Database*: move to db/

29 files changed, 2660 insertions, 0 deletions

diff --git a/src/db/update/InotifyDomain.cxx b/src/db/update/InotifyDomain.cxx
new file mode 100644
index 000000000..4a3ab2d79
--- /dev/null
+++ b/src/db/update/InotifyDomain.cxx
@@ -0,0 +1,23 @@
+/*
+ * 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.
+ */
+
+#include "InotifyDomain.hxx"
+#include "util/Domain.hxx"
+
+const Domain inotify_domain("inotify");
diff --git a/src/db/update/InotifyDomain.hxx b/src/db/update/InotifyDomain.hxx
new file mode 100644
index 000000000..ad6202361
--- /dev/null
+++ b/src/db/update/InotifyDomain.hxx
@@ -0,0 +1,25 @@
+/*
+ * 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_INOTIFY_DOMAIN_HXX
+#define MPD_INOTIFY_DOMAIN_HXX
+
+extern const class Domain inotify_domain;
+
+#endif
diff --git a/src/db/update/InotifyQueue.cxx b/src/db/update/InotifyQueue.cxx
new file mode 100644
index 000000000..f4bccf7ae
--- /dev/null
+++ b/src/db/update/InotifyQueue.cxx
@@ -0,0 +1,89 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "InotifyQueue.hxx"
+#include "InotifyDomain.hxx"
+#include "UpdateGlue.hxx"
+#include "Log.hxx"
+
+#include <string.h>
+
+/**
+ * Wait this long after the last change before calling
+ * update_enqueue().  This increases the probability that updates can
+ * be bundled.
+ */
+static constexpr unsigned INOTIFY_UPDATE_DELAY_S = 5;
+
+void
+InotifyQueue::OnTimeout()
+{
+	unsigned id;
+
+	while (!queue.empty()) {
+		const char *uri_utf8 = queue.front().c_str();
+
+		id = update_enqueue(uri_utf8, false);
+		if (id == 0) {
+			/* retry later */
+			ScheduleSeconds(INOTIFY_UPDATE_DELAY_S);
+			return;
+		}
+
+		FormatDebug(inotify_domain, "updating '%s' job=%u",
+			    uri_utf8, id);
+
+		queue.pop_front();
+	}
+}
+
+static bool
+path_in(const char *path, const char *possible_parent)
+{
+	size_t length = strlen(possible_parent);
+
+	return path[0] == 0 ||
+		(memcmp(possible_parent, path, length) == 0 &&
+		 (path[length] == 0 || path[length] == '/'));
+}
+
+void
+InotifyQueue::Enqueue(const char *uri_utf8)
+{
+	ScheduleSeconds(INOTIFY_UPDATE_DELAY_S);
+
+	for (auto i = queue.begin(), end = queue.end(); i != end;) {
+		const char *current_uri = i->c_str();
+
+		if (path_in(uri_utf8, current_uri))
+			/* already enqueued */
+			return;
+
+		if (path_in(current_uri, uri_utf8))
+			/* existing path is a sub-path of the new
+			   path; we can dequeue the existing path and
+			   update the new path instead */
+			i = queue.erase(i);
+		else
+			++i;
+	}
+
+	queue.emplace_back(uri_utf8);
+}
diff --git a/src/db/update/InotifyQueue.hxx b/src/db/update/InotifyQueue.hxx
new file mode 100644
index 000000000..99e2635b1
--- /dev/null
+++ b/src/db/update/InotifyQueue.hxx
@@ -0,0 +1,41 @@
+/*
+ * 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_INOTIFY_QUEUE_HXX
+#define MPD_INOTIFY_QUEUE_HXX
+
+#include "event/TimeoutMonitor.hxx"
+#include "Compiler.h"
+
+#include <list>
+#include <string>
+
+class InotifyQueue final : private TimeoutMonitor {
+	std::list<std::string> queue;
+
+public:
+	InotifyQueue(EventLoop &_loop):TimeoutMonitor(_loop) {}
+
+	void Enqueue(const char *uri_utf8);
+
+private:
+	virtual void OnTimeout() override;
+};
+
+#endif
diff --git a/src/db/update/InotifySource.cxx b/src/db/update/InotifySource.cxx
new file mode 100644
index 000000000..c2783690e
--- /dev/null
+++ b/src/db/update/InotifySource.cxx
@@ -0,0 +1,114 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "InotifySource.hxx"
+#include "InotifyDomain.hxx"
+#include "util/Error.hxx"
+#include "system/fd_util.h"
+#include "system/FatalError.hxx"
+#include "Log.hxx"
+
+#include <sys/inotify.h>
+#include <unistd.h>
+#include <errno.h>
+
+bool
+InotifySource::OnSocketReady(gcc_unused unsigned flags)
+{
+	const auto dest = buffer.Write();
+	if (dest.IsEmpty())
+		FatalError("buffer full");
+
+	ssize_t nbytes = read(Get(), dest.data, dest.size);
+	if (nbytes < 0)
+		FatalSystemError("Failed to read from inotify");
+	if (nbytes == 0)
+		FatalError("end of file from inotify");
+
+	buffer.Append(nbytes);
+
+	while (true) {
+		const char *name;
+
+		auto range = buffer.Read();
+		const struct inotify_event *event =
+			(const struct inotify_event *)
+			range.data;
+		if (range.size < sizeof(*event) ||
+		    range.size < sizeof(*event) + event->len)
+			break;
+
+		if (event->len > 0 && event->name[event->len - 1] == 0)
+			name = event->name;
+		else
+			name = nullptr;
+
+		callback(event->wd, event->mask, name, callback_ctx);
+		buffer.Consume(sizeof(*event) + event->len);
+	}
+
+	return true;
+}
+
+inline
+InotifySource::InotifySource(EventLoop &_loop,
+			     mpd_inotify_callback_t _callback, void *_ctx,
+			     int _fd)
+	:SocketMonitor(_fd, _loop),
+	 callback(_callback), callback_ctx(_ctx)
+{
+	ScheduleRead();
+
+}
+
+InotifySource *
+InotifySource::Create(EventLoop &loop,
+		      mpd_inotify_callback_t callback, void *callback_ctx,
+		      Error &error)
+{
+	int fd = inotify_init_cloexec();
+	if (fd < 0) {
+		error.SetErrno("inotify_init() has failed");
+		return nullptr;
+	}
+
+	return new InotifySource(loop, callback, callback_ctx, fd);
+}
+
+int
+InotifySource::Add(const char *path_fs, unsigned mask, Error &error)
+{
+	int wd = inotify_add_watch(Get(), path_fs, mask);
+	if (wd < 0)
+		error.SetErrno("inotify_add_watch() has failed");
+
+	return wd;
+}
+
+void
+InotifySource::Remove(unsigned wd)
+{
+	int ret = inotify_rm_watch(Get(), wd);
+	if (ret < 0 && errno != EINVAL)
+		LogErrno(inotify_domain, "inotify_rm_watch() has failed");
+
+	/* EINVAL may happen here when the file has been deleted; the
+	   kernel seems to auto-unregister deleted files */
+}
diff --git a/src/db/update/InotifySource.hxx b/src/db/update/InotifySource.hxx
new file mode 100644
index 000000000..77c11093c
--- /dev/null
+++ b/src/db/update/InotifySource.hxx
@@ -0,0 +1,74 @@
+/*
+ * 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_INOTIFY_SOURCE_HXX
+#define MPD_INOTIFY_SOURCE_HXX
+
+#include "event/SocketMonitor.hxx"
+#include "util/FifoBuffer.hxx"
+
+class Error;
+
+typedef void (*mpd_inotify_callback_t)(int wd, unsigned mask,
+				       const char *name, void *ctx);
+
+class InotifySource final : private SocketMonitor {
+	mpd_inotify_callback_t callback;
+	void *callback_ctx;
+
+	FifoBuffer<uint8_t, 4096> buffer;
+
+	InotifySource(EventLoop &_loop,
+		      mpd_inotify_callback_t callback, void *ctx, int fd);
+
+public:
+	~InotifySource() {
+		Close();
+	}
+
+	/**
+	 * Creates a new inotify source and registers it in the GLib main
+	 * loop.
