|
||
///
|
||
/// // Now we know this can't OOM in the middle of our complex work
|
||
/// output.push_str(data);
|
||
///
|
||
/// Ok(output)
|
||
/// }
|
||
/// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?");
|
||
/// ```
|
||
#[stable(feature = "try_reserve", since = "1.57.0")]
|
||
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
||
self.vec.try_reserve(additional)
|
||
}
|
||
|
||
/// Tries to reserve the minimum capacity for at least `additional` bytes
|
||
/// more than the current length. Unlike [`try_reserve`], this will not
|
||
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
||
/// After calling `try_reserve_exact`, capacity will be greater than or
|
||
/// equal to `self.len() + additional` if it returns `Ok(())`.
|
||
/// Does nothing if the capacity is already sufficient.
|
||
///
|
||
/// Note that the allocator may give the collection more space than it
|
||
/// requests. Therefore, capacity can not be relied upon to be precisely
|
||
/// minimal. Prefer [`try_reserve`] if future insertions are expected.
|
||
///
|
||
/// [`try_reserve`]: String::try_reserve
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the capacity overflows, or the allocator reports a failure, then an error
|
||
/// is returned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::collections::TryReserveError;
|
||
///
|
||
/// fn process_data(data: &str) -> Result<String, TryReserveError> {
|
||
/// let mut output = String::new();
|
||
///
|
||
/// // Pre-reserve the memory, exiting if we can't
|
||
/// output.try_reserve_exact(data.len())?;
|
||
///
|
||
/// // Now we know this can't OOM in the middle of our complex work
|
||
/// output.push_str(data);
|
||
///
|
||
/// Ok(output)
|
||
/// }
|
||
/// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?");
|
||
/// ```
|
||
#[stable(feature = "try_reserve", since = "1.57.0")]
|
||
pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
||
self.vec.try_reserve_exact(additional)
|
||
}
|
||
|
||
/// Shrinks the capacity of this `String` to match its length.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.reserve(100);
|
||
/// assert!(s.capacity() >= 100);
|
||
///
|
||
/// s.shrink_to_fit();
|
||
/// assert_eq!(3, s.capacity());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn shrink_to_fit(&mut self) {
|
||
self.vec.shrink_to_fit()
|
||
}
|
||
|
||
/// Shrinks the capacity of this `String` with a lower bound.
|
||
///
|
||
/// The capacity will remain at least as large as both the length
|
||
/// and the supplied value.
|
||
///
|
||
/// If the current capacity is less than the lower limit, this is a no-op.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.reserve(100);
|
||
/// assert!(s.capacity() >= 100);
|
||
///
|
||
/// s.shrink_to(10);
|
||
/// assert!(s.capacity() >= 10);
|
||
/// s.shrink_to(0);
|
||
/// assert!(s.capacity() >= 3);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "shrink_to", since = "1.56.0")]
|
||
pub fn shrink_to(&mut self, min_capacity: usize) {
|
||
self.vec.shrink_to(min_capacity)
|
||
}
|
||
|
||
/// Appends the given [`char`] to the end of this `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abc");
|
||
///
|
||
/// s.push('1');
|
||
/// s.push('2');
|
||
/// s.push('3');
|
||
///
|
||
/// assert_eq!("abc123", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn push(&mut self, ch: char) {
|
||
match ch.len_utf8() {
|
||
1 => self.vec.push(ch as u8),
|
||
_ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()),
|
||
}
|
||
}
|
||
|
||
/// Returns a byte slice of this `String`'s contents.
|
||
///
|
||
/// The inverse of this method is [`from_utf8`].
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("hello");
|
||
///
|
||
/// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn as_bytes(&self) -> &[u8] {
|
||
&self.vec
|
||
}
|
||
|
||
/// Shortens this `String` to the specified length.
|
||
///
|
||
/// If `new_len` is greater than or equal to the string's current length, this has no
|
||
/// effect.
|
||
///
|
||
/// Note that this method has no effect on the allocated capacity
|
||
/// of the string
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `new_len` does not lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("hello");
|
||
///
|
||
/// s.truncate(2);
|
||
///
|
||
/// assert_eq!("he", s);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn truncate(&mut self, new_len: usize) {
|
||
if new_len <= self.len() {
|
||
assert!(self.is_char_boundary(new_len));
|
||
self.vec.truncate(new_len)
|
||
}
|
||
}
|
||
|
||
/// Removes the last character from the string buffer and returns it.
|
||
///
|
||
/// Returns [`None`] if this `String` is empty.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abč");
|
||
///
|
||
/// assert_eq!(s.pop(), Some('č'));
|
||
/// assert_eq!(s.pop(), Some('b'));
|
||
/// assert_eq!(s.pop(), Some('a'));
|
||
///
|
||
/// assert_eq!(s.pop(), None);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn pop(&mut self) -> Option<char> {
|
||
let ch = self.chars().rev().next()?;
|
||
let newlen = self.len() - ch.len_utf8();
|
||
unsafe {
|
||
self.vec.set_len(newlen);
|
||
}
|
||
Some(ch)
|
||
}
|
||
|
||
/// Removes a [`char`] from this `String` at a byte position and returns it.
