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98 lines
2.5 KiB
C
98 lines
2.5 KiB
C
/* Copyright (C) 1995-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/*
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* The original strstr() file contains the following comment:
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*
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* My personal strstr() implementation that beats most other algorithms.
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* Until someone tells me otherwise, I assume that this is the
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* fastest implementation of strstr() in C.
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* I deliberately chose not to comment it. You should have at least
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* as much fun trying to understand it, as I had to write it :-).
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*
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* Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
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#include <wchar.h>
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wchar_t *
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wcsstr (const wchar_t *haystack, const wchar_t *needle)
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{
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wchar_t b, c;
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if ((b = *needle) != L'\0')
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{
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haystack--; /* possible ANSI violation */
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do
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if ((c = *++haystack) == L'\0')
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goto ret0;
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while (c != b);
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if (!(c = *++needle))
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goto foundneedle;
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++needle;
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goto jin;
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for (;;)
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{
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wchar_t a;
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const wchar_t *rhaystack, *rneedle;
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do
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{
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if (!(a = *++haystack))
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goto ret0;
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if (a == b)
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break;
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if ((a = *++haystack) == L'\0')
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goto ret0;
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shloop: ;
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}
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while (a != b);
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jin: if (!(a = *++haystack))
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goto ret0;
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if (a != c)
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goto shloop;
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if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
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do
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{
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if (a == L'\0')
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goto foundneedle;
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if (*++rhaystack != (a = *++needle))
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break;
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if (a == L'\0')
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goto foundneedle;
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}
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while (*++rhaystack == (a = *++needle));
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needle = rneedle; /* took the register-poor approach */
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if (a == L'\0')
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break;
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}
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}
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foundneedle:
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return (wchar_t*) haystack;
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ret0:
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return NULL;
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}
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/* This alias is for backward compatibility with drafts of the ISO C
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standard. Unfortunately the Unix(TM) standard requires this name. */
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weak_alias (wcsstr, wcswcs)
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