inet_pton.cpp

#ifdef _WIN32 // inet_pton is available from Vista only (based on inet_pton.c from wireshark)

#define NS_INADDRSZ_ 4
#define NS_IN6ADDRSZ_ 16
#define NS_INT16SZ_ 2

static int inet_pton4(const char *src, unsigned char *dst)
{
    char saw_digit = 0, octets = 0, ch;
    unsigned char tmp[NS_INADDRSZ_], *tp = tmp;
    *tp = 0;
    while ((ch = *src++) != '\0')
    {
        if (ch >= '0' && ch <= '9')
        {
            unsigned n = *tp * 10 + (ch - '0');
            if (n > 255)
                return 0;
            *tp = (unsigned char)n;
            if (!saw_digit)
            {
                if (++octets > 4)
                    return 0;
                saw_digit = 1;
            }
        }
        else if (ch == '.' && saw_digit)
        {
            if (octets == 4)
                return 0;
            *++tp = 0;
            saw_digit = 0;
        }
        else
            return 0;
    }
    if (octets < 4)
        return 0;
    memcpy(dst, tmp, NS_INADDRSZ_);
    return 1;
}

static bool nextHex(unsigned int& val, char c)
{
    if (c <= '9')
    {
        int ret = c - '0';
        if (ret >= 0)
        {
            val = val * 16 + ret;
            return true;
        }
    }
    else if ((c | ' ') <= 'f')
    {
        int ret = ((c | ' ') - 'a');
        if (ret >= 0)
        {
            val = val * 16 + 10 + ret;
            return true;
        }
    }
    return false;
}

static int inet_pton6(const char* src, unsigned char* dst)
{
    unsigned char tmp[NS_IN6ADDRSZ_] = { 0 }, *tp = tmp, *endp = tp + NS_IN6ADDRSZ_, *colonp = NULL;
    const char* curtok;
    char ch, saw_xdigit;
    unsigned int val;

    // Leading :: requires some special handling.
    if (*src == ':')
    {
        if (*++src != ':')
            return 0;
    }
    curtok = src;
    saw_xdigit = 0;
    val = 0;
    while ((ch = *src++) != '\0')
    {
        if (nextHex(val, ch))
        {
            if (val > 0xffff)
                return 0;
            saw_xdigit = 1;
            continue;
        }
        if (ch == ':')
        {
            curtok = src;
            if (!saw_xdigit)
            {
                if (colonp)
                    return 0;
                colonp = tp;
                continue;
            }
            else if (*src == '\0')
                return 0;
            if (tp + NS_INT16SZ_ > endp)
                return 0;
            *tp++ = (unsigned char)(val >> 8) & 0xff;
            *tp++ = (unsigned char)val & 0xff;
            saw_xdigit = 0;
            val = 0;
            continue;
        }
        if (ch == '.' && (tp + NS_INADDRSZ_) <= endp && inet_pton4(curtok, tp) > 0)
        {
            tp += NS_INADDRSZ_;
            saw_xdigit = 0;
            break;	// '\0' was seen by inet_pton4()
        }
        return 0;
    }
    if (saw_xdigit)
    {
        if (tp + NS_INT16SZ_ > endp)
            return 0;
        *tp++ = (unsigned char)(val >> 8) & 0xff;
        *tp++ = (unsigned char)val & 0xff;
    }
    if (colonp != NULL)
    {
        const int n = (int)(tp - colonp);
        if (tp == endp)
            return (0);
        for (int i = 1; i <= n; i++)
        {
            endp[-i] = colonp[n - i];
            colonp[n - i] = 0;
        }
        tp = endp;
    }
    if (tp != endp)
        return 0;
    memcpy(dst, tmp, NS_IN6ADDRSZ_);
    return 1;
}

#define inet_pton inet_pton_
int inet_pton_(int af, const char *src, void *dst)
{
    if (AF_INET == af)
        return inet_pton4(src, (unsigned char*)dst);
    else if (AF_INET6 == af)
        return inet_pton6(src, (unsigned char*)dst);
    else
    {
        WSASetLastError(EAFNOSUPPORT);
        return -1;
    }
}
#endif