code.delx.au - gnu-emacs/blob - lib/c-strncasecmp.c

   1 /* c-strncasecmp.c -- case insensitive string comparator in C locale
   2    Copyright (C) 1998-1999, 2005-2006, 2009-2015 Free Software
   3    Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "c-strcase.h"
  22
  23 #include <limits.h>
  24
  25 #include "c-ctype.h"
  26
  27 int
  28 c_strncasecmp (const char *s1, const char *s2, size_t n)
  29 {
  30   register const unsigned char *p1 = (const unsigned char *) s1;
  31   register const unsigned char *p2 = (const unsigned char *) s2;
  32   unsigned char c1, c2;
  33
  34   if (p1 == p2 || n == 0)
  35     return 0;
  36
  37   do
  38     {
  39       c1 = c_tolower (*p1);
  40       c2 = c_tolower (*p2);
  41
  42       if (--n == 0 || c1 == '\0')
  43         break;
  44
  45       ++p1;
  46       ++p2;
  47     }
  48   while (c1 == c2);
  49
  50   if (UCHAR_MAX <= INT_MAX)
  51     return c1 - c2;
  52   else
  53     /* On machines where 'char' and 'int' are types of the same size, the
  54        difference of two 'unsigned char' values - including the sign bit -
  55        doesn't fit in an 'int'.  */
  56     return (c1 > c2 ? 1 : c1 < c2 ? -1 : 0);
  57 }