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 <sys/cdefs.h>
26 __FBSDID("$FreeBSD$");
27
28 #include <limits.h>
29 #include <stdint.h>
30 #include <string.h>
31
32 #define SS (sizeof(size_t))
33 #define ALIGN (sizeof(size_t) - 1)
34 #define ONES ((size_t)-1 / UCHAR_MAX)
35 #define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
36 #define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)
37
38 void *
memchr(const void * src,int c,size_t n)39 memchr(const void *src, int c, size_t n)
40 {
41 const unsigned char *s = src;
42 c = (unsigned char)c;
43 #ifdef __GNUC__
44 for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--)
45 ;
46 if (n && *s != c) {
47 typedef size_t __attribute__((__may_alias__)) word;
48 const word *w;
49 size_t k = ONES * c;
50 for (w = (const void *)s; n >= SS && !HASZERO(*w ^ k);
51 w++, n -= SS)
52 ;
53 s = (const void *)w;
54 }
55 #endif
56 for (; n && *s != c; s++, n--)
57 ;
58 return n ? (void *)s : 0;
59 }
60