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

services/media/framework/stages/stage_output.h

Index: services/media/framework/stages/stage_output.h
diff --git a/services/media/framework/stages/stage_output.h b/services/media/framework/stages/stage_output.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_OUTPUT_H_
+#define SERVICES_MEDIA_FRAMEWORK_ENGINE_STAGE_OUTPUT_H_
+
+#include "services/media/framework/allocator.h"
+#include "services/media/framework/packet.h"
+
+namespace mojo {
+namespace media {
+
+class Stage;
+class Engine;
+class StageInput;
+class LpcmStageOutput;
+
+// Represents a stage's connector to an adjacent downstream stage.
+class StageOutput {
+ public:
+  StageOutput();
+
+  ~StageOutput();
+
+  // The stage to which this output is connected.
+  Stage* downstream_stage() const { return downstream_stage_; }
+
+  // The index of the input to which this output is connected.
+  uint32_t input_index() const { return input_index_; }
+
+  // Establishes a connection. Called only by the engine.
+  void connect(Stage* downstream_stage, uint32_t input_index);
+
+  // Breaks a connection. Called only by the engine.
+  void disconnect() {
+    downstream_stage_ = nullptr;
+    input_index_ = 0;
+  }
+
+  // Determines whether the output is connected to an input.
+  bool connected() const {
+    return downstream_stage_ != nullptr;
+  }
+
+  // The connected input.
+  StageInput& mate() const;
+
+  // Gets ready to move packets by negotiating the use of allocators. If the
+  // downstream input provides an allocator, and we can use it, this method
+  // returns the provided allocator. Otherwise, it returns nullptr.
+  virtual Allocator* Prepare(bool can_accept_allocator);
+
+  // Demand signalled from downstream, or kNegative if the downstream input
+  // is currently holding a packet.
+  Demand demand() const;
+
+  // Supplies a packet to mate. Called only by Stage::Update implementations.
+  void SupplyPacket(PacketPtr packet, Engine* engine) const;
+
+  // Updates packet demand. Called only by StageInput instances.
+  bool UpdateDemand(Demand demand);
+
+  // Returns the LPCM specialization if this instance is an LpcmStageOutput,
+  // nullptr otherwise.
+  virtual LpcmStageOutput* get_lpcm();
+
+ protected:
+  void SupplyPacketInternal(PacketPtr packet, Engine* engine) const;
+
+ private:
+  Stage* downstream_stage_;
+  uint32_t input_index_;
+  Demand demand_;
+  Allocator* copy_allocator_;
+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif  // SERVICES_MEDIA_FRAMEWORK_ENGINE_STAGE_OUTPUT_H_