michael@0: /* -*- Mode: C++; tab-width: 12; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_SyncRunnable_h
michael@0: #define mozilla_SyncRunnable_h
michael@0: 
michael@0: #include "nsThreadUtils.h"
michael@0: #include "mozilla/Monitor.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: /**
michael@0:  * This class will wrap a nsIRunnable and dispatch it to the main thread
michael@0:  * synchronously. This is different from nsIEventTarget.DISPATCH_SYNC:
michael@0:  * this class does not spin the event loop waiting for the event to be
michael@0:  * dispatched. This means that you don't risk reentrance from pending
michael@0:  * messages, but you must be sure that the target thread does not ever block
michael@0:  * on this thread, or else you will deadlock.
michael@0:  *
michael@0:  * Typical usage:
michael@0:  * nsRefPtr<SyncRunnable> sr = new SyncRunnable(new myrunnable...());
michael@0:  * sr->DispatchToThread(t);
michael@0:  *
michael@0:  * We also provide a convenience wrapper:
michael@0:  * SyncRunnable::DispatchToThread(new myrunnable...());
michael@0:  *
michael@0:  */
michael@0: class SyncRunnable : public nsRunnable
michael@0: {
michael@0: public:
michael@0:   SyncRunnable(nsIRunnable* r)
michael@0:     : mRunnable(r)
michael@0:     , mMonitor("SyncRunnable")
michael@0:     , mDone(false)
michael@0:   { }
michael@0: 
michael@0:   void DispatchToThread(nsIEventTarget* thread,
michael@0:                         bool forceDispatch = false)
michael@0:   {
michael@0:     nsresult rv;
michael@0:     bool on;
michael@0: 
michael@0:     if (!forceDispatch) {
michael@0:       rv = thread->IsOnCurrentThread(&on);
michael@0:       MOZ_ASSERT(NS_SUCCEEDED(rv));
michael@0:       if (NS_SUCCEEDED(rv) && on) {
michael@0:         mRunnable->Run();
michael@0:         return;
michael@0:       }
michael@0:     }
michael@0: 
michael@0:     rv = thread->Dispatch(this, NS_DISPATCH_NORMAL);
michael@0:     if (NS_SUCCEEDED(rv)) {
michael@0:       mozilla::MonitorAutoLock lock(mMonitor);
michael@0:       while (!mDone) {
michael@0:         lock.Wait();
michael@0:       }
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   static void DispatchToThread(nsIEventTarget* thread,
michael@0:                                nsIRunnable* r,
michael@0:                                bool forceDispatch = false)
michael@0:   {
michael@0:     nsRefPtr<SyncRunnable> s(new SyncRunnable(r));
michael@0:     s->DispatchToThread(thread, forceDispatch);
michael@0:   }
michael@0: 
michael@0: protected:
michael@0:   NS_IMETHODIMP Run()
michael@0:   {
michael@0:     mRunnable->Run();
michael@0: 
michael@0:     mozilla::MonitorAutoLock lock(mMonitor);
michael@0:     MOZ_ASSERT(!mDone);
michael@0: 
michael@0:     mDone = true;
michael@0:     mMonitor.Notify();
michael@0: 
michael@0:     return NS_OK;
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   nsCOMPtr<nsIRunnable> mRunnable;
michael@0:   mozilla::Monitor mMonitor;
michael@0:   bool mDone;
michael@0: };
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif // mozilla_SyncRunnable_h