string/strcasecmp.c

   1 /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #ifdef HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include <ctype.h>
  23 #include <string.h>
  24
  25 #ifndef _LIBC
  26 # define __strcasecmp strcasecmp
  27 # define TOLOWER(Ch) tolower (Ch)
  28 #else
  29 # include <locale/localeinfo.h>
  30 # ifdef USE_IN_EXTENDED_LOCALE_MODEL
  31 #  define __strcasecmp __strcasecmp_l
  32 # endif
  33 # define TOLOWER(Ch) __tolower_l ((Ch), loc)
  34 #endif
  35
  36 #ifdef USE_IN_EXTENDED_LOCALE_MODEL
  37 # define LOCALE_PARAM , locale_t loc
  38 #else
  39 # define LOCALE_PARAM
  40 #endif
  41
  42 /* Compare S1 and S2, ignoring case, returning less than, equal to or
  43    greater than zero if S1 is lexicographically less than,
  44    equal to or greater than S2.  */
  45 int
  46 __strcasecmp (const char *s1, const char *s2 LOCALE_PARAM)
  47 {
  48 #if defined _LIBC && !defined USE_IN_EXTENDED_LOCALE_MODEL
  49   locale_t loc = _NL_CURRENT_LOCALE;
  50 #endif
  51   const unsigned char *p1 = (const unsigned char *) s1;
  52   const unsigned char *p2 = (const unsigned char *) s2;
  53   int result;
  54
  55   if (p1 == p2)
  56     return 0;
  57
  58   while ((result = TOLOWER (*p1) - TOLOWER (*p2++)) == 0)
  59     if (*p1++ == '\0')
  60       break;
  61
  62   return result;
  63 }
  64 #ifndef __strcasecmp
  65 libc_hidden_def (__strcasecmp)
  66 weak_alias (__strcasecmp, strcasecmp)
  67 #endif