lib/libc/string/strnstr.c

   1 /*-
   2  * Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
   3  * Copyright (c) 1990, 1993
   4  *      The Regents of the University of California.  All rights reserved.
   5  *
   6  * This code is derived from software contributed to Berkeley by
   7  * Chris Torek.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)strstr.c 8.1 (Berkeley) 6/4/93
  34  * $FreeBSD: src/lib/libc/string/strnstr.c,v 1.4 2007/01/09 00:28:12 imp Exp $
  35  * $DragonFly: src/lib/libc/string/strnstr.c,v 1.4 2006/03/20 17:24:20 dillon Exp $
  36  */
  37
  38 #include <sys/types.h>
  39 #include <string.h>
  40
  41 /*
  42  * Find the first occurrence of find in s, where the search is limited to the
  43  * first slen characters of s.
  44  */
  45 char *
  46 strnstr(const char *s, const char *find, size_t slen)
  47 {
  48         char c, sc;
  49         size_t len;
  50
  51         if ((c = *find++) != '\0') {
  52                 len = strlen(find);
  53                 do {
  54                         do {
  55                                 if (slen < 1 || (sc = *s) == '\0')
  56                                         return (NULL);
  57                                 --slen;
  58                                 ++s;
  59                         } while (sc != c);
  60                         if (len > slen)
  61                                 return (NULL);
  62                 } while (strncmp(s, find, len) != 0);
  63                 s--;
  64         }
  65         return (__DECONST(char *, s));
  66 }