1 /* c-strcasecmp.c -- case insensitive string comparator in C locale
2 Copyright (C) 1998-1999, 2005-2006, 2009-2023 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 This file 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 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://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
27 c_strcasecmp (const char *s1, const char *s2)
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)
34 return 0;
35
36 do
37 {
38 c1 = c_tolower (*p1);
39 c2 = c_tolower (*p2);
40
41 if (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 _GL_CMP (c1, c2);
56 }