Implement Bus and ObjectProxy classes for our D-Bus library.

dbus/bus.cc

+// Copyright (c) 2011 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 "dbus/bus.h"
+
+#include "base/logging.h"
+#include "base/message_loop.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_restrictions.h"
+#include "dbus/object_proxy.h"
+
+namespace dbus {
+
+namespace {
+
+// The class is used for watching the file descriptor used for D-Bus
+// communication.
+class Watch : public base::MessagePumpLibevent::Watcher {
+ public:
+  Watch(DBusWatch* watch)
+      : raw_watch_(watch) {
+    dbus_watch_set_data(raw_watch_, this, NULL);
+  }
+
+  ~Watch() {
+    dbus_watch_set_data(raw_watch_, NULL, NULL);
+  }
+
+  // Returns true if the underlying file descriptor is ready to be watched.
+  bool IsReadyToBeWatched() {
+    return dbus_watch_get_enabled(raw_watch_);
+  }
+
+  // Starts watching the underlying file descriptor.
+  void StartWatching() {
+    const int fd = dbus_watch_get_unix_fd(raw_watch_);
+    const int flags = dbus_watch_get_flags(raw_watch_);
+
+    MessageLoopForIO::Mode mode;
+    if ((flags & DBUS_WATCH_READABLE) && (flags & DBUS_WATCH_WRITABLE))
+      mode = MessageLoopForIO::WATCH_READ_WRITE;
+    if (flags & DBUS_WATCH_READABLE)

[stevenjb, 2011/07/29 21:54:17]

else if

[satorux1, 2011/08/01 19:56:41]

Done.

+      mode = MessageLoopForIO::WATCH_READ;
+    if (flags & DBUS_WATCH_WRITABLE)

[stevenjb, 2011/07/29 21:54:17]

else if

[satorux1, 2011/08/01 19:56:41]

Done.

+      mode = MessageLoopForIO::WATCH_WRITE;

[stevenjb, 2011/07/29 21:54:17]

else NOTREACHED()

[satorux1, 2011/08/01 19:56:41]

Done.

+
+    const bool persistent = true;  // Watch persistently.
+    const bool success = MessageLoopForIO::current()->WatchFileDescriptor(
+        fd,
+        persistent,
+        mode,
+        &file_descriptor_watcher_,
+        this);
+    DCHECK(success) << "Unable to allocate memory";
+  }
+
+  // Stops watching the underlying file descriptor.
+  void StopWatching() {
+    file_descriptor_watcher_->StopWatchingFileDescriptor();
+  }
+
+ private:
+  // Implement MessagePumpLibevent::Watcher.
+  virtual void OnFileCanReadWithoutBlocking(int fd) {
+    const bool success = dbus_watch_handle(raw_watch_, DBUS_WATCH_READABLE);
+    DCHECK(success) << "Unable to allocate memory";
+  }
+
+  // Implement MessagePumpLibevent::Watcher.
+  virtual void OnFileCanWriteWithoutBlocking(int fd) {
+    const bool success = dbus_watch_handle(raw_watch_, DBUS_WATCH_WRITABLE);
+    DCHECK(success) << "Unable to allocate memory";
+  }
+
+  DBusWatch* raw_watch_;
+  base::MessagePumpLibevent::FileDescriptorWatcher file_descriptor_watcher_;
+};
+
+}  // namespace
+
+Bus::Options::Options()
+  : bus_type(SESSION),
+    connection_type(PRIVATE),
+    io_thread(NULL) {
+}
+
+Bus::Bus(const Options& options)
+    : bus_type_(options.bus_type),
+      connection_type_(options.connection_type),
+      io_thread_(options.io_thread),
+      connection_(NULL) {
+  if (io_thread_) {
+    DCHECK(io_thread_->IsRunning())
+        << "The IO thread should be running";
+    DCHECK_EQ(MessageLoop::TYPE_IO,
+              io_thread_->message_loop()->type())
+        << "The IO thread should have an MessageLoopForIO attached";
+  }
+}
+
+Bus::~Bus() {
+  // Private connection should be closed.
+  if (connection_ && connection_type_ == PRIVATE) {
+    dbus_connection_close(connection_);
+  }
+}
+
+ObjectProxy* Bus::GetObjectProxy(const std::string& service_name,
+                                 const std::string& object_path) {
+  return new ObjectProxy(this, service_name, object_path);
+}
+
+bool Bus::Init() {
+  // dbus_bus_get_private() and dbus_bus_get() are blocking calls.
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  // Check if it's already initialized.
+  if (connection_)
+    return true;
+
+  DBusError error = {};

[stevenjb, 2011/07/29 21:54:17]

nit: don't need to initialize error (and better not to; compiler will warn you
if it doesn't get set anywhere)

[satorux1, 2011/08/01 19:56:41]

Done.