+	 *
+	 * @param a callback invoked for events received from the kernel
+	 */
+	static InotifySource *Create(EventLoop &_loop,
+				     mpd_inotify_callback_t callback,
+				     void *ctx,
+				     Error &error);
+
+	/**
+	 * Adds a path to the notify list.
+	 *
+	 * @return a watch descriptor or -1 on error
+	 */
+	int Add(const char *path_fs, unsigned mask, Error &error);
+
+	/**
+	 * Removes a path from the notify list.
+	 *
+	 * @param wd the watch descriptor returned by mpd_inotify_source_add()
+	 */
+	void Remove(unsigned wd);
+
+private:
+	virtual bool OnSocketReady(unsigned flags) override;
+};
+
+#endif
diff --git a/src/db/update/InotifyUpdate.cxx b/src/db/update/InotifyUpdate.cxx
new file mode 100644
index 000000000..7515990d7
--- /dev/null
+++ b/src/db/update/InotifyUpdate.cxx
@@ -0,0 +1,339 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "InotifyUpdate.hxx"
+#include "InotifySource.hxx"
+#include "InotifyQueue.hxx"
+#include "InotifyDomain.hxx"
+#include "Mapper.hxx"
+#include "Main.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "fs/FileSystem.hxx"
+#include "util/Error.hxx"
+#include "Log.hxx"
+
+#include <string>
+#include <map>
+#include <forward_list>
+
+#include <assert.h>
+#include <sys/inotify.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <dirent.h>
+
+static constexpr unsigned IN_MASK =
+#ifdef IN_ONLYDIR
+	IN_ONLYDIR|
+#endif
+	IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_DELETE_SELF
+	|IN_MOVE|IN_MOVE_SELF;
+
+struct WatchDirectory {
+	WatchDirectory *parent;
+
+	AllocatedPath name;
+
+	int descriptor;
+
+	std::forward_list<WatchDirectory> children;
+
+	template<typename N>
+	WatchDirectory(WatchDirectory *_parent, N &&_name,
+		       int _descriptor)
+		:parent(_parent), name(std::forward<N>(_name)),
+		 descriptor(_descriptor) {}
+
+	WatchDirectory(const WatchDirectory &) = delete;
+	WatchDirectory &operator=(const WatchDirectory &) = delete;
+};
+
+static InotifySource *inotify_source;
+static InotifyQueue *inotify_queue;
+
+static unsigned inotify_max_depth;
+static WatchDirectory *inotify_root;
+static std::map<int, WatchDirectory *> inotify_directories;
+
+static void
+tree_add_watch_directory(WatchDirectory *directory)
+{
+	inotify_directories.insert(std::make_pair(directory->descriptor,
+						  directory));
+}
+
+static void
+tree_remove_watch_directory(WatchDirectory *directory)
+{
+	auto i = inotify_directories.find(directory->descriptor);
+	assert(i != inotify_directories.end());
+	inotify_directories.erase(i);
+}
+
+static WatchDirectory *
+tree_find_watch_directory(int wd)
+{
+	auto i = inotify_directories.find(wd);
+	if (i == inotify_directories.end())
+		return nullptr;
+
+	return i->second;
+}
+
+static void
+disable_watch_directory(WatchDirectory &directory)
+{
+	tree_remove_watch_directory(&directory);
+
+	for (WatchDirectory &child : directory.children)
+		disable_watch_directory(child);
+
+	inotify_source->Remove(directory.descriptor);
+}
+
+static void
+remove_watch_directory(WatchDirectory *directory)
+{
+	assert(directory != nullptr);
+
+	if (directory->parent == nullptr) {
+		LogWarning(inotify_domain,
+			   "music directory was removed - "
+			   "cannot continue to watch it");
+		return;
+	}
+
+	disable_watch_directory(*directory);
+
+	/* remove it from the parent, which effectively deletes it */
+	directory->parent->children.remove_if([directory](const WatchDirectory &child){
+			return &child == directory;
+		});
+}
+
+static AllocatedPath
+watch_directory_get_uri_fs(const WatchDirectory *directory)
+{
+	if (directory->parent == nullptr)
+		return AllocatedPath::Null();
+
+	const auto uri = watch_directory_get_uri_fs(directory->parent);
+	if (uri.IsNull())
+		return directory->name;
+
+	return AllocatedPath::Build(uri, directory->name);
+}
+
+/* we don't look at "." / ".." nor files with newlines in their name */
+static bool skip_path(const char *path)
+{
+	return (path[0] == '.' && path[1] == 0) ||
+		(path[0] == '.' && path[1] == '.' && path[2] == 0) ||
+		strchr(path, '\n') != nullptr;
+}
+
+static void
+recursive_watch_subdirectories(WatchDirectory *directory,
+			       const AllocatedPath &path_fs, unsigned depth)
+{
+	Error error;
+	DIR *dir;
+	struct dirent *ent;
+
+	assert(directory != nullptr);
+	assert(depth <= inotify_max_depth);
+	assert(!path_fs.IsNull());
+
+	++depth;
+
+	if (depth > inotify_max_depth)
+		return;
+
+	dir = opendir(path_fs.c_str());
+	if (dir == nullptr) {
+		FormatErrno(inotify_domain,
+			    "Failed to open directory %s", path_fs.c_str());
+		return;
+	}
+
+	while ((ent = readdir(dir))) {
+		struct stat st;
+		int ret;
+
+		if (skip_path(ent->d_name))
+			continue;
+
+		const auto child_path_fs =
+			AllocatedPath::Build(path_fs, ent->d_name);
+		ret = StatFile(child_path_fs, st);
+		if (ret < 0) {
+			FormatErrno(inotify_domain,
+				    "Failed to stat %s",
+				    child_path_fs.c_str());
+			continue;
+		}
+
+		if (!S_ISDIR(st.st_mode))
+			continue;
+
+		ret = inotify_source->Add(child_path_fs.c_str(), IN_MASK,
+					  error);
+		if (ret < 0) {
+			FormatError(error,
+				    "Failed to register %s",
+				    child_path_fs.c_str());
+			error.Clear();
+			continue;
+		}
+
+		WatchDirectory *child = tree_find_watch_directory(ret);
+		if (child != nullptr)
+			/* already being watched */
+			continue;
+
+		directory->children.emplace_front(directory,
+						  AllocatedPath::FromFS(ent->d_name),
+						  ret);
+		child = &directory->children.front();
+
+		tree_add_watch_directory(child);
+
+		recursive_watch_subdirectories(child, child_path_fs, depth);
+	}
+
+	closedir(dir);
+}
+
+gcc_pure
+static unsigned
+watch_directory_depth(const WatchDirectory *d)
+{
+	assert(d != nullptr);
+
+	unsigned depth = 0;
+	while ((d = d->parent) != nullptr)
+		++depth;
+
+	return depth;
+}
+
+static void
+mpd_inotify_callback(int wd, unsigned mask,
+		     gcc_unused const char *name, gcc_unused void *ctx)
+{
+	WatchDirectory *directory;
+
+	/*FormatDebug(inotify_domain, "wd=%d mask=0x%x name='%s'", wd, mask, name);*/
+
+	directory = tree_find_watch_directory(wd);
+	if (directory == nullptr)
+		return;
+
+	const auto uri_fs = watch_directory_get_uri_fs(directory);
+
+	if ((mask & (IN_DELETE_SELF|IN_MOVE_SELF)) != 0) {
+		remove_watch_directory(directory);
+		return;
+	}
+
+	if ((mask & (IN_ATTRIB|IN_CREATE|IN_MOVE)) != 0 &&
+	    (mask & IN_ISDIR) != 0) {
+		/* a sub directory was changed: register those in
+		   inotify */
+		const auto &root = mapper_get_music_directory_fs();
+
+		const auto path_fs = uri_fs.IsNull()
+			? root
+			: AllocatedPath::Build(root, uri_fs.c_str());
+
+		recursive_watch_subdirectories(directory, path_fs,
+					       watch_directory_depth(directory));
+	}
+
+	if ((mask & (IN_CLOSE_WRITE|IN_MOVE|IN_DELETE)) != 0 ||
+	    /* at the maximum depth, we watch out for newly created
+	       directories */
+	    (watch_directory_depth(directory) == inotify_max_depth &&
+	     (mask & (IN_CREATE|IN_ISDIR)) == (IN_CREATE|IN_ISDIR))) {
+		/* a file was changed, or a directory was
+		   moved/deleted: queue a database update */
+
+		if (!uri_fs.IsNull()) {
+			const std::string uri_utf8 = uri_fs.ToUTF8();
+			if (!uri_utf8.empty())
+				inotify_queue->Enqueue(uri_utf8.c_str());
+		}
+		else
+			inotify_queue->Enqueue("");
+	}
+}
+
+void
+mpd_inotify_init(unsigned max_depth)
+{
+	LogDebug(inotify_domain, "initializing inotify");
