lib/memcoll.c

   1 /* Locale-specific memory comparison.
   2    Copyright 1999, 2002 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Contributed by Paul Eggert <eggert@twinsun.com>.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include <errno.h>
  25 #ifndef errno
  26 extern int errno;
  27 #endif
  28
  29 #include <sys/types.h>
  30
  31 #if HAVE_STRING_H
  32 # include <string.h>
  33 #endif
  34
  35 /* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
  36    to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
  37    adjacent.  Temporarily modify the bytes after S1 and S2, but
  38    restore their original contents before returning.  Set errno to an
  39    error number if there is an error, and to zero otherwise.  */
  40 int
  41 memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
  42 {
  43   int diff;
  44   char n1 = s1[s1len];
  45   char n2 = s2[s2len];
  46
  47   s1[s1len++] = '\0';
  48   s2[s2len++] = '\0';
  49
  50   while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
  51     {
  52       /* strcoll found no difference, but perhaps it was fooled by NUL
  53          characters in the data.  Work around this problem by advancing
  54          past the NUL chars.  */
  55       size_t size1 = strlen (s1) + 1;
  56       size_t size2 = strlen (s2) + 1;
  57       s1 += size1;
  58       s2 += size2;
  59       s1len -= size1;
  60       s2len -= size2;
  61
  62       if (s1len == 0)
  63         {
  64           if (s2len != 0)
  65             diff = -1;
  66           break;
  67         }
  68       else if (s2len == 0)
  69         {
  70           diff = 1;
  71           break;
  72         }
  73     }
  74
  75   s1[s1len - 1] = n1;
  76   s2[s2len - 1] = n2;
  77
  78   return diff;
  79 }