lib/strcasecmp.c

   1 /* Case-insensitive string comparison function.
   2    Copyright (C) 1998-1999, 2005-2006 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2005,
   4    based on earlier glibc code.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program 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
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include "strcase.h"
  24
  25 #include <ctype.h>
  26 #include <limits.h>
  27
  28 #if HAVE_MBRTOWC
  29 # include "mbuiter.h"
  30 #endif
  31
  32 #define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
  33
  34 /* Compare strings S1 and S2, ignoring case, returning less than, equal to or
  35    greater than zero if S1 is lexicographically less than, equal to or greater
  36    than S2.
  37    Note: This function may, in multibyte locales, return 0 for strings of
  38    different lengths!  */
  39 int
  40 strcasecmp (const char *s1, const char *s2)
  41 {
  42   if (s1 == s2)
  43     return 0;
  44
  45   /* Be careful not to look at the entire extent of s1 or s2 until needed.
  46      This is useful because when two strings differ, the difference is
  47      most often already in the very few first characters.  */
  48 #if HAVE_MBRTOWC
  49   if (MB_CUR_MAX > 1)
  50     {
  51       mbui_iterator_t iter1;
  52       mbui_iterator_t iter2;
  53
  54       mbui_init (iter1, s1);
  55       mbui_init (iter2, s2);
  56
  57       while (mbui_avail (iter1) && mbui_avail (iter2))
  58         {
  59           int cmp = mb_casecmp (mbui_cur (iter1), mbui_cur (iter2));
  60
  61           if (cmp != 0)
  62             return cmp;
  63
  64           mbui_advance (iter1);
  65           mbui_advance (iter2);
  66         }
  67       if (mbui_avail (iter1))
  68         /* s2 terminated before s1.  */
  69         return 1;
  70       if (mbui_avail (iter2))
  71         /* s1 terminated before s2.  */
  72         return -1;
  73       return 0;
  74     }
  75   else
  76 #endif
  77     {
  78       const unsigned char *p1 = (const unsigned char *) s1;
  79       const unsigned char *p2 = (const unsigned char *) s2;
  80       unsigned char c1, c2;
  81
  82       do
  83         {
  84           c1 = TOLOWER (*p1);
  85           c2 = TOLOWER (*p2);
  86
  87           if (c1 == '\0')
  88             break;
  89
  90           ++p1;
  91           ++p2;
  92         }
  93       while (c1 == c2);
  94
  95       if (UCHAR_MAX <= INT_MAX)
  96         return c1 - c2;
  97       else
  98         /* On machines where 'char' and 'int' are types of the same size, the
  99            difference of two 'unsigned char' values - including the sign bit -
 100            doesn't fit in an 'int'.  */
 101         return (c1 > c2 ? 1 : c1 < c2 ? -1 : 0);
 102     }
 103 }