+
+	const auto &path = mapper_get_music_directory_fs();
+	if (path.IsNull()) {
+		LogDebug(inotify_domain, "no music directory configured");
+		return;
+	}
+
+	Error error;
+	inotify_source = InotifySource::Create(*main_loop,
+					       mpd_inotify_callback, nullptr,
+					       error);
+	if (inotify_source == nullptr) {
+		LogError(error);
+		return;
+	}
+
+	inotify_max_depth = max_depth;
+
+	int descriptor = inotify_source->Add(path.c_str(), IN_MASK, error);
+	if (descriptor < 0) {
+		LogError(error);
+		delete inotify_source;
+		inotify_source = nullptr;
+		return;
+	}
+
+	inotify_root = new WatchDirectory(nullptr, path, descriptor);
+
+	tree_add_watch_directory(inotify_root);
+
+	recursive_watch_subdirectories(inotify_root, path, 0);
+
+	inotify_queue = new InotifyQueue(*main_loop);
+
+	LogDebug(inotify_domain, "watching music directory");
+}
+
+void
+mpd_inotify_finish(void)
+{
+	if (inotify_source == nullptr)
+		return;
+
+	delete inotify_queue;
+	delete inotify_source;
+	delete inotify_root;
+	inotify_directories.clear();
+}
diff --git a/src/db/update/InotifyUpdate.hxx b/src/db/update/InotifyUpdate.hxx
new file mode 100644
index 000000000..2d7d4e3b4
--- /dev/null
+++ b/src/db/update/InotifyUpdate.hxx
@@ -0,0 +1,47 @@
+/*
+ * 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_INOTIFY_UPDATE_HXX
+#define MPD_INOTIFY_UPDATE_HXX
+
+#include "check.h"
+
+#ifdef HAVE_INOTIFY_INIT
+
+void
+mpd_inotify_init(unsigned max_depth);
+
+void
+mpd_inotify_finish(void);
+
+#else /* !HAVE_INOTIFY_INIT */
+
+static inline void
+mpd_inotify_init(gcc_unused unsigned max_depth)
+{
+}
+
+static inline void
+mpd_inotify_finish(void)
+{
+}
+
+#endif /* !HAVE_INOTIFY_INIT */
+
+#endif
diff --git a/src/db/update/UpdateArchive.cxx b/src/db/update/UpdateArchive.cxx
new file mode 100644
index 000000000..5e733202d
--- /dev/null
+++ b/src/db/update/UpdateArchive.cxx
@@ -0,0 +1,169 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateArchive.hxx"
+#include "UpdateInternal.hxx"
+#include "UpdateDomain.hxx"
+#include "db/DatabaseLock.hxx"
+#include "db/Directory.hxx"
+#include "db/Song.hxx"
+#include "Mapper.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "archive/ArchiveList.hxx"
+#include "archive/ArchivePlugin.hxx"
+#include "archive/ArchiveFile.hxx"
+#include "archive/ArchiveVisitor.hxx"
+#include "util/Error.hxx"
+#include "Log.hxx"
+
+#include <string>
+
+#include <string.h>
+
+static void
+update_archive_tree(Directory &directory, const char *name)
+{
+	const char *tmp = strchr(name, '/');
+	if (tmp) {
+		const std::string child_name(name, tmp);
+		//add dir is not there already
+		db_lock();
+		Directory *subdir =
+			directory.MakeChild(child_name.c_str());
+		subdir->device = DEVICE_INARCHIVE;
+		db_unlock();
+
+		//create directories first
+		update_archive_tree(*subdir, tmp+1);
+	} else {
+		if (strlen(name) == 0) {
+			LogWarning(update_domain,
+				   "archive returned directory only");
+			return;
+		}
+
+		//add file
+		db_lock();
+		Song *song = directory.FindSong(name);
+		db_unlock();
+		if (song == nullptr) {
+			song = Song::LoadFile(name, directory);
+			if (song != nullptr) {
+				db_lock();
+				directory.AddSong(song);
+				db_unlock();
+
+				modified = true;
+				FormatDefault(update_domain, "added %s/%s",
+					      directory.GetPath(), name);
+			}
+		}
+	}
+}
+
+/**
+ * Updates the file listing from an archive file.
+ *
+ * @param parent the parent directory the archive file resides in
+ * @param name the UTF-8 encoded base name of the archive file
+ * @param st stat() information on the archive file
+ * @param plugin the archive plugin which fits this archive type
+ */
+static void
+update_archive_file2(Directory &parent, const char *name,
+		     const struct stat *st,
+		     const struct archive_plugin *plugin)
+{
+	db_lock();
+	Directory *directory = parent.FindChild(name);
+	db_unlock();
+
+	if (directory != nullptr && directory->mtime == st->st_mtime &&
+	    !walk_discard)
+		/* MPD has already scanned the archive, and it hasn't
+		   changed since - don't consider updating it */
+		return;
+
+	const auto path_fs = map_directory_child_fs(parent, name);
+
+	/* open archive */
+	Error error;
+	ArchiveFile *file = archive_file_open(plugin, path_fs.c_str(), error);
+	if (file == nullptr) {
+		LogError(error);
+		return;
+	}
+
+	FormatDebug(update_domain, "archive %s opened", path_fs.c_str());
+
+	if (directory == nullptr) {
+		FormatDebug(update_domain,
+			    "creating archive directory: %s", name);
+		db_lock();
+		directory = parent.CreateChild(name);
+		/* mark this directory as archive (we use device for
+		   this) */
+		directory->device = DEVICE_INARCHIVE;
+		db_unlock();
+	}
+
+	directory->mtime = st->st_mtime;
+
+	class UpdateArchiveVisitor final : public ArchiveVisitor {
+		Directory *directory;
+
+	public:
+		UpdateArchiveVisitor(Directory *_directory)
+			:directory(_directory) {}
+
+		virtual void VisitArchiveEntry(const char *path_utf8) override {
+			FormatDebug(update_domain,
+				    "adding archive file: %s", path_utf8);
+			update_archive_tree(*directory, path_utf8);
+		}
+	};
+
+	UpdateArchiveVisitor visitor(directory);
+	file->Visit(visitor);
+	file->Close();
+}
+
+bool
+update_archive_file(Directory &directory,
+		    const char *name, const char *suffix,
+		    const struct stat *st)
+{
+#ifdef ENABLE_ARCHIVE
+	const struct archive_plugin *plugin =
+		archive_plugin_from_suffix(suffix);
+	if (plugin == nullptr)
+		return false;
+
+	update_archive_file2(directory, name, st, plugin);
+	return true;
+#else
+	(void)directory;
+	(void)name;
+	(void)suffix;
+	(void)st;
+
+	return false;
+#endif
+}
diff --git a/src/db/update/UpdateArchive.hxx b/src/db/update/UpdateArchive.hxx
new file mode 100644
index 000000000..1fc9af349
--- /dev/null
+++ b/src/db/update/UpdateArchive.hxx
@@ -0,0 +1,50 @@
+/*
+ * 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_UPDATE_ARCHIVE_HXX
+#define MPD_UPDATE_ARCHIVE_HXX
+
+#include "check.h"
+#include "Compiler.h"
+
+#include <sys/stat.h>
+
+struct Directory;
+
+#ifdef ENABLE_ARCHIVE
+
+bool
+update_archive_file(Directory &directory,
+		    const char *name, const char *suffix,
+		    const struct stat *st);
+
+#else
+
+static inline bool
+update_archive_file(gcc_unused Directory &directory,
+		    gcc_unused const char *name,
+		    gcc_unused const char *suffix,
+		    gcc_unused const struct stat *st)
+{
+	return false;
+}
+
+#endif
+
+#endif
diff --git a/src/db/update/UpdateContainer.cxx b/src/db/update/UpdateContainer.cxx
new file mode 100644
index 000000000..c03d88748
--- /dev/null
+++ b/src/db/update/UpdateContainer.cxx
@@ -0,0 +1,136 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateContainer.hxx"
+#include "UpdateInternal.hxx"
+#include "UpdateDatabase.hxx"
+#include "UpdateDomain.hxx"
+#include "db/DatabaseLock.hxx"
+#include "db/Directory.hxx"
+#include "db/Song.hxx"
+#include "decoder/DecoderPlugin.hxx"
+#include "decoder/DecoderList.hxx"
+#include "Mapper.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "tag/TagHandler.hxx"
+#include "tag/TagBuilder.hxx"
+#include "Log.hxx"
+
+#include <glib.h>
+
+/**
+ * Create the specified directory object if it does not exist already
+ * or if the #stat object indicates that it has been modified since
+ * the last update.  Returns nullptr when it exists already and is
+ * unmodified.
