libc/string/strstr.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 #include <string.h>
  21
  22 char *strstr (char const *s1, char const *s2)
  23 {
  24         int l1, l2;
  25
  26         l2 = strlen (s2);
  27
  28         if (!l2)
  29                 return (char *) s1;
  30
  31         l1 = strlen (s1);
  32
  33         while (l1 >= l2) {
  34                 l1 --;
  35
  36                 if (!memcmp (s1, s2, l2))
  37                         return (char *) s1;
  38
  39                 s1 ++;
  40         }
  41
  42         return (char *) 0;
  43 }