lib/dbus/FilterHelper: new class

src/lib/dbus/FilterHelper.cxx

+/*
+ * Copyright 2020 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "FilterHelper.hxx"
+
+namespace ODBus {
+
+inline DBusHandlerResult
+FilterHelper::HandleMessage(DBusConnection *dbus_connection,
+			    DBusMessage *message) noexcept
+{
+	return callback(dbus_connection, message);
+}
+
+DBusHandlerResult
+FilterHelper::HandleMessage(DBusConnection *dbus_connection,
+			    DBusMessage *message,
+			    void *user_data) noexcept
+{
+	auto &fh = *(FilterHelper *)user_data;
+	return fh.HandleMessage(dbus_connection, message);
+}
+
+} // namespace ODBus

src/lib/dbus/FilterHelper.hxx

+/*
+ * Copyright 2020 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ODBUS_FILTER_HELPER_HXX
+#define ODBUS_FILTER_HELPER_HXX
+
+#include "util/BindMethod.hxx"
+
+#include <dbus/dbus.h>
+
+#include <cassert>
+
+namespace ODBus {
+
+/**
+ * A helper for dbus_connection_add_filter() and
+ * dbus_connection_remove_filter().
+ */
+class FilterHelper final {
+	DBusConnection *connection = nullptr;
+
+	using Callback = BoundMethod<DBusHandlerResult(DBusConnection *dbus_connection,
+						       DBusMessage *message) noexcept>;
+	Callback callback;
+
+public:
+	FilterHelper() = default;
+
+	FilterHelper(DBusConnection *_connection, Callback _callback) noexcept {
+		Add(_connection, _callback);
+	}
+
+	~FilterHelper() noexcept {
+		Remove();
+	}
+
+	operator bool() const noexcept {
+		return connection != nullptr;
+	}
+
+	DBusConnection *GetConnection() noexcept {
+		assert(connection != nullptr);
+
+		return connection;
+	}
+
+	void Add(DBusConnection *_connection, Callback _callback) noexcept {
+		assert(connection == nullptr);
+
+		connection = _connection;
+		callback = _callback;
+
+		dbus_connection_add_filter(connection, HandleMessage, this,
+					   nullptr);
+	}
+
+	void Remove() noexcept {
+		if (!*this)
+			return;
+
+		dbus_connection_remove_filter(connection, HandleMessage, this);
+		connection = nullptr;
+	}
+
+private:
+	DBusHandlerResult HandleMessage(DBusConnection *dbus_connection,
+					DBusMessage *message) noexcept;
+
+	static DBusHandlerResult HandleMessage(DBusConnection *,
+					       DBusMessage *message,
+					       void *user_data) noexcept;
+};
+
+} // namespace ODBus
+
+#endif

src/lib/dbus/meson.build

@@ -17,6 +17,7 @@ dbus = static_library(
   'dbus',
   'Connection.cxx',
   'Error.cxx',
+  'FilterHelper.cxx',
   'Message.cxx',
   'UDisks2.cxx',
   'ScopeMatch.cxx',

src/neighbor/plugins/UdisksNeighborPlugin.cxx

@@ -21,6 +21,7 @@
 #include "lib/dbus/Connection.hxx"
 #include "lib/dbus/Error.hxx"
 #include "lib/dbus/Glue.hxx"
+#include "lib/dbus/FilterHelper.hxx"
 #include "lib/dbus/Message.hxx"
 #include "lib/dbus/AsyncRequest.hxx"
 #include "lib/dbus/ReadIter.hxx"
@@ -57,6 +58,8 @@ class UdisksNeighborExplorer final
 
 	Manual<SafeSingleton<ODBus::Glue>> dbus_glue;
 
+	ODBus::FilterHelper filter_helper;
+
 	ODBus::AsyncRequest list_request;
 
 	/**
@@ -97,9 +100,6 @@ private:
 
 	DBusHandlerResult HandleMessage(DBusConnection *dbus_connection,
 					DBusMessage *message) noexcept;
-	static DBusHandlerResult HandleMessage(DBusConnection *dbus_connection,
-					       DBusMessage *message,
-					       void *user_data) noexcept;
 };
 
 inline void
@@ -119,9 +119,8 @@ UdisksNeighborExplorer::DoOpen()
 		error.CheckThrow("DBus AddMatch error");
 
 		try {
-			dbus_connection_add_filter(connection,
-						   HandleMessage, this,
-						   nullptr);
+			filter_helper.Add(connection,
+					  BIND_THIS_METHOD(HandleMessage));
 
 			try {
 				auto msg = Message::NewMethodCall(UDISKS2_INTERFACE,
@@ -132,9 +131,7 @@ UdisksNeighborExplorer::DoOpen()
 					return OnListNotify(std::move(o));
 				});
 			} catch (...) {
-				dbus_connection_remove_filter(connection,
-							      HandleMessage,
-							      this);
+				filter_helper.Remove();
 				throw;
 			}
 		} catch (...) {
@@ -163,7 +160,7 @@ UdisksNeighborExplorer::DoClose() noexcept
 
 	auto &connection = GetConnection();
 
-	dbus_connection_remove_filter(connection, HandleMessage, this);
+	filter_helper.Remove();
 	dbus_bus_remove_match(connection, udisks_neighbor_match, nullptr);
 
 	dbus_glue.Destruct();
@@ -263,16 +260,6 @@ UdisksNeighborExplorer::HandleMessage(DBusConnection *, DBusMessage *message) no
 		return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 }
 
-DBusHandlerResult
-UdisksNeighborExplorer::HandleMessage(DBusConnection *connection,
-				      DBusMessage *message,
-				      void *user_data) noexcept
-{
-	auto &agent = *(UdisksNeighborExplorer *)user_data;
-
-	return agent.HandleMessage(connection, message);
-}
-
 static std::unique_ptr<NeighborExplorer>
 udisks_neighbor_create(EventLoop &event_loop,
 		     NeighborListener &listener,