+ *
+ * The caller must lock the database.
+ */
+static Directory *
+make_directory_if_modified(Directory &parent, const char *name,
+			   const struct stat *st)
+{
+	Directory *directory = parent.FindChild(name);
+
+	// directory exists already
+	if (directory != nullptr) {
+		if (directory->mtime == st->st_mtime && !walk_discard) {
+			/* not modified */
+			return nullptr;
+		}
+
+		delete_directory(directory);
+		modified = true;
+	}
+
+	directory = parent.MakeChild(name);
+	directory->mtime = st->st_mtime;
+	return directory;
+}
+
+static bool
+SupportsContainerSuffix(const DecoderPlugin &plugin, const char *suffix)
+{
+	return plugin.container_scan != nullptr &&
+		plugin.SupportsSuffix(suffix);
+}
+
+bool
+update_container_file(Directory &directory,
+		      const char *name,
+		      const struct stat *st,
+		      const char *suffix)
+{
+	const DecoderPlugin *_plugin = decoder_plugins_find([suffix](const DecoderPlugin &plugin){
+			return SupportsContainerSuffix(plugin, suffix);
+		});
+	if (_plugin == nullptr)
+		return false;
+	const DecoderPlugin &plugin = *_plugin;
+
+	db_lock();
+	Directory *contdir = make_directory_if_modified(directory, name, st);
+	if (contdir == nullptr) {
+		/* not modified */
+		db_unlock();
+		return true;
+	}
+
+	contdir->device = DEVICE_CONTAINER;
+	db_unlock();
+
+	const auto pathname = map_directory_child_fs(directory, name);
+
+	char *vtrack;
+	unsigned int tnum = 0;
+	TagBuilder tag_builder;
+	while ((vtrack = plugin.container_scan(pathname.c_str(), ++tnum)) != nullptr) {
+		Song *song = Song::NewFile(vtrack, *contdir);
+
+		// shouldn't be necessary but it's there..
+		song->mtime = st->st_mtime;
+
+		const auto child_path_fs =
+			map_directory_child_fs(*contdir, vtrack);
+
+		plugin.ScanFile(child_path_fs.c_str(),
+				add_tag_handler, &tag_builder);
+
+		tag_builder.Commit(song->tag);
+
+		db_lock();
+		contdir->AddSong(song);
+		db_unlock();
+
+		modified = true;
+
+		FormatDefault(update_domain, "added %s/%s",
+			      directory.GetPath(), vtrack);
+		g_free(vtrack);
+	}
+
+	if (tnum == 1) {
+		db_lock();
+		delete_directory(contdir);
+		db_unlock();
+		return false;
+	} else
+		return true;
+}
diff --git a/src/db/update/UpdateContainer.hxx b/src/db/update/UpdateContainer.hxx
new file mode 100644
index 000000000..8125f71ee
--- /dev/null
+++ b/src/db/update/UpdateContainer.hxx
@@ -0,0 +1,36 @@
+/*
+ * 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_UPDATE_CONTAINER_HXX
+#define MPD_UPDATE_CONTAINER_HXX
+
+#include "check.h"
+
+#include <sys/stat.h>
+
+struct Directory;
+struct DecoderPlugin;
+
+bool
+update_container_file(Directory &directory,
+		      const char *name,
+		      const struct stat *st,
+		      const char *suffix);
+
+#endif
diff --git a/src/db/update/UpdateDatabase.cxx b/src/db/update/UpdateDatabase.cxx
new file mode 100644
index 000000000..8ef0b6d82
--- /dev/null
+++ b/src/db/update/UpdateDatabase.cxx
@@ -0,0 +1,104 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateDatabase.hxx"
+#include "UpdateRemove.hxx"
+#include "PlaylistVector.hxx"
+#include "db/Directory.hxx"
+#include "db/Song.hxx"
+#include "db/DatabaseLock.hxx"
+
+#include <assert.h>
+#include <stddef.h>
+
+void
+delete_song(Directory &dir, Song *del)
+{
+	assert(del->parent == &dir);
+
+	/* first, prevent traversers in main task from getting this */
+	dir.RemoveSong(del);
+
+	db_unlock(); /* temporary unlock, because update_remove_song() blocks */
+
+	/* now take it out of the playlist (in the main_task) */
+	update_remove_song(del);
+
+	/* finally, all possible references gone, free it */
+	del->Free();
+
+	db_lock();
+}
+
+/**
+ * Recursively remove all sub directories and songs from a directory,
+ * leaving an empty directory.
+ *
+ * Caller must lock the #db_mutex.
+ */
+static void
+clear_directory(Directory &directory)
+{
+	Directory *child, *n;
+	directory_for_each_child_safe(child, n, directory)
+		delete_directory(child);
+
+	Song *song, *ns;
+	directory_for_each_song_safe(song, ns, directory) {
+		assert(song->parent == &directory);
+		delete_song(directory, song);
+	}
+}
+
+void
+delete_directory(Directory *directory)
+{
+	assert(directory->parent != nullptr);
+
+	clear_directory(*directory);
+
+	directory->Delete();
+}
+
+bool
+delete_name_in(Directory &parent, const char *name)
+{
+	bool modified = false;
+
+	db_lock();
+	Directory *directory = parent.FindChild(name);
+
+	if (directory != nullptr) {
+		delete_directory(directory);
+		modified = true;
+	}
+
+	Song *song = parent.FindSong(name);
+	if (song != nullptr) {
+		delete_song(parent, song);
+		modified = true;
+	}
+
+	parent.playlists.erase(name);
+
+	db_unlock();
+
+	return modified;
+}
diff --git a/src/db/update/UpdateDatabase.hxx b/src/db/update/UpdateDatabase.hxx
new file mode 100644
index 000000000..bd7c395f2
--- /dev/null
+++ b/src/db/update/UpdateDatabase.hxx
@@ -0,0 +1,50 @@
+/*
+ * 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_UPDATE_DATABASE_HXX
+#define MPD_UPDATE_DATABASE_HXX
+
+#include "check.h"
+
+struct Directory;
+struct Song;
+
+/**
+ * Caller must lock the #db_mutex.
+ */
+void
+delete_song(Directory &parent, Song *song);
+
+/**
+ * Recursively free a directory and all its contents.
+ *
+ * Caller must lock the #db_mutex.
+ */
+void
+delete_directory(Directory *directory);
+
+/**
+ * Caller must NOT lock the #db_mutex.
+ *
+ * @return true if the database was modified
+ */
+bool
+delete_name_in(Directory &parent, const char *name);
+
+#endif
diff --git a/src/db/update/UpdateDomain.cxx b/src/db/update/UpdateDomain.cxx
new file mode 100644
index 000000000..80ad4fd22
--- /dev/null
+++ b/src/db/update/UpdateDomain.cxx
@@ -0,0 +1,23 @@
+/*
+ * 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.