|
||
///
|
||
/// This is an *O*(*n*) operation, as it requires copying every element in the
|
||
/// buffer.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `idx` is larger than or equal to the `String`'s length,
|
||
/// or if it does not lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abç");
|
||
///
|
||
/// assert_eq!(s.remove(0), 'a');
|
||
/// assert_eq!(s.remove(1), 'ç');
|
||
/// assert_eq!(s.remove(0), 'b');
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("delete", "take")]
|
||
pub fn remove(&mut self, idx: usize) -> char {
|
||
let ch = match self[idx..].chars().next() {
|
||
Some(ch) => ch,
|
||
None => panic!("cannot remove a char from the end of a string"),
|
||
};
|
||
|
||
let next = idx + ch.len_utf8();
|
||
let len = self.len();
|
||
unsafe {
|
||
ptr::copy(self.vec.as_ptr().add(next), self.vec.as_mut_ptr().add(idx), len - next);
|
||
self.vec.set_len(len - (next - idx));
|
||
}
|
||
ch
|
||
}
|
||
|
||
/// Remove all matches of pattern `pat` in the `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(string_remove_matches)]
|
||
/// let mut s = String::from("Trees are not green, the sky is not blue.");
|
||
/// s.remove_matches("not ");
|
||
/// assert_eq!("Trees are green, the sky is blue.", s);
|
||
/// ```
|
||
///
|
||
/// Matches will be detected and removed iteratively, so in cases where
|
||
/// patterns overlap, only the first pattern will be removed:
|
||
///
|
||
/// ```
|
||
/// #![feature(string_remove_matches)]
|
||
/// let mut s = String::from("banana");
|
||
/// s.remove_matches("ana");
|
||
/// assert_eq!("bna", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")]
|
||
pub fn remove_matches<'a, P>(&'a mut self, pat: P)
|
||
where
|
||
P: for<'x> Pattern<'x>,
|
||
{
|
||
use core::str::pattern::Searcher;
|
||
|
||
let rejections = {
|
||
let mut searcher = pat.into_searcher(self);
|
||
// Per Searcher::next:
|
||
//
|
||
// A Match result needs to contain the whole matched pattern,
|
||
// however Reject results may be split up into arbitrary many
|
||
// adjacent fragments. Both ranges may have zero length.
|
||
//
|
||
// In practice the implementation of Searcher::next_match tends to
|
||
// be more efficient, so we use it here and do some work to invert
|
||
// matches into rejections since that's what we want to copy below.
|
||
let mut front = 0;
|
||
let rejections: Vec<_> = from_fn(|| {
|
||
let (start, end) = searcher.next_match()?;
|
||
let prev_front = front;
|
||
front = end;
|
||
Some((prev_front, start))
|
||
})
|
||
.collect();
|
||
rejections.into_iter().chain(core::iter::once((front, self.len())))
|
||
};
|
||
|
||
let mut len = 0;
|
||
let ptr = self.vec.as_mut_ptr();
|
||
|
||
for (start, end) in rejections {
|
||
let count = end - start;
|
||
if start != len {
|
||
// SAFETY: per Searcher::next:
|
||
//
|
||
// The stream of Match and Reject values up to a Done will
|
||
// contain index ranges that are adjacent, non-overlapping,
|
||
// covering the whole haystack, and laying on utf8
|
||
// boundaries.
|
||
unsafe {
|
||
ptr::copy(ptr.add(start), ptr.add(len), count);
|
||
}
|
||
}
|
||
len += count;
|
||
}
|
||
|
||
unsafe {
|
||
self.vec.set_len(len);
|
||
}
|
||
}
|
||
|
||
/// Retains only the characters specified by the predicate.
|
||
///
|
||
/// In other words, remove all characters `c` such that `f(c)` returns `false`.
|
||
/// This method operates in place, visiting each character exactly once in the
|
||
/// original order, and preserves the order of the retained characters.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("f_o_ob_ar");
|
||
///
|
||
/// s.retain(|c| c != '_');
|
||
///
|
||
/// assert_eq!(s, "foobar");
|
||
/// ```
|
||
///
|
||
/// Because the elements are visited exactly once in the original order,
|
||
/// external state may be used to decide which elements to keep.
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abcde");
|
||
/// let keep = [false, true, true, false, true];
|
||
/// let mut iter = keep.iter();
|
||
/// s.retain(|_| *iter.next().unwrap());
|
||
/// assert_eq!(s, "bce");
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "string_retain", since = "1.26.0")]
|
||
pub fn retain<F>(&mut self, mut f: F)
|
||
where
|
||
F: FnMut(char) -> bool,
|
||
{
|
||
struct SetLenOnDrop<'a> {
|
||
s: &'a mut String,
|
||
idx: usize,
|
||
del_bytes: usize,
|
||
}
|
||
|
||
impl<'a> Drop for SetLenOnDrop<'a> {
|
||
fn drop(&mut self) {
|
||
let new_len = self.idx - self.del_bytes;
|
||
debug_assert!(new_len <= self.s.len());
|
||
unsafe { self.s.vec.set_len(new_len) };
|
||
}
|
||
}
|
||
|
||
let len = self.len();
|
||
let mut guard = SetLenOnDrop { s: self, idx: 0, del_bytes: 0 };
|
||
|
||
while guard.idx < len {
|
||
let ch =
|
||
// SAFETY: `guard.idx` is positive-or-zero and less that len so the `get_unchecked`
|
||
// is in bound. `self` is valid UTF-8 like string and the returned slice starts at
|
||
// a unicode code point so the `Chars` always return one character.
|
||
unsafe { guard.s.get_unchecked(guard.idx..len).chars().next().unwrap_unchecked() };
|
||
let ch_len = ch.len_utf8();
|
||
|
||
if !f(ch) {
|
||
guard.del_bytes += ch_len;
|
||
} else if guard.del_bytes > 0 {
|
||
// SAFETY: `guard.idx` is in bound and `guard.del_bytes` represent the number of
|
||
// bytes that are erased from the string so the resulting `guard.idx -
|
||
// guard.del_bytes` always represent a valid unicode code point.
|
||
//
|
||
// `guard.del_bytes` >= `ch.len_utf8()`, so taking a slice with `ch.len_utf8()` len
|
||
// is safe.
|
||
ch.encode_utf8(unsafe {
|
||
crate::slice::from_raw_parts_mut(
|
||
guard.s.as_mut_ptr().add(guard.idx - guard.del_bytes),
|
||
ch.len_utf8(),
|
||
)
|
||
});
|
||
}
|
||
|
||
// Point idx to the next char
|
||
guard.idx += ch_len;
|
||
}
|
||
|
||
drop(guard);
|
||
}
|
||
|
||
/// Inserts a character into this `String` at a byte position.
