neighbor: new subsystem to detect file servers on the local network

This commit adds the NeighborPlugin API which can be used to detect
nearby file servers that can be used by input plugins.  This list of
servers is exported using the new "listneighbors" command.  The idle
even "neighbor" notifies interested clients when a new neighbor is
found or an existing one is lost.

There's a lot missing currently: protocol&user documentation, and a
way to "mount" remote servers into the music database.  Obviously,
some code from the UPnP database plugin can be moved to a neighbor
plugin.

1 files changed, 76 insertions, 0 deletions

diff --git a/src/neighbor/Glue.hxx b/src/neighbor/Glue.hxx
new file mode 100644
index 000000000..92c612d22
--- /dev/null
+++ b/src/neighbor/Glue.hxx
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_ALL_HXX
+#define MPD_NEIGHBOR_ALL_HXX
+
+#include "check.h"
+#include "Compiler.h"
+#include "thread/Mutex.hxx"
+
+#include <forward_list>
+
+struct config_param;
+class Error;
+class EventLoop;
+class NeighborExplorer;
+class NeighborListener;
+struct NeighborInfo;
+
+/**
+ * A class that initializes and opens all configured neighbor plugins.
+ */
+class NeighborGlue {
+	struct Explorer {
+		NeighborExplorer *const explorer;
+
+		Explorer(NeighborExplorer *_explorer):explorer(_explorer) {}
+		Explorer(const Explorer &) = delete;
+		~Explorer();
+	};
+
+	Mutex mutex;
+
+	std::forward_list<Explorer> explorers;
+
+public:
+	typedef std::forward_list<NeighborInfo> List;
+
+	NeighborGlue() = default;
+	NeighborGlue(const NeighborGlue &) = delete;
+	~NeighborGlue();
+
+	bool IsEmpty() const {
+		return explorers.empty();
+	}
+
+	bool Init(EventLoop &loop, NeighborListener &listener, Error &error);
+
+	bool Open(Error &error);
+	void Close();
+
+	/**
+	 * Get the combined list of all neighbors from all active
+	 * plugins.
+	 */
+	gcc_pure
+	List GetList() const;
+};
+
+#endif