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/*
* Copyright (C) 2019 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "TaskSource.h"
#include <wtf/Function.h>
#include <wtf/RefCounted.h>
#include <wtf/StdLibExtras.h>
#include <wtf/WeakHashSet.h>
#include <wtf/WeakPtr.h>
namespace WebCore {
class ActiveDOMCallbackMicrotask;
class EventLoopTaskGroup;
class EventTarget;
class MicrotaskQueue;
class ScriptExecutionContext;
class EventLoopTask {
WTF_MAKE_NONCOPYABLE(EventLoopTask);
WTF_MAKE_FAST_ALLOCATED;
public:
virtual ~EventLoopTask() = default;
TaskSource taskSource() { return m_taskSource; }
virtual void execute() = 0;
EventLoopTaskGroup* group() const { return m_group.get(); }
protected:
EventLoopTask(TaskSource, EventLoopTaskGroup&);
private:
const TaskSource m_taskSource;
WeakPtr<EventLoopTaskGroup> m_group;
};
// https://html.spec.whatwg.org/multipage/webappapis.html#event-loop
class EventLoop : public RefCounted<EventLoop>, public CanMakeWeakPtr<EventLoop> {
public:
virtual ~EventLoop() = default;
typedef Function<void ()> TaskFunction;
void queueTask(std::unique_ptr<EventLoopTask>&&);
// https://html.spec.whatwg.org/multipage/webappapis.html#queue-a-microtask
void queueMicrotask(std::unique_ptr<EventLoopTask>&&);
// https://html.spec.whatwg.org/multipage/webappapis.html#perform-a-microtask-checkpoint
void performMicrotaskCheckpoint();
virtual MicrotaskQueue& microtaskQueue() = 0;
void resumeGroup(EventLoopTaskGroup&);
void stopGroup(EventLoopTaskGroup&);
void registerGroup(EventLoopTaskGroup&);
void unregisterGroup(EventLoopTaskGroup&);
void stopAssociatedGroupsIfNecessary();
protected:
EventLoop() = default;
void run();
void clearAllTasks();
private:
void scheduleToRunIfNeeded();
virtual void scheduleToRun() = 0;
virtual bool isContextThread() const = 0;
// Use a global queue instead of multiple task queues since HTML5 spec allows UA to pick arbitrary queue.
Vector<std::unique_ptr<EventLoopTask>> m_tasks;
WeakHashSet<EventLoopTaskGroup> m_associatedGroups;
WeakHashSet<EventLoopTaskGroup> m_groupsWithSuspendedTasks;
bool m_isScheduledToRun { false };
};
class EventLoopTaskGroup : public CanMakeWeakPtr<EventLoopTaskGroup> {
WTF_MAKE_NONCOPYABLE(EventLoopTaskGroup);
WTF_MAKE_FAST_ALLOCATED;
public:
EventLoopTaskGroup(EventLoop& eventLoop)
: m_eventLoop(eventLoop)
{
eventLoop.registerGroup(*this);
}
~EventLoopTaskGroup()
{
if (auto* eventLoop = m_eventLoop.get())
eventLoop->unregisterGroup(*this);
}
bool hasSameEventLoopAs(EventLoopTaskGroup& otherGroup)
{
ASSERT(m_eventLoop);
return m_eventLoop == otherGroup.m_eventLoop;
}
bool matchesTask(EventLoopTask& task) const
{
auto* group = task.group();
return group == this;
}
// Marks the group as ready to stop but it won't actually be stopped
// until all groups in this event loop are ready to stop.
void markAsReadyToStop()
{
if (isReadyToStop() || isStoppedPermanently())
return;
bool wasSuspended = isSuspended();
m_state = State::ReadyToStop;
if (auto* eventLoop = m_eventLoop.get())
eventLoop->stopAssociatedGroupsIfNecessary();
if (wasSuspended && !isStoppedPermanently()) {
// We we get marked as ready to stop while suspended (happens when a CachedPage gets destroyed) then the
// queued tasks will never be able to run (since tasks don't run while suspended and we will never resume).
// As a result, we can simply discard our tasks and stop permanently.
stopAndDiscardAllTasks();
}
}
// This gets called by the event loop when all groups in the EventLoop as ready to stop.
void stopAndDiscardAllTasks()
{
ASSERT(isReadyToStop());
m_state = State::Stopped;
if (auto* eventLoop = m_eventLoop.get())
eventLoop->stopGroup(*this);
}
void suspend()
{
ASSERT(!isStoppedPermanently());
ASSERT(!isReadyToStop());
m_state = State::Suspended;
// We don't remove suspended tasks to preserve the ordering.
// EventLoop::run checks whether each task's group is suspended or not.
}
void resume()
{
ASSERT(!isStoppedPermanently());
ASSERT(!isReadyToStop());
m_state = State::Running;
if (auto* eventLoop = m_eventLoop.get())
eventLoop->resumeGroup(*this);
}
bool isStoppedPermanently() const { return m_state == State::Stopped; }
bool isSuspended() const { return m_state == State::Suspended; }
bool isReadyToStop() const { return m_state == State::ReadyToStop; }
void queueTask(std::unique_ptr<EventLoopTask>&&);
WEBCORE_EXPORT void queueTask(TaskSource, EventLoop::TaskFunction&&);
// https://html.spec.whatwg.org/multipage/webappapis.html#queue-a-microtask
WEBCORE_EXPORT void queueMicrotask(EventLoop::TaskFunction&&);
MicrotaskQueue& microtaskQueue() { return m_eventLoop->microtaskQueue(); }
// https://html.spec.whatwg.org/multipage/webappapis.html#perform-a-microtask-checkpoint
void performMicrotaskCheckpoint();
void runAtEndOfMicrotaskCheckpoint(EventLoop::TaskFunction&&);
private:
enum class State : uint8_t { Running, Suspended, ReadyToStop, Stopped };
WeakPtr<EventLoop> m_eventLoop;
State m_state { State::Running };
};
inline EventLoopTask::EventLoopTask(TaskSource source, EventLoopTaskGroup& group)
: m_taskSource(source)
, m_group(group)
{ }
} // namespace WebCore
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