Manage MIDI related objects and sessions' lifecycles correctly

media/midi/midi_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 "media/midi/midi_manager.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_loop_proxy.h"
 
 namespace media {
 
 MidiManager::MidiManager()
     : initialized_(false),
       result_(MIDI_NOT_SUPPORTED) {
 }
 
 MidiManager::~MidiManager() {
 }
 
 #if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(USE_ALSA) && \
     !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 MidiManager* MidiManager::Create() {
   return new MidiManager;
 }
 #endif
 
-void MidiManager::StartSession(MidiManagerClient* client, int client_id) {
+void MidiManager::StartSession(MidiManagerClient* client) {
   bool session_is_ready;
   bool session_needs_initialization = false;
   bool too_many_pending_clients_exist = false;
 
   {
     base::AutoLock auto_lock(lock_);
     session_is_ready = initialized_;
+    if (clients_.find(client) != clients_.end() ||
+        pending_clients_.find(client) != pending_clients_.end()) {
+      // Should not happen. But just in case the renderer is compromised.
+      NOTREACHED();
+      return;
+    }
     if (!session_is_ready) {
       // Do not accept a new request if the pending client list contains too
       // many clients.
       too_many_pending_clients_exist =
           pending_clients_.size() >= kMaxPendingClientCount;
 
       if (!too_many_pending_clients_exist) {
         // Call StartInitialization() only for the first request.
         session_needs_initialization = pending_clients_.empty();
-        pending_clients_.insert(std::make_pair(client, client_id));
+        pending_clients_.insert(client);
       }
     }
   }
 
   // Lazily initialize the MIDI back-end.
   if (!session_is_ready) {
     if (session_needs_initialization) {
       TRACE_EVENT0("midi", "MidiManager::StartInitialization");
       session_thread_runner_ =
           base::MessageLoop::current()->message_loop_proxy();
       StartInitialization();
     }
     if (too_many_pending_clients_exist) {
       // Return an error immediately if there are too many requests.
-      client->CompleteStartSession(client_id, MIDI_INITIALIZATION_ERROR);
+      client->CompleteStartSession(MIDI_INITIALIZATION_ERROR);
       return;
     }
     // CompleteInitialization() will be called asynchronously when platform
     // dependent initialization is finished.
     return;
   }
 
   // Platform dependent initialization was already finished for previously
   // initialized clients.
   MidiResult result;
   {
     base::AutoLock auto_lock(lock_);
     if (result_ == MIDI_OK)
       clients_.insert(client);
     result = result_;
   }
-  client->CompleteStartSession(client_id, result);
+  client->CompleteStartSession(result);
 }
 
 void MidiManager::EndSession(MidiManagerClient* client) {
+  // At this point, |client| can be in the destruction process, and calling
+  // any method of |client| is dangerous.
   base::AutoLock auto_lock(lock_);
   clients_.erase(client);
   pending_clients_.erase(client);
 }
 
 void MidiManager::DispatchSendMidiData(MidiManagerClient* client,
                                        uint32 port_index,
                                        const std::vector<uint8>& data,
                                        double timestamp) {
   NOTREACHED();
@@ skipping 22 matching lines @@
   output_ports_.push_back(info);
 }
 
 void MidiManager::ReceiveMidiData(
     uint32 port_index,
     const uint8* data,
     size_t length,
     double timestamp) {
   base::AutoLock auto_lock(lock_);
 
-  for (ClientList::iterator i = clients_.begin(); i != clients_.end(); ++i)
-    (*i)->ReceiveMidiData(port_index, data, length, timestamp);
+  for (MidiManagerClient* client : clients_)
+    client->ReceiveMidiData(port_index, data, length, timestamp);
 }
 
 void MidiManager::CompleteInitializationInternal(MidiResult result) {
   TRACE_EVENT0("midi", "MidiManager::CompleteInitialization");
 
   base::AutoLock auto_lock(lock_);
   DCHECK(clients_.empty());
   DCHECK(!initialized_);
   initialized_ = true;
   result_ = result;
 
-  for (PendingClientMap::iterator it = pending_clients_.begin();
-       it != pending_clients_.end();
-       ++it) {
+  for (MidiManagerClient* client : pending_clients_) {
     if (result_ == MIDI_OK)
-      clients_.insert(it->first);
-    it->first->CompleteStartSession(it->second, result_);
+      clients_.insert(client);
+    client->CompleteStartSession(result_);
   }
   pending_clients_.clear();
 }
 
 }  // namespace media