strnstr.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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#if defined(LIBC_SCCS) && !defined(lint)
37static char sccsid[] = "@(#)strstr.c	8.1 (Berkeley) 6/4/93";
38#endif /* LIBC_SCCS and not lint */
39#include <sys/cdefs.h>
40__FBSDID("$FreeBSD: stable/11/lib/libc/string/strnstr.c 330897 2018-03-14 03:19:51Z eadler $");
41
42#include <string.h>
43
44/*
45 * Find the first occurrence of find in s, where the search is limited to the
46 * first slen characters of s.
47 */
48char *
49strnstr(const char *s, const char *find, size_t slen)
50{
51	char c, sc;
52	size_t len;
53
54	if ((c = *find++) != '\0') {
55		len = strlen(find);
56		do {
57			do {
58				if (slen-- < 1 || (sc = *s++) == '\0')
59					return (NULL);
60			} while (sc != c);
61			if (len > slen)
62				return (NULL);
63		} while (strncmp(s, find, len) != 0);
64		s--;
65	}
66	return ((char *)s);
67}
68