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

services/media/framework/stages/active_sink_stage.cc

Index: services/media/framework/stages/active_sink_stage.cc
diff --git a/services/media/framework/stages/active_sink_stage.cc b/services/media/framework/stages/active_sink_stage.cc
new file mode 100644
index 0000000000000000000000000000000000000000..217f4e2a3c25b2c173d29c245c6b33ea7442057d
--- /dev/null
+++ b/services/media/framework/stages/active_sink_stage.cc
@@ -0,0 +1,67 @@
+// 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.
+
+#include "services/media/framework/stages/active_sink_stage.h"
+
+namespace mojo {
+namespace media {
+
+ActiveSinkStage::ActiveSinkStage(ActiveSinkPtr sink) : sink_(sink) {
+  DCHECK(sink_);
+
+  demand_function_ = [this](Demand demand) {
+    DCHECK(update_callback_);
+    if (sink_demand_ != demand) {
+      sink_demand_ = demand;
+      update_callback_(this);
+    }
+  };
+
+  sink_->RegisterDemandCallback(demand_function_);
+}
+
+ActiveSinkStage::~ActiveSinkStage() {}

[jeffbrown, 2016/02/02 05:35:48]

Do you need to remove your callback from the sink?  (Can't tell if that's a
unique or shared pointer here.)

[dalesat, 2016/02/02 21:46:40]

Yes, the framework currently lacks Unprepare, which is needed for lots of
things.

+
+uint32_t ActiveSinkStage::input_count() const {
+  return 1;
+};
+
+StageInput& ActiveSinkStage::input(uint32_t index) {
+  DCHECK_EQ(index, 0u);
+  return input_;
+}
+
+uint32_t ActiveSinkStage::output_count() const {
+  return 0;
+}
+
+StageOutput& ActiveSinkStage::output(uint32_t index) {
+  NOTREACHED();
+  static StageOutput result;
+  return result;
+}
+
+bool ActiveSinkStage::Prepare(UpdateCallback update_callback) {
+  input_.Prepare(sink_->allocator(), sink_->must_allocate());
+  update_callback_ = update_callback;
+  return true;
+}
+
+void ActiveSinkStage::Prime() {
+  sink_->Prime();
+}
+
+void ActiveSinkStage::Update(Engine* engine) {
+  DCHECK(engine);
+
+  if (input_.packet_from_upstream()) {
+    sink_demand_ =
+        sink_->SupplyPacket(std::move(input_.packet_from_upstream()));
+  }
+
+  input_.SetDemand(sink_demand_, engine);
+}
+
+}  // namespace media
+}  // namespace mojo