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373bb7bec4
SystemTimeNanos() will soon be replaced with another implementation when built with Chromium. This will break the assumption of SystemTimeNanos() being relative to the NTP epoch. To avoid breaking any UWP apps, call the TimeHelper::Ticks() function directly, which is synchronized with the NTP epoch during initialization. Bug: chromium:516700 Change-Id: I4e50cb3f88d06e1385e73b1a9ded52956501dc1f Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208520 Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Niels Moller <nisse@webrtc.org> Commit-Queue: Johannes Kron <kron@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33324}
92 lines
2.9 KiB
C++
92 lines
2.9 KiB
C++
/*
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* Copyright 2021 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include <stdint.h>
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#include <limits>
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#if defined(WEBRTC_POSIX)
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#include <sys/time.h>
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#if defined(WEBRTC_MAC)
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#include <mach/mach_time.h>
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#endif
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#endif
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#if defined(WEBRTC_WIN)
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// clang-format off
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// clang formatting would put <windows.h> last,
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// which leads to compilation failure.
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#include <windows.h>
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#include <mmsystem.h>
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#include <sys/timeb.h>
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// clang-format on
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#endif
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#include "rtc_base/checks.h"
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#include "rtc_base/numerics/safe_conversions.h"
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#include "rtc_base/system_time.h"
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#include "rtc_base/time_utils.h"
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namespace rtc {
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int64_t SystemTimeNanos() {
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int64_t ticks;
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#if defined(WEBRTC_MAC)
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static mach_timebase_info_data_t timebase;
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if (timebase.denom == 0) {
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// Get the timebase if this is the first time we run.
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// Recommended by Apple's QA1398.
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if (mach_timebase_info(&timebase) != KERN_SUCCESS) {
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RTC_NOTREACHED();
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}
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}
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// Use timebase to convert absolute time tick units into nanoseconds.
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const auto mul = [](uint64_t a, uint32_t b) -> int64_t {
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RTC_DCHECK_NE(b, 0);
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RTC_DCHECK_LE(a, std::numeric_limits<int64_t>::max() / b)
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<< "The multiplication " << a << " * " << b << " overflows";
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return rtc::dchecked_cast<int64_t>(a * b);
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};
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ticks = mul(mach_absolute_time(), timebase.numer) / timebase.denom;
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#elif defined(WEBRTC_POSIX)
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struct timespec ts;
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// TODO(deadbeef): Do we need to handle the case when CLOCK_MONOTONIC is not
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// supported?
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clock_gettime(CLOCK_MONOTONIC, &ts);
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ticks = kNumNanosecsPerSec * static_cast<int64_t>(ts.tv_sec) +
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static_cast<int64_t>(ts.tv_nsec);
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#elif defined(WINUWP)
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ticks = WinUwpSystemTimeNanos();
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#elif defined(WEBRTC_WIN)
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static volatile LONG last_timegettime = 0;
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static volatile int64_t num_wrap_timegettime = 0;
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volatile LONG* last_timegettime_ptr = &last_timegettime;
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DWORD now = timeGetTime();
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// Atomically update the last gotten time
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DWORD old = InterlockedExchange(last_timegettime_ptr, now);
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if (now < old) {
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// If now is earlier than old, there may have been a race between threads.
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// 0x0fffffff ~3.1 days, the code will not take that long to execute
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// so it must have been a wrap around.
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if (old > 0xf0000000 && now < 0x0fffffff) {
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num_wrap_timegettime++;
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}
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}
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ticks = now + (num_wrap_timegettime << 32);
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// TODO(deadbeef): Calculate with nanosecond precision. Otherwise, we're
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// just wasting a multiply and divide when doing Time() on Windows.
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ticks = ticks * kNumNanosecsPerMillisec;
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#else
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#error Unsupported platform.
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#endif
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return ticks;
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}
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} // namespace rtc
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