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