1 /* c-strncasecmp.c -- case insensitive string comparator in C locale
2    Copyright (C) 1998-1999, 2005-2006, 2009-2012 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 3, 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, see <http://www.gnu.org/licenses/>.  */
16 
17 #include <config.h>
18 
19 /* Specification.  */
20 #include "c-strcase.h"
21 
22 #include <limits.h>
23 
24 #include "c-ctype.h"
25 
26 int
c_strncasecmp(const char * s1,const char * s2,size_t n)27 c_strncasecmp (const char *s1, const char *s2, size_t n)
28 {
29   register const unsigned char *p1 = (const unsigned char *) s1;
30   register const unsigned char *p2 = (const unsigned char *) s2;
31   unsigned char c1, c2;
32 
33   if (p1 == p2 || n == 0)
34     return 0;
35 
36   do
37     {
38       c1 = c_tolower (*p1);
39       c2 = c_tolower (*p2);
40 
41       if (--n == 0 || c1 == '\0')
42         break;
43 
44       ++p1;
45       ++p2;
46     }
47   while (c1 == c2);
48 
49   if (UCHAR_MAX <= INT_MAX)
50     return c1 - c2;
51   else
52     /* On machines where 'char' and 'int' are types of the same size, the
53        difference of two 'unsigned char' values - including the sign bit -
54        doesn't fit in an 'int'.  */
55     return (c1 > c2 ? 1 : c1 < c2 ? -1 : 0);
56 }
57