79 lines
2.9 KiB
C
79 lines
2.9 KiB
C
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/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2021 Free Software
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Foundation, Inc.
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This file is part of the GNU C Library.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, see <https://www.gnu.org/licenses/>. */
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/* This particular implementation was written by Eric Blake, 2008. */
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#ifndef _LIBC
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# include <config.h>
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#endif
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/* Specification of strstr. */
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#include <string.h>
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#include <stdbool.h>
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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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#include "str-two-way.h"
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/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
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if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
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HAYSTACK. */
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char *
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strstr (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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ok &= *haystack++ == *needle++;
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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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/* Reduce the size of haystack using strchr, since it has a smaller
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linear coefficient than the Two-Way algorithm. */
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needle_len = needle - needle_start;
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haystack = strchr (haystack_start + 1, *needle_start);
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if (!haystack || __builtin_expect (needle_len == 1, 0))
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return (char *) haystack;
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needle -= needle_len;
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haystack_len = (haystack > haystack_start + needle_len ? 1
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: needle_len + haystack_start - haystack);
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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, 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, needle_len);
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}
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#undef LONG_NEEDLE_THRESHOLD
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