gecko-dev/xpcom/base/nsMessageLoop.cpp

162 lines
4.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsMessageLoop.h"
#include "mozilla/WeakPtr.h"
#include "base/message_loop.h"
#include "base/task.h"
#include "nsIRunnable.h"
#include "nsITimer.h"
#include "nsCOMPtr.h"
#include "nsAutoPtr.h"
#include "nsComponentManagerUtils.h"
#include "nsThreadUtils.h"
using namespace mozilla;
namespace {
/**
* This Task runs its nsIRunnable when Run() is called, or after
* aEnsureRunsAfterMS milliseconds have elapsed since the object was
* constructed.
*
* Note that the MessageLoop owns this object and will delete it after it calls
* Run(). Tread lightly.
*/
class MessageLoopIdleTask
: public Task
, public SupportsWeakPtr<MessageLoopIdleTask>
{
public:
MessageLoopIdleTask(nsIRunnable* aTask, uint32_t aEnsureRunsAfterMS);
virtual ~MessageLoopIdleTask() {}
virtual void Run();
private:
nsresult Init(uint32_t aEnsureRunsAfterMS);
nsCOMPtr<nsIRunnable> mTask;
nsCOMPtr<nsITimer> mTimer;
};
/**
* This timer callback calls MessageLoopIdleTask::Run() when its timer fires.
* (The timer can't call back into MessageLoopIdleTask directly since that's
* not a refcounted object; it's owned by the MessageLoop.)
*
* We keep a weak reference to the MessageLoopIdleTask, although a raw pointer
* should in theory suffice: When the MessageLoopIdleTask runs (right before
* the MessageLoop deletes it), it cancels its timer. But the weak pointer
* saves us from worrying about an edge case somehow messing us up here.
*/
class MessageLoopTimerCallback
: public nsITimerCallback
{
public:
MessageLoopTimerCallback(MessageLoopIdleTask* aTask);
virtual ~MessageLoopTimerCallback() {};
NS_DECL_ISUPPORTS
NS_DECL_NSITIMERCALLBACK
private:
WeakPtr<MessageLoopIdleTask> mTask;
};
MessageLoopIdleTask::MessageLoopIdleTask(nsIRunnable* aTask,
uint32_t aEnsureRunsAfterMS)
: mTask(aTask)
{
// Init() really shouldn't fail, but if it does, we schedule our runnable
// immediately, because it's more important to guarantee that we run the task
// eventually than it is to run the task when we're idle.
nsresult rv = Init(aEnsureRunsAfterMS);
if (NS_FAILED(rv)) {
NS_WARNING("Running idle task early because we couldn't initialize our timer.");
NS_DispatchToCurrentThread(mTask);
mTask = nullptr;
mTimer = nullptr;
}
}
nsresult
MessageLoopIdleTask::Init(uint32_t aEnsureRunsAfterMS)
{
mTimer = do_CreateInstance("@mozilla.org/timer;1");
if (NS_WARN_IF(!mTimer))
return NS_ERROR_UNEXPECTED;
nsRefPtr<MessageLoopTimerCallback> callback =
new MessageLoopTimerCallback(this);
return mTimer->InitWithCallback(callback, aEnsureRunsAfterMS,
nsITimer::TYPE_ONE_SHOT);
}
/* virtual */ void
MessageLoopIdleTask::Run()
{
// Null out our pointers because if Run() was called by the timer, this
// object will be kept alive by the MessageLoop until the MessageLoop calls
// Run().
if (mTimer) {
mTimer->Cancel();
mTimer = nullptr;
}
if (mTask) {
mTask->Run();
mTask = nullptr;
}
}
MessageLoopTimerCallback::MessageLoopTimerCallback(MessageLoopIdleTask* aTask)
: mTask(aTask->asWeakPtr())
{}
NS_IMETHODIMP
MessageLoopTimerCallback::Notify(nsITimer* aTimer)
{
// We don't expect to hit the case when the timer fires but mTask has been
// deleted, because mTask should cancel the timer before the mTask is
// deleted. But you never know...
NS_WARN_IF_FALSE(mTask, "This timer shouldn't have fired.");
if (mTask) {
mTask->Run();
}
return NS_OK;
}
NS_IMPL_ISUPPORTS1(MessageLoopTimerCallback, nsITimerCallback)
} // anonymous namespace
NS_IMPL_ISUPPORTS1(nsMessageLoop, nsIMessageLoop)
NS_IMETHODIMP
nsMessageLoop::PostIdleTask(nsIRunnable* aTask, uint32_t aEnsureRunsAfterMS)
{
// The message loop owns MessageLoopIdleTask and deletes it after calling
// Run(). Be careful...
MessageLoop::current()->PostIdleTask(FROM_HERE,
new MessageLoopIdleTask(aTask, aEnsureRunsAfterMS));
return NS_OK;
}
nsresult
nsMessageLoopConstructor(nsISupports* aOuter,
const nsIID& aIID,
void** aInstancePtr)
{
if (NS_WARN_IF(aOuter))
return NS_ERROR_NO_AGGREGATION;
nsISupports* messageLoop = new nsMessageLoop();
return messageLoop->QueryInterface(aIID, aInstancePtr);
}