kopia lustrzana https://github.com/Hamlib/Hamlib
165 wiersze
4.4 KiB
C
165 wiersze
4.4 KiB
C
// ---------------------------------------------------------------------
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// precise_time.cxx
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//
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// Copyright (C) 2023
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// Dave Freese, W1HKJ
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//
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// This file is part of flrig
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//
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// flrig 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, either version 3 of the License, or
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// (at your option) any later version.
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//
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// flrig is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU 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 fldigi. If not, see <http://www.gnu.org/licenses/>.
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// ---------------------------------------------------------------------
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#include <errno.h>
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#include <time.h>
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#include <sys/time.h>
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#if 0
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// return current tick time in seconds
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double monotonic_seconds()
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{
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static struct timeval t1;
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gettimeofday(&t1, NULL);
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return t1.tv_sec + t1.tv_usec / 1e6;
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}
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#else
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//======================================================================
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//
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// A cross platform monotonic timer.
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// Copyright 2013 Alex Reece.
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//
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#include <unistd.h>
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#define NANOS_PER_SECF 1000000000.0
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#define USECS_PER_SEC 1000000
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static int showme = 0;
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#if _POSIX_TIMERS > 0 && defined(_POSIX_MONOTONIC_CLOCK)
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// If we have it, use clock_gettime and CLOCK_MONOTONIC.
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#include <time.h>
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double monotonic_seconds() {
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if (showme) {
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showme = 0;
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}
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struct timespec time;
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// Note: Make sure to link with -lrt to define clock_gettime.
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clock_gettime(CLOCK_MONOTONIC, &time);
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return ((double) time.tv_sec) + ((double) time.tv_nsec / (NANOS_PER_SECF));
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}
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#elif defined(__APPLE__)
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// If we don't have CLOCK_MONOTONIC, we might be on a Mac. There we instead
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// use mach_absolute_time().
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#include <mach/mach_time.h>
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static mach_timebase_info_data_t info;
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static void __attribute__((constructor)) init_info() {
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mach_timebase_info(&info);
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}
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double monotonic_seconds() {
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uint64_t time = mach_absolute_time();
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double dtime = (double) time;
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dtime *= (double) info.numer;
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dtime /= (double) info.denom;
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return dtime / NANOS_PER_SECF;
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}
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#elif defined(__WIN32__)
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// On Windows, use QueryPerformanceCounter and QueryPerformanceFrequency.
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#include <windows.h>
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static double PCFreq = 0.0;
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// According to http://stackoverflow.com/q/1113409/447288, this will
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// make this function a constructor.
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// TODO(awreece) Actually attempt to compile on windows.
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// w1hkj - builds OK on mingw32
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static void __cdecl init_pcfreq();
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__declspec(allocate(".CRT$XCU")) void (__cdecl*init_pcfreq_)() = init_pcfreq;
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static void __cdecl init_pcfreq() {
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// Accoring to http://stackoverflow.com/a/1739265/447288, this will
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// properly initialize the QueryPerformanceCounter.
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LARGE_INTEGER li;
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int has_qpc = QueryPerformanceFrequency(&li);
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assert(has_qpc);
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PCFreq = ((double) li.QuadPart) / 1000.0;
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}
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double monotonic_seconds() {
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LARGE_INTEGER li;
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QueryPerformanceCounter(&li);
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return ((double) li.QuadPart) / PCFreq;
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}
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#else
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// Fall back to rdtsc. The reason we don't use clock() is this scary message
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// from the man page:
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// "On several other implementations, the value returned by clock() also
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// includes the times of any children whose status has been collected via
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// wait(2) (or another wait-type call)."
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//
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// Also, clock() only has microsecond accuracy.
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//
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// This whitepaper offered excellent advice on how to use rdtscp for
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// profiling: http://download.intel.com/embedded/software/IA/324264.pdf
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//
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// Unfortunately, we can't follow its advice exactly with our semantics,
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// so we're just going to use rdtscp with cpuid.
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//
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// Note that rdtscp will only be available on new processors.
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#include <stdint.h>
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static inline uint64_t rdtsc() {
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uint32_t hi, lo;
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asm volatile("rdtscp\n"
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"movl %%edx, %0\n"
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"movl %%eax, %1\n"
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"cpuid"
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: "=r" (hi), "=r" (lo) : : "%rax", "%rbx", "%rcx", "%rdx");
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return (((uint64_t)hi) << 32) | (uint64_t)lo;
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}
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static uint64_t rdtsc_per_sec = 0;
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static void __attribute__((constructor)) init_rdtsc_per_sec() {
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uint64_t before, after;
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before = rdtsc();
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usleep(USECS_PER_SEC);
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after = rdtsc();
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rdtsc_per_sec = after - before;
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}
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double monotonic_seconds() {
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if (showme) {
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showme = false;
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}
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return (double) rdtsc() / (double) rdtsc_per_sec;
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}
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#endif
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#endif
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