/* $Id: inet_ntop.c,v 1.12 2009-11-02 11:55:54 yangtse Exp $ */

/* Copyright (c) 1996 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 "ares_setup.h"

#ifdef HAVE_SYS_SOCKET_H
#  include <sys/socket.h>
#endif
#ifdef HAVE_NETINET_IN_H
#  include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#  include <arpa/inet.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#  include <arpa/nameser.h>
#else
#  include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#  include <arpa/nameser_compat.h>
#endif

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

#include "ares_ipv6.h"
#include "inet_ntop.h"


#ifndef HAVE_INET_NTOP

#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(const unsigned char *src, char *dst, size_t size);
static const char *inet_ntop6(const unsigned 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).
 * note:
 *      On Windows we store the error in the thread errno, not
 *      in the winsock error code. This is to avoid loosing the
 *      actual last winsock error. So use macro ERRNO to fetch the
 *      errno this funtion sets when returning NULL, not SOCKERRNO.
 * author:
 *     Paul Vixie, 1996.
 */
const char *
ares_inet_ntop(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:
      SET_ERRNO(EAFNOSUPPORT);
      return (NULL);
    }
  /* NOTREACHED */
}

/* const char *
 * inet_ntop4(src, dst, size)
 *     format an IPv4 address, more or less like inet_ntoa()
 * return:
 *     `dst' (as a const)
 * notes:
 *     (1) uses no statics
 *     (2) takes a unsigned char* not an in_addr as input
 * author:
 *     Paul Vixie, 1996.
 */
static const char *
inet_ntop4(const unsigned 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)
    {
      SET_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(const unsigned 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")];
  char *tp;
  struct {
    long base;
    long len;
  } best, cur;
  unsigned long 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;
  best.len = 0;
  cur.len = 0;

  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, "%lx", 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)
    {
      SET_ERRNO(ENOSPC);
      return (NULL);
    }
  strcpy(dst, tmp);
  return (dst);
}
#endif