55 lines
2.6 KiB
C
55 lines
2.6 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 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/intrin/pcmpeqb.h"
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#include "libc/intrin/pmovmskb.h"
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#include "libc/nexgen32e/bsf.h"
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#include "libc/str/str.h"
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/**
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* Compares memory.
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*
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* @return unsigned char subtraction at stop index
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* @asyncsignalsafe
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*/
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int memcmp(const void *a, const void *b, size_t n) {
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int c;
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size_t i;
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unsigned m;
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uint8_t *p1, *p2;
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uint8_t v1[16], v2[16];
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if (n) {
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for (p1 = a, p2 = b, i = 0; i + 16 <= n; i += 16) {
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memcpy(v1, p1 + i, 16);
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memcpy(v2, p2 + i, 16);
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pcmpeqb(v1, v1, v2);
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if ((m = pmovmskb(v1) - 0xffff)) {
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i += bsf(m);
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return p1[i] - p2[i];
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}
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}
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for (; i < n; ++i) {
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if ((c = p1[i] - p2[i])) {
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return c;
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}
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}
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}
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return 0;
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}
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