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 (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
37 && ((h_l) = (j) + (n_l)))
38#define CHECK_EOL (1)
39#define RET0_IF_0(a) if (!a) goto ret0
40#include "str-two-way.h"
41
42#undef strstr
43
44#ifndef STRSTR
45#define STRSTR strstr
46#endif
47
48/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
49 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
50 HAYSTACK. */
51char *
52STRSTR (const char *haystack_start, const char *needle_start)
53{
54 const char *haystack = haystack_start;
55 const char *needle = needle_start;
56 size_t needle_len; /* Length of NEEDLE. */
57 size_t haystack_len; /* Known minimum length of HAYSTACK. */
58 bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
59
60 /* Determine length of NEEDLE, and in the process, make sure
61 HAYSTACK is at least as long (no point processing all of a long
62 NEEDLE if HAYSTACK is too short). */
63 while (*haystack && *needle)
64 ok &= *haystack++ == *needle++;
65 if (*needle)
66 return NULL;
67 if (ok)
68 return (char *) haystack_start;
69
70 /* Reduce the size of haystack using strchr, since it has a smaller
71 linear coefficient than the Two-Way algorithm. */
72 needle_len = needle - needle_start;
73 haystack = strchr (haystack_start + 1, *needle_start);
74 if (!haystack || __builtin_expect (needle_len == 1, 0))
75 return (char *) haystack;
76 needle -= needle_len;
77 haystack_len = (haystack > haystack_start + needle_len ? 1
78 : needle_len + haystack_start - haystack);
79
80 /* Perform the search. Abstract memory is considered to be an array
81 of 'unsigned char' values, not an array of 'char' values. See
82 ISO C 99 section 6.2.6.1. */
83 if (needle_len < LONG_NEEDLE_THRESHOLD)
84 return two_way_short_needle ((const unsigned char *) haystack,
85 haystack_len,
86 (const unsigned char *) needle, needle_len);
87 return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
88 (const unsigned char *) needle, needle_len);
89}
90libc_hidden_builtin_def (strstr)
91
92#undef LONG_NEEDLE_THRESHOLD
93