lib/libc/string/memmem.c

   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  * $FreeBSD: src/lib/libc/string/memmem.c,v 1.1 2005/08/25 18:26:58 andre Exp $
  29  */
  30
  31 #include <string.h>
  32
  33 /*
  34  * Find the first occurrence of the byte string s in byte string l.
  35  */
  36
  37 void *
  38 memmem(const void *l, size_t l_len, const void *s, size_t s_len)
  39 {
  40         char *cur, *last;
  41         const char *cl = (const char *)l;
  42         const char *cs = (const char *)s;
  43
  44         /* we need something to compare */
  45         if (l_len == 0 || s_len == 0)
  46                 return (NULL);
  47
  48         /* "s" must be smaller or equal to "l" */
  49         if (l_len < s_len)
  50                 return (NULL);
  51
  52         /* special case where s_len == 1 */
  53         if (s_len == 1)
  54                 return (memchr(l, (int)*cs, l_len));
  55
  56         /* the last position where its possible to find "s" in "l" */
  57         last = (char *)cl + l_len - s_len;
  58
  59         for (cur = (char *)cl; cur <= last; cur++)
  60                 if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
  61                         return (cur);
  62
  63         return (NULL);
  64 }