string/strncase.c

   1 /* Compare at most N characters of two strings without taking care for
   2    the case.
   3    Copyright (C) 1992-2023 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #ifdef HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include <string.h>
  25 #include <ctype.h>
  26
  27 #ifndef weak_alias
  28 # define __strncasecmp strncasecmp
  29 # define TOLOWER(Ch) tolower (Ch)
  30 #else
  31 # include <locale/localeinfo.h>
  32 # ifdef USE_IN_EXTENDED_LOCALE_MODEL
  33 #  define __strncasecmp __strncasecmp_l
  34 # endif
  35 # define TOLOWER(Ch) __tolower_l ((Ch), loc)
  36 #endif
  37
  38 #ifdef USE_IN_EXTENDED_LOCALE_MODEL
  39 # define LOCALE_PARAM , locale_t loc
  40 #else
  41 # define LOCALE_PARAM
  42 #endif
  43
  44 /* Compare no more than N characters of S1 and S2,
  45    ignoring case, returning less than, equal to or
  46    greater than zero if S1 is lexicographically less
  47    than, equal to or greater than S2.  */
  48 int
  49 __strncasecmp (const char *s1, const char *s2, size_t n LOCALE_PARAM)
  50 {
  51 #if defined _LIBC && !defined USE_IN_EXTENDED_LOCALE_MODEL
  52   locale_t loc = _NL_CURRENT_LOCALE;
  53 #endif
  54   const unsigned char *p1 = (const unsigned char *) s1;
  55   const unsigned char *p2 = (const unsigned char *) s2;
  56   int result;
  57
  58   if (p1 == p2 || n == 0)
  59     return 0;
  60
  61   while ((result = TOLOWER (*p1) - TOLOWER (*p2++)) == 0)
  62     if (*p1++ == '\0' || --n == 0)
  63       break;
  64
  65   return result;
  66 }
  67 #ifndef __strncasecmp
  68 weak_alias (__strncasecmp, strncasecmp)
  69 #endif