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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "extensions/common/one_shot_event.h"
      6 
      7 #include "base/callback.h"
      8 #include "base/location.h"
      9 #include "base/message_loop/message_loop_proxy.h"
     10 #include "base/task_runner.h"
     11 
     12 using base::TaskRunner;
     13 
     14 namespace extensions {
     15 
     16 struct OneShotEvent::TaskInfo {
     17   TaskInfo() {}
     18   TaskInfo(const tracked_objects::Location& from_here,
     19            const scoped_refptr<TaskRunner>& runner,
     20            const base::Closure& task)
     21       : from_here(from_here), runner(runner), task(task) {
     22     CHECK(runner.get());  // Detect mistakes with a decent stack frame.
     23   }
     24   tracked_objects::Location from_here;
     25   scoped_refptr<TaskRunner> runner;
     26   base::Closure task;
     27 };
     28 
     29 OneShotEvent::OneShotEvent() : signaled_(false) {
     30   // It's acceptable to construct the OneShotEvent on one thread, but
     31   // immediately move it to another thread.
     32   thread_checker_.DetachFromThread();
     33 }
     34 OneShotEvent::~OneShotEvent() {}
     35 
     36 void OneShotEvent::Post(const tracked_objects::Location& from_here,
     37                         const base::Closure& task) const {
     38   Post(from_here, task, base::MessageLoopProxy::current());
     39 }
     40 
     41 void OneShotEvent::Post(const tracked_objects::Location& from_here,
     42                         const base::Closure& task,
     43                         const scoped_refptr<TaskRunner>& runner) const {
     44   DCHECK(thread_checker_.CalledOnValidThread());
     45 
     46   if (is_signaled()) {
     47     runner->PostTask(from_here, task);
     48   } else {
     49     tasks_.push_back(TaskInfo(from_here, runner, task));
     50   }
     51 }
     52 
     53 void OneShotEvent::Signal() {
     54   DCHECK(thread_checker_.CalledOnValidThread());
     55 
     56   CHECK(!signaled_) << "Only call Signal once.";
     57 
     58   signaled_ = true;
     59   // After this point, a call to Post() from one of the queued tasks
     60   // could proceed immediately, but the fact that this object is
     61   // single-threaded prevents that from being relevant.
     62 
     63   // We could randomize tasks_ in debug mode in order to check that
     64   // the order doesn't matter...
     65   for (size_t i = 0; i < tasks_.size(); ++i) {
     66     tasks_[i].runner->PostTask(tasks_[i].from_here, tasks_[i].task);
     67   }
     68 }
     69 
     70 }  // namespace extensions
     71