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

services/media/framework/engine.cc

+// 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/engine.h"
+
+namespace mojo {
+namespace media {
+
+uint32_t Engine::Part::input_count() {
+  DCHECK(stage_ != nullptr);
+  return stage_->input_count();
+}
+
+Engine::Input Engine::Part::input(uint32_t index) {
+  DCHECK(stage_ != nullptr && index < stage_->input_count());
+  return Input(stage_, index);
+}
+
+Engine::Input Engine::Part::input() {
+  DCHECK(stage_ != nullptr && stage_->input_count() == 1);
+  return Input(stage_, 0);
+}
+
+uint32_t Engine::Part::output_count() {
+  DCHECK(stage_ != nullptr);
+  return stage_->output_count();
+}
+
+Engine::Output Engine::Part::output(uint32_t index) {
+  DCHECK(stage_ != nullptr && index < stage_->output_count());
+  return Output(stage_, index);
+}
+
+Engine::Output Engine::Part::output() {
+  DCHECK(stage_ != nullptr && stage_->output_count() == 1);
+  return Output(stage_, 0);
+}
+
+Engine::Part Engine::Part::upstream_part(uint32_t index) {
+  DCHECK(stage_ != nullptr && index < stage_->input_count());
+  return Part(stage_->input(index).upstream_stage());
+}
+
+Engine::Part Engine::Part::upstream_part() {
+  DCHECK(stage_ != nullptr && stage_->input_count() == 1);
+  return Part(stage_->input(0).upstream_stage());
+}
+
+Engine::Part Engine::Part::downstream_part(uint32_t index) {
+  DCHECK(stage_ != nullptr && index < stage_->output_count());
+  return Part(stage_->output(index).downstream_stage());
+}
+
+Engine::Part Engine::Part::downstream_part() {
+  DCHECK(stage_ != nullptr && stage_->output_count() == 1);
+  return Part(stage_->output(0).downstream_stage());
+}
+
+Engine::Engine() {
+  update_function_ = [this](Stage* stage) {
+    DCHECK(stage);
+    base::AutoLock lock(lock_);
+    UpdateUnsafe(stage);
+    UpdateUnsafe();
+  };
+}
+
+Engine::~Engine() {
+  Reset();
+}
+
+void Engine::RemovePart(Part part) {
+  DCHECK(part);
+  base::AutoLock lock(lock_);
+  RemoveUnsafe(part.stage_);
+}
+
+Engine::Part Engine::Connect(Output output, Input input) {
+  DCHECK(output);
+  DCHECK(input);
+
+  base::AutoLock lock(lock_);
+
+  if (output.connected()) {
+    DisconnectOutputUnsafe(output.stage_, output.index_);
+  }
+  if (input.connected()) {
+    DisconnectInputUnsafe(input.stage_, input.index_);
+  }
+
+  output.stage_output().connect(input.stage_, input.index_);
+  input.stage_input().connect(output.stage_, output.index_);
+
+  return input.part();
+}
+
+Engine::Part Engine::ConnectParts(Part upstream_part, Part downstream_part) {
+  DCHECK(upstream_part);
+  DCHECK(downstream_part);
+  Connect(upstream_part.output(), downstream_part.input());
+  return downstream_part;
+}
+
+Engine::Part Engine::ConnectOutputToPart(
+    Output output,
+    Part downstream_part) {
+  DCHECK(output);
+  DCHECK(downstream_part);
+  Connect(output, downstream_part.input());
+  return downstream_part;
+}
+
+Engine::Part Engine::ConnectPartToInput(Part upstream_part, Input input) {
+  DCHECK(upstream_part);
+  DCHECK(input);
+  Connect(upstream_part.output(), input);
+  return input.part();
+}
+
+void Engine::DisconnectOutput(Output output) {
+  DCHECK(output);
+
+  base::AutoLock lock(lock_);
+  DisconnectOutputUnsafe(output.stage_, output.index_);
+}
+
+void Engine::DisconnectInput(Input input) {
+  DCHECK(input);
+
+  base::AutoLock lock(lock_);
+  DisconnectInputUnsafe(input.stage_, input.index_);
+}
+
