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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/bits.h"
#include "libc/bits/initializer.internal.h"
#include "libc/bits/safemacros.h"
#include "libc/calls/calls.h"
#include "libc/dce.h"
#include "libc/nexgen32e/rdtsc.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/sysv/consts/clock.h"
#include "libc/time/time.h"
static struct Now {
bool once;
uint64_t k0;
long double r0, cpn;
} g_now;
static long double GetTimeSample(void) {
uint64_t tick1, tick2;
long double time1, time2;
sched_yield();
time1 = dtime(CLOCK_MONOTONIC);
tick1 = rdtsc();
nanosleep(&(struct timespec){0, 100000}, NULL);
time2 = dtime(CLOCK_MONOTONIC);
tick2 = rdtsc();
return (time2 - time1) * 1e9 / MAX(1, tick2 - tick1);
}
static long double MeasureNanosPerCycle(void) {
int i;
long double avg, samp;
for (avg = 1.0L, i = 1; i < 5; ++i) {
samp = GetTimeSample();
avg += (samp - avg) / i;
}
return avg;
}
static void InitTime(void) {
g_now.cpn = MeasureNanosPerCycle();
g_now.r0 = dtime(CLOCK_REALTIME);
g_now.k0 = rdtsc();
g_now.once = true;
}
long double converttickstonanos(uint64_t ticks) {
if (!g_now.once) InitTime();
return ticks * g_now.cpn; /* pico scale */
}
long double converttickstoseconds(uint64_t ticks) {
return 1 / 1e9 * converttickstonanos(ticks);
}
long double nowl$sys(void) {
return dtime(CLOCK_REALTIME);
}
long double nowl$art(void) {
uint64_t ticks;
if (!g_now.once) InitTime();
ticks = unsignedsubtract(rdtsc(), g_now.k0);
return g_now.r0 + converttickstoseconds(ticks);
}