lib/strstr.c

   1 /* strstr.c -- return the offset of one string within another
   2    Copyright (C) 1989, 1990 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 /* Written by Mike Rendell <michael@cs.mun.ca>.  */
  19
  20 /* Return the starting address of string S2 in S1;
  21    return 0 if it is not found. */
  22
  23 char *
  24 strstr (s1, s2)
  25      char *s1;
  26      char *s2;
  27 {
  28   int i;
  29   char *p1;
  30   char *p2;
  31   char *s = s1;
  32
  33   for (p2 = s2, i = 0; *s; p2 = s2, i++, s++)
  34     {
  35       for (p1 = s; *p1 && *p2 && *p1 == *p2; p1++, p2++)
  36         ;
  37       if (!*p2)
  38         break;
  39     }
  40   if (!*p2)
  41     return s1 + i;
  42
  43   return 0;
  44 }