compat/strnstr.c

   1 /*****************************************************************************
   2  * strnstr.c: BSD strnstr() replacement
   3  *****************************************************************************
   4  * Copyright © 2015 VLC authors and VideoLAN
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <string.h>
  26 #include <assert.h>
  27
  28 char * strnstr (const char *haystack, const char *needle, size_t len)
  29 {
  30     assert(needle != NULL);
  31
  32     const size_t i = strlen(needle);
  33     if (i == 0) /* corner case (if haystack is NULL, memcmp not allowed) */
  34         return (char *)haystack;
  35
  36     if( len < i )
  37       return NULL;
  38
  39     size_t count = len - i;
  40
  41     do
  42     {
  43       if( memcmp(haystack, needle, i) == 0 )
  44         return (char*) haystack;
  45       haystack++;
  46     }
  47     while(count--);
  48
  49     return NULL;
  50 }