Motown: Remove LPCM optimizations, fix prepare, add flush, add ActiveMultistreamSink model/stage

services/media/framework/graph.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 SERVICES_MEDIA_FRAMEWORK_GRAPH_H_
+#define SERVICES_MEDIA_FRAMEWORK_GRAPH_H_
+
+#include <list>
+
+#include "services/media/framework/engine.h"
+#include "services/media/framework/refs.h"
+#include "services/media/framework/stages/active_sink_stage.h"
+#include "services/media/framework/stages/active_source_stage.h"
+#include "services/media/framework/stages/multistream_source_stage.h"
+#include "services/media/framework/stages/stage.h"
+#include "services/media/framework/stages/transform_stage.h"
+
+namespace mojo {
+namespace media {
+
+namespace {
+
+// StageCreator::Create creates a stage for a part. DEFINE_STAGE_CREATOR defines
+// a specialization for a particular model/stage type pair. Every new
+// model/stage type pair that's defined will need an entry here.
+template<typename T, typename Enable = void> class StageCreator;
+
+#define DEFINE_STAGE_CREATOR(TModel, TStage) \
+template<typename T> \
+class StageCreator<T, typename std::enable_if< \
+    std::is_base_of<TModel, T>::value>::type> { \
+ public: \
+  static inline Stage* Create(std::shared_ptr<T> t_ptr) { \
+    return new TStage(std::shared_ptr<TModel>(t_ptr)); \
+  } \
+};
+
+DEFINE_STAGE_CREATOR(MultistreamSource, MultistreamSourceStage);
+DEFINE_STAGE_CREATOR(Transform, TransformStage);
+DEFINE_STAGE_CREATOR(ActiveSource, ActiveSourceStage);
+DEFINE_STAGE_CREATOR(ActiveSink, ActiveSinkStage);
+
+#undef DEFINE_STAGE_CREATOR
+
+} // namespace
+
+//
+// USAGE
+//
+// Graph is a container for sources, sinks and transforms ('parts') connected
+// in a graph. PartRef, InputRef and OutputRef are all
+// references to parts and their inputs and outputs. Graph provides a variety
+// of methods for adding and removing parts and for connecting inputs and
+// outputs to form a graph.
+//
+// The graph isn't thread-safe. If the graph is to be modified and/or
+// interrogated on multiple threads, the caller must provide its own lock
+// to prevent collisions. In this case, the caller must also acquire the same
+// lock when making calls that cause parts to add or remove inputs or outputs.
+//
+// The graph prevents the disconnection of prepared inputs and outputs. Once
+// a connected input/output pair is prepared, it must be unprepared before
+// disconnection. This allows the engine to operate freely over prepared
+// portions of the graph (prepare and unprepare are synchronized with the
+// engine).
+//
+// Parts added to the graph are referenced using shared pointers. The graph
+// holds pointers to the parts it contains, and the application, in many cases,
+// also holds pointers to the parts so it can call methods that are outside the
+// graph's scope. When a part is added, the graph returns a PartRef
+// object, which can be used to reference the part when the graph is modified.
+// PartRef objects can be interrogated to retrieve inputs (as
+// InputRef objects) and outputs (as OutputRef objects).
+//
+// Parts come in various flavors, defined by 'model' abstract classes. The
+// current list of supported models is:
+//
+//  ActiveSink              - a sink that consumes packets asynchronously
+//  ActiveSource            - a source that produces packets asynchronously

[johngro, 2016/02/08 22:33:36]

<nit> indentation </nit>

[dalesat, 2016/02/09 00:34:11]

