1 /* $OpenBSD: strnstr.c,v 1.1 2023/12/21 02:57:14 jsg Exp $ */
2
3 /*-
4 * Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
5 * Copyright (c) 1990, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Chris Torek.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include <sys/param.h>
37 #include <lib/libkern/libkern.h>
38
39 /*
40 * Find the first occurrence of find in s, where the search is limited to the
41 * first slen characters of s.
42 */
43 char *
strnstr(const char * s,const char * find,size_t slen)44 strnstr(const char *s, const char *find, size_t slen)
45 {
46 char c, sc;
47 size_t len;
48
49 if ((c = *find++) != '\0') {
50 len = strlen(find);
51 do {
52 do {
53 if (slen-- < 1 || (sc = *s++) == '\0')
54 return (NULL);
55 } while (sc != c);
56 if (len > slen)
57 return (NULL);
58 } while (strncmp(s, find, len) != 0);
59 s--;
60 }
61 return ((char *)s);
62 }
63