Re-land extract state management from WebMediaPlayerImpl.

media/filters/pipeline_controller.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_FILTERS_PIPELINE_CONTROLLER_H_
+#define MEDIA_FILTERS_PIPELINE_CONTROLLER_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+#include "media/base/media_export.h"
+#include "media/base/pipeline.h"
+#include "media/base/renderer.h"
+
+namespace media {
+
+class ChunkDemuxer;
+class Demuxer;
+
+// PipelineController wraps a Pipeline to expose the one-at-a-time operations
+// (Seek(), Suspend(), and Resume()) with a simpler API. Internally it tracks
+// pending operations and dispatches them when possible. Duplicate requests
+// (such as seeking twice to the same time) may be elided.
+//
+// TODO(sandersd):
+//   - Expose an operation that restarts via suspend+resume.
+//   - Block invalid calls after an error occurs.
+class MEDIA_EXPORT PipelineController {
+ public:
+  enum class State {
+    CREATED,
+    STARTING,
+    PLAYING,
+    SEEKING,
+    SUSPENDING,
+    SUSPENDED,
+    RESUMING,
+  };
+
+  using RendererFactoryCB = base::Callback<scoped_ptr<Renderer>(void)>;
+  using SeekedCB = base::Callback<void(bool time_updated)>;
+  using SuspendedCB = base::Callback<void()>;
+  using ResumedCB = base::Callback<void()>;
+
+  // Construct a PipelineController wrapping |pipeline_|. |pipeline_| must
+  // outlive the resulting PipelineController. The callbacks are:
+  //   - |renderer_factory_cb| is called by PipelineController to create new
+  //     renderers when starting and resuming.
+  //   - |seeked_cb| is called upon reaching a stable state if a seek occured.
+  //   - |suspended_cb| is called immediately after suspendeding.
+  //   - |resumed_cb| is called immediately after resuming.
+  //   - |error_cb| is called if any operation on |pipeline_| does not result
+  //     in PIPELINE_OK or its error callback is called.
+  PipelineController(Pipeline* pipeline,
+                     const RendererFactoryCB& renderer_factory_cb,
+                     const SeekedCB& seeked_cb,
+                     const SuspendedCB& suspended_cb,
+                     const ResumedCB& resumed_cb,
+                     const PipelineStatusCB& error_cb);
+  ~PipelineController();
+
+  // Start |pipeline_|. If provided, |chunk_demuxer| will be stored and
+  // StartWaitingForSeek()/CancelPendingSeek() will be issued to it as
+  // necessary.
+  //
+  // When |is_streaming| is true, Resume() will always start at the
+  // beginning of the stream, rather than attempting to seek to the current
+  // time.
+  //
+  // The other parameters are just passed directly to pipeline_.Start().
+  void Start(ChunkDemuxer* chunk_demuxer,
+             Demuxer* demuxer,
+             bool is_streaming,
+             const base::Closure& ended_cb,
+             const PipelineMetadataCB& metadata_cb,
+             const BufferingStateCB& buffering_state_cb,
+             const base::Closure& duration_change_cb,
+             const AddTextTrackCB& add_text_track_cb,
+             const base::Closure& waiting_for_decryption_key_cb);
+
+  // Request a seek to |time|. If |time_updated| is true, then the eventual
+  // |seeked_cb| callback will also have |time_updated| set to true; it
+  // indicates that the seek was requested by Blink and a time update is
+  // expected so that Blink can fire the seeked event.
+  void Seek(base::TimeDelta time, bool time_updated);
+
+  // Request that |pipeline_| be suspended. This is a no-op if |pipeline_| has
+  // been suspended.
+  void Suspend();
+
+  // Request that |pipeline_| be resumed. This is a no-op if |pipeline_| has not
+  // been suspended.
+  void Resume();
+
+  // Returns true if the current state is stable. This means that |state_| is
+  // PLAYING and there are no pending operations. Requests are processed
+  // immediately when the state is stable, otherwise they are queued.
+  //
+  // Exceptions to the above:
+  //   - Start() is processed immediately while in the CREATED state.
+  //   - Resume() is processed immediately while in the SUSPENDED state.
+  bool IsStable();
+
+  // Returns true if |pipeline_| is suspended.
+  bool IsSuspended();
+
+ private:
+  // Attempts to make progress from the current state to the target state.
+  void Dispatch();
+
+  // PipelineStaus callback that also carries the target state.
+  void OnPipelineStatus(State state, PipelineStatus pipeline_status);
+
+  // The Pipeline we are managing state for.
+  Pipeline* pipeline_ = nullptr;
+
+  // Factory for Renderers, used for Start() and Resume().
+  RendererFactoryCB renderer_factory_cb_;
+
+  // Called after seeks (which includes Start()) upon reaching a stable state.
+  // Multiple seeks result in only one callback if no stable state occurs
+  // between them.
+  SeekedCB seeked_cb_;
+
+  // Called immediately when |pipeline_| completes a suspend operation.
+  SuspendedCB suspended_cb_;
+
+  // Called immediately when |pipeline_| completes a resume operation.
+  ResumedCB resumed_cb_;
+
+  // Called immediately when any operation on |pipeline_| results in an error.
+  PipelineStatusCB error_cb_;
+
+  // State for handling StartWaitingForSeek()/CancelPendingSeek().
+  ChunkDemuxer* chunk_demuxer_ = nullptr;
+  bool waiting_for_seek_ = false;
+
+  // When true, Resume() will start at time zero instead of seeking to the
+  // current time.
+  bool is_streaming_ = false;
+
+  // Tracks the current state of |pipeline_|.
+  State state_ = State::CREATED;
+
+  // Indicates that a seek has occurred. When set, a seeked callback will be
+  // issued at the next stable state.
+  bool pending_seeked_cb_ = false;
+
+  // Indicates that time has been changed by a seek, which will be reported at
+  // the next seeked callback.
+  bool pending_time_updated_ = false;
+
+  // Indicates that the |pipeline_| was suspended, and therefore that a resumed
+  // callback should be issued the next time we enter State::PLAYING.
+  bool pending_resumed_cb_ = false;
+
+  // The target time of the active seek; valid while SEEKING or RESUMING.
+  base::TimeDelta seek_time_;
+
+  // Target state which we will work to achieve. |pending_seek_time_| is only
+  // valid when |pending_seek_| is true.
+  bool pending_seek_ = false;
+  base::TimeDelta pending_seek_time_;
+  bool pending_suspend_ = false;
+  bool pending_resume_ = false;
+
+  base::ThreadChecker thread_checker_;
+  base::WeakPtrFactory<PipelineController> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PipelineController);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_PIPELINE_CONTROLLER_H_