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#ifndef BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_
6#define BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_
7
8#include "base/base_export.h"
9#include "base/memory/ref_counted.h"
10#include "base/pending_task.h"
11#include "base/synchronization/lock.h"
12#include "base/time/time.h"
13
14namespace base {
15
16class MessageLoop;
17class WaitableEvent;
18
19namespace internal {
20
21// Implements a queue of tasks posted to the message loop running on the current
22// thread. This class takes care of synchronizing posting tasks from different
23// threads and together with MessageLoop ensures clean shutdown.
24class BASE_EXPORT IncomingTaskQueue
25    : public RefCountedThreadSafe<IncomingTaskQueue> {
26 public:
27  explicit IncomingTaskQueue(MessageLoop* message_loop);
28
29  // Appends a task to the incoming queue. Posting of all tasks is routed though
30  // AddToIncomingQueue() or TryAddToIncomingQueue() to make sure that posting
31  // task is properly synchronized between different threads.
32  //
33  // Returns true if the task was successfully added to the queue, otherwise
34  // returns false. In all cases, the ownership of |task| is transferred to the
35  // called method.
36  bool AddToIncomingQueue(const tracked_objects::Location& from_here,
37                          const Closure& task,
38                          TimeDelta delay,
39                          bool nestable);
40
41  // Returns true if the queue contains tasks that require higher than default
42  // timer resolution. Currently only needed for Windows.
43  bool HasHighResolutionTasks();
44
45  // Returns true if the message loop is "idle". Provided for testing.
46  bool IsIdleForTesting();
47
48  // Loads tasks from the |incoming_queue_| into |*work_queue|. Must be called
49  // from the thread that is running the loop. Returns the number of tasks that
50  // require high resolution timers.
51  int ReloadWorkQueue(TaskQueue* work_queue);
52
53  // Disconnects |this| from the parent message loop.
54  void WillDestroyCurrentMessageLoop();
55
56 private:
57  friend class RefCountedThreadSafe<IncomingTaskQueue>;
58  virtual ~IncomingTaskQueue();
59
60  // Calculates the time at which a PendingTask should run.
61  TimeTicks CalculateDelayedRuntime(TimeDelta delay);
62
63  // Adds a task to |incoming_queue_|. The caller retains ownership of
64  // |pending_task|, but this function will reset the value of
65  // |pending_task->task|. This is needed to ensure that the posting call stack
66  // does not retain |pending_task->task| beyond this function call.
67  bool PostPendingTask(PendingTask* pending_task);
68
69  // Number of tasks that require high resolution timing. This value is kept
70  // so that ReloadWorkQueue() completes in constant time.
71  int high_res_task_count_;
72
73  // The lock that protects access to the members of this class.
74  base::Lock incoming_queue_lock_;
75
76  // An incoming queue of tasks that are acquired under a mutex for processing
77  // on this instance's thread. These tasks have not yet been been pushed to
78  // |message_loop_|.
79  TaskQueue incoming_queue_;
80
81  // Points to the message loop that owns |this|.
82  MessageLoop* message_loop_;
83
84  // The next sequence number to use for delayed tasks.
85  int next_sequence_num_;
86
87  DISALLOW_COPY_AND_ASSIGN(IncomingTaskQueue);
88};
89
90}  // namespace internal
91}  // namespace base
92
93#endif  // BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_
94