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/* -*- Mode: C++; tab-width: 8; 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/. */
#if !defined(AbstractThread_h_)
#define AbstractThread_h_
#include "nscore.h"
#include "nsIRunnable.h"
#include "nsISupportsImpl.h"
#include "nsIThread.h"
#include "mozilla/RefPtr.h"
#include "mozilla/ThreadLocal.h"
namespace mozilla {
class TaskQueue;
class TaskDispatcher;
/*
* We often want to run tasks on a target that guarantees that events will never
* run in parallel. There are various target types that achieve this - namely
* nsIThread and TaskQueue. Note that nsIThreadPool (which implements
* nsIEventTarget) does not have this property, so we do not want to use
* nsIEventTarget for this purpose. This class encapsulates the specifics of
* the structures we might use here and provides a consistent interface.
*
* At present, the supported AbstractThread implementations are TaskQueue
* and AbstractThread::MainThread. If you add support for another thread that is
* not the MainThread, you'll need to figure out how to make it unique such that
* comparing AbstractThread pointers is equivalent to comparing nsIThread pointers.
*/
class AbstractThread
{
public:
// Returns the AbstractThread that the caller is currently running in, or null
// if the caller is not running in an AbstractThread.
static AbstractThread* GetCurrent() { return sCurrentThreadTLS.get(); }
AbstractThread(bool aSupportsTailDispatch) : mSupportsTailDispatch(aSupportsTailDispatch) {}
static already_AddRefed<AbstractThread>
CreateXPCOMThreadWrapper(nsIThread* aThread, bool aRequireTailDispatch);
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AbstractThread);
enum DispatchFailureHandling { AssertDispatchSuccess, DontAssertDispatchSuccess };
enum DispatchReason { NormalDispatch, TailDispatch };
virtual void Dispatch(already_AddRefed<nsIRunnable> aRunnable,
DispatchFailureHandling aHandling = AssertDispatchSuccess,
DispatchReason aReason = NormalDispatch) = 0;
virtual bool IsCurrentThreadIn() = 0;
// Returns true if dispatch is generally reliable. This is used to guard
// against FlushableTaskQueues, which should go away.
virtual bool IsDispatchReliable() { return true; }
// Returns a TaskDispatcher that will dispatch its tasks when the currently-
// running tasks pops off the stack.
//
// May only be called when running within the it is invoked up, and only on
// threads which support it.
virtual TaskDispatcher& TailDispatcher() = 0;
// Returns true if we have tail tasks scheduled, or if this isn't known.
// Returns false if we definitely don't have any tail tasks.
virtual bool MightHaveTailTasks() { return true; }
// Helper functions for methods on the tail TasklDispatcher. These check
// HasTailTasks to avoid allocating a TailDispatcher if it isn't
// needed.
void TailDispatchTasksFor(AbstractThread* aThread);
bool HasTailTasksFor(AbstractThread* aThread);
// Returns true if this supports the tail dispatcher.
bool SupportsTailDispatch() const { return mSupportsTailDispatch; }
// Returns true if this thread requires all dispatches originating from
// aThread go through the tail dispatcher.
bool RequiresTailDispatch(AbstractThread* aThread) const;
bool RequiresTailDispatchFromCurrentThread() const;
virtual TaskQueue* AsTaskQueue() { MOZ_CRASH("Not a task queue!"); }
virtual nsIThread* AsXPCOMThread() { MOZ_CRASH("Not an XPCOM thread!"); }
// Convenience method for getting an AbstractThread for the main thread.
static AbstractThread* MainThread();
// Must be called exactly once during startup.
static void InitStatics();
void DispatchStateChange(already_AddRefed<nsIRunnable> aRunnable);
static void DispatchDirectTask(already_AddRefed<nsIRunnable> aRunnable);
protected:
virtual ~AbstractThread() {}
static MOZ_THREAD_LOCAL(AbstractThread*) sCurrentThreadTLS;
// True if we want to require that every task dispatched from tasks running in
// this queue go through our queue's tail dispatcher.
const bool mSupportsTailDispatch;
};
} // namespace mozilla
#endif
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