common/lib/libc/string/strstr.c

   1 /*      $NetBSD: strstr.c,v 1.2 2007/06/04 18:19:28 christos Exp $      */
   2
   3 /*-
   4  * Copyright (c) 1990, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Chris Torek.
   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  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 #if 0
  38 static char sccsid[] = "@(#)strstr.c    8.1 (Berkeley) 6/4/93";
  39 #else
  40 __RCSID("$NetBSD: strstr.c,v 1.2 2007/06/04 18:19:28 christos Exp $");
  41 #endif
  42 #endif /* LIBC_SCCS and not lint */
  43
  44 #if !defined(_KERNEL) && !defined(_STANDALONE)
  45 #include <assert.h>
  46 #include <string.h>
  47 #else
  48 #include <sys/param.h>
  49 #include <lib/libkern/libkern.h>
  50 #endif
  51
  52 /*
  53  * Find the first occurrence of find in s.
  54  */
  55 char *
  56 strstr(const char *s, const char *find)
  57 {
  58         char c, sc;
  59         size_t len;
  60
  61         _DIAGASSERT(s != NULL);
  62         _DIAGASSERT(find != NULL);
  63
  64         if ((c = *find++) != 0) {
  65                 len = strlen(find);
  66                 do {
  67                         do {
  68                                 if ((sc = *s++) == 0)
  69                                         return (NULL);
  70                         } while (sc != c);
  71                 } while (strncmp(s, find, len) != 0);
  72                 s--;
  73         }
  74         return __UNCONST(s);
  75 }