1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/threads/SyncRunnable.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,93 @@
1.4 +/* -*- Mode: C++; tab-width: 12; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef mozilla_SyncRunnable_h
1.10 +#define mozilla_SyncRunnable_h
1.11 +
1.12 +#include "nsThreadUtils.h"
1.13 +#include "mozilla/Monitor.h"
1.14 +
1.15 +namespace mozilla {
1.16 +
1.17 +/**
1.18 + * This class will wrap a nsIRunnable and dispatch it to the main thread
1.19 + * synchronously. This is different from nsIEventTarget.DISPATCH_SYNC:
1.20 + * this class does not spin the event loop waiting for the event to be
1.21 + * dispatched. This means that you don't risk reentrance from pending
1.22 + * messages, but you must be sure that the target thread does not ever block
1.23 + * on this thread, or else you will deadlock.
1.24 + *
1.25 + * Typical usage:
1.26 + * nsRefPtr<SyncRunnable> sr = new SyncRunnable(new myrunnable...());
1.27 + * sr->DispatchToThread(t);
1.28 + *
1.29 + * We also provide a convenience wrapper:
1.30 + * SyncRunnable::DispatchToThread(new myrunnable...());
1.31 + *
1.32 + */
1.33 +class SyncRunnable : public nsRunnable
1.34 +{
1.35 +public:
1.36 + SyncRunnable(nsIRunnable* r)
1.37 + : mRunnable(r)
1.38 + , mMonitor("SyncRunnable")
1.39 + , mDone(false)
1.40 + { }
1.41 +
1.42 + void DispatchToThread(nsIEventTarget* thread,
1.43 + bool forceDispatch = false)
1.44 + {
1.45 + nsresult rv;
1.46 + bool on;
1.47 +
1.48 + if (!forceDispatch) {
1.49 + rv = thread->IsOnCurrentThread(&on);
1.50 + MOZ_ASSERT(NS_SUCCEEDED(rv));
1.51 + if (NS_SUCCEEDED(rv) && on) {
1.52 + mRunnable->Run();
1.53 + return;
1.54 + }
1.55 + }
1.56 +
1.57 + rv = thread->Dispatch(this, NS_DISPATCH_NORMAL);
1.58 + if (NS_SUCCEEDED(rv)) {
1.59 + mozilla::MonitorAutoLock lock(mMonitor);
1.60 + while (!mDone) {
1.61 + lock.Wait();
1.62 + }
1.63 + }
1.64 + }
1.65 +
1.66 + static void DispatchToThread(nsIEventTarget* thread,
1.67 + nsIRunnable* r,
1.68 + bool forceDispatch = false)
1.69 + {
1.70 + nsRefPtr<SyncRunnable> s(new SyncRunnable(r));
1.71 + s->DispatchToThread(thread, forceDispatch);
1.72 + }
1.73 +
1.74 +protected:
1.75 + NS_IMETHODIMP Run()
1.76 + {
1.77 + mRunnable->Run();
1.78 +
1.79 + mozilla::MonitorAutoLock lock(mMonitor);
1.80 + MOZ_ASSERT(!mDone);
1.81 +
1.82 + mDone = true;
1.83 + mMonitor.Notify();
1.84 +
1.85 + return NS_OK;
1.86 + }
1.87 +
1.88 +private:
1.89 + nsCOMPtr<nsIRunnable> mRunnable;
1.90 + mozilla::Monitor mMonitor;
1.91 + bool mDone;
1.92 +};
1.93 +
1.94 +} // namespace mozilla
1.95 +
1.96 +#endif // mozilla_SyncRunnable_h
