Implementation of PostTaskAndReply() in MessageLoopProxy and BrowserThread.

base/task.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TASK_H_
 #define BASE_TASK_H_
 #pragma once
 
 #include "base/base_api.h"
+#include "base/callback.h"
 #include "base/debug/alias.h"
 #include "base/memory/raw_scoped_refptr_mismatch_checker.h"
 #include "base/memory/weak_ptr.h"
 #include "base/tracked.h"
 #include "base/tuple.h"
 
 namespace base {
 const size_t kDeadTask = 0xDEAD7A53;
 }
 
@@ skipping 537 matching lines @@
   ~ScopedTaskRunner();
 
   Task* Release();
 
  private:
   Task* task_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedTaskRunner);
 };
 
+namespace internal {
+
+class PostTaskAndReplyRelay {
+ public:
+  PostTaskAndReplyRelay(const Closure& task, const Closure& reply);
+
+  ~PostTaskAndReplyRelay();
+
+  void Run();
+
+ private:
+  void RunReplyAndSelfDestruct();
+
+  base::Closure task_;
+  base::Closure reply_;
+};
+}  // namespace internal

[darin (slow to review), 2011/07/01 04:15:32]

nit: add a new line above the close of the namespace

[awong, 2011/07/02 00:36:57]

Done.

+
+template <typename MessageLoopType, typename ResponseType>

[darin (slow to review), 2011/07/01 04:15:32]

I guess ResponseType is just a placeholder.

[awong, 2011/07/02 00:36:57]

No...just a mistake due to rushing this CL out. Removed.

+void PostTaskAndReply(MessageLoopType loop, const Closure& task,

[willchan no longer on Chromium, 2011/07/01 15:13:54]

Why is MessageLoopType templated? Is this to make it work for WorkerPool also?
Note that there is no WorkerPool instance right now, it's a class static API.
That'll have to change for this to work.

I guess I had originally imagined we'd use an abstract TaskRunner interface, but
I guess templating works too, since we're only using one method.

I'd advocate for naming the template parameter as TaskRunner or Executor.

[awong, 2011/07/02 00:36:57]

Actually, I was trying bridge between MessageLoopProxy and MessageLoop, but just
got it completely wrong.

It's irksome that syntactically BrowserThread, MessageLoop, and MessageLoopProxy
all have slightly different PostTask semantics.  But I don't think there's a way
to unify.  In the long term, I think that each class should provide syntactic
sugar for this function.

I'm going to reduce this to just one function, no templates or overloads, and
then we can add syntactic sugar to each of BrowserThread, MessageLoop,
MessageLoopProxy, WorkerPool, etc., as wanted.

+                      const Closure& reply) {
+  PostTaskAndReplyRelay* relay = new PostTaskAndReplyRelay(task, reply);
+  loop.PostTask(&PostTaskAndReplyRelay::Run, base::Unretained(relay));

[willchan no longer on Chromium, 2011/07/01 15:13:54]

Does this code actually work? Is there no need for FROM_HERE?

[awong, 2011/07/02 00:36:57]

Nope...doesn't work yet. Will soon.

+}
+
+template <typename MessageLoopType, typename ResponseType>
+void PostTaskAndReply<MessageLoopType, ResponseType>(
+    MessageLoopType* loop, const Closure& task, const Closure& reply) {
+  PostTaskAndReplyRelay* relay = new PostTaskAndReplyRelay(task, reply);
+  loop->PostTask(&PostTaskAndReplyRelay::Run, base::Unretained(relay));
+}
+
 }  // namespace base
 
 #endif  // BASE_TASK_H_