Add DBusConnection helper class to use instead of DBusDaemon.

This CL moves the logic in DBusDaemon to a helper class that can be
included in another class inheriting from Daemon without needed to use
multiple inheritance nor forcing a DBus connection to succeed.
DBusDaemon was modified to re-use this class without changing its
behaviour to be compatible with existing code.

Bug: 26690086
TEST=mm; Update update_engine to use this class and tested it on edison.

Change-Id: If05a5582158552b6aeebf86dbde2aaa161f5a29f

2 files changed, 98 insertions, 0 deletions

diff --git a/brillo/dbus/dbus_connection.cc b/brillo/dbus/dbus_connection.cc
new file mode 100644
index 0000000..b60cf44
--- /dev/null
+++ b/brillo/dbus/dbus_connection.cc
@@ -0,0 +1,58 @@
+// Copyright 2016 The Chromium OS 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 <brillo/dbus/dbus_connection.h>
+
+#include <sysexits.h>
+
+#include <base/bind.h>
+#include <brillo/dbus/async_event_sequencer.h>
+#include <brillo/dbus/exported_object_manager.h>
+
+using brillo::dbus_utils::AsyncEventSequencer;
+using brillo::dbus_utils::ExportedObjectManager;
+
+namespace brillo {
+
+DBusConnection::DBusConnection() {
+}
+
+DBusConnection::~DBusConnection() {
+  if (bus_)
+    bus_->ShutdownAndBlock();
+}
+
+scoped_refptr<dbus::Bus> DBusConnection::Connect() {
+  return ConnectWithTimeout(base::TimeDelta());
+}
+
+scoped_refptr<dbus::Bus> DBusConnection::ConnectWithTimeout(
+    base::TimeDelta timeout) {
+  if (bus_)
+    return bus_;
+
+  base::TimeTicks deadline = base::TimeTicks::Now() + timeout;
+
+  dbus::Bus::Options options;
+  options.bus_type = dbus::Bus::SYSTEM;
+
+  scoped_refptr<dbus::Bus> bus = new dbus::Bus(options);
+
+  do {
+    if (bus->Connect()) {
+      bus_ = bus;
+      return bus_;
+    }
+    LOG(WARNING) << "Failed to get system bus.";
+    // Wait 1 second to prevent trashing the device while waiting for the
+    // dbus-daemon to start.
+    sleep(1);
+  } while (base::TimeTicks::Now() < deadline);
+
+  LOG(ERROR) << "Failed to get system bus after " << timeout.InSeconds()
+             << " seconds.";
+  return nullptr;
+}
+
+}  // namespace brillo
diff --git a/brillo/dbus/dbus_connection.h b/brillo/dbus/dbus_connection.h
new file mode 100644
index 0000000..aecf434
--- /dev/null
+++ b/brillo/dbus/dbus_connection.h
@@ -0,0 +1,40 @@
+// Copyright 2016 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef LIBBRILLO_BRILLO_DBUS_DBUS_CONNECTION_H_
+#define LIBBRILLO_BRILLO_DBUS_DBUS_CONNECTION_H_
+
+#include <base/memory/ref_counted.h>
+#include <base/time/time.h>
+#include <dbus/bus.h>
+
+#include <brillo/brillo_export.h>
+
+namespace brillo {
+
+// DBusConnection adds D-Bus support to Daemon.
+class BRILLO_EXPORT DBusConnection final {
+ public:
+  DBusConnection();
+  ~DBusConnection();
+
+  // Instantiates dbus::Bus and establishes a D-Bus connection. Returns a
+  // reference to the connected bus, or an empty pointer in case of error.
+  scoped_refptr<dbus::Bus> Connect();
+
+  // Instantiates dbus::Bus and tries to establish a D-Bus connection for up to
+  // |timeout|. If the connection can't be established after the timeout, fails
+  // returning an empty pointer.
+  scoped_refptr<dbus::Bus> ConnectWithTimeout(base::TimeDelta timeout);
+
+ private:
+  scoped_refptr<dbus::Bus> bus_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DBusConnection);
+};
+
+}  // namespace brillo
+
+#endif  // LIBBRILLO_BRILLO_DAEMONS_DBUS_DAEMON_H_