|
||
///
|
||
/// This is an *O*(*n*) operation as it requires copying every element in the
|
||
/// buffer.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `idx` is larger than the `String`'s length, or if it does not
|
||
/// lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(3);
|
||
///
|
||
/// s.insert(0, 'f');
|
||
/// s.insert(1, 'o');
|
||
/// s.insert(2, 'o');
|
||
///
|
||
/// assert_eq!("foo", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("set")]
|
||
pub fn insert(&mut self, idx: usize, ch: char) {
|
||
assert!(self.is_char_boundary(idx));
|
||
let mut bits = [0; 4];
|
||
let bits = ch.encode_utf8(&mut bits).as_bytes();
|
||
|
||
unsafe {
|
||
self.insert_bytes(idx, bits);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) {
|
||
let len = self.len();
|
||
let amt = bytes.len();
|
||
self.vec.reserve(amt);
|
||
|
||
unsafe {
|
||
ptr::copy(self.vec.as_ptr().add(idx), self.vec.as_mut_ptr().add(idx + amt), len - idx);
|
||
ptr::copy_nonoverlapping(bytes.as_ptr(), self.vec.as_mut_ptr().add(idx), amt);
|
||
self.vec.set_len(len + amt);
|
||
}
|
||
}
|
||
|
||
/// Inserts a string slice into this `String` at a byte position.
|
||
///
|
||
/// This is an *O*(*n*) operation as it requires copying every element in the
|
||
/// buffer.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `idx` is larger than the `String`'s length, or if it does not
|
||
/// lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("bar");
|
||
///
|
||
/// s.insert_str(0, "foo");
|
||
///
|
||
/// assert_eq!("foobar", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "insert_str", since = "1.16.0")]
|
||
pub fn insert_str(&mut self, idx: usize, string: &str) {
|
||
assert!(self.is_char_boundary(idx));
|
||
|
||
unsafe {
|
||
self.insert_bytes(idx, string.as_bytes());
|
||
}
|
||
}
|
||
|
||
/// Returns a mutable reference to the contents of this `String`.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This function is unsafe because the returned `&mut Vec` allows writing
|
||
/// bytes which are not valid UTF-8. If this constraint is violated, using
|
||
/// the original `String` after dropping the `&mut Vec` may violate memory
|
||
/// safety, as the rest of the standard library assumes that `String`s are
|
||
/// valid UTF-8.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("hello");
|
||
///
|
||
/// unsafe {
|
||
/// let vec = s.as_mut_vec();
|
||
/// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);
|
||
///
|
||
/// vec.reverse();
|
||
/// }
|
||
/// assert_eq!(s, "olleh");
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> {
|
||
&mut self.vec
|
||
}
|
||
|
||
/// Returns the length of this `String`, in bytes, not [`char`]s or
|
||
/// graphemes. In other words, it might not be what a human considers the
|
||
/// length of the string.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let a = String::from("foo");
|
||
/// assert_eq!(a.len(), 3);
|
||
///
|
||
/// let fancy_f = String::from("ƒoo");
|
||
/// assert_eq!(fancy_f.len(), 4);
|
||
/// assert_eq!(fancy_f.chars().count(), 3);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("length", "size")]
|
||
pub fn len(&self) -> usize {
|
||
self.vec.len()
|
||
}
|
||
|
||
/// Returns `true` if this `String` has a length of zero, and `false` otherwise.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut v = String::new();
|
||
/// assert!(v.is_empty());
|
||
///
|
||
/// v.push('a');
|
||
/// assert!(!v.is_empty());
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn is_empty(&self) -> bool {
|
||
self.len() == 0
|
||
}
|
||
|
||
/// Splits the string into two at the given byte index.
|
||
///
|
||
/// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and
|
||
/// the returned `String` contains bytes `[at, len)`. `at` must be on the
|
||
/// boundary of a UTF-8 code point.
|
||
///
|
||
/// Note that the capacity of `self` does not change.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last
|
||
/// code point of the string.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// # fn main() {
|
||
/// let mut hello = String::from("Hello, World!");
|
||
/// let world = hello.split_off(7);
|
||
/// assert_eq!(hello, "Hello, ");
|
||
/// assert_eq!(world, "World!");
|
||
/// # }
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "string_split_off", since = "1.16.0")]
|
||
#[must_use = "use `.truncate()` if you don't need the other half"]
|
||
pub fn split_off(&mut self, at: usize) -> String {
|
||
assert!(self.is_char_boundary(at));
|
||
let other = self.vec.split_off(at);
|
||
unsafe { String::from_utf8_unchecked(other) }
|
||
}
|
||
|
||
/// Truncates this `String`, removing all contents.
|
||
///
|
||
/// While this means the `String` will have a length of zero, it does not
|
||
/// touch its capacity.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.clear();
|
||
///
|
||
/// assert!(s.is_empty());
|
||
/// assert_eq!(0, s.len());
|
||
/// assert_eq!(3, s.capacity());
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn clear(&mut self) {
|
||
self.vec.clear()
|
||
}
|
||
|
||
/// Removes the specified range from the string in bulk, returning all
|
||
/// removed characters as an iterator.
|
||
///
|
||
/// The returned iterator keeps a mutable borrow on the string to optimize
|
||
/// its implementation.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the starting point or end point do not lie on a [`char`]
|
||
/// boundary, or if they're out of bounds.
