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130 lines
3.3 KiB
130 lines
3.3 KiB
// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "util/alarm.h"
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#include "util/osp_logging.h"
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namespace openscreen {
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class Alarm::CancelableFunctor {
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public:
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explicit CancelableFunctor(Alarm* alarm) : alarm_(alarm) {
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OSP_DCHECK(alarm_);
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OSP_DCHECK(!alarm_->queued_fire_);
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alarm_->queued_fire_ = this;
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}
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~CancelableFunctor() { Cancel(); }
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CancelableFunctor(CancelableFunctor&& other) : alarm_(other.alarm_) {
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other.alarm_ = nullptr;
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if (alarm_) {
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OSP_DCHECK_EQ(alarm_->queued_fire_, &other);
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alarm_->queued_fire_ = this;
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}
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}
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CancelableFunctor& operator=(CancelableFunctor&& other) {
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Cancel();
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alarm_ = other.alarm_;
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other.alarm_ = nullptr;
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if (alarm_) {
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OSP_DCHECK_EQ(alarm_->queued_fire_, &other);
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alarm_->queued_fire_ = this;
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}
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return *this;
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}
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void operator()() noexcept {
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if (alarm_) {
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OSP_DCHECK_EQ(alarm_->queued_fire_, this);
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alarm_->queued_fire_ = nullptr;
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alarm_->TryInvoke();
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alarm_ = nullptr;
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}
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}
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void Cancel() {
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if (alarm_) {
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OSP_DCHECK_EQ(alarm_->queued_fire_, this);
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alarm_->queued_fire_ = nullptr;
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alarm_ = nullptr;
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}
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}
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private:
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Alarm* alarm_;
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};
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Alarm::Alarm(ClockNowFunctionPtr now_function, TaskRunner* task_runner)
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: now_function_(now_function), task_runner_(task_runner) {
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OSP_DCHECK(now_function_);
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OSP_DCHECK(task_runner_);
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}
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Alarm::~Alarm() {
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if (queued_fire_) {
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queued_fire_->Cancel();
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OSP_DCHECK(!queued_fire_);
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}
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}
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void Alarm::Cancel() {
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scheduled_task_ = TaskRunner::Task();
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}
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void Alarm::ScheduleWithTask(TaskRunner::Task task,
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Clock::time_point desired_alarm_time) {
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OSP_DCHECK(task.valid());
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scheduled_task_ = std::move(task);
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const Clock::time_point now = now_function_();
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alarm_time_ = std::max(now, desired_alarm_time);
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// Ensure that a later firing will occur, and not too late.
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if (queued_fire_) {
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if (next_fire_time_ <= alarm_time_) {
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return;
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}
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queued_fire_->Cancel();
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OSP_DCHECK(!queued_fire_);
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}
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InvokeLater(now, alarm_time_);
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}
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void Alarm::InvokeLater(Clock::time_point now, Clock::time_point fire_time) {
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OSP_DCHECK(!queued_fire_);
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next_fire_time_ = fire_time;
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// Note: Instantiating the CancelableFunctor below sets |this->queued_fire_|.
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task_runner_->PostTaskWithDelay(CancelableFunctor(this), fire_time - now);
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}
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void Alarm::TryInvoke() {
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if (!scheduled_task_.valid()) {
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return; // This Alarm was canceled in the meantime.
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}
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// If this is an early firing, re-schedule for later. This happens if
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// Schedule() was called again before this firing had occurred.
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const Clock::time_point now = now_function_();
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if (now < alarm_time_) {
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InvokeLater(now, alarm_time_);
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return;
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}
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// Move the client Task to the stack before executing, just in case the task
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// itself: a) calls any Alarm methods re-entrantly, or b) causes the
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// destruction of this Alarm instance.
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// WARNING: |this| is not valid after here!
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TaskRunner::Task task = std::move(scheduled_task_);
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task();
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}
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// static
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constexpr Clock::time_point Alarm::kImmediately;
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} // namespace openscreen
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