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_TASK_RUNNER_H_
   6 #define BASE_DEFERRED_SEQUENCED_TASK_RUNNER_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/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   bool PostDelayedTask(const tracked_objects::Location& from_here,
  31                        const Closure& task,
  32                        TimeDelta delay) override;
  33   bool RunsTasksOnCurrentThread() const override;
  34
  35   // SequencedTaskRunner implementation
  36   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
  37                                   const Closure& task,
  38                                   TimeDelta delay) override;
  39
  40   // Start the execution - posts all queued tasks to the target executor. The
  41   // deferred tasks are posted with their initial delay, meaning that the task
  42   // execution delay is actually measured from Start.
  43   // Fails when called a second time.
  44   void Start();
  45
  46  private:
  47   struct DeferredTask  {
  48     DeferredTask();
  49     ~DeferredTask();
  50
  51     tracked_objects::Location posted_from;
  52     Closure task;
  53     // The delay this task was initially posted with.
  54     TimeDelta delay;
  55     bool is_non_nestable;
  56   };
  57
  58   ~DeferredSequencedTaskRunner() override;
  59
  60   // Creates a |Task| object and adds it to |deferred_tasks_queue_|.
  61   void QueueDeferredTask(const tracked_objects::Location& from_here,
  62                          const Closure& task,
  63                          TimeDelta delay,
  64                          bool is_non_nestable);
  65
  66   // // Protects |started_| and |deferred_tasks_queue_|.
  67   mutable Lock lock_;
  68
  69   bool started_;
  70   const scoped_refptr<SequencedTaskRunner> target_task_runner_;
  71   std::vector<DeferredTask> deferred_tasks_queue_;
  72
  73   DISALLOW_COPY_AND_ASSIGN(DeferredSequencedTaskRunner);
  74 };
  75
  76 }  // namespace base
  77
  78 #endif  // BASE_DEFERRED_SEQUENCED_TASK_RUNNER_H_