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