|
||
///
|
||
/// # Leaking
|
||
///
|
||
/// If the returned iterator goes out of scope without being dropped (due to
|
||
/// [`core::mem::forget`], for example), the string may still contain a copy
|
||
/// of any drained characters, or may have lost characters arbitrarily,
|
||
/// including characters outside the range.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("α is alpha, β is beta");
|
||
/// let beta_offset = s.find('β').unwrap_or(s.len());
|
||
///
|
||
/// // Remove the range up until the β from the string
|
||
/// let t: String = s.drain(..beta_offset).collect();
|
||
/// assert_eq!(t, "α is alpha, ");
|
||
/// assert_eq!(s, "β is beta");
|
||
///
|
||
/// // A full range clears the string, like `clear()` does
|
||
/// s.drain(..);
|
||
/// assert_eq!(s, "");
|
||
/// ```
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
pub fn drain<R>(&mut self, range: R) -> Drain<'_>
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
// Memory safety
|
||
//
|
||
// The String version of Drain does not have the memory safety issues
|
||
// of the vector version. The data is just plain bytes.
|
||
// Because the range removal happens in Drop, if the Drain iterator is leaked,
|
||
// the removal will not happen.
|
||
let Range { start, end } = slice::range(range, ..self.len());
|
||
assert!(self.is_char_boundary(start));
|
||
assert!(self.is_char_boundary(end));
|
||
|
||
// Take out two simultaneous borrows. The &mut String won't be accessed
|
||
// until iteration is over, in Drop.
|
||
let self_ptr = self as *mut _;
|
||
// SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks.
|
||
let chars_iter = unsafe { self.get_unchecked(start..end) }.chars();
|
||
|
||
Drain { start, end, iter: chars_iter, string: self_ptr }
|
||
}
|
||
|
||
/// Removes the specified range in the string,
|
||
/// and replaces it with the given string.
|
||
/// The given string doesn't need to be the same length as the range.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the starting point or end point do not lie on a [`char`]
|
||
/// boundary, or if they're out of bounds.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("α is alpha, β is beta");
|
||
/// let beta_offset = s.find('β').unwrap_or(s.len());
|
||
///
|
||
/// // Replace the range up until the β from the string
|
||
/// s.replace_range(..beta_offset, "Α is capital alpha; ");
|
||
/// assert_eq!(s, "Α is capital alpha; β is beta");
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "splice", since = "1.27.0")]
|
||
pub fn replace_range<R>(&mut self, range: R, replace_with: &str)
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
// Memory safety
|
||
//
|
||
// Replace_range does not have the memory safety issues of a vector Splice.
|
||
// of the vector version. The data is just plain bytes.
|
||
|
||
// WARNING: Inlining this variable would be unsound (#81138)
|
||
let start = range.start_bound();
|
||
match start {
|
||
Included(&n) => assert!(self.is_char_boundary(n)),
|
||
Excluded(&n) => assert!(self.is_char_boundary(n + 1)),
|
||
Unbounded => {}
|
||
};
|
||
// WARNING: Inlining this variable would be unsound (#81138)
|
||
let end = range.end_bound();
|
||
match end {
|
||
Included(&n) => assert!(self.is_char_boundary(n + 1)),
|
||
Excluded(&n) => assert!(self.is_char_boundary(n)),
|
||
Unbounded => {}
|
||
};
|
||
|
||
// Using `range` again would be unsound (#81138)
|
||
// We assume the bounds reported by `range` remain the same, but
|
||
// an adversarial implementation could change between calls
|
||
unsafe { self.as_mut_vec() }.splice((start, end), replace_with.bytes());
|
||
}
|
||
|
||
/// Converts this `String` into a <code>[Box]<[str]></code>.
|
||
///
|
||
/// This will drop any excess capacity.
|
||
///
|
||
/// [str]: prim@str "str"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("hello");
|
||
///
|
||
/// let b = s.into_boxed_str();
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_str", since = "1.4.0")]
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[inline]
|
||
pub fn into_boxed_str(self) -> Box<str> {
|
||
let slice = self.vec.into_boxed_slice();
|
||
unsafe { from_boxed_utf8_unchecked(slice) }
|
||
}
|
||
|
||
/// Consumes and leaks the `String`, returning a mutable reference to the contents,
|
||
/// `&'a mut str`.
|
||
///
|
||
/// The caller has free choice over the returned lifetime, including `'static`. Indeed,
|
||
/// this function is ideally used for data that lives for the remainder of the program's life,
|
||
/// as dropping the returned reference will cause a memory leak.
|
||
///
|
||
/// It does not reallocate or shrink the `String`,
|
||
/// so the leaked allocation may include unused capacity that is not part
|
||
/// of the returned slice. If you don't want that, call [`into_boxed_str`],
|
||
/// and then [`Box::leak`].
|
||
///
|
||
/// [`into_boxed_str`]: Self::into_boxed_str
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let x = String::from("bucket");
|
||
/// let static_ref: &'static mut str = x.leak();
|
||
/// assert_eq!(static_ref, "bucket");
|
||
/// ```
|
||
#[stable(feature = "string_leak", since = "1.72.0")]
|
||
#[inline]
|
||
pub fn leak<'a>(self) -> &'a mut str {
|
||
let slice = self.vec.leak();
|
||
unsafe { from_utf8_unchecked_mut(slice) }
|
||
}
|
||
}
|
||
|
||
impl FromUtf8Error {
|
||
/// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let value = String::from_utf8(bytes);
|
||
///
|
||
/// assert_eq!(&[0, 159], value.unwrap_err().as_bytes());
|
||
/// ```
|
||
#[must_use]
|
||
#[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")]
|
||
pub fn as_bytes(&self) -> &[u8] {
|
||
&self.bytes[..]
|
||
}
|
||
|
||
/// Returns the bytes that were attempted to convert to a `String`.
|
||
///
|
||
/// This method is carefully constructed to avoid allocation. It will
|
||
/// consume the error, moving out the bytes, so that a copy of the bytes
|
||
/// does not need to be made.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let value = String::from_utf8(bytes);
|
||
///
|
||
/// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
|
||
/// ```
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn into_bytes(self) -> Vec<u8> {
|
||
self.bytes
|
||
}
|
||
|
||
/// Fetch a `Utf8Error` to get more details about the conversion failure.
|
||
///
|
||
/// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
|
||
/// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
|
||
/// an analogue to `FromUtf8Error`. See its documentation for more details
|
||
/// on using it.
