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50 lines
2.8 KiB
C
50 lines
2.8 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/str/str.h"
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/**
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* Returns pointer to first instance of character.
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*
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* @param m is memory to search
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* @param c is search byte which is masked with 255
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* @param n is byte length of p
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* @return is pointer to first instance of c or NULL if not found
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* @asyncsignalsafe
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*/
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void *memchr(const void *m, int c, size_t n) {
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uint64_t v, w;
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const char *p, *pe;
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c &= 255;
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v = 0x0101010101010101ul * c;
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for (p = m, pe = p + n; p + 8 <= pe; p += 8) {
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w = (uint64_t)(255 & p[7]) << 070 | (uint64_t)(255 & p[6]) << 060 |
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(uint64_t)(255 & p[5]) << 050 | (uint64_t)(255 & p[4]) << 040 |
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(uint64_t)(255 & p[3]) << 030 | (uint64_t)(255 & p[2]) << 020 |
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(uint64_t)(255 & p[1]) << 010 | (uint64_t)(255 & p[0]) << 000;
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if ((w = ~(w ^ v) & ((w ^ v) - 0x0101010101010101) & 0x8080808080808080)) {
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return p + ((unsigned)__builtin_ctzll(w) >> 3);
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}
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}
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for (; p < pe; ++p) {
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if ((*p & 255) == c) {
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return p;
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}
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}
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return NULL;
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}
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