/* Locale-specific memory comparison.

   Copyright (C) 1999, 2002-2004, 2006, 2009-2010 Free Software Foundation,
   Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Contributed by Paul Eggert <eggert@twinsun.com>.  */

#include <config.h>

#include "memcoll.h"

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

/* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
   to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
   adjacent.  Perhaps temporarily modify the bytes after S1 and S2,
   but restore their original contents before returning.  Set errno to an
   error number if there is an error, and to zero otherwise.  */
int
memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
{
  int diff;

#if HAVE_STRCOLL

  /* strcoll is slow on many platforms, so check for the common case
     where the arguments are bytewise equal.  Otherwise, walk through
     the buffers using strcoll on each substring.  */

  if (s1len == s2len && memcmp (s1, s2, s1len) == 0)
    {
      errno = 0;
      diff = 0;
    }
  else
    {
      char n1 = s1[s1len];
      char n2 = s2[s2len];

      s1[s1len++] = '\0';
      s2[s2len++] = '\0';

      while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
        {
          /* strcoll found no difference, but perhaps it was fooled by NUL
             characters in the data.  Work around this problem by advancing
             past the NUL chars.  */
          size_t size1 = strlen (s1) + 1;
          size_t size2 = strlen (s2) + 1;
          s1 += size1;
          s2 += size2;
          s1len -= size1;
          s2len -= size2;

          if (s1len == 0)
            {
              if (s2len != 0)
                diff = -1;
              break;
            }
          else if (s2len == 0)
            {
              diff = 1;
              break;
            }
        }

      s1[s1len - 1] = n1;
      s2[s2len - 1] = n2;
    }

#else

  diff = memcmp (s1, s2, s1len < s2len ? s1len : s2len);
  if (! diff)
    diff = s1len < s2len ? -1 : s1len != s2len;
  errno = 0;

#endif

  return diff;
}