mirror of
https://github.com/jart/cosmopolitan.git
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86 lines
3.5 KiB
C
86 lines
3.5 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 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/runtime/clktck.h"
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#include "libc/calls/calls.h"
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#include "libc/dce.h"
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#include "libc/fmt/wintime.internal.h"
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#include "libc/intrin/getauxval.internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/auxv.h"
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struct clockinfo_netbsd {
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int32_t hz; // number of clock ticks per second
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int32_t tick; // µs per tick
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int32_t tickadj; // skew rate for adjtime()
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int32_t stathz; // statistics clock frequency
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int32_t profhz; // profiling clock frequency
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};
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static int clk_tck;
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static dontinline int __clk_tck_init(void) {
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int x;
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int cmd[2];
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size_t len;
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struct clockinfo_netbsd clock;
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if (IsWindows()) {
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// MSVC defines CLK_TCK as 1000 but 1ms is obviously not the
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// scheduling quantum Windows actually uses. If we define it
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// as 30 rather than 1000, then clock_nanosleep is much more
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// accurately able to predict the duration of its busy waits
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x = 30;
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} else if (IsXnu() || IsOpenbsd()) {
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x = 100;
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} else if (IsFreebsd()) {
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x = 128;
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} else if (IsNetbsd()) {
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cmd[0] = 1; // CTL_KERN
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cmd[1] = 12; // KERN_CLOCKRATE
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len = sizeof(clock);
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if (sysctl(cmd, 2, &clock, &len, NULL, 0) != -1) {
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x = clock.hz;
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} else {
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x = -1;
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}
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} else {
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x = __getauxval(AT_CLKTCK).value;
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}
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if (x < 1)
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x = 100;
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clk_tck = x;
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return x;
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}
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/**
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* Returns system clock ticks per second.
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*
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* The returned value is memoized. This function is intended to be
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* used via the `CLK_TCK` macro wrapper.
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*
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* The returned value is always greater than zero. It's usually 100
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* hertz which means each clock tick is 10 milliseconds long.
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*/
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int __clk_tck(void) {
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if (clk_tck) {
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return clk_tck;
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} else {
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return __clk_tck_init();
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}
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}
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