91 lines
2.4 KiB
C++
91 lines
2.4 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/threading/post_task_and_reply_impl.h"
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#include "base/bind.h"
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#include "base/location.h"
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#include "base/message_loop/message_loop_proxy.h"
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namespace base {
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namespace {
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// This relay class remembers the MessageLoop that it was created on, and
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// ensures that both the |task| and |reply| Closures are deleted on this same
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// thread. Also, |task| is guaranteed to be deleted before |reply| is run or
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// deleted.
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//
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// If this is not possible because the originating MessageLoop is no longer
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// available, the the |task| and |reply| Closures are leaked. Leaking is
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// considered preferable to having a thread-safetey violations caused by
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// invoking the Closure destructor on the wrong thread.
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class PostTaskAndReplyRelay {
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public:
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PostTaskAndReplyRelay(const tracked_objects::Location& from_here,
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const Closure& task, const Closure& reply)
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: from_here_(from_here),
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origin_loop_(MessageLoopProxy::current()) {
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task_ = task;
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reply_ = reply;
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}
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~PostTaskAndReplyRelay() {
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DCHECK(origin_loop_->BelongsToCurrentThread());
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task_.Reset();
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reply_.Reset();
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}
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void Run() {
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task_.Run();
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origin_loop_->PostTask(
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from_here_,
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Bind(&PostTaskAndReplyRelay::RunReplyAndSelfDestruct,
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base::Unretained(this)));
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}
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private:
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void RunReplyAndSelfDestruct() {
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DCHECK(origin_loop_->BelongsToCurrentThread());
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// Force |task_| to be released before |reply_| is to ensure that no one
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// accidentally depends on |task_| keeping one of its arguments alive while
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// |reply_| is executing.
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task_.Reset();
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reply_.Run();
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// Cue mission impossible theme.
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delete this;
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}
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tracked_objects::Location from_here_;
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scoped_refptr<MessageLoopProxy> origin_loop_;
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Closure reply_;
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Closure task_;
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};
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} // namespace
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namespace internal {
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bool PostTaskAndReplyImpl::PostTaskAndReply(
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const tracked_objects::Location& from_here,
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const Closure& task,
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const Closure& reply) {
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PostTaskAndReplyRelay* relay =
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new PostTaskAndReplyRelay(from_here, task, reply);
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if (!PostTask(from_here, Bind(&PostTaskAndReplyRelay::Run,
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Unretained(relay)))) {
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delete relay;
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return false;
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}
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return true;
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}
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} // namespace internal
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} // namespace base
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