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/* Copyright (C) 1994 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, 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, berg@pool.informatik.rwth-aachen.de */
#include <ansidecl.h>
#include <string.h>
#include <sys/types.h>
typedef unsigned chartype;
char *
DEFUN(strstr, (phaystack, pneedle),
const char *phaystack AND const char *pneedle)
{
register const unchar *haystack, *needle;
register chartype b, c;
haystack = (const unchar *)phaystack;
if ((b= *(needle=(const unchar*)pneedle)))
{
haystack--; /* possible ANSI violation */
do
if (!(c= *++haystack))
goto ret0;
while (c!=b);
if (!(c= *++needle))
goto foundneedle;
++needle;
goto jin;
for (;;)
{
register chartype a;
register const unchar *rhaystack, *rneedle;
do
{
if (!(a= *++haystack))
goto ret0;
if (a==b)
break;
if (!(a= *++haystack))
goto ret0;
shloop: }
while (a!=b);
jin: if (!(a= *++haystack))
goto ret0;
if (a!=c)
goto shloop;
if (*(rhaystack=haystack--+1) == (a= *(rneedle=needle)))
do
{
if (!a)
goto foundneedle;
if (*++rhaystack!=(a= *++needle))
break;
if (!a)
goto foundneedle;
}
while (*++rhaystack == (a= *++needle));
needle=rneedle; /* took the register-poor aproach */
if (!a)
break;
}
}
foundneedle:
return (char*)haystack;
ret0:
return 0;
}
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