The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/libkern/memmem.c

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    1 /*-
    2  * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  * 3. The name of the author may not be used to endorse or promote
   13  *    products derived from this software without specific prior written
   14  *    permission.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: releng/11.1/sys/libkern/memmem.c 319284 2017-05-31 05:45:06Z delphij $");
   31 
   32 #include <sys/libkern.h>
   33 #include <sys/param.h>
   34 
   35 void *
   36 memmem(const void *l, size_t l_len, const void *s, size_t s_len)
   37 {
   38         char *cur, *last;
   39         const char *cl = (const char *)l;
   40         const char *cs = (const char *)s;
   41 
   42         /* we need something to compare */
   43         if (l_len == 0 || s_len == 0)
   44                 return NULL;
   45 
   46         /* "s" must be smaller or equal to "l" */
   47         if (l_len < s_len)
   48                 return NULL;
   49 
   50         /* special case where s_len == 1 */
   51         if (s_len == 1)
   52                 return memchr(l, (int)*cs, l_len);
   53 
   54         /* the last position where its possible to find "s" in "l" */
   55         last = __DECONST(char *, cl) + l_len - s_len;
   56 
   57         for (cur = __DECONST(char *, cl); cur <= last; cur++)
   58                 if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
   59                         return cur;
   60 
   61         return NULL;
   62 }

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