|
||
///
|
||
/// [`std::str`]: core::str "std::str"
|
||
/// [`&str`]: prim@str "&str"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let error = String::from_utf8(bytes).unwrap_err().utf8_error();
|
||
///
|
||
/// // the first byte is invalid here
|
||
/// assert_eq!(1, error.valid_up_to());
|
||
/// ```
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn utf8_error(&self) -> Utf8Error {
|
||
self.error
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Display for FromUtf8Error {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt(&self.error, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Display for FromUtf16Error {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt("invalid utf-16: lone surrogate found", f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Error for FromUtf8Error {
|
||
#[allow(deprecated)]
|
||
fn description(&self) -> &str {
|
||
"invalid utf-8"
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Error for FromUtf16Error {
|
||
#[allow(deprecated)]
|
||
fn description(&self) -> &str {
|
||
"invalid utf-16"
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Clone for String {
|
||
fn clone(&self) -> Self {
|
||
String { vec: self.vec.clone() }
|
||
}
|
||
|
||
/// Clones the contents of `source` into `self`.
|
||
///
|
||
/// This method is preferred over simply assigning `source.clone()` to `self`,
|
||
/// as it avoids reallocation if possible.
|
||
fn clone_from(&mut self, source: &Self) {
|
||
self.vec.clone_from(&source.vec);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl FromIterator<char> for String {
|
||
fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_from_iter_by_ref", since = "1.17.0")]
|
||
impl<'a> FromIterator<&'a char> for String {
|
||
fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> FromIterator<&'a str> for String {
|
||
fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_string", since = "1.4.0")]
|
||
impl FromIterator<String> for String {
|
||
fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String {
|
||
let mut iterator = iter.into_iter();
|
||
|
||
// Because we're iterating over `String`s, we can avoid at least
|
||
// one allocation by getting the first string from the iterator
|
||
// and appending to it all the subsequent strings.
|
||
match iterator.next() {
|
||
None => String::new(),
|
||
Some(mut buf) => {
|
||
buf.extend(iterator);
|
||
buf
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_str2", since = "1.45.0")]
|
||
impl FromIterator<Box<str>> for String {
|
||
fn from_iter<I: IntoIterator<Item = Box<str>>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "herd_cows", since = "1.19.0")]
|
||
impl<'a> FromIterator<Cow<'a, str>> for String {
|
||
fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String {
|
||
let mut iterator = iter.into_iter();
|
||
|
||
// Because we're iterating over CoWs, we can (potentially) avoid at least
|
||
// one allocation by getting the first item and appending to it all the
|
||
// subsequent items.
|
||
match iterator.next() {
|
||
None => String::new(),
|
||
Some(cow) => {
|
||
let mut buf = cow.into_owned();
|
||
buf.extend(iterator);
|
||
buf
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Extend<char> for String {
|
||
fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) {
|
||
let iterator = iter.into_iter();
|
||
let (lower_bound, _) = iterator.size_hint();
|
||
self.reserve(lower_bound);
|
||
iterator.for_each(move |c| self.push(c));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, c: char) {
|
||
self.push(c);
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_reserve(&mut self, additional: usize) {
|
||
self.reserve(additional);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_ref", since = "1.2.0")]
|
||
impl<'a> Extend<&'a char> for String {
|
||
fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) {
|
||
self.extend(iter.into_iter().cloned());
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, &c: &'a char) {
|
||
self.push(c);
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_reserve(&mut self, additional: usize) {
|
||
self.reserve(additional);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> Extend<&'a str> for String {
|
||
fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(s));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, s: &'a str) {
|
||
self.push_str(s);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_str2", since = "1.45.0")]
|
||
impl Extend<Box<str>> for String {
|
||
fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(&s));
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_string", since = "1.4.0")]
|
||
impl Extend<String> for String {
|
||
fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(&s));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, s: String) {
|
||
self.push_str(&s);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "herd_cows", since = "1.19.0")]
|
||
impl<'a> Extend<Cow<'a, str>> for String {
|
||
fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(&s));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, s: Cow<'a, str>) {
|
||
self.push_str(&s);
|
||
}
|
||
}
|
||
|
||
/// A convenience impl that delegates to the impl for `&str`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(String::from("Hello world").find("world"), Some(6));
|
||
/// ```
|
||
#[unstable(
|
||
feature = "pattern",
|
||
reason = "API not fully fleshed out and ready to be stabilized",
|
||
issue = "27721"
|
||
)]
|
||
impl<'a, 'b> Pattern<'a> for &'b String {
|
||
type Searcher = <&'b str as Pattern<'a>>::Searcher;
|
||
|
||
fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher {
|
||
self[..].into_searcher(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_contained_in(self, haystack: &'a str) -> bool {
|
||
self[..].is_contained_in(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_prefix_of(self, haystack: &'a str) -> bool {
|
||
self[..].is_prefix_of(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> {
|
||
self[..].strip_prefix_of(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_suffix_of(self, haystack: &'a str) -> bool {
|
||
self[..].is_suffix_of(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> {
|
||
self[..].strip_suffix_of(haystack)
|
||
}
|
||
}
|
||
|
||
macro_rules! impl_eq {
|
||
($lhs:ty, $rhs: ty) => {
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[allow(unused_lifetimes)]
|
||
impl<'a, 'b> PartialEq<$rhs> for $lhs {
|
||
#[inline]
|
||
fn eq(&self, other: &$rhs) -> bool {
|
||
PartialEq::eq(&self[..], &other[..])
|
||
}
|
||
#[inline]
|
||
fn ne(&self, other: &$rhs) -> bool {
|
||
PartialEq::ne(&self[..], &other[..])
