123 lines
3.6 KiB
C
123 lines
3.6 KiB
C
/* Return the offset of one string within another.
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Copyright (C) 1994,1996,1997,1998,1999,2000 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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/* Faster looping by precalculating bl, bu, cl, cu before looping.
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* 2004 Apr 08 Jose Da Silva, digital@joescat@com */
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#include <string.h>
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#include <ctype.h>
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typedef unsigned chartype;
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char* strcasestr (const char* phaystack, const char* pneedle)
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{
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const unsigned char *haystack, *needle;
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chartype bl, bu, cl, cu;
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haystack = (const unsigned char *) phaystack;
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needle = (const unsigned char *) pneedle;
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bl = tolower (*needle);
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if (bl != '\0')
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{
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bu = toupper (bl);
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haystack--;/* possible ANSI violation */
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do
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{
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cl = *++haystack;
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if (cl == '\0')
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goto ret0;
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}
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while ((cl != bl) && (cl != bu));
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cl = tolower (*++needle);
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if (cl == '\0')
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goto foundneedle;
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cu = toupper (cl);
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++needle;
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goto jin;
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for (;;)
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{
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chartype a;
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const unsigned char *rhaystack, *rneedle;
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do
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{
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a = *++haystack;
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if (a == '\0')
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goto ret0;
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if ((a == bl) || (a == bu))
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break;
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a = *++haystack;
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if (a == '\0')
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goto ret0;
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shloop:
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;
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}
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while ((a != bl) && (a != bu));
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jin: a = *++haystack;
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if (a == '\0')
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goto ret0;
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if ((a != cl) && (a != cu))
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goto shloop;
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rhaystack = haystack-- + 1;
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rneedle = needle;
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a = tolower (*rneedle);
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if (tolower (*rhaystack) == (int) a)
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do
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{
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if (a == '\0')
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goto foundneedle;
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++rhaystack;
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a = tolower (*++needle);
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if (tolower (*rhaystack) != (int) a)
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break;
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if (a == '\0')
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goto foundneedle;
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++rhaystack;
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a = tolower (*++needle);
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}
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while (tolower (*rhaystack) == (int) a);
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needle = rneedle;/* took the register-poor approach */
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if (a == '\0')
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break;
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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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