Function CPLBase64Encode

port/cpl_base64.cpp:196–255

/** Base64 encode a buffer. */

char *CPLBase64Encode(int nDataLen, const GByte *pabyBytesToEncode)
{
    constexpr char base64Chars[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    const int kCharArray3Size = 3;
    const int kCharArray4Size = 4;
    unsigned char charArray3[kCharArray3Size] = {};

    std::string result("");
    int array3_idx = 0;
    while (nDataLen--)
    {
        charArray3[array3_idx++] = *(pabyBytesToEncode++);

        if (array3_idx == kCharArray3Size)
        {
            const unsigned char charArray4[kCharArray4Size] = {
                static_cast<unsigned char>((charArray3[0] & 0xfc) >> 2),
                static_cast<unsigned char>(((charArray3[0] & 0x03) << 4) +
                                           ((charArray3[1] & 0xf0) >> 4)),
                static_cast<unsigned char>(((charArray3[1] & 0x0f) << 2) +
                                           ((charArray3[2] & 0xc0) >> 6)),
                static_cast<unsigned char>(charArray3[2] & 0x3f)};

            for (int idx = 0; idx < kCharArray4Size; ++idx)
            {
                result += base64Chars[charArray4[idx]];
            }

            array3_idx = 0;
        }
    }

    if (array3_idx)
    {
        for (int idx = array3_idx; idx < kCharArray3Size; ++idx)
        {
            charArray3[idx] = '\0';
        }

        const unsigned char charArray4[kCharArray4Size] = {
            static_cast<unsigned char>((charArray3[0] & 0xfc) >> 2),
            static_cast<unsigned char>(((charArray3[0] & 0x03) << 4) +
                                       ((charArray3[1] & 0xf0) >> 4)),
            static_cast<unsigned char>(((charArray3[1] & 0x0f) << 2) +
                                       ((charArray3[2] & 0xc0) >> 6)),
            static_cast<unsigned char>(charArray3[2] & 0x3f)};

        for (int idx = 0; idx < (array3_idx + 1); ++idx)
        {
            result += base64Chars[charArray4[idx]];
        }

        while (array3_idx++ < kCharArray3Size)
            result += '=';
    }