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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 }