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my_inet_ntop.c

/*
 * Copyright (c) 1996-1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

#include "config.h"

#include <sys/types.h>
#include "my_inet_ntop.h"

#ifdef HAVE_INET_NTOP

#include <sys/socket.h>
#include <arpa/inet.h>

const char * my_inet_ntop(int af, const void *src, char*dst, size_t size)
{
      return inet_ntop(af,src,dst,size);
}

#else /* ! HAVE_INET_NTOP */

#if defined(LIBC_SCCS) && !defined(lint)
static const char rcsid[] = "$Id: my_inet_ntop.c,v 1.1 2002/07/23 03:29:32 riq Exp $";
#endif /* LIBC_SCCS and not lint */

/*#include "port_before.h"*/

#include <sys/param.h>
#include <sys/socket.h>

#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>

#include <errno.h>
#include <stdio.h>
#include <string.h>

/*#include "port_after.h"*/

#define NS_INT16SZ      2
#define NS_IN6ADDRSZ   16

#ifdef SPRINTF_CHAR
# define SPRINTF(x) strlen(sprintf/**/x)
#else
# define SPRINTF(x) ((size_t)sprintf x)
#endif

/*
 * WARNING: Don't even consider trying to compile this on a system where
 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
 */

static const char *inet_ntop4 __P((const u_char *src, char *dst, size_t size));
static const char *inet_ntop6 __P((const u_char *src, char *dst, size_t size));

/* char *
 * inet_ntop(af, src, dst, size)
 *    convert a network format address to presentation format.
 * return:
 *    pointer to presentation format address (`dst'), or NULL (see errno).
 * author:
 *    Paul Vixie, 1996.
 */
const char *
my_inet_ntop(af, src, dst, size)
      int af;
      const void *src;
      char *dst;
      size_t size;
{
      switch (af) {
      case AF_INET:
            return (inet_ntop4(src, dst, size));
      case AF_INET6:
            return (inet_ntop6(src, dst, size));
      default:
            errno = EAFNOSUPPORT;
            return (NULL);
      }
      /* NOTREACHED */
}

/* const char *
 * inet_ntop4(src, dst, size)
 *    format an IPv4 address
 * return:
 *    `dst' (as a const)
 * notes:
 *    (1) uses no statics
 *    (2) takes a u_char* not an in_addr as input
 * author:
 *    Paul Vixie, 1996.
 */
static const char *
inet_ntop4(src, dst, size)
      const u_char *src;
      char *dst;
      size_t size;
{
      static const char fmt[] = "%u.%u.%u.%u";
      char tmp[sizeof "255.255.255.255"];

      if (SPRINTF((tmp, fmt, src[0], src[1], src[2], src[3])) >= size) {
            errno = ENOSPC;
            return (NULL);
      }
      strcpy(dst, tmp);
      return (dst);
}

/* const char *
 * inet_ntop6(src, dst, size)
 *    convert IPv6 binary address into presentation (printable) format
 * author:
 *    Paul Vixie, 1996.
 */
static const char *
inet_ntop6(src, dst, size)
      const u_char *src;
      char *dst;
      size_t size;
{
      /*
       * Note that int32_t and int16_t need only be "at least" large enough
       * to contain a value of the specified size.  On some systems, like
       * Crays, there is no such thing as an integer variable with 16 bits.
       * Keep this in mind if you think this function should have been coded
       * to use pointer overlays.  All the world's not a VAX.
       */
      char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
      struct { int base, len; } best, cur;
      u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
      int i;

      /*
       * Preprocess:
       *    Copy the input (bytewise) array into a wordwise array.
       *    Find the longest run of 0x00's in src[] for :: shorthanding.
       */
      memset(words, '\0', sizeof words);
      for (i = 0; i < NS_IN6ADDRSZ; i++)
            words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
      best.base = -1;
      cur.base = -1;
      for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
            if (words[i] == 0) {
                  if (cur.base == -1)
                        cur.base = i, cur.len = 1;
                  else
                        cur.len++;
            } else {
                  if (cur.base != -1) {
                        if (best.base == -1 || cur.len > best.len)
                              best = cur;
                        cur.base = -1;
                  }
            }
      }
      if (cur.base != -1) {
            if (best.base == -1 || cur.len > best.len)
                  best = cur;
      }
      if (best.base != -1 && best.len < 2)
            best.base = -1;

      /*
       * Format the result.
       */
      tp = tmp;
      for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
            /* Are we inside the best run of 0x00's? */
            if (best.base != -1 && i >= best.base &&
                i < (best.base + best.len)) {
                  if (i == best.base)
                        *tp++ = ':';
                  continue;
            }
            /* Are we following an initial run of 0x00s or any real hex? */
            if (i != 0)
                  *tp++ = ':';
            /* Is this address an encapsulated IPv4? */
            if (i == 6 && best.base == 0 &&
                (best.len == 6 || (best.len == 5 && words[5] == 0xffff))) {
                  if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
                        return (NULL);
                  tp += strlen(tp);
                  break;
            }
            tp += SPRINTF((tp, "%x", words[i]));
      }
      /* Was it a trailing run of 0x00's? */
      if (best.base != -1 && (best.base + best.len) ==
          (NS_IN6ADDRSZ / NS_INT16SZ))
            *tp++ = ':';
      *tp++ = '\0';

      /*
       * Check for overflow, copy, and we're done.
       */
      if ((size_t)(tp - tmp) > size) {
            errno = ENOSPC;
            return (NULL);
      }
      strcpy(dst, tmp);
      return (dst);
}

#endif /* ! HAVE_INET_NTOP */

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