1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
/* Copyright (C) 2011-2013 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<http://www.gnu.org/licenses/>. */
#include <string.h>
#include <stdint.h>
#include "string-endian.h"
void *
__memchr (const void *s, int c, size_t n)
{
const uint64_t *last_word_ptr;
const uint64_t *p;
const char *last_byte_ptr;
uintptr_t s_int;
uint64_t goal, before_mask, v, bits;
char *ret;
if (__builtin_expect (n == 0, 0))
{
/* Don't dereference any memory if the array is empty. */
return NULL;
}
/* Get an aligned pointer. */
s_int = (uintptr_t) s;
p = (const uint64_t *) (s_int & -8);
/* Create eight copies of the byte for which we are looking. */
goal = copy_byte(c);
/* Read the first word, but munge it so that bytes before the array
will not match goal. */
before_mask = MASK (s_int);
v = (*p | before_mask) ^ (goal & before_mask);
/* Compute the address of the last byte. */
last_byte_ptr = (const char *) s + n - 1;
/* Compute the address of the word containing the last byte. */
last_word_ptr = (const uint64_t *) ((uintptr_t) last_byte_ptr & -8);
while ((bits = __insn_v1cmpeq (v, goal)) == 0)
{
if (__builtin_expect (p == last_word_ptr, 0))
{
/* We already read the last word in the array, so give up. */
return NULL;
}
v = *++p;
}
/* We found a match, but it might be in a byte past the end
of the array. */
ret = ((char *) p) + (CFZ (bits) >> 3);
return (ret <= last_byte_ptr) ? ret : NULL;
}
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)
|
