123 lines
2.8 KiB
C
123 lines
2.8 KiB
C
/* Return the offset of one string within another.
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Copyright (C) 1994, 1996, 1997, 2000, 2001 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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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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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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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#if defined _LIBC || defined HAVE_STRING_H
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# include <string.h>
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#endif
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typedef unsigned chartype;
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#undef strstr
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char *
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strstr (phaystack, pneedle)
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const char *phaystack;
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const char *pneedle;
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{
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const unsigned char *haystack, *needle;
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chartype b;
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const unsigned char *rneedle;
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haystack = (const unsigned char *) phaystack;
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if ((b = *(needle = (const unsigned char *) pneedle)))
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{
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chartype c;
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haystack--; /* possible ANSI violation */
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{
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chartype a;
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do
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if (!(a = *++haystack))
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goto ret0;
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while (a != b);
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}
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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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{
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chartype a;
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if (0)
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jin:{
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if ((a = *++haystack) == c)
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goto crest;
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}
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else
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a = *++haystack;
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do
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{
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for (; a != b; a = *++haystack)
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{
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if (!a)
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goto ret0;
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if ((a = *++haystack) == b)
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break;
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if (!a)
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goto ret0;
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}
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}
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while ((a = *++haystack) != c);
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}
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crest:
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{
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chartype a;
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{
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const unsigned char *rhaystack;
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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)
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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)
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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 aproach */
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}
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if (!a)
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break;
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}
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}
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}
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foundneedle:
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return (char *) haystack;
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ret0:
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return 0;
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}
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