ByteBuffer AlibabaCloud::OSS::Base64Decode()

in sdk/src/utils/Utils.cc [221:264]

• 40 lines of code
• 17 McCabe index (conditional complexity)

ByteBuffer AlibabaCloud::OSS::Base64Decode(const char *data, int len)
{
    int in_len = len;
    int i = 0;
    int in_ = 0;
    unsigned char part4[4];

    const int max_len = (len * 3 / 4);
    ByteBuffer ret(max_len);
    int idx = 0;

    while (in_len-- && (data[in_] != '=')) {
        unsigned char ch = data[in_++];
        if ('A' <= ch && ch <= 'Z')  ch = ch - 'A';           // A - Z
        else if ('a' <= ch && ch <= 'z') ch = ch - 'a' + 26;  // a - z
        else if ('0' <= ch && ch <= '9') ch = ch - '0' + 52;  // 0 - 9
        else if ('+' == ch) ch = 62;                          // +
        else if ('/' == ch) ch = 63;                          // /
        else if ('=' == ch) ch = 64;                          // =
        else ch = 0xff;                                       // something wrong
        part4[i++] = ch;
        if (i == 4) {
            ret[idx++] = (part4[0] << 2) + ((part4[1] & 0x30) >> 4);
            ret[idx++] = ((part4[1] & 0xf) << 4) + ((part4[2] & 0x3c) >> 2);
            ret[idx++] = ((part4[2] & 0x3) << 6) + part4[3];
            i = 0;
        }
    }

    if (i) {
        for (int j = i; j < 4; j++)
            part4[j] = 0xFF;
        ret[idx++] = (part4[0] << 2) + ((part4[1] & 0x30) >> 4);
        if (part4[2] != 0xFF) {
            ret[idx++] = ((part4[1] & 0xf) << 4) + ((part4[2] & 0x3c) >> 2);
            if (part4[3] != 0xFF) {
                ret[idx++] = ((part4[2] & 0x3) << 6) + part4[3];
            }
        }
    }

    ret.resize(idx);
    return ret;
}