117 lines
2.6 KiB
C
117 lines
2.6 KiB
C
/* Copyright (C) 1994 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 <string.h>
|
|
#include <sys/types.h>
|
|
|
|
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;
|
|
}
|