+  dbus_error_init(&error);
+  const DBusBusType dbus_bus_type = static_cast<DBusBusType>(bus_type_);
+  if (connection_type_ == PRIVATE) {
+    connection_ = dbus_bus_get_private(dbus_bus_type, &error);
+  } else {
+    connection_ = dbus_bus_get(dbus_bus_type, &error);
+  }
+  if (!connection_) {
+    if (dbus_error_is_set(&error)) {
+      LOG(ERROR) << error.message;
+    }
+    return false;
+  }
+
+  // This is unnecessary if client only uses synchronous APIs, but it
+  // won't hurt.
+  SetUpAsyncOperations();
+
+  return true;
+}
+
+void Bus::SetUpAsyncOperations() {
+  // Process all the incoming data if any, so that OnDispatchStatus() will
+  // be called when the incoming data is ready.
+  ProcessAllIncomingDataIfAny(connection_);
+
+  dbus_connection_set_watch_functions(connection_,
+                                      &Bus::OnAddWatchStub,
+                                      &Bus::OnRemoveWatchStub,
+                                      &Bus::OnToggleWatchStub,
+                                      this,
+                                      NULL);
+  // TODO(satorux): Timeout is not yet implemented.
+  dbus_connection_set_timeout_functions(connection_,
+                                        NULL,
+                                        NULL,
+                                        NULL,
+                                        NULL,
+                                        NULL);
+  dbus_connection_set_dispatch_status_function(
+      connection_,
+      &Bus::OnDispatchStatusChangedStub,
+      connection_,
+      NULL);
+}
+
+void Bus::ProcessAllIncomingDataIfAny(DBusConnection* connection) {
+  if (dbus_connection_get_dispatch_status(connection) ==
+      DBUS_DISPATCH_DATA_REMAINS) {
+    while (dbus_connection_dispatch(connection) ==
+           DBUS_DISPATCH_DATA_REMAINS);
+  }
+}
+
+void Bus::PostTaskToIoThread(const tracked_objects::Location& from_here,
+                             const base::Closure& task) {
+  DCHECK(io_thread_);
+  io_thread_->message_loop()->PostTask(from_here, task);
+}
+
+dbus_bool_t Bus::OnAddWatch(DBusWatch* raw_watch) {
+  Watch* watch = new Watch(raw_watch);

[stevenjb, 2011/07/29 21:54:17]

This confused me for a while re: when Watch gets deleted.
It might be more clear do do something like:
  Watch* watch = new Watch();
  // Set raw_watch data -> watch; watch will be deleted when raw_watch is
removed.
  watch->SetDBusWatch(raw_watch);

[satorux1, 2011/08/01 19:56:41]

Good point. I think adding a comment is sufficient, so added a comment about
when it'll be deleted.

+  if (watch->IsReadyToBeWatched()) {
+    watch->StartWatching();
+  }
+  return true;
+}
+
+void Bus::OnRemoveWatch(DBusWatch* raw_watch) {
+  Watch* watch = reinterpret_cast<Watch*>(dbus_watch_get_data(raw_watch));

[stevenjb, 2011/07/29 21:54:17]

dbus_watch_get_data should return a void*, so static_cast<> can be used instead.

[satorux1, 2011/08/01 19:56:41]

You are right. Done.

+  delete watch;
+}
+
+void Bus::OnToggleWatch(DBusWatch* raw_watch) {
+  Watch* watch = reinterpret_cast<Watch*>(dbus_watch_get_data(raw_watch));
+  if (watch->IsReadyToBeWatched()) {
+    watch->StartWatching();
+  } else {
+    watch->StopWatching();

[stevenjb, 2011/07/29 21:54:17]

Is it safe to call this if StartWatching() was never called?

[satorux1, 2011/08/01 19:56:41]

Good point. Yes it's safe. Added a comment about it.

+  }
+}
+
+void Bus::OnDispatchStatusChanged(DBusConnection* connection,
+                                  DBusDispatchStatus status) {
+  if (!dbus_connection_get_is_connected(connection))
+    return;
+  ProcessAllIncomingDataIfAny(connection);
+}
+
+dbus_bool_t Bus::OnAddWatchStub(DBusWatch* raw_watch, void* data) {

[stevenjb, 2011/07/29 21:54:17]

These could be local functions instead of class statics.

[satorux1, 2011/08/01 19:56:41]

Here, we need to call self->OnAddWatch(), which is private, hence these stub
functions are class statics.

+  Bus* self = reinterpret_cast<Bus*>(data);
+  return self->OnAddWatch(raw_watch);
+}
+
+void Bus::OnRemoveWatchStub(DBusWatch* raw_watch, void* data) {
+  Bus* self = reinterpret_cast<Bus*>(data);
+  return self->OnRemoveWatch(raw_watch);
+}
+
+void Bus::OnToggleWatchStub(DBusWatch* raw_watch, void* data) {
+  Bus* self = reinterpret_cast<Bus*>(data);
+  return self->OnToggleWatch(raw_watch);
+}
+
+void Bus::OnDispatchStatusChangedStub(DBusConnection* connection,
+                                      DBusDispatchStatus status,
+                                      void* data) {
+  Bus* self = reinterpret_cast<Bus*>(data);
+  return self->OnDispatchStatusChanged(connection, status);
+}
+
+}  // namespace dbus