Hazard of grep

+//  MultistreamSource - a source that produces multiple streams of packets
+//                            synchronously
+//  Transform         - a synchronous transform that consumes and produces
+//                            packets via one input and one output
+//
+// Other models will be defined in the future as needed.
+//
+
+//
+// DESIGN
+//
+// The Graph is implemented as a system of cooperating objects. Of those
+// objects, only the graph itself is of relevance to code that uses Graph and
+// to part implementations. The other objects are:
+//
+// Stage
+// A stage hosts a single part. There are many subclasses of Stage, one for
+// each supported part model. The stage's job is to implement the contract
+// represented by the model so the parts that conform to the model can
+// participate in the operation of the graph. Stages are uniform with respect
+// to how they interact with graph. PartRef references a stage.
+//
+// Input
+// A stage possesses zero or more Input instances. Input objects
+// implement the supply of media into the stage and demand for media signalled
+// upstream. Inputs recieve media from Outputs in the form of packets
+// (type Packet).
+//
+// Output
+// A stage possesses zero or more Output instances. Output objects
+// implement the supply of media output of the stage to a downstream input and
+// demand for media signalled from that input.
+//
+
+// Host for a source, sink or transform.
+class Graph {
+ public:
+  Graph();
+
+  ~Graph();
+
+  // Adds a part to the graph.
+  template<typename T>
+  PartRef Add(std::shared_ptr<T> t_ptr) {
+    DCHECK(t_ptr);
+    return Add(StageCreator<T>::Create(t_ptr));
+  }
+
+  // Removes a part from the graph after disconnecting it from other parts.
+  void RemovePart(PartRef part);
+
+  // Connects an output connector to an input connector. Returns the dowstream
+  // part.
+  PartRef Connect(const OutputRef& output, const InputRef& input);
+
+  // Connects a part with exactly one output to a part with exactly one input.
+  // Returns the downstream part.
+  PartRef ConnectParts(PartRef upstream_part, PartRef downstream_part);
+
+  // Connects an output connector to a part that has exactly one input. Returns
+  // the downstream part.
+  PartRef ConnectOutputToPart(const OutputRef& output, PartRef downstream_part);
+
+  // Connects a part with exactly one output to an input connector. Returns the
+  // downstream part.
+  PartRef ConnectPartToInput(PartRef upstream_part, const InputRef& input);
+
+  // Disconnects an output connector and the input connector to which it's
+  // connected.
+  void DisconnectOutput(const OutputRef& output);
+
+  // Disconnects an input connector and the output connector to which it's
+  // connected.
+  void DisconnectInput(const InputRef& input);
+
+  // Disconnects and removes part and everything connected to it.
+  void RemovePartsConnectedToPart(PartRef part);
+
+  // Disconnects and removes everything connected to output.
+  void RemovePartsConnectedToOutput(const OutputRef& output);
+
+  // Disconnects and removes everything connected to input.
+  void RemovePartsConnectedToInput(const InputRef& input);
+
+  // Adds all the parts in t (which must all have one input and one output) and
+  // connects them in sequence to the output connector. Returns the output
+  // connector of the last part or the output parameter if it is empty.
+  template<typename T>
+  OutputRef AddAndConnectAll(OutputRef output, const T& t) {
+    for (auto& element : t) {

[johngro, 2016/02/08 22:33:36]

const auto&

[dalesat, 2016/02/09 00:34:11]

Done.

+      PartRef part = Add(StageCreator<T>::Create(element));
+      Connect(output, part.input());
+      output = part.output();
+    }
+    return output;
+  }
+
+  // Removes all parts from the graph.
+  void Reset();
+
+  // Prepares the graph for operation.
+  void Prepare();
+
+  // Prepares the input and everything upstream of it. This method is used to
+  // prepare subgraphs added when the rest of the graph is already prepared.
+  void PrepareInput(const InputRef& input);
+
+  // Primes all the sinks in the graph.
+  void PrimeSinks();
+
+ private:
+  // Adds a stage to the graph.
+  PartRef Add(Stage* stage);
+
+  std::list<Stage*> stages_;
+  std::list<Stage*> sources_;
+  std::list<Stage*> sinks_;
+
+  Engine engine_;
+  Stage::UpdateCallback update_function_;
+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif  // SERVICES_MEDIA_FRAMEWORK_GRAPH_H_