cocos-engine/native/cocos/base/base64.cpp

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 Copyright (c) 2017-2022 Xiamen Yaji Software Co., Ltd.

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#include "base/base64.h"

#include <cstdio>
#include <cstdlib>
#include <string>
#include <vector>

namespace cc {

std::string alphabet{"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"};

int doBase64Decode(const unsigned char *input, unsigned int inputLen, unsigned char *output, unsigned int *outputLen) {
    static std::vector<char> inalphabet(256);
    static std::vector<char> decoder(256);
    int                      i;
    int                      bits;
    int                      c = 0;
    int                      charCount;
    int                      errors    = 0;
    unsigned int             inputIdx  = 0;
    unsigned int             outputIdx = 0;
    int                      length    = static_cast<int>(alphabet.length());
    for (i = length - 1; i >= 0; i--) {
        inalphabet[alphabet[i]] = 1;
        decoder[alphabet[i]]    = i;
    }

    charCount = 0;
    bits      = 0;
    for (inputIdx = 0; inputIdx < inputLen; inputIdx++) {
        c = input[inputIdx];
        if (c == '=') {
            break;
        }

        if (c > 255 || !inalphabet[c]) {
            continue;
        }

        bits += decoder[c];
        ++charCount;
        if (charCount == 4) {
            output[outputIdx++] = (bits >> 16);
            output[outputIdx++] = ((bits >> 8) & 0xff);
            output[outputIdx++] = (bits & 0xff);
            bits                = 0;
            charCount           = 0;
        } else {
            bits <<= 6;
        }
    }

    if (c == '=') {
        switch (charCount) {
            case 1:
#if (CC_PLATFORM != CC_PLATFORM_BADA)
                fprintf(stderr, "base64Decode: encoding incomplete: at least 2 bits missing");
#endif
                ++errors;
                break;
            case 2:
                output[outputIdx++] = (bits >> 10);
                break;
            case 3:
                output[outputIdx++] = (bits >> 16);
                output[outputIdx++] = ((bits >> 8) & 0xff);
                break;
        }
    } else if (inputIdx < inputLen) {
        if (charCount) {
#if (CC_PLATFORM != CC_PLATFORM_BADA)
            fprintf(stderr, "base64 encoding incomplete: at least %d bits truncated",
                    ((4 - charCount) * 6));
#endif
            ++errors;
        }
    }

    *outputLen = outputIdx;
    return errors;
}

void doBase64Encode(const unsigned char *input, unsigned int inputLen, char *output) {
    unsigned int charCount;
    unsigned int bits;
    unsigned int inputIdx  = 0;
    unsigned int outputIdx = 0;

    charCount = 0;
    bits      = 0;
    for (inputIdx = 0; inputIdx < inputLen; inputIdx++) {
        bits |= input[inputIdx];

        charCount++;
        if (charCount == 3) {
            output[outputIdx++] = alphabet[(bits >> 18) & 0x3f];
            output[outputIdx++] = alphabet[(bits >> 12) & 0x3f];
            output[outputIdx++] = alphabet[(bits >> 6) & 0x3f];
            output[outputIdx++] = alphabet[bits & 0x3f];
            bits                = 0;
            charCount           = 0;
        } else {
            bits <<= 8;
        }
    }

    if (charCount) {
        if (charCount == 1) {
            bits <<= 8;
        }

        output[outputIdx++] = alphabet[(bits >> 18) & 0x3f];
        output[outputIdx++] = alphabet[(bits >> 12) & 0x3f];
        if (charCount > 1) {
            output[outputIdx++] = alphabet[(bits >> 6) & 0x3f];
        } else {
            output[outputIdx++] = '=';
        }
        output[outputIdx++] = '=';
    }

    output[outputIdx++] = 0;
}

int base64Decode(const unsigned char *in, unsigned int inLength, unsigned char **out) {
    unsigned int outLength = 0;

    //should be enough to store 6-bit buffers in 8-bit buffers
    *out = static_cast<unsigned char *>(malloc(inLength / 4 * 3 + 1));
    if (*out) {
        int ret = doBase64Decode(in, inLength, *out, &outLength);

        if (ret > 0) {
            free(*out);
            *out      = nullptr;
            outLength = 0;
        }
    }
    return static_cast<int>(outLength);
}

int base64Encode(const unsigned char *in, unsigned int inLength, char **out) {
    unsigned int outLength = (inLength + 2) / 3 * 4;

    //should be enough to store 8-bit buffers in 6-bit buffers
    *out = static_cast<char *>(malloc(outLength + 1));
    if (*out) {
        doBase64Encode(in, inLength, *out);
    }
    return static_cast<int>(outLength);
}

} // namespace cc