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  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by the University of
  20  *      California, Berkeley and its contributors.
  21  * 4. Neither the name of the University nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  *
  37  * @(#)strstr.c 8.1 (Berkeley) 6/4/93
  38  * $FreeBSD: src/lib/libc/string/strnstr.c,v 1.2.2.1 2001/12/09 06:50:03 mike Exp $
  39  * $DragonFly: src/lib/libc/string/strnstr.c,v 1.4 2006/03/20 17:24:20 dillon Exp $
  40  */
  41
  42 #include <sys/types.h>
  43 #include <string.h>
  44
  45 /*
  46  * Find the first occurrence of find in s, where the search is limited to the
  47  * first slen characters of s.
  48  */
  49 char *
  50 strnstr(const char *s, const char *find, size_t slen)
  51 {
  52         char c, sc;
  53         size_t len;
  54
  55         if ((c = *find++) != '\0') {
  56                 len = strlen(find);
  57                 do {
  58                         do {
  59                                 if (slen < 1 || (sc = *s) == '\0')
  60                                         return (NULL);
  61                                 --slen;
  62                                 ++s;
  63                         } while (sc != c);
  64                         if (len > slen)
  65                                 return (NULL);
  66                 } while (strncmp(s, find, len) != 0);
  67                 s--;
  68         }
  69         return (__DECONST(char *, s));
  70 }