/* Copyright (C) 1994, 1999, 2002-2003, 2005-2006 Free Software Foundation, Inc.
This file is part of the GNU C Library.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/*
* My personal strstr() implementation that beats most other algorithms.
* Until someone tells me otherwise, I assume that this is the
* fastest implementation of strstr() in C.
* I deliberately chose not to comment it.  You should have at least
* as much fun trying to understand it, as I had to write it :-).
*
* Stephen R. van den Berg, [email protected] */

#include <config.h>

/* Specification.  */
#include "c-strstr.h"

#include <string.h>

typedef unsigned chartype;

char *
c_strstr (const char *phaystack, const char *pneedle)
{
 register const unsigned char *haystack, *needle;
 register chartype b, c;

 haystack = (const unsigned char *) phaystack;
 needle = (const unsigned char *) pneedle;

 b = *needle;
 if (b != '\0')
   {
     haystack--;                               /* possible ANSI violation */
     do
       {
         c = *++haystack;
         if (c == '\0')
           goto ret0;
       }
     while (c != b);

     c = *++needle;
     if (c == '\0')
       goto foundneedle;
     ++needle;
     goto jin;

     for (;;)
       {
         register chartype a;
         register const unsigned char *rhaystack, *rneedle;

         do
           {
             a = *++haystack;
             if (a == '\0')
               goto ret0;
             if (a == b)
               break;
             a = *++haystack;
             if (a == '\0')
               goto ret0;
shloop:;    }
         while (a != b);

jin:      a = *++haystack;
         if (a == '\0')
           goto ret0;

         if (a != c)
           goto shloop;

         rhaystack = haystack-- + 1;
         rneedle = needle;
         a = *rneedle;

         if (*rhaystack == a)
           do
             {
               if (a == '\0')
                 goto foundneedle;
               ++rhaystack;
               a = *++needle;
               if (*rhaystack != a)
                 break;
               if (a == '\0')
                 goto foundneedle;
               ++rhaystack;
               a = *++needle;
             }
           while (*rhaystack == a);

         needle = rneedle;                /* took the register-poor approach */

         if (a == '\0')
           break;
       }
   }
foundneedle:
 return (char *) haystack;
ret0:
 return 0;
}