1/*-
2 * SPDX-License-Identifier: MIT
3 *
4 * Copyright (c) 2005-2014 Rich Felker, et al.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining
7 * a copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sublicense, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be
15 * included in all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
20 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
21 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
22 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
23 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24 */
25#include <limits.h>
26#include <stdint.h>
27#include <string.h>
28
29#define SS (sizeof(size_t))
30#define ALIGN (sizeof(size_t) - 1)
31#define ONES ((size_t)-1 / UCHAR_MAX)
32#define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
33#define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)
34
35void *
36memchr(const void *src, int c, size_t n)
37{
38	const unsigned char *s = src;
39	c = (unsigned char)c;
40#ifdef __GNUC__
41	for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--)
42		;
43	if (n && *s != c) {
44		typedef size_t __attribute__((__may_alias__)) word;
45		const word *w;
46		size_t k = ONES * c;
47		for (w = (const void *)s; n >= SS && !HASZERO(*w ^ k);
48		     w++, n -= SS)
49			;
50		s = (const void *)w;
51	}
52#endif
53	for (; n && *s != c; s++, n--)
54		;
55	return n ? (void *)s : 0;
56}
57