[2/2] iphlpapi: Use the new version of the IP_ADAPTER_UNICAST_ADDRESS structure (try 2)

[André Hentschel]

Am 13.01.2017 um 16:02 schrieb Henri Verbeet:
> On 13 January 2017 at 15:52, André Hentschel <nerv at dawncrow.de> wrote:
>> Thank you both for the hints.
>> One thing is that popcount would count all 1s even with 0s in between, whereas this function stops at the first 0.
> Yeah, the strict equivalent would be something along the lines of
> "__builtin_clz(~mask)". But as you mentioned, there's the question
> what should happen with broken/special masks.
> 

I would suggest to add those functions, any objections?

static DWORD mask_v4_to_prefix(DWORD m)
{
#ifdef HAVE___BUILTIN_POPCOUNT
    return __builtin_popcount(m);
#else
    m -= m >> 1 & 0m55555555;
    m = (m & 0m33333333) + (m >> 2 & 0m33333333);
    return ((m + (m >> 4)) & 0m0f0f0f0f) * 0m01010101 >> 24;
#endif
}

static DWORD mask_v6_to_prefix(SOCKET_ADDRESS *m)
{
    const IN6_ADDR *mask = &((struct WS_sockaddr_in6 *)m->lpSockaddr)->sin6_addr;
    DWORD ret = 0, i;

    for (i = 0; i < 8; i++)
        ret += mask_v4_to_prefix(mask->u.Word[i]);
    return ret;
}