Motown in-proc streaming framework used to implement media services.

services/media/framework/stages/stage.h

Index: services/media/framework/stages/stage.h
diff --git a/services/media/framework/stages/stage.h b/services/media/framework/stages/stage.h
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+// 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_ENGINE_STAGE_H_
+#define SERVICES_MEDIA_FRAMEWORK_ENGINE_STAGE_H_
+
+#include <vector>
+
+#include "services/media/framework/packet.h"
+#include "services/media/framework/stages/lpcm_stage_input.h"
+#include "services/media/framework/stages/lpcm_stage_output.h"
+#include "services/media/framework/stages/stage_input.h"
+#include "services/media/framework/stages/stage_output.h"
+
+namespace mojo {
+namespace media {
+
+class Engine;
+
+// Host for a source, sink or transform.
+class Stage {
+ public:
+  using UpdateCallback = std::function<void(Stage* stage)>;
+
+  Stage();
+
+  virtual ~Stage();
+
+  // Returns the number of input connections.
+  virtual uint32_t input_count() const = 0;
+
+  // Returns the indicated input connection.
+  virtual StageInput& input(uint32_t index) = 0;
+
+  // Returns the number of output connections.
+  virtual uint32_t output_count() const = 0;
+
+  // Returns the indicated output connection.
+  virtual StageOutput& output(uint32_t index) = 0;
+
+  // Prepares the stage for operation, providing a callback used to signal the
+  // need to update this stage. Returns true if the stage will call the
+  // callback, false if not. The default implementation of this method returns
+  // false.
+  // TODO(dalesat): Should this be const UpdateCallback&?
+  virtual bool Prepare(UpdateCallback update_callback);
+
+  // Initiates demand. Called on sink stages after the graph is prepared. The
+  // default implementation does nothing.
+  virtual void Prime();
+
+  // Performs processing.
+  virtual void Update(Engine* engine) = 0;
+
+  // Returns a bool indicating whether the stage is prepared.
+  bool prepared() {
+    return prepared_;
+  }
+
+ private:
+  bool prepared_;
+  bool in_supply_backlog_;
+  bool in_demand_backlog_;
+
+  friend class Engine;
+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif  // SERVICES_MEDIA_FRAMEWORK_ENGINE_STAGE_H_