base/message_loop/incoming_task_queue.h

   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
  14 namespace base {
  15
  16 class MessageLoop;
  17 class WaitableEvent;
  18
  19 namespace 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.
  24 class 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 message loop has high resolution timers enabled.
  42   // Provided for testing.
  43   bool IsHighResolutionTimerEnabledForTesting();
  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.
  50   void ReloadWorkQueue(TaskQueue* work_queue);
  51
  52   // Disconnects |this| from the parent message loop.
  53   void WillDestroyCurrentMessageLoop();
  54
  55  private:
  56   friend class RefCountedThreadSafe<IncomingTaskQueue>;
  57   virtual ~IncomingTaskQueue();
  58
  59   // Calculates the time at which a PendingTask should run.
  60   TimeTicks CalculateDelayedRuntime(TimeDelta delay);
  61
  62   // Adds a task to |incoming_queue_|. The caller retains ownership of
  63   // |pending_task|, but this function will reset the value of
  64   // |pending_task->task|. This is needed to ensure that the posting call stack
  65   // does not retain |pending_task->task| beyond this function call.
  66   bool PostPendingTask(PendingTask* pending_task);
  67
  68 #if defined(OS_WIN)
  69   TimeTicks high_resolution_timer_expiration_;
  70 #endif
  71
  72   // The lock that protects access to |incoming_queue_|, |message_loop_| and
  73   // |next_sequence_num_|.
  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_