1 files changed, 111 insertions, 0 deletions
diff --git a/xpcom/threads/AbstractThread.h b/xpcom/threads/AbstractThread.h
new file mode 100644
index 000000000..ca6ec1b84
--- /dev/null
+++ b/xpcom/threads/AbstractThread.h
@@ -0,0 +1,111 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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