blob: 4974292a553498bc789dae5e4e938e95e311051c [file] [log] [blame]
Chris Metcalf867e3592010-05-28 23:09:12 -04001/*
2 * Copyright 2010 Tilera Corporation. All Rights Reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation, version 2.
7 *
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 * NON INFRINGEMENT. See the GNU General Public License for
12 * more details.
13 */
14
15#include <linux/types.h>
16#include <linux/string.h>
17#include <linux/module.h>
18
Chris Metcalf29507662010-10-14 16:39:42 -040019#undef strlen
20
Chris Metcalf867e3592010-05-28 23:09:12 -040021size_t strlen(const char *s)
22{
23 /* Get an aligned pointer. */
24 const uintptr_t s_int = (uintptr_t) s;
25 const uint32_t *p = (const uint32_t *)(s_int & -4);
26
27 /* Read the first word, but force bytes before the string to be nonzero.
28 * This expression works because we know shift counts are taken mod 32.
29 */
30 uint32_t v = *p | ((1 << (s_int << 3)) - 1);
31
32 uint32_t bits;
33 while ((bits = __insn_seqb(v, 0)) == 0)
34 v = *++p;
35
36 return ((const char *)p) + (__insn_ctz(bits) >> 3) - s;
37}
38EXPORT_SYMBOL(strlen);