1#include <sys/socket.h>
2#include <arpa/inet.h>
3#include <errno.h>
4#include <stdio.h>
5#include <string.h>
6
7const char *inet_ntop(int af, const void *restrict a0, char *restrict s, socklen_t l)
8{
9	const unsigned char *a = a0;
10	int i, j, max, best;
11	char buf[100];
12
13	switch (af) {
14	case AF_INET:
15		if (snprintf(s, l, "%d.%d.%d.%d", a[0],a[1],a[2],a[3]) < l)
16			return s;
17		break;
18	case AF_INET6:
19		if (memcmp(a, "\0\0\0\0\0\0\0\0\0\0\377\377", 12))
20			snprintf(buf, sizeof buf,
21				"%x:%x:%x:%x:%x:%x:%x:%x",
22				256*a[0]+a[1],256*a[2]+a[3],
23				256*a[4]+a[5],256*a[6]+a[7],
24				256*a[8]+a[9],256*a[10]+a[11],
25				256*a[12]+a[13],256*a[14]+a[15]);
26		else
27			snprintf(buf, sizeof buf,
28				"%x:%x:%x:%x:%x:%x:%d.%d.%d.%d",
29				256*a[0]+a[1],256*a[2]+a[3],
30				256*a[4]+a[5],256*a[6]+a[7],
31				256*a[8]+a[9],256*a[10]+a[11],
32				a[12],a[13],a[14],a[15]);
33		/* Replace longest /(^0|:)[:0]{2,}/ with "::" */
34		for (i=best=0, max=2; buf[i]; i++) {
35			if (i && buf[i] != ':') continue;
36			j = strspn(buf+i, ":0");
37			if (j>max) best=i, max=j;
38		}
39		if (max>2) {
40			buf[best] = buf[best+1] = ':';
41			memmove(buf+best+2, buf+best+max, i-best-max+1);
42		}
43		if (strlen(buf) < l) {
44			strcpy(s, buf);
45			return s;
46		}
47		break;
48	default:
49		errno = EAFNOSUPPORT;
50		return 0;
51	}
52	errno = ENOSPC;
53	return 0;
54}
55