1/*
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);
49