51 lines
2.6 KiB
C
51 lines
2.6 KiB
C
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/*-*- 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/assert.h"
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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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* Returns length of NUL-terminated string.
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*
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* @param s is non-null NUL-terminated string pointer
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* @return number of bytes (excluding NUL)
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* @asyncsignalsafe
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*/
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size_t strlen(const char *s) {
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const char *p;
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unsigned k, m;
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uint8_t v1[16], vz[16];
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k = (uintptr_t)s & 15;
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p = (const char *)((uintptr_t)s & -16);
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memset(vz, 0, 16);
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memcpy(v1, p, 16);
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pcmpeqb(v1, v1, vz);
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m = pmovmskb(v1) >> k << k;
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while (!m) {
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p += 16;
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memcpy(v1, p, 16);
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pcmpeqb(v1, v1, vz);
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m = pmovmskb(v1);
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}
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return p + bsf(m) - s;
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}
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