tkislan / base64 Goto Github PK

size_t DecodedLength(const char *str, size_t len)
{
    size_t numEq = 0;
    size_t size = 0;

    for (size_t i = 0; i < len; i++) {
        char ch = str[i];
        if (ch == '\n' || ch == '\r')
            continue;

        if (ch == '=')
            numEq++;

        size++;
    }

    return ((6 * size) / 8) - numEq;
}

bool Decode(const char *str, size_t len, std::string &out)
{
    int i = 0, j = 0;
    size_t dec_len = 0;
    unsigned char a3[3];
    unsigned char a4[4];

    out.resize(DecodedLength(str, len));

    while (len--) {
        char ch = *str;
        if (ch == '=') {
            break;
        }

        if (ch == '\n' || ch == '\r') {
            str++;
            continue;
        }

        a4[i++] = *(str++);
        if (i == 4) {
            for (i = 0; i < 4; i++) {
                a4[i] = b64_lookup(a4[i]);
            }

            a4_to_a3(a3, a4);

            for (i = 0; i < 3; i++) {
                out[dec_len++] = a3[i];
            }

            i = 0;
        }
    }

    if (i) {
        for (j = i; j < 4; j++) {
            a4[j] = '\0';
        }

        for (j = 0; j < 4; j++) {
            a4[j] = b64_lookup(a4[j]);
        }

        a4_to_a3(a3, a4);

        for (j = 0; j < i - 1; j++) {
            out[dec_len++] = a3[j];
        }
    }

    return (dec_len == out.size());
}