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[allow(unused_lifetimes)]
|
||
impl<'a, 'b> PartialEq<$lhs> for $rhs {
|
||
#[inline]
|
||
fn eq(&self, other: &$lhs) -> bool {
|
||
PartialEq::eq(&self[..], &other[..])
|
||
}
|
||
#[inline]
|
||
fn ne(&self, other: &$lhs) -> bool {
|
||
PartialEq::ne(&self[..], &other[..])
|
||
}
|
||
}
|
||
};
|
||
}
|
||
|
||
impl_eq! { String, str }
|
||
impl_eq! { String, &'a str }
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl_eq! { Cow<'a, str>, str }
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl_eq! { Cow<'a, str>, &'b str }
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl_eq! { Cow<'a, str>, String }
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Default for String {
|
||
/// Creates an empty `String`.
|
||
#[inline]
|
||
fn default() -> String {
|
||
String::new()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Display for String {
|
||
#[inline]
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Debug for String {
|
||
#[inline]
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl hash::Hash for String {
|
||
#[inline]
|
||
fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
|
||
(**self).hash(hasher)
|
||
}
|
||
}
|
||
|
||
/// Implements the `+` operator for concatenating two strings.
|
||
///
|
||
/// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if
|
||
/// necessary). This is done to avoid allocating a new `String` and copying the entire contents on
|
||
/// every operation, which would lead to *O*(*n*^2) running time when building an *n*-byte string by
|
||
/// repeated concatenation.
|
||
///
|
||
/// The string on the right-hand side is only borrowed; its contents are copied into the returned
|
||
/// `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Concatenating two `String`s takes the first by value and borrows the second:
|
||
///
|
||
/// ```
|
||
/// let a = String::from("hello");
|
||
/// let b = String::from(" world");
|
||
/// let c = a + &b;
|
||
/// // `a` is moved and can no longer be used here.
|
||
/// ```
|
||
///
|
||
/// If you want to keep using the first `String`, you can clone it and append to the clone instead:
|
||
///
|
||
/// ```
|
||
/// let a = String::from("hello");
|
||
/// let b = String::from(" world");
|
||
/// let c = a.clone() + &b;
|
||
/// // `a` is still valid here.
|
||
/// ```
|
||
///
|
||
/// Concatenating `&str` slices can be done by converting the first to a `String`:
|
||
///
|
||
/// ```
|
||
/// let a = "hello";
|
||
/// let b = " world";
|
||
/// let c = a.to_string() + b;
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Add<&str> for String {
|
||
type Output = String;
|
||
|
||
#[inline]
|
||
fn add(mut self, other: &str) -> String {
|
||
self.push_str(other);
|
||
self
|
||
}
|
||
}
|
||
|
||
/// Implements the `+=` operator for appending to a `String`.
|
||
///
|
||
/// This has the same behavior as the [`push_str`][String::push_str] method.
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "stringaddassign", since = "1.12.0")]
|
||
impl AddAssign<&str> for String {
|
||
#[inline]
|
||
fn add_assign(&mut self, other: &str) {
|
||
self.push_str(other);
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I> ops::Index<I> for String
|
||
where
|
||
I: slice::SliceIndex<str>,
|
||
{
|
||
type Output = I::Output;
|
||
|
||
#[inline]
|
||
fn index(&self, index: I) -> &I::Output {
|
||
index.index(self.as_str())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I> ops::IndexMut<I> for String
|
||
where
|
||
I: slice::SliceIndex<str>,
|
||
{
|
||
#[inline]
|
||
fn index_mut(&mut self, index: I) -> &mut I::Output {
|
||
index.index_mut(self.as_mut_str())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl ops::Deref for String {
|
||
type Target = str;
|
||
|
||
#[inline]
|
||
fn deref(&self) -> &str {
|
||
unsafe { str::from_utf8_unchecked(&self.vec) }
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "deref_pure_trait", issue = "87121")]
|
||
unsafe impl ops::DerefPure for String {}
|
||
|
||
#[stable(feature = "derefmut_for_string", since = "1.3.0")]
|
||
impl ops::DerefMut for String {
|
||
#[inline]
|
||
fn deref_mut(&mut self) -> &mut str {
|
||
unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
|
||
}
|
||
}
|
||
|
||
/// A type alias for [`Infallible`].
|
||
///
|
||
/// This alias exists for backwards compatibility, and may be eventually deprecated.
|
||
///
|
||
/// [`Infallible`]: core::convert::Infallible "convert::Infallible"
|
||
#[stable(feature = "str_parse_error", since = "1.5.0")]
|
||
pub type ParseError = core::convert::Infallible;
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl FromStr for String {
|
||
type Err = core::convert::Infallible;
|
||
#[inline]
|
||
fn from_str(s: &str) -> Result<String, Self::Err> {
|
||
Ok(String::from(s))
|
||
}
|
||
}
|
||
|
||
/// A trait for converting a value to a `String`.
|
||
///
|
||
/// This trait is automatically implemented for any type which implements the
|
||
/// [`Display`] trait. As such, `ToString` shouldn't be implemented directly:
|
||
/// [`Display`] should be implemented instead, and you get the `ToString`
|
||
/// implementation for free.
|
||
///
|
||
/// [`Display`]: fmt::Display
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "ToString")]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait ToString {
|
||
/// Converts the given value to a `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let i = 5;
|
||
/// let five = String::from("5");
|
||
///
|
||
/// assert_eq!(five, i.to_string());
|
||
/// ```
|
||
#[rustc_conversion_suggestion]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "to_string_method")]
|
||
fn to_string(&self) -> String;
|
||
}
|
||
|
||
/// # Panics
|
||
///
|
||
/// In this implementation, the `to_string` method panics
|
||
/// if the `Display` implementation returns an error.
|
||
/// This indicates an incorrect `Display` implementation
|
||
/// since `fmt::Write for String` never returns an error itself.