+ */
+
+#include "UpdateDomain.hxx"
+#include "util/Domain.hxx"
+
+const Domain update_domain("update");
diff --git a/src/db/update/UpdateDomain.hxx b/src/db/update/UpdateDomain.hxx
new file mode 100644
index 000000000..a6e994390
--- /dev/null
+++ b/src/db/update/UpdateDomain.hxx
@@ -0,0 +1,25 @@
+/*
+ * 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_UPDATE_DOMAIN_HXX
+#define MPD_UPDATE_DOMAIN_HXX
+
+extern const class Domain update_domain;
+
+#endif
diff --git a/src/db/update/UpdateGlue.cxx b/src/db/update/UpdateGlue.cxx
new file mode 100644
index 000000000..d18747ba1
--- /dev/null
+++ b/src/db/update/UpdateGlue.cxx
@@ -0,0 +1,181 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "UpdateGlue.hxx"
+#include "UpdateQueue.hxx"
+#include "UpdateWalk.hxx"
+#include "UpdateRemove.hxx"
+#include "UpdateDomain.hxx"
+#include "Mapper.hxx"
+#include "db/DatabaseSimple.hxx"
+#include "Idle.hxx"
+#include "GlobalEvents.hxx"
+#include "util/Error.hxx"
+#include "Log.hxx"
+#include "Main.hxx"
+#include "Instance.hxx"
+#include "system/FatalError.hxx"
+#include "thread/Id.hxx"
+#include "thread/Thread.hxx"
+#include "thread/Util.hxx"
+
+#include <assert.h>
+
+static enum update_progress {
+	UPDATE_PROGRESS_IDLE = 0,
+	UPDATE_PROGRESS_RUNNING = 1,
+	UPDATE_PROGRESS_DONE = 2
+} progress;
+
+static bool modified;
+
+static Thread update_thread;
+
+static const unsigned update_task_id_max = 1 << 15;
+
+static unsigned update_task_id;
+
+static UpdateQueueItem next;
+
+unsigned
+isUpdatingDB(void)
+{
+	return next.id;
+}
+
+static void
+update_task(gcc_unused void *ctx)
+{
+	if (!next.path_utf8.empty())
+		FormatDebug(update_domain, "starting: %s",
+			    next.path_utf8.c_str());
+	else
+		LogDebug(update_domain, "starting");
+
+	SetThreadIdlePriority();
+
+	modified = update_walk(next.path_utf8.c_str(), next.discard);
+
+	if (modified || !db_exists()) {
+		Error error;
+		if (!db_save(error))
+			LogError(error, "Failed to save database");
+	}
+
+	if (!next.path_utf8.empty())
+		FormatDebug(update_domain, "finished: %s",
+			    next.path_utf8.c_str());
+	else
+		LogDebug(update_domain, "finished");
+
+	progress = UPDATE_PROGRESS_DONE;
+	GlobalEvents::Emit(GlobalEvents::UPDATE);
+}
+
+static void
+spawn_update_task(UpdateQueueItem &&i)
+{
+	assert(main_thread.IsInside());
+
+	progress = UPDATE_PROGRESS_RUNNING;
+	modified = false;
+
+	next = std::move(i);
+
+	Error error;
+	if (!update_thread.Start(update_task, nullptr, error))
+		FatalError(error);
+
+	FormatDebug(update_domain,
+		    "spawned thread for update job id %i", next.id);
+}
+
+static unsigned
+generate_update_id()
+{
+	unsigned id = update_task_id + 1;
+	if (id > update_task_id_max)
+		id = 1;
+	return id;
+}
+
+unsigned
+update_enqueue(const char *path, bool discard)
+{
+	assert(main_thread.IsInside());
+
+	if (!db_is_simple() || !mapper_has_music_directory())
+		return 0;
+
+	if (progress != UPDATE_PROGRESS_IDLE) {
+		const unsigned id = generate_update_id();
+		if (!update_queue_push(path, discard, id))
+			return 0;
+
+		update_task_id = id;
+		return id;
+	}
+
+	const unsigned id = update_task_id = generate_update_id();
+	spawn_update_task(UpdateQueueItem(path, discard, id));
+
+	idle_add(IDLE_UPDATE);
+
+	return id;
+}
+
+/**
+ * Called in the main thread after the database update is finished.
+ */
+static void update_finished_event(void)
+{
+	assert(progress == UPDATE_PROGRESS_DONE);
+	assert(next.IsDefined());
+
+	update_thread.Join();
+	next = UpdateQueueItem();
+
+	idle_add(IDLE_UPDATE);
+
+	if (modified)
+		/* send "idle" events */
+		instance->DatabaseModified();
+
+	auto i = update_queue_shift();
+	if (i.IsDefined()) {
+		/* schedule the next path */
+		spawn_update_task(std::move(i));
+	} else {
+		progress = UPDATE_PROGRESS_IDLE;
+	}
+}
+
+void update_global_init(void)
+{
+	GlobalEvents::Register(GlobalEvents::UPDATE, update_finished_event);
+
+	update_remove_global_init();
+	update_walk_global_init();
+}
+
+void update_global_finish(void)
+{
+	update_walk_global_finish();
+}
diff --git a/src/db/update/UpdateGlue.hxx b/src/db/update/UpdateGlue.hxx
new file mode 100644
index 000000000..6e247414e
--- /dev/null
+++ b/src/db/update/UpdateGlue.hxx
@@ -0,0 +1,43 @@
+/*
+ * 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_UPDATE_GLUE_HXX
+#define MPD_UPDATE_GLUE_HXX
+
+#include "Compiler.h"
+
+void update_global_init(void);
+
+void update_global_finish(void);
+
+unsigned
+isUpdatingDB(void);
+
+/**
+ * Add this path to the database update queue.
+ *
+ * @param path a path to update; if an empty string,
+ * the whole music directory is updated
+ * @return the job id, or 0 on error
+ */
+gcc_nonnull_all
+unsigned
+update_enqueue(const char *path, bool discard);
+
+#endif
diff --git a/src/db/update/UpdateIO.cxx b/src/db/update/UpdateIO.cxx
new file mode 100644
index 000000000..f91caf359
--- /dev/null
+++ b/src/db/update/UpdateIO.cxx
@@ -0,0 +1,113 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateIO.hxx"
+#include "UpdateDomain.hxx"
+#include "db/Directory.hxx"
+#include "Mapper.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "fs/FileSystem.hxx"
+#include "Log.hxx"
+
+#include <errno.h>
+#include <unistd.h>
+
+int
+stat_directory(const Directory &directory, struct stat *st)
+{
+	const auto path_fs = map_directory_fs(directory);
+	if (path_fs.IsNull())
+		return -1;
+
+	if (!StatFile(path_fs, *st)) {
+		int error = errno;
+		const std::string path_utf8 = path_fs.ToUTF8();
+		FormatErrno(update_domain, error,
+			    "Failed to stat %s", path_utf8.c_str());
+		return -1;
+	}
+
+	return 0;
+}
+
+int
+stat_directory_child(const Directory &parent, const char *name,
+		     struct stat *st)
+{
+	const auto path_fs = map_directory_child_fs(parent, name);
+	if (path_fs.IsNull())
+		return -1;
+
+	if (!StatFile(path_fs, *st)) {
+		int error = errno;
+		const std::string path_utf8 = path_fs.ToUTF8();
+		FormatErrno(update_domain, error,
+			    "Failed to stat %s", path_utf8.c_str());
+		return -1;
+	}
+
+	return 0;
+}
+
+bool
+directory_exists(const Directory &directory)
+{
+	const auto path_fs = map_directory_fs(directory);
+	if (path_fs.IsNull())
+		/* invalid path: cannot exist */
+		return false;
+
+	return directory.device == DEVICE_INARCHIVE ||
+		directory.device == DEVICE_CONTAINER
+		? FileExists(path_fs)
+		: DirectoryExists(path_fs);
+}
+
+bool
+directory_child_is_regular(const Directory &directory,
+			   const char *name_utf8)
+{
+	const auto path_fs = map_directory_child_fs(directory, name_utf8);
+	if (path_fs.IsNull())
+		return false;
+
+	return FileExists(path_fs);
+}
+
+bool
+directory_child_access(const Directory &directory,
+		       const char *name, int mode)
+{
+#ifdef WIN32
+	/* CheckAccess() is useless on WIN32 */
+	(void)directory;
+	(void)name;
+	(void)mode;
+	return true;
+#else
+	const auto path = map_directory_child_fs(directory, name);
+	if (path.IsNull())
+		/* something went wrong, but that isn't a permission
+		   problem */
+		return true;
+
+	return CheckAccess(path, mode) || errno != EACCES;
+#endif
+}
diff --git a/src/db/update/UpdateIO.hxx b/src/db/update/UpdateIO.hxx
new file mode 100644
index 000000000..819879422
--- /dev/null
+++ b/src/db/update/UpdateIO.hxx
@@ -0,0 +1,50 @@
+/*
+ * 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_UPDATE_IO_HXX
+#define MPD_UPDATE_IO_HXX
+
+#include "check.h"
+
+#include <sys/stat.h>
+
+struct Directory;
+
+int
+stat_directory(const Directory &directory, struct stat *st);
+
+int
+stat_directory_child(const Directory &parent, const char *name,
+		     struct stat *st);
+
+bool
+directory_exists(const Directory &directory);
+
+bool
+directory_child_is_regular(const Directory &directory,
+			   const char *name_utf8);
+
+/**
+ * Checks if the given permissions on the mapped file are given.
