release/src/router/apcupsd/src/lib/strstr.c

   1 /*
   2  * strstr.c -- return the offset of one string within another.
   3  *
   4  * Copyright (C) 1997 Free Software Foundation, Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it under
   7  * the terms of the GNU General Public License as published by the Free
   8  * Software Foundation; either version 2, or (at your option) any later
   9  * version.
  10  *
  11  * This program is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14  * more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along with
  17  * this program; if not, write to the Free Software Foundation, Inc., 59
  18  * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 /* Written by Philippe De Muyter <phdm@info.ucl.ac.be>.  */
  22
  23 /*
  24  * NAME
  25  *
  26  * strstr -- locate first occurence of a substring
  27  *
  28  * SYNOPSIS
  29  *
  30  * char *strstr (char *s1, char *s2)
  31  *
  32  * DESCRIPTION
  33  *
  34  * Locates the first occurence in the string pointed to by S1 of the string
  35  * pointed to by S2.  Returns a pointer to the substring found, or a NULL
  36  * pointer if not found.  If S2 points to a string with zero length, the
  37  * function returns S1.
  38  *
  39  * BUGS
  40  *
  41  */
  42
  43 char *
  44 strstr (buf, sub)
  45      register char *buf;
  46      register char *sub;
  47 {
  48   register char *bp;
  49
  50   if (!*sub)
  51     return buf;
  52   for (;;)
  53     {
  54       if (!*buf)
  55         break;
  56       bp = buf;
  57       for (;;)
  58         {
  59           if (!*sub)
  60             return buf;
  61           if (*bp++ != *sub++)
  62             break;
  63         }
  64       sub -= (unsigned long) bp;
  65       sub += (unsigned long) buf;
  66       buf += 1;
  67     }
  68   return 0;
  69 }
  70