lib/strcasecmp.c

   1 /* strcasecmp.c -- case insensitive string comparator
   2    Copyright (C) 1998, 1999 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 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #ifdef LENGTH_LIMIT
  23 # define STRXCASECMP_FUNCTION strncasecmp
  24 # define STRXCASECMP_DECLARE_N , size_t n
  25 # define LENGTH_LIMIT_EXPR(Expr) Expr
  26 #else
  27 # define STRXCASECMP_FUNCTION strcasecmp
  28 # define STRXCASECMP_DECLARE_N /* empty */
  29 # define LENGTH_LIMIT_EXPR(Expr) 0
  30 #endif
  31
  32 #include <stddef.h>
  33 #include <ctype.h>
  34
  35 #define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
  36
  37 /* Compare {{no more than N characters of }}strings S1 and S2,
  38    ignoring case, returning less than, equal to or
  39    greater than zero if S1 is lexicographically less
  40    than, equal to or greater than S2.  */
  41
  42 int
  43 STRXCASECMP_FUNCTION (const char *s1, const char *s2 STRXCASECMP_DECLARE_N)
  44 {
  45   register const unsigned char *p1 = (const unsigned char *) s1;
  46   register const unsigned char *p2 = (const unsigned char *) s2;
  47   unsigned char c1, c2;
  48
  49   if (p1 == p2 || LENGTH_LIMIT_EXPR (n == 0))
  50     return 0;
  51
  52   do
  53     {
  54       c1 = TOLOWER (*p1);
  55       c2 = TOLOWER (*p2);
  56
  57       if (LENGTH_LIMIT_EXPR (--n == 0) || c1 == '\0')
  58         break;
  59
  60       ++p1;
  61       ++p2;
  62     }
  63   while (c1 == c2);
  64
  65   return c1 - c2;
  66 }