+ */
+bool
+directory_child_access(const Directory &directory,
+		       const char *name, int mode);
+
+#endif
diff --git a/src/db/update/UpdateInternal.hxx b/src/db/update/UpdateInternal.hxx
new file mode 100644
index 000000000..2e373bd06
--- /dev/null
+++ b/src/db/update/UpdateInternal.hxx
@@ -0,0 +1,28 @@
+/*
+ * 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_UPDATE_INTERNAL_H
+#define MPD_UPDATE_INTERNAL_H
+
+#include "check.h"
+
+extern bool walk_discard;
+extern bool modified;
+
+#endif
diff --git a/src/db/update/UpdateQueue.cxx b/src/db/update/UpdateQueue.cxx
new file mode 100644
index 000000000..a6002f854
--- /dev/null
+++ b/src/db/update/UpdateQueue.cxx
@@ -0,0 +1,49 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "UpdateQueue.hxx"
+
+#include <queue>
+#include <list>
+
+static constexpr unsigned MAX_UPDATE_QUEUE_SIZE = 32;
+
+static std::queue<UpdateQueueItem, std::list<UpdateQueueItem>> update_queue;
+
+bool
+update_queue_push(const char *path, bool discard, unsigned id)
+{
+	if (update_queue.size() >= MAX_UPDATE_QUEUE_SIZE)
+		return false;
+
+	update_queue.emplace(path, discard, id);
+	return true;
+}
+
+UpdateQueueItem
+update_queue_shift()
+{
+	if (update_queue.empty())
+		return UpdateQueueItem();
+
+	auto i = std::move(update_queue.front());
+	update_queue.pop();
+	return i;
+}
diff --git a/src/db/update/UpdateQueue.hxx b/src/db/update/UpdateQueue.hxx
new file mode 100644
index 000000000..e4228f5ed
--- /dev/null
+++ b/src/db/update/UpdateQueue.hxx
@@ -0,0 +1,48 @@
+/*
+ * 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_UPDATE_QUEUE_HXX
+#define MPD_UPDATE_QUEUE_HXX
+
+#include "check.h"
+
+#include <string>
+
+struct UpdateQueueItem {
+	std::string path_utf8;
+	unsigned id;
+	bool discard;
+
+	UpdateQueueItem():id(0) {}
+	UpdateQueueItem(const char *_path, bool _discard,
+			unsigned _id)
+		:path_utf8(_path), id(_id), discard(_discard) {}
+
+	bool IsDefined() const {
+		return id != 0;
+	}
+};
+
+bool
+update_queue_push(const char *path, bool discard, unsigned id);
+
+UpdateQueueItem
+update_queue_shift();
+
+#endif
diff --git a/src/db/update/UpdateRemove.cxx b/src/db/update/UpdateRemove.cxx
new file mode 100644
index 000000000..c57758aef
--- /dev/null
+++ b/src/db/update/UpdateRemove.cxx
@@ -0,0 +1,97 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateRemove.hxx"
+#include "UpdateDomain.hxx"
+#include "GlobalEvents.hxx"
+#include "thread/Mutex.hxx"
+#include "thread/Cond.hxx"
+#include "db/Song.hxx"
+#include "db/LightSong.hxx"
+#include "Main.hxx"
+#include "Instance.hxx"
+#include "Log.hxx"
+
+#ifdef ENABLE_SQLITE
+#include "sticker/StickerDatabase.hxx"
+#include "sticker/SongSticker.hxx"
+#endif
+
+#include <assert.h>
+
+static const Song *removed_song;
+
+static Mutex remove_mutex;
+static Cond remove_cond;
+
+/**
+ * Safely remove a song from the database.  This must be done in the
+ * main task, to be sure that there is no pointer left to it.
+ */
+static void
+song_remove_event(void)
+{
+	assert(removed_song != nullptr);
+
+	{
+		const auto uri = removed_song->GetURI();
+		FormatDefault(update_domain, "removing %s", uri.c_str());
+	}
+
+#ifdef ENABLE_SQLITE
+	/* if the song has a sticker, remove it */
+	if (sticker_enabled())
+		sticker_song_delete(removed_song->Export());
+#endif
+
+	{
+		const auto uri = removed_song->GetURI();
+		instance->DeleteSong(uri.c_str());
+	}
+
+	/* clear "removed_song" and send signal to update thread */
+	remove_mutex.lock();
+	removed_song = nullptr;
+	remove_cond.signal();
+	remove_mutex.unlock();
+}
+
+void
+update_remove_global_init(void)
+{
+	GlobalEvents::Register(GlobalEvents::DELETE, song_remove_event);
+}
+
+void
+update_remove_song(const Song *song)
+{
+	assert(removed_song == nullptr);
+
+	removed_song = song;
+
+	GlobalEvents::Emit(GlobalEvents::DELETE);
+
+	remove_mutex.lock();
+
+	while (removed_song != nullptr)
+		remove_cond.wait(remove_mutex);
+
+	remove_mutex.unlock();
+}
diff --git a/src/db/update/UpdateRemove.hxx b/src/db/update/UpdateRemove.hxx
new file mode 100644
index 000000000..d54e3aa80
--- /dev/null
+++ b/src/db/update/UpdateRemove.hxx
@@ -0,0 +1,38 @@
+/*
+ * 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_UPDATE_REMOVE_HXX
+#define MPD_UPDATE_REMOVE_HXX
+
+#include "check.h"
+
+struct Song;
+
+void
+update_remove_global_init(void);
+
+/**
+ * Sends a signal to the main thread which will in turn remove the
+ * song: from the sticker database and from the playlist.  This
+ * serialized access is implemented to avoid excessive locking.
