| 1 | /* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2021 Free Software
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| 2 | Foundation, Inc.
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| 3 | This file is part of the GNU C Library.
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| 4 |
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| 5 | This file is free software: you can redistribute it and/or modify
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| 6 | it under the terms of the GNU Lesser General Public License as
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| 7 | published by the Free Software Foundation; either version 2.1 of the
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| 8 | License, or (at your option) any later version.
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| 9 |
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| 10 | This file is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU Lesser General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU Lesser General Public License
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| 16 | along with this program. If not, see <https://www.gnu.org/licenses/>. */
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| 17 |
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| 18 | /* This particular implementation was written by Eric Blake, 2008. */
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| 19 |
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| 20 | #ifndef _LIBC
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| 21 | # include <config.h>
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| 22 | #endif
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| 23 |
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| 24 | /* Specification of strstr. */
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| 25 | #include <string.h>
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| 26 |
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| 27 | #include <stdbool.h>
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| 28 |
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| 29 | #define RETURN_TYPE char *
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| 30 | #define AVAILABLE(h, h_l, j, n_l) \
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| 31 | (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
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| 32 | && ((h_l) = (j) + (n_l)))
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| 33 | #include "str-two-way.h"
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| 34 |
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| 35 | /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
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| 36 | if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
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| 37 | HAYSTACK. */
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| 38 | char *
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| 39 | strstr (const char *haystack_start, const char *needle_start)
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| 40 | {
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| 41 | const char *haystack = haystack_start;
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| 42 | const char *needle = needle_start;
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| 43 | size_t needle_len; /* Length of NEEDLE. */
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| 44 | size_t haystack_len; /* Known minimum length of HAYSTACK. */
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| 45 | bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
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| 46 |
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| 47 | /* Determine length of NEEDLE, and in the process, make sure
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| 48 | HAYSTACK is at least as long (no point processing all of a long
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| 49 | NEEDLE if HAYSTACK is too short). */
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| 50 | while (*haystack && *needle)
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| 51 | ok &= *haystack++ == *needle++;
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| 52 | if (*needle)
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| 53 | return NULL;
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| 54 | if (ok)
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| 55 | return (char *) haystack_start;
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| 56 |
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| 57 | /* Reduce the size of haystack using strchr, since it has a smaller
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| 58 | linear coefficient than the Two-Way algorithm. */
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| 59 | needle_len = needle - needle_start;
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| 60 | haystack = strchr (haystack_start + 1, *needle_start);
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| 61 | if (!haystack || __builtin_expect (needle_len == 1, 0))
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| 62 | return (char *) haystack;
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| 63 | needle -= needle_len;
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| 64 | haystack_len = (haystack > haystack_start + needle_len ? 1
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| 65 | : needle_len + haystack_start - haystack);
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| 66 |
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| 67 | /* Perform the search. Abstract memory is considered to be an array
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| 68 | of 'unsigned char' values, not an array of 'char' values. See
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| 69 | ISO C 99 section 6.2.6.1. */
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| 70 | if (needle_len < LONG_NEEDLE_THRESHOLD)
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| 71 | return two_way_short_needle ((const unsigned char *) haystack,
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| 72 | haystack_len,
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| 73 | (const unsigned char *) needle, needle_len);
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| 74 | return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
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| 75 | (const unsigned char *) needle, needle_len);
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| 76 | }
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| 77 |
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| 78 | #undef LONG_NEEDLE_THRESHOLD
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