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57 lines
1.9 KiB
C
57 lines
1.9 KiB
C
/*-
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* SPDX-License-Identifier: MIT
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*
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* Copyright (c) 2005-2014 Rich Felker, et al.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* This is a lightly patched version of FreeBSD's memchr.
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* https://cgit.freebsd.org/src/tree/lib/libc/string/memchr.c?h=releng/13.1
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*/
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#include <stdint.h>
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#include <string.h>
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#define SS (sizeof(size_t))
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#define ALIGN (sizeof(size_t) - 1)
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#define ONES ((size_t)-1 / 255)
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#define HIGHS (ONES * (255 / 2 + 1))
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#define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)
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void * memchr(const void *src, int c, size_t n) {
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const unsigned char *s = src;
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c = (unsigned char)c;
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for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--)
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;
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if (n && *s != c) {
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typedef size_t __attribute__((__may_alias__)) word;
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const word *w;
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size_t k = ONES * c;
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for (w = (const void *)s; n >= SS && !HASZERO(*w ^ k);
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w++, n -= SS)
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;
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s = (const void *)w;
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}
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for (; n && *s != c; s++, n--)
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;
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return n ? (void *)s : 0;
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}
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