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: fmt::Display + ?Sized> ToString for T {
|
||
// A common guideline is to not inline generic functions. However,
|
||
// removing `#[inline]` from this method causes non-negligible regressions.
|
||
// See <https://github.com/rust-lang/rust/pull/74852>, the last attempt
|
||
// to try to remove it.
|
||
#[inline]
|
||
default fn to_string(&self) -> String {
|
||
let mut buf = String::new();
|
||
let mut formatter = core::fmt::Formatter::new(&mut buf);
|
||
// Bypass format_args!() to avoid write_str with zero-length strs
|
||
fmt::Display::fmt(self, &mut formatter)
|
||
.expect("a Display implementation returned an error unexpectedly");
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "ascii_char", issue = "110998")]
|
||
impl ToString for core::ascii::Char {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
self.as_str().to_owned()
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "char_to_string_specialization", since = "1.46.0")]
|
||
impl ToString for char {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
String::from(self.encode_utf8(&mut [0; 4]))
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "bool_to_string_specialization", since = "1.68.0")]
|
||
impl ToString for bool {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
String::from(if *self { "true" } else { "false" })
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "u8_to_string_specialization", since = "1.54.0")]
|
||
impl ToString for u8 {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
let mut buf = String::with_capacity(3);
|
||
let mut n = *self;
|
||
if n >= 10 {
|
||
if n >= 100 {
|
||
buf.push((b'0' + n / 100) as char);
|
||
n %= 100;
|
||
}
|
||
buf.push((b'0' + n / 10) as char);
|
||
n %= 10;
|
||
}
|
||
buf.push((b'0' + n) as char);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "i8_to_string_specialization", since = "1.54.0")]
|
||
impl ToString for i8 {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
let mut buf = String::with_capacity(4);
|
||
if self.is_negative() {
|
||
buf.push('-');
|
||
}
|
||
let mut n = self.unsigned_abs();
|
||
if n >= 10 {
|
||
if n >= 100 {
|
||
buf.push('1');
|
||
n -= 100;
|
||
}
|
||
buf.push((b'0' + n / 10) as char);
|
||
n %= 10;
|
||
}
|
||
buf.push((b'0' + n) as char);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
|
||
impl ToString for str {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
String::from(self)
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")]
|
||
impl ToString for Cow<'_, str> {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
self[..].to_owned()
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_to_string_specialization", since = "1.17.0")]
|
||
impl ToString for String {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
self.to_owned()
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "fmt_arguments_to_string_specialization", since = "1.71.0")]
|
||
impl ToString for fmt::Arguments<'_> {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
crate::fmt::format(*self)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl AsRef<str> for String {
|
||
#[inline]
|
||
fn as_ref(&self) -> &str {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "string_as_mut", since = "1.43.0")]
|
||
impl AsMut<str> for String {
|
||
#[inline]
|
||
fn as_mut(&mut self) -> &mut str {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl AsRef<[u8]> for String {
|
||
#[inline]
|
||
fn as_ref(&self) -> &[u8] {
|
||
self.as_bytes()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl From<&str> for String {
|
||
/// Converts a `&str` into a [`String`].
|
||
///
|
||
/// The result is allocated on the heap.
|
||
#[inline]
|
||
fn from(s: &str) -> String {
|
||
s.to_owned()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_mut_str_for_string", since = "1.44.0")]
|
||
impl From<&mut str> for String {
|
||
/// Converts a `&mut str` into a [`String`].
|
||
///
|
||
/// The result is allocated on the heap.
|
||
#[inline]
|
||
fn from(s: &mut str) -> String {
|
||
s.to_owned()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_ref_string", since = "1.35.0")]
|
||
impl From<&String> for String {
|
||
/// Converts a `&String` into a [`String`].
|
||
///
|
||
/// This clones `s` and returns the clone.
|
||
#[inline]
|
||
fn from(s: &String) -> String {
|
||
s.clone()
|
||
}
|
||
}
|
||
|
||
// note: test pulls in std, which causes errors here
|
||
#[cfg(not(test))]
|
||
#[stable(feature = "string_from_box", since = "1.18.0")]
|
||
impl From<Box<str>> for String {
|
||
/// Converts the given boxed `str` slice to a [`String`].
|
||
/// It is notable that the `str` slice is owned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s1: String = String::from("hello world");
|
||
/// let s2: Box<str> = s1.into_boxed_str();
|
||
/// let s3: String = String::from(s2);
|
||
///
|
||
/// assert_eq!("hello world", s3)
|
||
/// ```
|
||
fn from(s: Box<str>) -> String {
|
||
s.into_string()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_str", since = "1.20.0")]
|
||
impl From<String> for Box<str> {
|
||
/// Converts the given [`String`] to a boxed `str` slice that is owned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s1: String = String::from("hello world");
|
||
/// let s2: Box<str> = Box::from(s1);
|
||
/// let s3: String = String::from(s2);
|
||
///
|
||
/// assert_eq!("hello world", s3)
|
||
/// ```
|
||
fn from(s: String) -> Box<str> {
|
||
s.into_boxed_str()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_from_cow_str", since = "1.14.0")]
|
||
impl<'a> From<Cow<'a, str>> for String {
|
||
/// Converts a clone-on-write string to an owned
|
||
/// instance of [`String`].
|
||
///
|
||
/// This extracts the owned string,
|
||
/// clones the string if it is not already owned.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// // If the string is not owned...
|
||
/// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
|
||
/// // It will allocate on the heap and copy the string.
|
||
/// let owned: String = String::from(cow);
|
||
/// assert_eq!(&owned[..], "eggplant");
|
||
/// ```
|
||
fn from(s: Cow<'a, str>) -> String {
|
||
s.into_owned()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> From<&'a str> for Cow<'a, str> {
|
||
/// Converts a string slice into a [`Borrowed`] variant.
|
||
/// No heap allocation is performed, and the string
|
||
/// is not copied.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant"));
|
||
/// ```
|
||
///
|
||
/// [`Borrowed`]: crate::borrow::Cow::Borrowed "borrow::Cow::Borrowed"
|
||
#[inline]
|
||
fn from(s: &'a str) -> Cow<'a, str> {
|
||
Cow::Borrowed(s)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> From<String> for Cow<'a, str> {
|
||
/// Converts a [`String`] into an [`Owned`] variant.
