blob: adad3d80e474976ea332b31f45f9372cd6841d26 (
plain) (
blame)
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
|
/* Copyright (C) 2011-2017 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>
size_t
strlen (const char *s)
{
/* Get an aligned pointer. */
const uintptr_t s_int = (uintptr_t) s;
const uint32_t *p = (const uint32_t *) (s_int & -4);
/* Read the first word, but force bytes before the string to be nonzero.
This expression works because we know shift counts are taken mod 32. */
uint32_t v = *p | ((1 << (s_int << 3)) - 1);
uint32_t bits;
while ((bits = __insn_seqb (v, 0)) == 0)
v = *++p;
return ((const char *) p) + (__insn_ctz (bits) >> 3) - s;
}
libc_hidden_builtin_def (strlen)
|
