1/* Return the offset of one string within another.
2 Copyright (C) 1994-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19/* This particular implementation was written by Eric Blake, 2008. */
20
21#ifndef _LIBC
22# include <config.h>
23#endif
24
25/* Specification of strstr. */
26#include <string.h>
27
28#include <stdbool.h>
29
30#ifndef _LIBC
31# define __builtin_expect(expr, val) (expr)
32#endif
33
34#define RETURN_TYPE char *
35#define AVAILABLE(h, h_l, j, n_l) \
36 (((j) + (n_l) <= (h_l)) || ((h_l) += __strnlen ((void*)((h) + (h_l)), 512), \
37 (j) + (n_l) <= (h_l)))
38#define CHECK_EOL (1)
39#define RET0_IF_0(a) if (!a) goto ret0
40#define FASTSEARCH(S,C,N) (void*) strchr ((void*)(S), (C))
41#include "str-two-way.h"
42
43#undef strstr
44
45#ifndef STRSTR
46#define STRSTR strstr
47#endif
48
49/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
50 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
51 HAYSTACK. */
52char *
53STRSTR (const char *haystack_start, const char *needle_start)
54{
55 const char *haystack = haystack_start;
56 const char *needle = needle_start;
57 size_t needle_len; /* Length of NEEDLE. */
58 size_t haystack_len; /* Known minimum length of HAYSTACK. */
59 bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
60
61 /* Determine length of NEEDLE, and in the process, make sure
62 HAYSTACK is at least as long (no point processing all of a long
63 NEEDLE if HAYSTACK is too short). */
64 while (*haystack && *needle)
65 ok &= *haystack++ == *needle++;
66 if (*needle)
67 return NULL;
68 if (ok)
69 return (char *) haystack_start;
70
71 /* Reduce the size of haystack using strchr, since it has a smaller
72 linear coefficient than the Two-Way algorithm. */
73 needle_len = needle - needle_start;
74 haystack = strchr (haystack_start + 1, *needle_start);
75 if (!haystack || __builtin_expect (needle_len == 1, 0))
76 return (char *) haystack;
77 needle -= needle_len;
78 haystack_len = (haystack > haystack_start + needle_len ? 1
79 : needle_len + haystack_start - haystack);
80
81 /* Perform the search. Abstract memory is considered to be an array
82 of 'unsigned char' values, not an array of 'char' values. See
83 ISO C 99 section 6.2.6.1. */
84 if (needle_len < LONG_NEEDLE_THRESHOLD)
85 return two_way_short_needle ((const unsigned char *) haystack,
86 haystack_len,
87 (const unsigned char *) needle, needle_len);
88 return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
89 (const unsigned char *) needle, needle_len);
90}
91libc_hidden_builtin_def (strstr)
92
93#undef LONG_NEEDLE_THRESHOLD
94