media/base/serial_runner.h

   1 // Copyright (c) 2012 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 MEDIA_BASE_SERIAL_RUNNER_H_
   6 #define MEDIA_BASE_SERIAL_RUNNER_H_
   7
   8 #include <queue>
   9
  10 #include "base/callback.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/memory/weak_ptr.h"
  14 #include "media/base/media_export.h"
  15 #include "media/base/pipeline_status.h"
  16
  17 namespace base {
  18 class SingleThreadTaskRunner;
  19 }
  20
  21 namespace media {
  22
  23 // Runs a series of bound functions accepting Closures or PipelineStatusCB.
  24 // SerialRunner doesn't use regular Closure/PipelineStatusCBs as it late binds
  25 // the completion callback as the series progresses.
  26 class MEDIA_EXPORT SerialRunner {
  27  public:
  28   typedef base::Callback<void(const base::Closure&)> BoundClosure;
  29   typedef base::Callback<void(const PipelineStatusCB&)> BoundPipelineStatusCB;
  30
  31   // Serial queue of bound functions to run.
  32   class MEDIA_EXPORT Queue {
  33    public:
  34     Queue();
  35     ~Queue();
  36
  37     void Push(const base::Closure& closure);
  38     void Push(const BoundClosure& bound_fn);
  39     void Push(const BoundPipelineStatusCB& bound_fn);
  40
  41    private:
  42     friend class SerialRunner;
  43
  44     BoundPipelineStatusCB Pop();
  45     bool empty();
  46
  47     std::queue<BoundPipelineStatusCB> bound_fns_;
  48   };
  49
  50   // Executes the bound functions in series, executing |done_cb| when finished.
  51   //
  52   // All bound functions are executed on the thread that Run() is called on,
  53   // including |done_cb|.
  54   //
  55   // To eliminate an unnecessary posted task, the first function is executed
  56   // immediately on the caller's stack. It is *strongly advised* to ensure
  57   // the calling code does no more work after the call to Run().
  58   //
  59   // In all cases, |done_cb| is guaranteed to execute on a separate calling
  60   // stack.
  61   //
  62   // Deleting the object will prevent execution of any unstarted bound
  63   // functions, including |done_cb|.
  64   static scoped_ptr<SerialRunner> Run(
  65       const Queue& bound_fns, const PipelineStatusCB& done_cb);
  66
  67  private:
  68   friend struct base::DefaultDeleter<SerialRunner>;
  69
  70   SerialRunner(const Queue& bound_fns, const PipelineStatusCB& done_cb);
  71   ~SerialRunner();
  72
  73   void RunNextInSeries(PipelineStatus last_status);
  74
  75   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
  76   Queue bound_fns_;
  77   PipelineStatusCB done_cb_;
  78
  79   // NOTE: Weak pointers must be invalidated before all other member variables.
  80   base::WeakPtrFactory<SerialRunner> weak_factory_;
  81
  82   DISALLOW_COPY_AND_ASSIGN(SerialRunner);
  83 };
  84
  85 }  // namespace media
  86
  87 #endif  // MEDIA_BASE_SERIAL_RUNNER_H_