strncasecmp.c revision 302408 
1/*
2 * Copyright (c) 1987 Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms are permitted
6 * provided that this notice is preserved and that due credit is given
7 * to the University of California at Berkeley. The name of the University
8 * may not be used to endorse or promote products derived from this
9 * software without specific written prior permission. This software
10 * is provided ``as is'' without express or implied warranty.
11 */
12
13/*
14
15@deftypefn Supplemental int strncasecmp (const char *@var{s1}, const char *@var{s2})
16
17A case-insensitive @code{strncmp}.
18
19@end deftypefn
20
21*/
22
23#if defined(LIBC_SCCS) && !defined(lint)
24static char sccsid[] = "@(#)strcasecmp.c	5.5 (Berkeley) 11/24/87";
25#endif /* LIBC_SCCS and not lint */
26
27#include <ansidecl.h>
28#include <stddef.h>
29
30/*
31 * This array is designed for mapping upper and lower case letter
32 * together for a case independent comparison.  The mappings are
33 * based upon ascii character sequences.
34 */
35static const unsigned char charmap[] = {
36	'\000', '\001', '\002', '\003', '\004', '\005', '\006', '\007',
37	'\010', '\011', '\012', '\013', '\014', '\015', '\016', '\017',
38	'\020', '\021', '\022', '\023', '\024', '\025', '\026', '\027',
39	'\030', '\031', '\032', '\033', '\034', '\035', '\036', '\037',
40	'\040', '\041', '\042', '\043', '\044', '\045', '\046', '\047',
41	'\050', '\051', '\052', '\053', '\054', '\055', '\056', '\057',
42	'\060', '\061', '\062', '\063', '\064', '\065', '\066', '\067',
43	'\070', '\071', '\072', '\073', '\074', '\075', '\076', '\077',
44	'\100', '\141', '\142', '\143', '\144', '\145', '\146', '\147',
45	'\150', '\151', '\152', '\153', '\154', '\155', '\156', '\157',
46	'\160', '\161', '\162', '\163', '\164', '\165', '\166', '\167',
47	'\170', '\171', '\172', '\133', '\134', '\135', '\136', '\137',
48	'\140', '\141', '\142', '\143', '\144', '\145', '\146', '\147',
49	'\150', '\151', '\152', '\153', '\154', '\155', '\156', '\157',
50	'\160', '\161', '\162', '\163', '\164', '\165', '\166', '\167',
51	'\170', '\171', '\172', '\173', '\174', '\175', '\176', '\177',
52	'\200', '\201', '\202', '\203', '\204', '\205', '\206', '\207',
53	'\210', '\211', '\212', '\213', '\214', '\215', '\216', '\217',
54	'\220', '\221', '\222', '\223', '\224', '\225', '\226', '\227',
55	'\230', '\231', '\232', '\233', '\234', '\235', '\236', '\237',
56	'\240', '\241', '\242', '\243', '\244', '\245', '\246', '\247',
57	'\250', '\251', '\252', '\253', '\254', '\255', '\256', '\257',
58	'\260', '\261', '\262', '\263', '\264', '\265', '\266', '\267',
59	'\270', '\271', '\272', '\273', '\274', '\275', '\276', '\277',
60	'\300', '\341', '\342', '\343', '\344', '\345', '\346', '\347',
61	'\350', '\351', '\352', '\353', '\354', '\355', '\356', '\357',
62	'\360', '\361', '\362', '\363', '\364', '\365', '\366', '\367',
63	'\370', '\371', '\372', '\333', '\334', '\335', '\336', '\337',
64	'\340', '\341', '\342', '\343', '\344', '\345', '\346', '\347',
65	'\350', '\351', '\352', '\353', '\354', '\355', '\356', '\357',
66	'\360', '\361', '\362', '\363', '\364', '\365', '\366', '\367',
67	'\370', '\371', '\372', '\373', '\374', '\375', '\376', '\377',
68};
69
70int
71strncasecmp(const char *s1, const char *s2, register size_t n)
72{
73    register unsigned char u1, u2;
74
75    for (; n != 0; --n) {
76	u1 = (unsigned char) *s1++;
77	u2 = (unsigned char) *s2++;
78	if (charmap[u1] != charmap[u2]) {
79	    return charmap[u1] - charmap[u2];
80	}
81	if (u1 == '\0') {
82	    return 0;
83	}
84    }
85    return 0;
86}
87