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e16a7d8f3b
`et` means `expandtab`. ```sh rg 'vi: .* :vi' -l -0 | \ xargs -0 sed -i '' 's/vi: \(.*\) et\(.*\) :vi/vi: \1 xoet\2:vi/' rg 'vi: .* :vi' -l -0 | \ xargs -0 sed -i '' 's/vi: \(.*\)noet\(.*\):vi/vi: \1et\2 :vi/' rg 'vi: .* :vi' -l -0 | \ xargs -0 sed -i '' 's/vi: \(.*\)xoet\(.*\):vi/vi: \1noet\2:vi/' ```
58 lines
3 KiB
C
58 lines
3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 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/atomic.h"
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#include "libc/calls/struct/timespec.h"
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#include "libc/cosmo.h"
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#include "libc/errno.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/nexgen32e/x86feature.h"
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/**
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* @fileoverview Fast Monotonic Clock Polyfill for XNU/NT.
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*/
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static struct {
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atomic_uint once;
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struct timespec base_wall;
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uint64_t base_tick;
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} g_mono;
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static void sys_clock_gettime_mono_init(void) {
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g_mono.base_wall = timespec_real();
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g_mono.base_tick = rdtsc();
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}
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int sys_clock_gettime_mono(struct timespec *time) {
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uint64_t nanos;
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uint64_t cycles;
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#ifdef __x86_64__
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// intel architecture guarantees that a mapping exists between rdtsc &
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// nanoseconds only if the cpu advertises invariant timestamps support
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if (!X86_HAVE(INVTSC)) return -EINVAL;
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#endif
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cosmo_once(&g_mono.once, sys_clock_gettime_mono_init);
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cycles = rdtsc() - g_mono.base_tick;
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// this is a crude approximation, that's worked reasonably well so far
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// only the kernel knows the actual mapping between rdtsc and nanosecs
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// which we could attempt to measure ourselves using clock_gettime but
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// we'd need to impose 100 ms of startup latency for a guess this good
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nanos = cycles / 3;
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*time = timespec_add(g_mono.base_wall, timespec_fromnanos(nanos));
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return 0;
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}
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