Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/asyncinvoker.h

@@ -0,0 +1,134 @@
+/*
+ *  Copyright 2014 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_ASYNCINVOKER_H_
+#define WEBRTC_BASE_ASYNCINVOKER_H_
+
+#include "webrtc/base/asyncinvoker-inl.h"
+#include "webrtc/base/bind.h"
+#include "webrtc/base/sigslot.h"
+#include "webrtc/base/scopedptrcollection.h"
+#include "webrtc/base/thread.h"
+
+namespace rtc {
+
+// Invokes function objects (aka functors) asynchronously on a Thread, and
+// owns the lifetime of calls (ie, when this object is destroyed, calls in
+// flight are cancelled). AsyncInvoker can optionally execute a user-specified
+// function when the asynchronous call is complete, or operates in
+// fire-and-forget mode otherwise.
+//
+// AsyncInvoker does not own the thread it calls functors on.
+//
+// A note about async calls and object lifetimes: users should
+// be mindful of object lifetimes when calling functions asynchronously and
+// ensure objects used by the function _cannot_ be deleted between the
+// invocation and execution of the functor. AsyncInvoker is designed to
+// help: any calls in flight will be cancelled when the AsyncInvoker used to
+// make the call is destructed, and any calls executing will be allowed to
+// complete before AsyncInvoker destructs.
+//
+// The easiest way to ensure lifetimes are handled correctly is to create a
+// class that owns the Thread and AsyncInvoker objects, and then call its
+// methods asynchronously as needed.
+//
+// Example:
+//   class MyClass {
+//    public:
+//     void FireAsyncTaskWithResult(Thread* thread, int x) {
+//       // Specify a callback to get the result upon completion.
+//       invoker_.AsyncInvoke<int>(
+//           thread, Bind(&MyClass::AsyncTaskWithResult, this, x),
+//           &MyClass::OnTaskComplete, this);
+//     }
+//     void FireAnotherAsyncTask(Thread* thread) {
+//       // No callback specified means fire-and-forget.
+//       invoker_.AsyncInvoke<void>(
+//           thread, Bind(&MyClass::AnotherAsyncTask, this));
+//
+//    private:
+//     int AsyncTaskWithResult(int x) {
+//       // Some long running process...
+//       return x * x;
+//     }
+//     void AnotherAsyncTask() {
+//       // Some other long running process...
+//     }
+//     void OnTaskComplete(int result) { result_ = result; }
+//
+//     AsyncInvoker invoker_;
+//     int result_;
+//   };
+class AsyncInvoker : public MessageHandler {
+ public:
+  AsyncInvoker();
+  virtual ~AsyncInvoker();
+
+  // Call |functor| asynchronously on |thread|, with no callback upon
+  // completion. Returns immediately.
+  template <class ReturnT, class FunctorT>
+  void AsyncInvoke(Thread* thread,
+                   const FunctorT& functor,
+                   uint32 id = 0) {
+    AsyncClosure* closure =
+        new RefCountedObject<FireAndForgetAsyncClosure<FunctorT> >(functor);
+    DoInvoke(thread, closure, id);
+  }
+
+  // Call |functor| asynchronously on |thread|, calling |callback| when done.
+  template <class ReturnT, class FunctorT, class HostT>
+  void AsyncInvoke(Thread* thread,
+                   const FunctorT& functor,
+                   void (HostT::*callback)(ReturnT),
+                   HostT* callback_host,
+                   uint32 id = 0) {
+    AsyncClosure* closure =
+        new RefCountedObject<NotifyingAsyncClosure<ReturnT, FunctorT, HostT> >(
+            this, Thread::Current(), functor, callback, callback_host);
+    DoInvoke(thread, closure, id);
+  }
+
+  // Call |functor| asynchronously on |thread|, calling |callback| when done.
+  // Overloaded for void return.
+  template <class ReturnT, class FunctorT, class HostT>
+  void AsyncInvoke(Thread* thread,
+                   const FunctorT& functor,
+                   void (HostT::*callback)(),
+                   HostT* callback_host,
+                   uint32 id = 0) {
+    AsyncClosure* closure =
+        new RefCountedObject<NotifyingAsyncClosure<void, FunctorT, HostT> >(
+            this, Thread::Current(), functor, callback, callback_host);
+    DoInvoke(thread, closure, id);
+  }
+
+  // Synchronously execute on |thread| all outstanding calls we own
+  // that are pending on |thread|, and wait for calls to complete
+  // before returning. Optionally filter by message id.
+  // The destructor will not wait for outstanding calls, so if that
+  // behavior is desired, call Flush() before destroying this object.
+  void Flush(Thread* thread, uint32 id = MQID_ANY);
+
+  // Signaled when this object is destructed.
+  sigslot::signal0<> SignalInvokerDestroyed;
+
+ private:
+  virtual void OnMessage(Message* msg);
+  void DoInvoke(Thread* thread, AsyncClosure* closure, uint32 id);
+
+  bool destroying_;
+
+  DISALLOW_COPY_AND_ASSIGN(AsyncInvoker);
+};
+
+}  // namespace rtc
+
+
+#endif  // WEBRTC_BASE_ASYNCINVOKER_H_