lib/libc/string/memmem.c

   1 /*      $NetBSD: memmem.c,v 1.2 2008/04/28 20:23:00 martin Exp $        */
   2
   3 /*-
   4  * Copyright (c) 2005 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Perry E. Metzger of Metzger, Dowdeswell & Co. LLC.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: memmem.c,v 1.2 2008/04/28 20:23:00 martin Exp $");
  35 #endif /* LIBC_SCCS and not lint */
  36
  37 #if !defined(_KERNEL) && !defined(_STANDALONE)
  38 #include <assert.h>
  39 #include <string.h>
  40 #else
  41 #include <lib/libkern/libkern.h>
  42 #define _DIAGASSERT(x)  (void)0
  43 #define NULL            ((void *)0)
  44 #endif
  45
  46 void *
  47 memmem(const void *block, size_t blen, const void *pat, size_t plen)
  48 {
  49         const unsigned char *bp, *pp, *endp;
  50
  51         _DIAGASSERT(block != NULL);
  52         _DIAGASSERT(pat != NULL);
  53
  54         /*
  55          * Following the precedent in ststr(3) and glibc, a zero
  56          * length pattern matches the start of block.
  57          */
  58         if (plen == 0)
  59                 return __UNCONST(block);
  60
  61         if (blen < plen)
  62                 return NULL;
  63
  64         bp = block;
  65         pp = pat;
  66         endp = bp + (blen - plen) + 1;
  67
  68         /*
  69          * As a cheezy optimization, check that the first chars are
  70          * the same before calling memcmp. Really we should use bm(3)
  71          * to speed this up if blen is large enough.
  72          */
  73         while (bp < endp) {
  74                 if ((*bp == *pp) && (memcmp(bp, pp, plen) == 0))
  75                         return __UNCONST(bp);
  76                 bp++;
  77         }
  78
  79         return NULL;
  80 }