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glibc/string/strstr.c
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/* Return the offset of one string within another. | |
Copyright (C) 1994,1996,1997,2000,2001,2003 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 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. | |
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 | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; 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 */ | |
#if HAVE_CONFIG_H | |
# include <config.h> | |
#endif | |
#if defined _LIBC || defined HAVE_STRING_H | |
# include <string.h> | |
#endif | |
typedef unsigned chartype; | |
#undef strstr | |
char * | |
strstr (phaystack, pneedle) | |
const char *phaystack; | |
const char *pneedle; | |
{ | |
const unsigned char *haystack, *needle; | |
chartype b; | |
const unsigned char *rneedle; | |
haystack = (const unsigned char *) phaystack; | |
if ((b = *(needle = (const unsigned char *) pneedle))) | |
{ | |
chartype c; | |
haystack--; /* possible ANSI violation */ | |
{ | |
chartype a; | |
do | |
if (!(a = *++haystack)) | |
goto ret0; | |
while (a != b); | |
} | |
if (!(c = *++needle)) | |
goto foundneedle; | |
++needle; | |
goto jin; | |
for (;;) | |
{ | |
{ | |
chartype a; | |
if (0) | |
jin:{ | |
if ((a = *++haystack) == c) | |
goto crest; | |
} | |
else | |
a = *++haystack; | |
do | |
{ | |
for (; a != b; a = *++haystack) | |
{ | |
if (!a) | |
goto ret0; | |
if ((a = *++haystack) == b) | |
break; | |
if (!a) | |
goto ret0; | |
} | |
} | |
while ((a = *++haystack) != c); | |
} | |
crest: | |
{ | |
chartype a; | |
{ | |
const unsigned char *rhaystack; | |
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; | |
} | |
libc_hidden_builtin_def (strstr) |