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1 // Copyright (c) 2010 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "base/message_loop_proxy.h" | 5 #include "base/message_loop_proxy.h" |
6 | 6 |
| 7 #include "base/bind.h" |
| 8 |
7 namespace base { | 9 namespace base { |
8 | 10 |
| 11 namespace { |
| 12 |
| 13 // This relay class remembers the MessageLoop that it was created on, and |
| 14 // ensures that both the |task| and |reply| Closures are deleted on this same |
| 15 // thread. Also, |task| is guaranteed to be deleted before |reply| is run or |
| 16 // deleted. |
| 17 // |
| 18 // If this is not possible because the originating MessageLoop is no longer |
| 19 // available, the the |task| and |reply| Closures are leaked. Leaking is |
| 20 // considered preferable to having a thread-safetey violations caused by |
| 21 // invoking the Closure destructor on the wrong thread. |
| 22 class PostTaskAndReplyRelay { |
| 23 public: |
| 24 PostTaskAndReplyRelay(const tracked_objects::Location& from_here, |
| 25 const Closure& task, const Closure& reply) |
| 26 : from_here_(from_here), |
| 27 origin_loop_(MessageLoopProxy::current()) { |
| 28 task_ = task; |
| 29 reply_ = reply; |
| 30 } |
| 31 |
| 32 ~PostTaskAndReplyRelay() { |
| 33 DCHECK(origin_loop_->BelongsToCurrentThread()); |
| 34 task_.Reset(); |
| 35 reply_.Reset(); |
| 36 } |
| 37 |
| 38 void Run() { |
| 39 task_.Run(); |
| 40 origin_loop_->PostTask( |
| 41 from_here_, |
| 42 Bind(&PostTaskAndReplyRelay::RunReplyAndSelfDestruct, |
| 43 base::Unretained(this))); |
| 44 } |
| 45 |
| 46 private: |
| 47 void RunReplyAndSelfDestruct() { |
| 48 DCHECK(origin_loop_->BelongsToCurrentThread()); |
| 49 |
| 50 // Force |task_| to be released before |reply_| is to ensure that no one |
| 51 // accidentally depends on |task_| keeping one of its arguments alive while |
| 52 // |reply_| is executing. |
| 53 task_.Reset(); |
| 54 |
| 55 reply_.Run(); |
| 56 |
| 57 // Cue mission impossible theme. |
| 58 delete this; |
| 59 } |
| 60 |
| 61 tracked_objects::Location from_here_; |
| 62 scoped_refptr<MessageLoopProxy> origin_loop_; |
| 63 Closure reply_; |
| 64 Closure task_; |
| 65 }; |
| 66 |
| 67 } // namespace |
| 68 |
9 MessageLoopProxy::MessageLoopProxy() { | 69 MessageLoopProxy::MessageLoopProxy() { |
10 } | 70 } |
11 | 71 |
12 MessageLoopProxy::~MessageLoopProxy() { | 72 MessageLoopProxy::~MessageLoopProxy() { |
13 } | 73 } |
14 | 74 |
| 75 bool MessageLoopProxy::PostTaskAndReply( |
| 76 const tracked_objects::Location& from_here, |
| 77 const Closure& task, |
| 78 const Closure& reply) { |
| 79 PostTaskAndReplyRelay* relay = |
| 80 new PostTaskAndReplyRelay(from_here, task, reply); |
| 81 if (!PostTask(from_here, Bind(&PostTaskAndReplyRelay::Run, |
| 82 Unretained(relay)))) { |
| 83 delete relay; |
| 84 return false; |
| 85 } |
| 86 |
| 87 return true; |
| 88 } |
| 89 |
15 void MessageLoopProxy::OnDestruct() const { | 90 void MessageLoopProxy::OnDestruct() const { |
16 delete this; | 91 delete this; |
17 } | 92 } |
18 | 93 |
19 } // namespace base | 94 } // namespace base |
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