+ */
+void
+update_remove_song(const Song *song);
+
+#endif
diff --git a/src/db/update/UpdateSong.cxx b/src/db/update/UpdateSong.cxx
new file mode 100644
index 000000000..ac2d01cd2
--- /dev/null
+++ b/src/db/update/UpdateSong.cxx
@@ -0,0 +1,113 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateSong.hxx"
+#include "UpdateInternal.hxx"
+#include "UpdateIO.hxx"
+#include "UpdateDatabase.hxx"
+#include "UpdateContainer.hxx"
+#include "UpdateDomain.hxx"
+#include "db/DatabaseLock.hxx"
+#include "db/Directory.hxx"
+#include "db/Song.hxx"
+#include "decoder/DecoderList.hxx"
+#include "Log.hxx"
+
+#include <unistd.h>
+
+static void
+update_song_file2(Directory &directory,
+		  const char *name, const struct stat *st,
+		  const char *suffix)
+{
+	db_lock();
+	Song *song = directory.FindSong(name);
+	db_unlock();
+
+	if (!directory_child_access(directory, name, R_OK)) {
+		FormatError(update_domain,
+			    "no read permissions on %s/%s",
+			    directory.GetPath(), name);
+		if (song != nullptr) {
+			db_lock();
+			delete_song(directory, song);
+			db_unlock();
+		}
+
+		return;
+	}
+
+	if (!(song != nullptr && st->st_mtime == song->mtime &&
+	      !walk_discard) &&
+	    update_container_file(directory, name, st, suffix)) {
+		if (song != nullptr) {
+			db_lock();
+			delete_song(directory, song);
+			db_unlock();
+		}
+
+		return;
+	}
+
+	if (song == nullptr) {
+		FormatDebug(update_domain, "reading %s/%s",
+			    directory.GetPath(), name);
+		song = Song::LoadFile(name, directory);
+		if (song == nullptr) {
+			FormatDebug(update_domain,
+				    "ignoring unrecognized file %s/%s",
+				    directory.GetPath(), name);
+			return;
+		}
+
+		db_lock();
+		directory.AddSong(song);
+		db_unlock();
+
+		modified = true;
+		FormatDefault(update_domain, "added %s/%s",
+			      directory.GetPath(), name);
+	} else if (st->st_mtime != song->mtime || walk_discard) {
+		FormatDefault(update_domain, "updating %s/%s",
+			      directory.GetPath(), name);
+		if (!song->UpdateFile()) {
+			FormatDebug(update_domain,
+				    "deleting unrecognized file %s/%s",
+				    directory.GetPath(), name);
+			db_lock();
+			delete_song(directory, song);
+			db_unlock();
+		}
+
+		modified = true;
+	}
+}
+
+bool
+update_song_file(Directory &directory,
+		 const char *name, const char *suffix,
+		 const struct stat *st)
+{
+	if (!decoder_plugins_supports_suffix(suffix))
+		return false;
+
+	update_song_file2(directory, name, st, suffix);
+	return true;
+}
diff --git a/src/db/update/UpdateSong.hxx b/src/db/update/UpdateSong.hxx
new file mode 100644
index 000000000..5feb01928
--- /dev/null
+++ b/src/db/update/UpdateSong.hxx
@@ -0,0 +1,34 @@
+/*
+ * 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_UPDATE_SONG_HXX
+#define MPD_UPDATE_SONG_HXX
+
+#include "check.h"
+
+#include <sys/stat.h>
+
+struct Directory;
+
+bool
+update_song_file(Directory &directory,
+		 const char *name, const char *suffix,
+		 const struct stat *st);
+
+#endif
diff --git a/src/db/update/UpdateWalk.cxx b/src/db/update/UpdateWalk.cxx
new file mode 100644
index 000000000..c5a9936e9
--- /dev/null
+++ b/src/db/update/UpdateWalk.cxx
@@ -0,0 +1,484 @@
+/*
+ * 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.
+ */
+
+#include "config.h" /* must be first for large file support */
+#include "UpdateWalk.hxx"
+#include "UpdateIO.hxx"
+#include "UpdateDatabase.hxx"
+#include "UpdateSong.hxx"
+#include "UpdateArchive.hxx"
+#include "UpdateDomain.hxx"
+#include "db/DatabaseLock.hxx"
+#include "db/DatabaseSimple.hxx"
+#include "db/Directory.hxx"
+#include "db/Song.hxx"
+#include "PlaylistVector.hxx"
+#include "playlist/PlaylistRegistry.hxx"
+#include "Mapper.hxx"
+#include "ExcludeList.hxx"
+#include "config/ConfigGlobal.hxx"
+#include "config/ConfigOption.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "fs/Traits.hxx"
+#include "fs/FileSystem.hxx"
+#include "fs/DirectoryReader.hxx"
+#include "util/Alloc.hxx"
+#include "util/UriUtil.hxx"
+#include "Log.hxx"
+
+#include <assert.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+bool walk_discard;
+bool modified;
+
+#ifndef WIN32
+
+static constexpr bool DEFAULT_FOLLOW_INSIDE_SYMLINKS = true;
+static constexpr bool DEFAULT_FOLLOW_OUTSIDE_SYMLINKS = true;
+
+static bool follow_inside_symlinks;
+static bool follow_outside_symlinks;
+
+#endif
+
+void
+update_walk_global_init(void)
+{
+#ifndef WIN32
+	follow_inside_symlinks =
+		config_get_bool(CONF_FOLLOW_INSIDE_SYMLINKS,
+				DEFAULT_FOLLOW_INSIDE_SYMLINKS);
+
+	follow_outside_symlinks =
+		config_get_bool(CONF_FOLLOW_OUTSIDE_SYMLINKS,
+				DEFAULT_FOLLOW_OUTSIDE_SYMLINKS);
+#endif
+}
+
+void
+update_walk_global_finish(void)
+{
+}
+
+static void
+directory_set_stat(Directory &dir, const struct stat *st)
+{
+	dir.inode = st->st_ino;
+	dir.device = st->st_dev;
+	dir.have_stat = true;
+}
+
+static void
+remove_excluded_from_directory(Directory &directory,
+			       const ExcludeList &exclude_list)
+{
+	db_lock();
+
+	Directory *child, *n;
+	directory_for_each_child_safe(child, n, directory) {
+		const auto name_fs = AllocatedPath::FromUTF8(child->GetName());
+
+		if (name_fs.IsNull() || exclude_list.Check(name_fs)) {
+			delete_directory(child);
+			modified = true;
+		}
+	}
+
+	Song *song, *ns;
+	directory_for_each_song_safe(song, ns, directory) {
+		assert(song->parent == &directory);
+
+		const auto name_fs = AllocatedPath::FromUTF8(song->uri);
+		if (name_fs.IsNull() || exclude_list.Check(name_fs)) {
+			delete_song(directory, song);
+			modified = true;
+		}
+	}
+
+	db_unlock();
+}
+
+static void
+purge_deleted_from_directory(Directory &directory)
+{
+	Directory *child, *n;
+	directory_for_each_child_safe(child, n, directory) {
+		if (directory_exists(*child))
+			continue;
+
+		db_lock();
+		delete_directory(child);
+		db_unlock();
+
+		modified = true;
+	}
+
+	Song *song, *ns;
+	directory_for_each_song_safe(song, ns, directory) {
+		const auto path = map_song_fs(*song);
+		if (path.IsNull() || !FileExists(path)) {
+			db_lock();
+			delete_song(directory, song);
+			db_unlock();
+
+			modified = true;
+		}
+	}
+
+	for (auto i = directory.playlists.begin(),
+		     end = directory.playlists.end();
+	     i != end;) {
+		if (!directory_child_is_regular(directory, i->name.c_str())) {
+			db_lock();
+			i = directory.playlists.erase(i);
+			db_unlock();
+		} else
+			++i;
+	}
+}
+
+#ifndef WIN32
+static int
+update_directory_stat(Directory &directory)
+{
+	struct stat st;
+	if (stat_directory(directory, &st) < 0)
+		return -1;
+
+	directory_set_stat(directory, &st);
+	return 0;
+}
+#endif
+
+static int
+find_inode_ancestor(Directory *parent, ino_t inode, dev_t device)
+{
+#ifndef WIN32
+	while (parent) {
+		if (!parent->have_stat && update_directory_stat(*parent) < 0)
+			return -1;
+
+		if (parent->inode == inode && parent->device == device) {
+			LogDebug(update_domain, "recursive directory found");
+			return 1;
+		}
+
+		parent = parent->parent;
+	}
+#else
+	(void)parent;
+	(void)inode;
+	(void)device;
+#endif
+
+	return 0;
+}
+
+static bool
+update_playlist_file2(Directory &directory,
+		      const char *name, const char *suffix,
+		      const struct stat *st)
+{
+	if (!playlist_suffix_supported(suffix))
+		return false;
+
+	PlaylistInfo pi(name, st->st_mtime);
+
+	db_lock();
