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glibc/wcsmbs/wcsstr.c
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/* Copyright (C) 1995-2016 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, see | |
<http://www.gnu.org/licenses/>. */ | |
/* | |
* The original strstr() file contains the following comment: | |
* | |
* 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 <wchar.h> | |
wchar_t * | |
wcsstr (const wchar_t *haystack, const wchar_t *needle) | |
{ | |
wchar_t b, c; | |
if ((b = *needle) != L'\0') | |
{ | |
haystack--; /* possible ANSI violation */ | |
do | |
if ((c = *++haystack) == L'\0') | |
goto ret0; | |
while (c != b); | |
if (!(c = *++needle)) | |
goto foundneedle; | |
++needle; | |
goto jin; | |
for (;;) | |
{ | |
wchar_t a; | |
const wchar_t *rhaystack, *rneedle; | |
do | |
{ | |
if (!(a = *++haystack)) | |
goto ret0; | |
if (a == b) | |
break; | |
if ((a = *++haystack) == L'\0') | |
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 == L'\0') | |
goto foundneedle; | |
if (*++rhaystack != (a = *++needle)) | |
break; | |
if (a == L'\0') | |
goto foundneedle; | |
} | |
while (*++rhaystack == (a = *++needle)); | |
needle = rneedle; /* took the register-poor approach */ | |
if (a == L'\0') | |
break; | |
} | |
} | |
foundneedle: | |
return (wchar_t*) haystack; | |
ret0: | |
return NULL; | |
} | |
/* This alias is for backward compatibility with drafts of the ISO C | |
standard. Unfortunately the Unix(TM) standard requires this name. */ | |
weak_alias (wcsstr, wcswcs) |