Update.
[glibc.git] / resolv / inet_ntop.c
blobbbdabd0fe00862c61e12edaa21165644cad99d35
1 /* Copyright (c) 1996 by Internet Software Consortium.
3 * Permission to use, copy, modify, and distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
7 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
8 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
9 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
10 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
11 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
12 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
13 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
14 * SOFTWARE.
17 #if defined(LIBC_SCCS) && !defined(lint)
18 static char rcsid[] = "$Id$";
19 #endif /* LIBC_SCCS and not lint */
21 #include <sys/param.h>
22 #include <sys/types.h>
23 #include <sys/socket.h>
24 #include <netinet/in.h>
25 #include <arpa/inet.h>
26 #include <arpa/nameser.h>
27 #include <string.h>
28 #include <errno.h>
29 #include <stdio.h>
30 #include "../conf/portability.h"
32 #ifdef SPRINTF_CHAR
33 # define SPRINTF(x) strlen(sprintf/**/x)
34 #else
35 # define SPRINTF(x) ((size_t)sprintf x)
36 #endif
39 * WARNING: Don't even consider trying to compile this on a system where
40 * sizeof(int) < 4. sizeof(int) > 4 is fine; all the world's not a VAX.
43 static const char *inet_ntop4 __P((const u_char *src, char *dst, size_t size));
44 static const char *inet_ntop6 __P((const u_char *src, char *dst, size_t size));
46 /* char *
47 * inet_ntop(af, src, dst, size)
48 * convert a network format address to presentation format.
49 * return:
50 * pointer to presentation format address (`dst'), or NULL (see errno).
51 * author:
52 * Paul Vixie, 1996.
54 const char *
55 inet_ntop(af, src, dst, size)
56 int af;
57 const void *src;
58 char *dst;
59 size_t size;
61 switch (af) {
62 case AF_INET:
63 return (inet_ntop4(src, dst, size));
64 case AF_INET6:
65 return (inet_ntop6(src, dst, size));
66 default:
67 __set_errno (EAFNOSUPPORT);
68 return (NULL);
70 /* NOTREACHED */
73 /* const char *
74 * inet_ntop4(src, dst, size)
75 * format an IPv4 address, more or less like inet_ntoa()
76 * return:
77 * `dst' (as a const)
78 * notes:
79 * (1) uses no statics
80 * (2) takes a u_char* not an in_addr as input
81 * author:
82 * Paul Vixie, 1996.
84 static const char *
85 inet_ntop4(src, dst, size)
86 const u_char *src;
87 char *dst;
88 size_t size;
90 static const char fmt[] = "%u.%u.%u.%u";
91 char tmp[sizeof "255.255.255.255"];
93 if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) > size) {
94 __set_errno (ENOSPC);
95 return (NULL);
97 strcpy(dst, tmp);
98 return (dst);
101 /* const char *
102 * inet_ntop6(src, dst, size)
103 * convert IPv6 binary address into presentation (printable) format
104 * author:
105 * Paul Vixie, 1996.
107 static const char *
108 inet_ntop6(src, dst, size)
109 const u_char *src;
110 char *dst;
111 size_t size;
114 * Note that int32_t and int16_t need only be "at least" large enough
115 * to contain a value of the specified size. On some systems, like
116 * Crays, there is no such thing as an integer variable with 16 bits.
117 * Keep this in mind if you think this function should have been coded
118 * to use pointer overlays. All the world's not a VAX.
120 char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
121 struct { int base, len; } best, cur;
122 u_int words[IN6ADDRSZ / INT16SZ];
123 int i;
126 * Preprocess:
127 * Copy the input (bytewise) array into a wordwise array.
128 * Find the longest run of 0x00's in src[] for :: shorthanding.
130 memset(words, '\0', sizeof words);
131 for (i = 0; i < IN6ADDRSZ; i++)
132 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
133 best.base = -1;
134 cur.base = -1;
135 for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
136 if (words[i] == 0) {
137 if (cur.base == -1)
138 cur.base = i, cur.len = 1;
139 else
140 cur.len++;
141 } else {
142 if (cur.base != -1) {
143 if (best.base == -1 || cur.len > best.len)
144 best = cur;
145 cur.base = -1;
149 if (cur.base != -1) {
150 if (best.base == -1 || cur.len > best.len)
151 best = cur;
153 if (best.base != -1 && best.len < 2)
154 best.base = -1;
157 * Format the result.
159 tp = tmp;
160 for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
161 /* Are we inside the best run of 0x00's? */
162 if (best.base != -1 && i >= best.base &&
163 i < (best.base + best.len)) {
164 if (i == best.base)
165 *tp++ = ':';
166 continue;
168 /* Are we following an initial run of 0x00s or any real hex? */
169 if (i != 0)
170 *tp++ = ':';
171 /* Is this address an encapsulated IPv4? */
172 if (i == 6 && best.base == 0 &&
173 (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
174 if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
175 return (NULL);
176 tp += strlen(tp);
177 break;
179 tp += SPRINTF((tp, "%x", words[i]));
181 /* Was it a trailing run of 0x00's? */
182 if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
183 *tp++ = ':';
184 *tp++ = '\0';
187 * Check for overflow, copy, and we're done.
189 if ((size_t)(tp - tmp) > size) {
190 __set_errno (ENOSPC);
191 return (NULL);
193 strcpy(dst, tmp);
194 return (dst);