+void Engine::RemovePartsConnectedToPart(Part part) {
+  DCHECK(part);
+
+  base::AutoLock lock(lock_);
+
+  std::deque<Part> to_remove { part };
+
+  while (!to_remove.empty()) {
+    Part part = to_remove.front();
+    to_remove.pop_front();
+
+    for (uint32_t i = 0; i < part.input_count(); ++i) {
+      to_remove.push_back(part.upstream_part(i));
+    }
+
+    for (uint32_t i = 0; i < part.output_count(); ++i) {
+      to_remove.push_back(part.downstream_part(i));
+    }
+
+    RemoveUnsafe(part.stage_);
+  }
+}
+
+void Engine::RemovePartsConnectedToOutput(Output output) {
+  DCHECK(output);
+
+  if (!output.connected()) {
+    return;
+  }
+
+  Part downstream_part = output.downstream_part();
+  DisconnectOutput(output);
+  RemovePartsConnectedToPart(downstream_part);
+}
+
+void Engine::RemovePartsConnectedToInput(Input input) {
+  DCHECK(input);
+
+  if (!input.connected()) {
+    return;
+  }
+
+  Part upstream_part = input.upstream_part();
+  DisconnectInput(input);
+  RemovePartsConnectedToPart(upstream_part);
+}
+
+void Engine::Prepare() {
+  base::AutoLock lock(lock_);
+  for (Stage* sink : sinks_) {
+    sink->Prepare(update_function_);
+    sink->prepared_ = true;
+    uint32_t input_count = sink->input_count();
+    for (uint32_t input_index = 0; input_index < input_count; input_index++) {
+      MaybePrepareUnsafe(sink->input(input_index).upstream_stage());
+    }
+  }
+}
+
+void Engine::Prepare(Part part) {
+  DCHECK(part);
+  base::AutoLock lock(lock_);
+  MaybePrepareUnsafe(part.stage_);
+}
+
+void Engine::PrimeSinks() {
+  lock_.Acquire();
+  std::list<Stage*> sinks(sinks_);
+  lock_.Release();
+
+  // TODO(dalesat): Threading issue: these sinks may go away during priming.
+  for (Stage* sink : sinks) {
+    sink->Prime();
+  }
+}
+
+void Engine::Reset() {
+  base::AutoLock lock(lock_);
+  while (!supply_backlog_.empty()) {
+    supply_backlog_.pop();
+  }
+  while (!demand_backlog_.empty()) {
+    demand_backlog_.pop();
+  }
+  sources_.clear();
+  sinks_.clear();
+  while (!stages_.empty()) {
+    Stage* stage = stages_.front();
+    stages_.pop_front();
+    delete stage;
+  }
+}
+
+void Engine::PushToSupplyBacklogUnsafe(Stage* stage) {
+  lock_.AssertAcquired();
+
+  DCHECK(stage);
+  packets_produced_ = true;
+  if (!stage->in_supply_backlog_) {
+    supply_backlog_.push(stage);
+    stage->in_supply_backlog_ = true;
+  }
+}
+
+void Engine::PushToDemandBacklogUnsafe(Stage* stage) {
+  lock_.AssertAcquired();
+
+  DCHECK(stage);
+  if (!stage->in_demand_backlog_) {
+    demand_backlog_.push(stage);
+    stage->in_demand_backlog_ = true;
+  }
+}
+
+Engine::Part Engine::Add(Stage* stage) {
+  base::AutoLock lock(lock_);
+
+  stages_.push_back(stage);
+  if (stage->input_count() == 0) {
+    sources_.push_back(stage);
+  }
+  if (stage->output_count() == 0) {
+    sinks_.push_back(stage);
+  }
+  return Part(stage);
+}
+
+void Engine::DisconnectOutputUnsafe(Stage* stage, uint32_t index) {
+  DCHECK(stage);
+  DCHECK(index < stage->output_count());
+
+  lock_.AssertAcquired();
+
+  StageOutput& stage_output = stage->output(index);
+
+  if (stage_output.downstream_stage() == nullptr) {
+    return;
+  }
+
+  stage_output.mate().disconnect();
+  stage_output.disconnect();
+}
+
+void Engine::DisconnectInputUnsafe(Stage* stage, uint32_t index) {
+  DCHECK(stage);
+  DCHECK(index < stage->input_count());
+
+  lock_.AssertAcquired();
+
+  StageInput& stage_input = stage->input(index);
+
+  if (stage_input.upstream_stage() == nullptr) {
