зеркало из https://github.com/mozilla/gecko-dev.git
116 строки
4.2 KiB
C++
116 строки
4.2 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* Implementation of the OS-independent methods of the TimeStamp class
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*/
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#include "mozilla/TimeStamp.h"
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#include "mozilla/Uptime.h"
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#include <string.h>
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#include <stdlib.h>
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namespace mozilla {
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/**
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* Wrapper class used to initialize static data used by the TimeStamp class
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*/
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struct TimeStampInitialization {
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/**
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* First timestamp taken when the class static initializers are run. This
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* timestamp is used to sanitize timestamps coming from different sources.
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*/
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TimeStamp mFirstTimeStamp;
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/**
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* Timestamp representing the time when the process was created. This field
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* is populated lazily the first time this information is required and is
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* replaced every time the process is restarted.
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*/
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TimeStamp mProcessCreation;
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TimeStampInitialization() {
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TimeStamp::Startup();
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mFirstTimeStamp = TimeStamp::Now();
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// On Windows < 10, initializing the uptime requires `mFirstTimeStamp` to be
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// valid.
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mozilla::InitializeUptime();
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}
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~TimeStampInitialization() { TimeStamp::Shutdown(); }
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};
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static TimeStampInitialization sInitOnce;
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MFBT_API TimeStamp TimeStamp::ProcessCreation() {
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if (sInitOnce.mProcessCreation.IsNull()) {
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char* mozAppRestart = getenv("MOZ_APP_RESTART");
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TimeStamp ts;
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/* When calling PR_SetEnv() with an empty value the existing variable may
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* be unset or set to the empty string depending on the underlying platform
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* thus we have to check if the variable is present and not empty. */
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if (mozAppRestart && (strcmp(mozAppRestart, "") != 0)) {
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/* Firefox was restarted, use the first time-stamp we've taken as the new
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* process startup time. */
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ts = sInitOnce.mFirstTimeStamp;
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} else {
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TimeStamp now = Now();
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uint64_t uptime = ComputeProcessUptime();
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ts = now - TimeDuration::FromMicroseconds(static_cast<double>(uptime));
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if ((ts > sInitOnce.mFirstTimeStamp) || (uptime == 0)) {
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ts = sInitOnce.mFirstTimeStamp;
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}
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}
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sInitOnce.mProcessCreation = ts;
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}
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return sInitOnce.mProcessCreation;
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}
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void TimeStamp::RecordProcessRestart() {
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sInitOnce.mProcessCreation = TimeStamp();
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}
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MFBT_API TimeStamp TimeStamp::FirstTimeStamp() {
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return sInitOnce.mFirstTimeStamp;
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}
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class TimeStampTests {
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// Check that nullity is set/not set correctly.
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static_assert(TimeStamp{TimeStampValue{0}}.IsNull());
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static_assert(!TimeStamp{TimeStampValue{1}}.IsNull());
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// Check that some very basic comparisons work correctly.
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static constexpr uint64_t sMidTime = (uint64_t)1 << 63;
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static_assert(TimeStampValue{sMidTime + 5} > TimeStampValue{sMidTime - 5});
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static_assert(TimeStampValue{sMidTime + 5} >= TimeStampValue{sMidTime - 5});
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static_assert(TimeStampValue{sMidTime - 5} < TimeStampValue{sMidTime + 5});
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static_assert(TimeStampValue{sMidTime - 5} <= TimeStampValue{sMidTime + 5});
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static_assert(TimeStampValue{sMidTime} == TimeStampValue{sMidTime});
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static_assert(TimeStampValue{sMidTime} >= TimeStampValue{sMidTime});
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static_assert(TimeStampValue{sMidTime} <= TimeStampValue{sMidTime});
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static_assert(TimeStampValue{sMidTime - 5} != TimeStampValue{sMidTime + 5});
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// Check that comparisons involving very large and very small TimeStampValue's
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// work correctly. This may seem excessive, but these asserts would have
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// failed in the past due to a comparison such as "a > b" being implemented as
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// "<cast to signed 64-bit value>(a - b) > 0". When a-b didn't fit into a
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// signed 64-bit value, this would have given an incorrect result.
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static_assert(TimeStampValue{UINT64_MAX} > TimeStampValue{1});
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static_assert(TimeStampValue{1} < TimeStampValue{UINT64_MAX});
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// NOTE/TODO: It would be nice to add some additional tests here that involve
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// arithmetic between TimeStamps and TimeDurations (and verifying some of the
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// special behaviors in some cases such as not wrapping around below zero) but
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// that is not possible right now because those operators are not constexpr.
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};
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} // namespace mozilla
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