cashew: defer all D-Bus signal processing to main loop

src/property_changed_handler.h

+// Copyright (c) 2010 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 SRC_PROPERTY_CHANGED_HANDLER_H_
+#define SRC_PROPERTY_CHANGED_HANDLER_H_
+
+#include <glib.h>
+
+#include <queue>
+#include <string>
+#include <utility>
+
+#include <base/basictypes.h>  // NOLINT
+#include <dbus-c++/dbus.h>  // NOLINT
+
+namespace cashew {
+
+class PropertyChangedDelegate;
+
+// tuple of (property name, new property value) representing a D-Bus
+// PropertyChanged signal
+typedef std::pair<const std::string, const DBus::Variant> PropertyChangedSignal;
+
+// queue of PropertyChangedSignal tuples
+typedef std::queue<PropertyChangedSignal> PropertyChangedQueue;
+
+// PropertyChangedHandler allows tuples representing D-Bus PropertyChanged
+// signals to be enqueued for deferred handling from the glib main loop.
+class PropertyChangedHandler {
+  public:
+    PropertyChangedHandler();
+    virtual ~PropertyChangedHandler();
+
+    // set delegate that will receive OnPropertyChanged callbacks
+    // ok to clear delegate by setting it to NULL
+    virtual void delegate(PropertyChangedDelegate *delegate);
+
+    // add a PropertyChangedSignal to |signal_queue_|
+    // schedules a glib callback for deferred signal processing if one is not
+    // already scheduled
+    virtual void EnqueueSignal(const PropertyChangedSignal& signal);
+
+  private:
+    // delegate for OnPropertyChanged callbacks
+    PropertyChangedDelegate *delegate_;
+
+    // glib source id for deferred processing callback
+    guint source_id_;
+
+    // queue of PropertyChangedSignal tuples awaiting deferred processing
+    PropertyChangedQueue signal_queue_;
+
+    // glib integration: static wrapper
+    // takes PropertyChangedDelegate as data and invokes
+    // delegate->OnPropertyChanged for each signal in |signal_queue_|
+    static gboolean StaticOnPropertyChangedCallback(gpointer data);
+
+    // clear |signal_queue_|
+    void DeletePendingSignals();
+
+    DISALLOW_COPY_AND_ASSIGN(PropertyChangedHandler);
+};
+
+// callback interface for deferred PropertyChanged signal processing
+class PropertyChangedDelegate {
+  public:
+    PropertyChangedDelegate() {}
+    virtual ~PropertyChangedDelegate() {}
+
+    // callback method for deferred PropertyChanged signal processing
+    virtual void OnPropertyChanged(const PropertyChangedHandler *handler,
+                                   const std::string& property_name,
+                                   const DBus::Variant& new_value) = 0;
+
+  private:
+    DISALLOW_COPY_AND_ASSIGN(PropertyChangedDelegate);
+};
+
+}  // namespace cashew
+
+#endif  // SRC_PROPERTY_CHANGED_HANDLER_H_