/* strstr.c - search for a substring in string.

  Copyright 2008, 2010 Karl Berry.
  Copyright 1994, 1995 Free Software Foundation, Inc.
  This file was part of the GNU C Library.
  Modified for kpathsea by Karl Berry.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with this library; if not, see <http://www.gnu.org/licenses/>.  */

/*
* 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] */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

typedef unsigned chartype;

char *
strstr (phaystack, pneedle)
    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 aproach */

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