Function punycode_status punycode_decode

src/rustDemangle.cpp:298–390

#define SMALL_PUNYCODE_LEN 128

static NODISCARD punycode_status punycode_decode(const char *start, size_t ascii_len, const char *punycode_start, size_t punycode_len, uint32_t (*out_)[SMALL_PUNYCODE_LEN], size_t *out_len) {
    uint32_t *out = *out_;

    if (punycode_len == 0) {
        return PunycodeError;
    }

    if (ascii_len > SMALL_PUNYCODE_LEN) {
        return PunycodeError;
    }
    for (size_t i = 0; i < ascii_len; i++) {
        out[i] = start[i];
    }
    size_t len = ascii_len;

    size_t base = 36, t_min = 1, t_max = 26, skew = 38, damp = 700, bias = 72, i = 0, n = 0x80;
    for (;;) {
        size_t delta = 0, w = 1, k = 0;
        for (;;) {
            k += base;
            size_t biased = k < bias ? 0 : k - bias;
            size_t t = MIN(MAX(biased, t_min), t_max);
            size_t d;
            if (punycode_len == 0) {
                return PunycodeError;
            }
            char nx = *punycode_start++;
            punycode_len--;
            if ('a' <= nx && nx <= 'z') {
                d = nx - 'a';
            } else if ('0' <= nx && nx <= '9') {
                d = 26 + (nx - '0');
            } else {
                return PunycodeError;
            }
            if (w == 0 || d > SIZE_MAX / w || d*w > SIZE_MAX - delta) {
                return PunycodeError;
            }
            delta += d * w;
            if (d < t) {
                break;
            }
            if (base < t || w == 0 || (base - t) > SIZE_MAX / w) {
                return PunycodeError;
            }
            w *= (base - t);
        }

        len += 1;
        if (i > SIZE_MAX - delta) {
            return PunycodeError;
        }
        i += delta;
        if (n > SIZE_MAX - i / len) {
            return PunycodeError;
        }
        n += i / len;
        i %= len;