+    return;
+  }
+
+  stage_input.mate().disconnect();
+  stage_input.disconnect();
+}
+
+void Engine::RemoveUnsafe(Stage* stage) {
+  DCHECK(stage);
+
+  lock_.AssertAcquired();
+
+  uint32_t input_count = stage->input_count();
+  for (uint32_t input_index = 0; input_index < input_count; input_index++) {
+    if (stage->input(input_index).connected()) {
+      DisconnectInputUnsafe(stage, input_index);
+    }
+  }
+
+  uint32_t output_count = stage->output_count();
+  for (uint32_t output_index = 0; output_index < output_count; output_index++) {
+    if (stage->output(output_index).connected()) {
+      DisconnectOutputUnsafe(stage, output_index);
+    }
+  }
+
+  sources_.remove(stage);
+  sinks_.remove(stage);
+  stages_.remove(stage);
+  delete stage;
+}
+
+// static
+Stage* Engine::CreateStage(MultiStreamPacketSourcePtr source) {
+  return new DistributorStage(source);
+}
+
+// static
+Stage* Engine::CreateStage(PacketTransformPtr transform) {
+  return new PacketTransformStage(transform);
+}
+
+// static
+Stage* Engine::CreateStage(ActiveSourcePtr source) {
+  return new ActiveSourceStage(source);
+}
+
+// static
+Stage* Engine::CreateStage(ActiveSinkPtr sink) {
+  return new ActiveSinkStage(sink);
+}
+
+// static
+Stage* Engine::CreateStage(LpcmTransformPtr transform) {
+  return new LpcmTransformStage(transform);
+}
+
+void Engine::MaybePrepareUnsafe(Stage* stage) {
+  lock_.AssertAcquired();
+
+  if (stage == nullptr || stage->prepared_) {
+    return;
+  }
+
+  // Make sure all downstream stages have been prepared.
+  uint32_t output_count = stage->output_count();
+  for (uint32_t output_index = 0; output_index < output_count; output_index++) {
+    StageOutput& output = stage->output(output_index);
+    if (output.connected() && !output.downstream_stage()->prepared()) {
+      return;
+    }
+  }
+
+  stage->Prepare(update_function_);
+  stage->prepared_ = true;
+
+  // Prepare all upstream stages.
+  uint32_t input_count = stage->input_count();
+  for (uint32_t input_index = 0; input_index < input_count; input_index++) {
+    MaybePrepareUnsafe(stage->input(input_index).upstream_stage());
+  }
+}
+
+void Engine::UpdateUnsafe() {
+  lock_.AssertAcquired();
+
+  while (true) {
+    Stage* stage = PopFromSupplyBacklogUnsafe();
+    if (stage != nullptr) {
+      UpdateUnsafe(stage);
+      continue;
+    }
+
+    stage = PopFromDemandBacklogUnsafe();
+    if (stage != nullptr) {
+      UpdateUnsafe(stage);
+      continue;
+    }
+
+    break;
+  }
+}
+
+void Engine::UpdateUnsafe(Stage *stage) {
+  lock_.AssertAcquired();
+
+  DCHECK(stage);
+
+  packets_produced_ = false;
+
+  stage->Update(this);
+
+  // If the stage produced packets, it may need to reevaluate demand later.
+  if (packets_produced_) {
+    PushToDemandBacklogUnsafe(stage);
+  }
+}
+
+Stage* Engine::PopFromSupplyBacklogUnsafe() {
+  lock_.AssertAcquired();
+
+  if (supply_backlog_.empty()) {
+    return nullptr;
+  }
+
+  Stage* stage = supply_backlog_.front();
+  supply_backlog_.pop();
+  DCHECK(stage->in_supply_backlog_);
+  stage->in_supply_backlog_ = false;
+  return stage;
+}
+
+Stage* Engine::PopFromDemandBacklogUnsafe() {
+  lock_.AssertAcquired();
+
+  if (demand_backlog_.empty()) {
+    return nullptr;
+  }
+
+  Stage* stage = demand_backlog_.top();
+  demand_backlog_.pop();
+  DCHECK(stage->in_demand_backlog_);
+  stage->in_demand_backlog_ = false;
+  return stage;
+}
+
+}  // namespace media
+}  // namespace mojo