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.
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.
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.
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/>. */
19 /* This particular implementation was written by Eric Blake, 2008. */
25 /* Specification of strstr. */
31 # define __builtin_expect(expr, val) (expr)
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)))
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"
49 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
50 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
53 STRSTR (const char *haystack_start
, const char *needle_start
)
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. */
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
++;
69 return (char *) haystack_start
;
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
;
78 haystack_len
= (haystack
> haystack_start
+ needle_len
? 1
79 : needle_len
+ haystack_start
- haystack
);
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
,
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
);
91 libc_hidden_builtin_def (strstr
)
93 #undef LONG_NEEDLE_THRESHOLD