Tab Audio Capture: Browser-side connect/disconnect functionality.

content/browser/renderer_host/media/audio_mirroring_manager.cc

+// Copyright (c) 2013 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 "content/browser/renderer_host/media/audio_mirroring_manager.h"
+
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+AudioMirroringManager::AudioMirroringManager() {}
+
+AudioMirroringManager::~AudioMirroringManager() {
+  DCHECK(diverters_.empty());
+  DCHECK(sessions_.empty());
+}
+
+void AudioMirroringManager::AddDiverter(
+    int render_process_id, int render_view_id, Diverter* diverter) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK(diverter);
+
+  // DCHECK(diverter not already in diverters_ under any key)
+#ifndef NDEBUG
+  for (DiverterMap::const_iterator it = diverters_.begin();
+       it != diverters_.end(); ++it) {
+    DCHECK_NE(diverter, it->second);
+  }
+#endif
+
+  // Add the diverter to the set of active diverters.
+  const Target target(render_process_id, render_view_id);
+  diverters_.insert(std::make_pair(target, diverter));
+
+  // If a mirroring session is active, start diverting the audio stream
+  // immediately.
+  SessionMap::iterator session_it = sessions_.find(target);
+  if (session_it != sessions_.end()) {
+    diverter->StartDiverting(
+        session_it->second->AddInput(diverter->GetAudioParameters()));
+  }
+}
+
+void AudioMirroringManager::RemoveDiverter(
+    int render_process_id, int render_view_id, Diverter* diverter) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  // Stop diverting the audio stream if a mirroring session is active.
+  const Target target(render_process_id, render_view_id);
+  SessionMap::iterator session_it = sessions_.find(target);
+  if (session_it != sessions_.end())
+    diverter->StopDiverting();
+
+  // Remove the diverter from the set of active diverters.
+  for (DiverterMap::iterator it = diverters_.lower_bound(target);
+       it != diverters_.end() && it->first == target; ++it) {
+    if (it->second == diverter) {
+      diverters_.erase(it);
+      break;
+    }
+  }
+}
+
+void AudioMirroringManager::StartMirroring(
+    int render_process_id, int render_view_id,
+    MirroringDestination* destination) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK(destination);
+
+  // Insert an entry into the set of active mirroring sessions.  If a mirroring
+  // session is already active for |render_process_id| + |render_view_id|,
+  // replace the entry.
+  const Target target(render_process_id, render_view_id);
+  SessionMap::iterator session_it = sessions_.find(target);
+  MirroringDestination* old_destination;
+  if (session_it == sessions_.end()) {
+    old_destination = NULL;
+    sessions_.insert(std::make_pair(target, destination));
+
+    DVLOG(1) << "Start mirroring render_process_id:render_view_id="
+             << render_process_id << ':' << render_view_id
+             << " --> MirroringDestination@" << destination;
+  } else {
+    old_destination = session_it->second;
+    session_it->second = destination;
+
+    DVLOG(1) << "Switch mirroring of render_process_id:render_view_id="
+             << render_process_id << ':' << render_view_id
+             << "  MirroringDestination@" << old_destination
+             << " --> MirroringDestination@" << destination;
+  }
+
+  // Divert audio streams coming from |target| to |destination|.  If streams
+  // were already diverted to the |old_destination|, remove them.
+  for (DiverterMap::iterator it = diverters_.lower_bound(target);
+       it != diverters_.end() && it->first == target; ++it) {
+    Diverter* const diverter = it->second;
+    if (old_destination)
+      diverter->StopDiverting();
+    diverter->StartDiverting(

[darin (slow to review), 2013/01/09 05:06:53]

What happens if a Diverter calls Add/RemoveDiverter inside this loop? 
DiverterMap is probably not safe to mutate during iteration, right?  For
example, maybe a Diverter would call RemoveDiverter during StopDiverting?

[miu, 2013/01/09 07:21:49]

Added a comment in the header file to warn about the re-entrancy issue.  I'm
reluctant to take further steps since this can't happen the way the code is
currently written, and I don't anticipate anyone would want/need to do such a
thing in future coding.

+        destination->AddInput(diverter->GetAudioParameters()));
+  }
+}
+
+void AudioMirroringManager::StopMirroring(
+    int render_process_id, int render_view_id,
+    MirroringDestination* destination) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  // Stop mirroring if there is an active session *and* the destination
+  // matches.
+  const Target target(render_process_id, render_view_id);
+  SessionMap::iterator session_it = sessions_.find(target);
+  if (session_it == sessions_.end() || destination != session_it->second)
+    return;
+
+  DVLOG(1) << "Stop mirroring render_process_id:render_view_id="
+           << render_process_id << ':' << render_view_id
+           << " --> MirroringDestination@" << destination;
+
+  // Stop diverting each audio stream in the mirroring session being stopped.
+  for (DiverterMap::iterator it = diverters_.lower_bound(target);
+       it != diverters_.end() && it->first == target; ++it) {
+    it->second->StopDiverting();
+  }
+
+  // Remove the entry from the set of active mirroring sessions.
+  sessions_.erase(session_it);
+}
+
+AudioMirroringManager::MirroringDestination::~MirroringDestination() {}
+
+}  // namespace content