base/deferred_sequenced_task_runner.h

   1 // Copyright (c) 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_DEFERRED_SEQUENCED_TASKRUNNER_H_
   6 #define BASE_DEFERRED_SEQUENCED_TASKRUNNER_H_
   7
   8 #include <vector>
   9
  10 #include "base/base_export.h"
  11 #include "base/basictypes.h"
  12 #include "base/callback.h"
  13 #include "base/compiler_specific.h"
  14 #include "base/memory/ref_counted.h"
  15 #include "base/sequenced_task_runner.h"
  16 #include "base/synchronization/lock.h"
  17 #include "base/time.h"
  18 #include "base/tracked_objects.h"
  19
  20 namespace base {
  21
  22 // A DeferredSequencedTaskRunner is a subclass of SequencedTaskRunner that
  23 // queues up all requests until the first call to Start() is issued.
  24 class BASE_EXPORT DeferredSequencedTaskRunner : public SequencedTaskRunner {
  25  public:
  26   explicit DeferredSequencedTaskRunner(
  27       const scoped_refptr<SequencedTaskRunner>& target_runner);
  28
  29   // TaskRunner implementation
  30   virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
  31                                const Closure& task,
  32                                TimeDelta delay) OVERRIDE;
  33   virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
  34
  35   // SequencedTaskRunner implementation
  36   virtual bool PostNonNestableDelayedTask(
  37       const tracked_objects::Location& from_here,
  38       const Closure& task,
  39       TimeDelta delay) OVERRIDE;
  40
  41   // Start the execution - posts all queued tasks to the target executor. The
  42   // deferred tasks are posted with their initial delay, meaning that the task
  43   // execution delay is actually measured from Start.
  44   // Fails when called a second time.
  45   void Start();
  46
  47  private:
  48   struct DeferredTask  {
  49     DeferredTask();
  50     ~DeferredTask();
  51
  52     tracked_objects::Location posted_from;
  53     Closure task;
  54     // The delay this task was initially posted with.
  55     TimeDelta delay;
  56     bool is_non_nestable;
  57   };
  58
  59   virtual ~DeferredSequencedTaskRunner();
  60
  61   // Creates a |Task| object and adds it to |deferred_tasks_queue_|.
  62   void QueueDeferredTask(const tracked_objects::Location& from_here,
  63                          const Closure& task,
  64                          TimeDelta delay,
  65                          bool is_non_nestable);
  66
  67   // // Protects |started_| and |deferred_tasks_queue_|.
  68   mutable Lock lock_;
  69
  70   bool started_;
  71   const scoped_refptr<SequencedTaskRunner> target_task_runner_;
  72   std::vector<DeferredTask> deferred_tasks_queue_;
  73
  74   DISALLOW_COPY_AND_ASSIGN(DeferredSequencedTaskRunner);
  75 };
  76
  77 }  // namespace base
  78
  79 #endif  // BASE_DEFERRED_SEQUENCED_TASKRUNNER_H_