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 /* Author:
  19         Mike Rendell                    Department of Computer Science
  20         michael@garfield.mun.edu        Memorial University of Newfoundland
  21         ..!uunet!garfield!michael       St. John's, Nfld., Canada
  22         (709) 737-4550                  A1C 5S7
  23 */
  24
  25 /* Return the starting address of string S2 in S1;
  26    return 0 if it is not found. */
  27
  28 char *
  29 strstr (s1, s2)
  30      char *s1;
  31      char *s2;
  32 {
  33   int i;
  34   char *p1;
  35   char *p2;
  36   char *s = s1;
  37
  38   for (p2 = s2, i = 0; *s; p2 = s2, i++, s++)
  39     {
  40       for (p1 = s; *p1 && *p2 && *p1 == *p2; p1++, p2++)
  41         ;
  42       if (!*p2)
  43         break;
  44     }
  45   if (!*p2)
  46     return s1 + i;
  47
  48   return 0;
  49 }