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/* strstr.c - search for a substring in string.
Copyright (C) 1994, 95 Free Software Foundation, Inc.
This file was part of the GNU C Library. Modified by kb@mail.tug.org.
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, write to the Free Software
Foundation, Inc., 51 Franklin St, 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, berg@pool.informatik.rwth-aachen.de */
#if !defined (__STDC__) || !__STDC__
/* This is a separate conditional since some stdc systems
reject `defined (const)'. */
#ifndef const
#define const
#endif
#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;
}
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