inet_ntop.c raw

   1  #include <sys/socket.h>
   2  #include <arpa/inet.h>
   3  #include <errno.h>
   4  #include <stdio.h>
   5  #include <string.h>
   6  
   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  			if (j>max) best=i, max=j;
  38  		}
  39  		if (max>3) {
  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