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2b7a8664fa
This patch implements SSE4.2 strstr/strcasestr, using Knuth-Morris-Pratt string searching algorithm.
107 lines
3.5 KiB
C
107 lines
3.5 KiB
C
/* Return the offset of one string within another.
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Copyright (C) 1994, 1996-2000, 2004, 2008, 2009
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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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/* Specification. */
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#include <string.h>
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#include <ctype.h>
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#include <stdbool.h>
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#include <strings.h>
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#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
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/* Two-Way algorithm. */
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#define RETURN_TYPE char *
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#define AVAILABLE(h, h_l, j, n_l) \
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(!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
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&& ((h_l) = (j) + (n_l)))
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#define CANON_ELEMENT(c) TOLOWER (c)
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#define CMP_FUNC(p1, p2, l) \
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__strncasecmp ((const char *) (p1), (const char *) (p2), l)
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#include "str-two-way.h"
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#undef strcasestr
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#undef __strcasestr
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#ifndef STRCASESTR
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#define STRCASESTR __strcasestr
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#endif
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/* Find the first occurrence of NEEDLE in HAYSTACK, using
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case-insensitive comparison. This function gives unspecified
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results in multibyte locales. */
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char *
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STRCASESTR (const char *haystack_start, const char *needle_start)
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{
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const char *haystack = haystack_start;
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const char *needle = needle_start;
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size_t needle_len; /* Length of NEEDLE. */
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size_t haystack_len; /* Known minimum length of HAYSTACK. */
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bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
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/* Determine length of NEEDLE, and in the process, make sure
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HAYSTACK is at least as long (no point processing all of a long
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NEEDLE if HAYSTACK is too short). */
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while (*haystack && *needle)
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{
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ok &= (TOLOWER ((unsigned char) *haystack)
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== TOLOWER ((unsigned char) *needle));
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haystack++;
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needle++;
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}
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if (*needle)
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return NULL;
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if (ok)
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return (char *) haystack_start;
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needle_len = needle - needle_start;
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haystack = haystack_start + 1;
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haystack_len = needle_len - 1;
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/* Perform the search. Abstract memory is considered to be an array
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of 'unsigned char' values, not an array of 'char' values. See
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ISO C 99 section 6.2.6.1. */
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if (needle_len < LONG_NEEDLE_THRESHOLD)
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return two_way_short_needle ((const unsigned char *) haystack,
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haystack_len,
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(const unsigned char *) needle_start,
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needle_len);
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return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
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(const unsigned char *) needle_start,
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needle_len);
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}
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#undef LONG_NEEDLE_THRESHOLD
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weak_alias (__strcasestr, strcasestr)
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