#include <features.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#if __GNUC__ < 4
#define restrict
#endif

const char *__inet_ntop(int af, const void *restrict a0, char *restrict s, socklen_t l)
{
        const unsigned char *a = a0;
        int i, j, max, best;
        char buf[100];

        switch (af) {
        case AF_INET:
                if (snprintf(s, l, "%d.%d.%d.%d", a[0],a[1],a[2],a[3]) < l)
                        return s;
                break;
        case AF_INET6:
                if (memcmp(a, "\0\0\0\0\0\0\0\0\0\0\377\377", 12))
                        snprintf(buf, sizeof buf,
                                "%x:%x:%x:%x:%x:%x:%x:%x",
                                256*a[0]+a[1],256*a[2]+a[3],
                                256*a[4]+a[5],256*a[6]+a[7],
                                256*a[8]+a[9],256*a[10]+a[11],
                                256*a[12]+a[13],256*a[14]+a[15]);
                else
                        snprintf(buf, sizeof buf,
                                "%x:%x:%x:%x:%x:%x:%d.%d.%d.%d",
                                256*a[0]+a[1],256*a[2]+a[3],
                                256*a[4]+a[5],256*a[6]+a[7],
                                256*a[8]+a[9],256*a[10]+a[11],
                                a[12],a[13],a[14],a[15]);
                /* Replace longest /(^0|:)[:0]{2,}/ with "::" */
                for (i=best=0, max=2; buf[i]; i++) {
                        if (i && buf[i] != ':') continue;
                        j = strspn(buf+i, ":0");
                        if (j>max) best=i, max=j;
                }
                if (max>3) {
                        buf[best] = buf[best+1] = ':';
                        memmove(buf+best+2, buf+best+max, i-best-max+1);
                }
                if (strlen(buf) < l) {
                        strcpy(s, buf);
                        return s;
                }
                break;
        default:
                errno = EAFNOSUPPORT;
                return 0;
        }
        errno = ENOSPC;
        return 0;
}

weak_alias(__inet_ntop, inet_ntop);