1 #include <sys/socket.h>
2 #include <arpa/inet.h>
3 #include <errno.h>
4 #include <stdio.h>
5 #include <string.h>
6
inet_ntop(int af,const void * restrict a0,char * restrict s,socklen_t l)7 const 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 /* The leading sequence of zeros (best==0) is
38 * disadvantaged compared to sequences elsewhere
39 * as it doesn't have a leading colon. One extra
40 * character is required for another sequence to
41 * beat it fairly. */
42 if (j>max+(best==0)) best=i, max=j;
43 }
44 if (max>3) {
45 buf[best] = buf[best+1] = ':';
46 memmove(buf+best+2, buf+best+max, i-best-max+1);
47 }
48 if (strlen(buf) < l) {
49 strcpy(s, buf);
50 return s;
51 }
52 break;
53 default:
54 errno = EAFNOSUPPORT;
55 return 0;
56 }
57 errno = ENOSPC;
58 return 0;
59 }
60