blob: 2e8de6a5136f3f8ed3bd38916a336a79fefd3929 [file] [log] [blame]
Ken Steele59167002013-08-01 15:55:07 -04001/*
2 * Copyright 2013 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#include "string-endian.h"
19
20size_t strnlen(const char *s, size_t count)
21{
22 /* Get an aligned pointer. */
23 const uintptr_t s_int = (uintptr_t) s;
24 const uint64_t *p = (const uint64_t *)(s_int & -8);
25 size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1));
26 size_t len;
27 uint64_t v, bits;
28
29 /* Avoid page fault risk by not reading any bytes when count is 0. */
30 if (count == 0)
31 return 0;
32
33 /* Read and MASK the first word. */
34 v = *p | MASK(s_int);
35
36 while ((bits = __insn_v1cmpeqi(v, 0)) == 0) {
37 if (bytes_read >= count) {
38 /* Read COUNT bytes and didn't find the terminator. */
39 return count;
40 }
41 v = *++p;
42 bytes_read += sizeof(v);
43 }
44
45 len = ((const char *) p) + (CFZ(bits) >> 3) - s;
46 return (len < count ? len : count);
47}
48EXPORT_SYMBOL(strnlen);