|
||
/// No heap allocation is performed, and the string
|
||
/// is not copied.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// let s = "eggplant".to_string();
|
||
/// let s2 = "eggplant".to_string();
|
||
/// assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2));
|
||
/// ```
|
||
///
|
||
/// [`Owned`]: crate::borrow::Cow::Owned "borrow::Cow::Owned"
|
||
#[inline]
|
||
fn from(s: String) -> Cow<'a, str> {
|
||
Cow::Owned(s)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_from_string_ref", since = "1.28.0")]
|
||
impl<'a> From<&'a String> for Cow<'a, str> {
|
||
/// Converts a [`String`] reference into a [`Borrowed`] variant.
|
||
/// No heap allocation is performed, and the string
|
||
/// is not copied.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// let s = "eggplant".to_string();
|
||
/// assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant"));
|
||
/// ```
|
||
///
|
||
/// [`Borrowed`]: crate::borrow::Cow::Borrowed "borrow::Cow::Borrowed"
|
||
#[inline]
|
||
fn from(s: &'a String) -> Cow<'a, str> {
|
||
Cow::Borrowed(s.as_str())
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
|
||
impl<'a> FromIterator<char> for Cow<'a, str> {
|
||
fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> {
|
||
Cow::Owned(FromIterator::from_iter(it))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
|
||
impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> {
|
||
fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> {
|
||
Cow::Owned(FromIterator::from_iter(it))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
|
||
impl<'a> FromIterator<String> for Cow<'a, str> {
|
||
fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> {
|
||
Cow::Owned(FromIterator::from_iter(it))
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "from_string_for_vec_u8", since = "1.14.0")]
|
||
impl From<String> for Vec<u8> {
|
||
/// Converts the given [`String`] to a vector [`Vec`] that holds values of type [`u8`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s1 = String::from("hello world");
|
||
/// let v1 = Vec::from(s1);
|
||
///
|
||
/// for b in v1 {
|
||
/// println!("{b}");
|
||
/// }
|
||
/// ```
|
||
fn from(string: String) -> Vec<u8> {
|
||
string.into_bytes()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Write for String {
|
||
#[inline]
|
||
fn write_str(&mut self, s: &str) -> fmt::Result {
|
||
self.push_str(s);
|
||
Ok(())
|
||
}
|
||
|
||
#[inline]
|
||
fn write_char(&mut self, c: char) -> fmt::Result {
|
||
self.push(c);
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
/// A draining iterator for `String`.
|
||
///
|
||
/// This struct is created by the [`drain`] method on [`String`]. See its
|
||
/// documentation for more.
|
||
///
|
||
/// [`drain`]: String::drain
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
pub struct Drain<'a> {
|
||
/// Will be used as &'a mut String in the destructor
|
||
string: *mut String,
|
||
/// Start of part to remove
|
||
start: usize,
|
||
/// End of part to remove
|
||
end: usize,
|
||
/// Current remaining range to remove
|
||
iter: Chars<'a>,
|
||
}
|
||
|
||
#[stable(feature = "collection_debug", since = "1.17.0")]
|
||
impl fmt::Debug for Drain<'_> {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
f.debug_tuple("Drain").field(&self.as_str()).finish()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
unsafe impl Sync for Drain<'_> {}
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
unsafe impl Send for Drain<'_> {}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
impl Drop for Drain<'_> {
|
||
fn drop(&mut self) {
|
||
unsafe {
|
||
// Use Vec::drain. "Reaffirm" the bounds checks to avoid
|
||
// panic code being inserted again.
|
||
let self_vec = (*self.string).as_mut_vec();
|
||
if self.start <= self.end && self.end <= self_vec.len() {
|
||
self_vec.drain(self.start..self.end);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<'a> Drain<'a> {
|
||
/// Returns the remaining (sub)string of this iterator as a slice.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abc");
|
||
/// let mut drain = s.drain(..);
|
||
/// assert_eq!(drain.as_str(), "abc");
|
||
/// let _ = drain.next().unwrap();
|
||
/// assert_eq!(drain.as_str(), "bc");
|
||
/// ```
|
||
#[must_use]
|
||
#[stable(feature = "string_drain_as_str", since = "1.55.0")]
|
||
pub fn as_str(&self) -> &str {
|
||
self.iter.as_str()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "string_drain_as_str", since = "1.55.0")]
|
||
impl<'a> AsRef<str> for Drain<'a> {
|
||
fn as_ref(&self) -> &str {
|
||
self.as_str()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "string_drain_as_str", since = "1.55.0")]
|
||
impl<'a> AsRef<[u8]> for Drain<'a> {
|
||
fn as_ref(&self) -> &[u8] {
|
||
self.as_str().as_bytes()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
impl Iterator for Drain<'_> {
|
||
type Item = char;
|
||
|
||
#[inline]
|
||
fn next(&mut self) -> Option<char> {
|
||
self.iter.next()
|
||
}
|
||
|
||
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
self.iter.size_hint()
|
||
}
|
||
|
||
#[inline]
|
||
fn last(mut self) -> Option<char> {
|
||
self.next_back()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
impl DoubleEndedIterator for Drain<'_> {
|
||
#[inline]
|
||
fn next_back(&mut self) -> Option<char> {
|
||
self.iter.next_back()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "fused", since = "1.26.0")]
|
||
impl FusedIterator for Drain<'_> {}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_char_for_string", since = "1.46.0")]
|
||
impl From<char> for String {
|
||
/// Allocates an owned [`String`] from a single character.
|
||
///
|
||
/// # Example
|
||
/// ```rust
|
||
/// let c: char = 'a';
|
||
/// let s: String = String::from(c);
|
||
/// assert_eq!("a", &s[..]);
|
||
/// ```
|
||
#[inline]
|
||
fn from(c: char) -> Self {
|
||
c.to_string()
|
||
}
|
||
}
|