+	if (directory.playlists.UpdateOrInsert(std::move(pi)))
+		modified = true;
+	db_unlock();
+	return true;
+}
+
+static bool
+update_regular_file(Directory &directory,
+		    const char *name, const struct stat *st)
+{
+	const char *suffix = uri_get_suffix(name);
+	if (suffix == nullptr)
+		return false;
+
+	return update_song_file(directory, name, suffix, st) ||
+		update_archive_file(directory, name, suffix, st) ||
+		update_playlist_file2(directory, name, suffix, st);
+}
+
+static bool
+update_directory(Directory &directory, const struct stat *st);
+
+static void
+update_directory_child(Directory &directory,
+		       const char *name, const struct stat *st)
+{
+	assert(strchr(name, '/') == nullptr);
+
+	if (S_ISREG(st->st_mode)) {
+		update_regular_file(directory, name, st);
+	} else if (S_ISDIR(st->st_mode)) {
+		if (find_inode_ancestor(&directory, st->st_ino, st->st_dev))
+			return;
+
+		db_lock();
+		Directory *subdir = directory.MakeChild(name);
+		db_unlock();
+
+		assert(&directory == subdir->parent);
+
+		if (!update_directory(*subdir, st)) {
+			db_lock();
+			delete_directory(subdir);
+			db_unlock();
+		}
+	} else {
+		FormatDebug(update_domain,
+			    "%s is not a directory, archive or music", name);
+	}
+}
+
+/* we don't look at "." / ".." nor files with newlines in their name */
+gcc_pure
+static bool skip_path(Path path_fs)
+{
+	const char *path = path_fs.c_str();
+	return (path[0] == '.' && path[1] == 0) ||
+		(path[0] == '.' && path[1] == '.' && path[2] == 0) ||
+		strchr(path, '\n') != nullptr;
+}
+
+gcc_pure
+static bool
+skip_symlink(const Directory *directory, const char *utf8_name)
+{
+#ifndef WIN32
+	const auto path_fs = map_directory_child_fs(*directory, utf8_name);
+	if (path_fs.IsNull())
+		return true;
+
+	const auto target = ReadLink(path_fs);
+	if (target.IsNull())
+		/* don't skip if this is not a symlink */
+		return errno != EINVAL;
+
+	if (!follow_inside_symlinks && !follow_outside_symlinks) {
+		/* ignore all symlinks */
+		return true;
+	} else if (follow_inside_symlinks && follow_outside_symlinks) {
+		/* consider all symlinks */
+		return false;
+	}
+
+	const char *target_str = target.c_str();
+
+	if (PathTraitsFS::IsAbsolute(target_str)) {
+		/* if the symlink points to an absolute path, see if
+		   that path is inside the music directory */
+		const char *relative = map_to_relative_path(target_str);
+		return relative > target_str
+			? !follow_inside_symlinks
+			: !follow_outside_symlinks;
+	}
+
+	const char *p = target_str;
+	while (*p == '.') {
+		if (p[1] == '.' && PathTraitsFS::IsSeparator(p[2])) {
+			/* "../" moves to parent directory */
+			directory = directory->parent;
+			if (directory == nullptr) {
+				/* we have moved outside the music
+				   directory - skip this symlink
+				   if such symlinks are not allowed */
+				return !follow_outside_symlinks;
+			}
+			p += 3;
+		} else if (PathTraitsFS::IsSeparator(p[1]))
+			/* eliminate "./" */
+			p += 2;
+		else
+			break;
+	}
+
+	/* we are still in the music directory, so this symlink points
+	   to a song which is already in the database - skip according
+	   to the follow_inside_symlinks param*/
+	return !follow_inside_symlinks;
+#else
+	/* no symlink checking on WIN32 */
+
+	(void)directory;
+	(void)utf8_name;
+
+	return false;
+#endif
+}
+
+static bool
+update_directory(Directory &directory, const struct stat *st)
+{
+	assert(S_ISDIR(st->st_mode));
+
+	directory_set_stat(directory, st);
+
+	const auto path_fs = map_directory_fs(directory);
+	if (path_fs.IsNull())
+		return false;
+
+	DirectoryReader reader(path_fs);
+	if (reader.HasFailed()) {
+		int error = errno;
+		const auto path_utf8 = path_fs.ToUTF8();
+		FormatErrno(update_domain, error,
+			    "Failed to open directory %s",
+			    path_utf8.c_str());
+		return false;
+	}
+
+	ExcludeList exclude_list;
+	exclude_list.LoadFile(AllocatedPath::Build(path_fs, ".mpdignore"));
+
+	if (!exclude_list.IsEmpty())
+		remove_excluded_from_directory(directory, exclude_list);
+
+	purge_deleted_from_directory(directory);
+
+	while (reader.ReadEntry()) {
+		std::string utf8;
+		struct stat st2;
+
+		const auto entry = reader.GetEntry();
+
+		if (skip_path(entry) || exclude_list.Check(entry))
+			continue;
+
+		utf8 = entry.ToUTF8();
+		if (utf8.empty())
+			continue;
+
+		if (skip_symlink(&directory, utf8.c_str())) {
+			modified |= delete_name_in(directory, utf8.c_str());
+			continue;
+		}
+
+		if (stat_directory_child(directory, utf8.c_str(), &st2) == 0)
+			update_directory_child(directory, utf8.c_str(), &st2);
+		else
+			modified |= delete_name_in(directory, utf8.c_str());
+	}
+
+	directory.mtime = st->st_mtime;
+
+	return true;
+}
+
+static Directory *
+directory_make_child_checked(Directory &parent, const char *name_utf8)
+{
+	db_lock();
+	Directory *directory = parent.FindChild(name_utf8);
+	db_unlock();
+
+	if (directory != nullptr)
+		return directory;
+
+	struct stat st;
+	if (stat_directory_child(parent, name_utf8, &st) < 0 ||
+	    find_inode_ancestor(&parent, st.st_ino, st.st_dev))
+		return nullptr;
+
+	if (skip_symlink(&parent, name_utf8))
+		return nullptr;
+
+	/* if we're adding directory paths, make sure to delete filenames
+	   with potentially the same name */
+	db_lock();
+	Song *conflicting = parent.FindSong(name_utf8);
+	if (conflicting)
+		delete_song(parent, conflicting);
+
+	directory = parent.CreateChild(name_utf8);
+	db_unlock();
+
+	directory_set_stat(*directory, &st);
+	return directory;
+}
+
+static Directory *
+directory_make_uri_parent_checked(const char *uri)
+{
+	Directory *directory = db_get_root();
+	char *duplicated = xstrdup(uri);
+	char *name_utf8 = duplicated, *slash;
+
+	while ((slash = strchr(name_utf8, '/')) != nullptr) {
+		*slash = 0;
+
+		if (*name_utf8 == 0)
+			continue;
+
+		directory = directory_make_child_checked(*directory,
+							 name_utf8);
+		if (directory == nullptr)
+			break;
+
+		name_utf8 = slash + 1;
+	}
+
+	free(duplicated);
+	return directory;
+}
+
+static void
+update_uri(const char *uri)
+{
+	Directory *parent = directory_make_uri_parent_checked(uri);
+	if (parent == nullptr)
+		return;
+
+	const char *name = PathTraitsUTF8::GetBase(uri);
+
+	struct stat st;
+	if (!skip_symlink(parent, name) &&
+	    stat_directory_child(*parent, name, &st) == 0)
+		update_directory_child(*parent, name, &st);
+	else
+		modified |= delete_name_in(*parent, name);
+}
+
+bool
+update_walk(const char *path, bool discard)
+{
+	walk_discard = discard;
+	modified = false;
+
+	if (path != nullptr && !isRootDirectory(path)) {
+		update_uri(path);
+	} else {
+		Directory *directory = db_get_root();
+		struct stat st;
+
+		if (stat_directory(*directory, &st) == 0)
+			update_directory(*directory, &st);
+	}
+
+	return modified;
+}
diff --git a/src/db/update/UpdateWalk.hxx b/src/db/update/UpdateWalk.hxx
new file mode 100644
index 000000000..e908829e3
--- /dev/null
+++ b/src/db/update/UpdateWalk.hxx
@@ -0,0 +1,37 @@
+/*
+ * 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_UPDATE_WALK_HXX
+#define MPD_UPDATE_WALK_HXX
+
+#include "check.h"
+
+void
+update_walk_global_init(void);
+
+void
+update_walk_global_finish(void);
+
+/**
+ * Returns true if the database was modified.
+ */
+bool
+update_walk(const char *path, bool discard);
+
+#endif