sbase

suckless unix tools
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memmem.c (2328B)


      1 /*	$OpenBSD: memmem.c,v 1.4 2015/08/31 02:53:57 guenther Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  * 3. The name of the author may not be used to endorse or promote
     15  *    products derived from this software without specific prior written
     16  *    permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  * SUCH DAMAGE.
     29  */
     30 
     31 #include <string.h>
     32 
     33 #include "../util.h"
     34 
     35 /*
     36  * Find the first occurrence of the byte string s in byte string l.
     37  */
     38 
     39 void *
     40 memmem(const void *l, size_t l_len, const void *s, size_t s_len)
     41 {
     42 	const char *cur, *last;
     43 	const char *cl = l;
     44 	const char *cs = s;
     45 
     46 	/* a zero length needle should just return the haystack */
     47 	if (s_len == 0)
     48 		return (void *)cl;
     49 
     50 	/* "s" must be smaller or equal to "l" */
     51 	if (l_len < s_len)
     52 		return NULL;
     53 
     54 	/* special case where s_len == 1 */
     55 	if (s_len == 1)
     56 		return memchr(l, *cs, l_len);
     57 
     58 	/* the last position where its possible to find "s" in "l" */
     59 	last = cl + l_len - s_len;
     60 
     61 	for (cur = cl; cur <= last; cur++)
     62 		if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
     63 			return (void *)cur;
     64 
     65 	return NULL;
     66 }