automatically update the database with Linux inotify

This patch implements a light-weight inotify library, and watches all
directories below the music directory.  It updates all directories
where files changed after a delay of 5 seconds.

src/inotify_source.h

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2003-2009 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_INOTIFY_SOURCE_H
+#define MPD_INOTIFY_SOURCE_H
+
+#include <glib.h>
+
+typedef void (*mpd_inotify_callback_t)(int wd, unsigned mask,
+				       const char *name, void *ctx);
+
+struct mpd_inotify_source;
+
+/**
+ * Creates a new inotify source and registers it in the GLib main
+ * loop.
+ *
+ * @param a callback invoked for events received from the kernel
+ */
+struct mpd_inotify_source *
+mpd_inotify_source_new(mpd_inotify_callback_t callback, void *callback_ctx,
+		       GError **error_r);
+
+void
+mpd_inotify_source_free(struct mpd_inotify_source *source);
+
+/**
+ * Adds a path to the notify list.
+ *
+ * @return a watch descriptor or -1 on error
+ */
+int
+mpd_inotify_source_add(struct mpd_inotify_source *source,
+		       const char *path_fs, unsigned mask,
+		       GError **error_r);
+
+/**
+ * Removes a path from the notify list.
+ *
+ * @param wd the watch descriptor returned by mpd_inotify_source_add()
+ */
+void
+mpd_inotify_source_rm(struct mpd_inotify_source *source, unsigned wd);
+
+#endif