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
35 void *
memchr(const void * src,int c,size_t n)36 memchr(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