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83a552b0bb
The generic strstr in GLIBC 2.28 fails to match huge needles. The optimized AVAILABLE macro reads ahead a large fixed amount to reduce the overhead of repeatedly checking for the end of the string. However if the needle length is larger than this, two_way_long_needle may confuse this as meaning the end of the string and return NULL. This is fixed by adding the needle length to the amount to read ahead. [BZ #23637] * string/test-strstr.c (pr23637): New function. (test_main): Add tests with longer needles. * string/strcasestr.c (AVAILABLE): Fix readahead distance. * string/strstr.c (AVAILABLE): Likewise.
94 lines
3.1 KiB
C
94 lines
3.1 KiB
C
/* Return the offset of one string within another.
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Copyright (C) 1994-2018 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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<http://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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#ifndef _LIBC
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# define __builtin_expect(expr, val) (expr)
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#endif
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#define RETURN_TYPE char *
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#define AVAILABLE(h, h_l, j, n_l) \
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(((j) + (n_l) <= (h_l)) \
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|| ((h_l) += __strnlen ((void*)((h) + (h_l)), (n_l) + 512), \
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(j) + (n_l) <= (h_l)))
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#define CHECK_EOL (1)
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#define RET0_IF_0(a) if (!a) goto ret0
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#define FASTSEARCH(S,C,N) (void*) strchr ((void*)(S), (C))
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#include "str-two-way.h"
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#undef strstr
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#ifndef STRSTR
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#define STRSTR strstr
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#endif
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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, const char *needle)
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{
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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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/* Handle empty NEEDLE special case. */
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if (needle[0] == '\0')
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return (char *) haystack;
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/* Skip until we find the first matching char from NEEDLE. */
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haystack = strchr (haystack, needle[0]);
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if (haystack == NULL || needle[1] == '\0')
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return (char *) haystack;
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/* Ensure HAYSTACK length is at least as long as NEEDLE length.
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Since a match may occur early on in a huge HAYSTACK, use strnlen
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and read ahead a few cachelines for improved performance. */
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needle_len = strlen (needle);
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haystack_len = __strnlen (haystack, needle_len + 256);
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if (haystack_len < needle_len)
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return NULL;
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/* Check whether we have a match. This improves performance since we avoid
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the initialization overhead of the two-way algorithm. */
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if (memcmp (haystack, needle, needle_len) == 0)
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return (char *) 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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libc_hidden_builtin_def (strstr)
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#undef LONG_NEEDLE_THRESHOLD
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