Playlist*: move to queue/

src/queue/Playlist.cxx

@@ -0,0 +1,333 @@
+/*
+ * 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 "Playlist.hxx"
+#include "PlaylistError.hxx"
+#include "PlayerControl.hxx"
+#include "DetachedSong.hxx"
+#include "Idle.hxx"
+#include "Log.hxx"
+
+#include <assert.h>
+
+void
+playlist::TagModified(DetachedSong &&song)
+{
+	if (!playing)
+		return;
+
+	assert(current >= 0);
+
+	DetachedSong &current_song = queue.GetOrder(current);
+	if (song.IsSame(current_song))
+		current_song.MoveTagFrom(std::move(song));
+
+	queue.ModifyAtOrder(current);
+	queue.IncrementVersion();
+	idle_add(IDLE_PLAYLIST);
+}
+
+/**
+ * Queue a song, addressed by its order number.
+ */
+static void
+playlist_queue_song_order(playlist &playlist, PlayerControl &pc,
+			  unsigned order)
+{
+	assert(playlist.queue.IsValidOrder(order));
+
+	playlist.queued = order;
+
+	const DetachedSong &song = playlist.queue.GetOrder(order);
+
+	FormatDebug(playlist_domain, "queue song %i:\"%s\"",
+		    playlist.queued, song.GetURI());
+
+	pc.EnqueueSong(new DetachedSong(song));
+}
+
+/**
+ * Called if the player thread has started playing the "queued" song.
+ */
+static void
+playlist_song_started(playlist &playlist, PlayerControl &pc)
+{
+	assert(pc.next_song == nullptr);
+	assert(playlist.queued >= -1);
+
+	/* queued song has started: copy queued to current,
+	   and notify the clients */
+
+	int current = playlist.current;
+	playlist.current = playlist.queued;
+	playlist.queued = -1;
+
+	if(playlist.queue.consume)
+		playlist.DeleteOrder(pc, current);
+
+	idle_add(IDLE_PLAYER);
+}
+
+const DetachedSong *
+playlist::GetQueuedSong() const
+{
+	return playing && queued >= 0
+		? &queue.GetOrder(queued)
+		: nullptr;
+}
+
+void
+playlist::UpdateQueuedSong(PlayerControl &pc, const DetachedSong *prev)
+{
+	if (!playing)
+		return;
+
+	assert(!queue.IsEmpty());
+	assert((queued < 0) == (prev == nullptr));
+
+	const int next_order = current >= 0
+		? queue.GetNextOrder(current)
+		: 0;
+
+	if (next_order == 0 && queue.random && !queue.single) {
+		/* shuffle the song order again, so we get a different
+		   order each time the playlist is played
+		   completely */
+		const unsigned current_position =
+			queue.OrderToPosition(current);
+
+		queue.ShuffleOrder();
+
+		/* make sure that the current still points to
+		   the current song, after the song order has been
+		   shuffled */
+		current = queue.PositionToOrder(current_position);
+	}
+
+	const DetachedSong *const next_song = next_order >= 0
+		? &queue.GetOrder(next_order)
+		: nullptr;
+
+	if (prev != nullptr && next_song != prev) {
+		/* clear the currently queued song */
+		pc.Cancel();
+		queued = -1;
+	}
+
+	if (next_order >= 0) {
+		if (next_song != prev)
+			playlist_queue_song_order(*this, pc, next_order);
+		else
+			queued = next_order;
+	}
+}
+
+void
+playlist::PlayOrder(PlayerControl &pc, int order)
+{
+	playing = true;
+	queued = -1;
+
+	const DetachedSong &song = queue.GetOrder(order);
+
+	FormatDebug(playlist_domain, "play %i:\"%s\"", order, song.GetURI());
+
+	pc.Play(new DetachedSong(song));
+	current = order;
+}
+
+static void
+playlist_resume_playback(playlist &playlist, PlayerControl &pc);
+
+void
+playlist::SyncWithPlayer(PlayerControl &pc)
+{
+	if (!playing)
+		/* this event has reached us out of sync: we aren't
+		   playing anymore; ignore the event */
+		return;
+
+	pc.Lock();
+	const PlayerState pc_state = pc.GetState();
+	const DetachedSong *pc_next_song = pc.next_song;
+	pc.Unlock();
+
+	if (pc_state == PlayerState::STOP)
+		/* the player thread has stopped: check if playback
+		   should be restarted with the next song.  That can
+		   happen if the playlist isn't filling the queue fast
+		   enough */
+		playlist_resume_playback(*this, pc);
+	else {
+		/* check if the player thread has already started
+		   playing the queued song */
+		if (pc_next_song == nullptr && queued != -1)
+			playlist_song_started(*this, pc);
+
+		pc.Lock();
+		pc_next_song = pc.next_song;
+		pc.Unlock();
+
+		/* make sure the queued song is always set (if
+		   possible) */
+		if (pc_next_song == nullptr && queued < 0)
+			UpdateQueuedSong(pc, nullptr);
+	}
+}
+
+/**
+ * The player has stopped for some reason.  Check the error, and
+ * decide whether to re-start playback
+ */
+static void
+playlist_resume_playback(playlist &playlist, PlayerControl &pc)
+{
+	assert(playlist.playing);
+	assert(pc.GetState() == PlayerState::STOP);
+
+	const auto error = pc.GetErrorType();
+	if (error == PlayerError::NONE)
+		playlist.error_count = 0;
+	else
+		++playlist.error_count;
+
+	if ((playlist.stop_on_error && error != PlayerError::NONE) ||
+	    error == PlayerError::OUTPUT ||
+	    playlist.error_count >= playlist.queue.GetLength())
+		/* too many errors, or critical error: stop
+		   playback */
+		playlist.Stop(pc);
+	else
+		/* continue playback at the next song */
+		playlist.PlayNext(pc);
+}
+
+void
+playlist::SetRepeat(PlayerControl &pc, bool status)
+{
+	if (status == queue.repeat)
+		return;
+
+	queue.repeat = status;
+
+	pc.SetBorderPause(queue.single && !queue.repeat);
+
+	/* if the last song is currently being played, the "next song"
+	   might change when repeat mode is toggled */
+	UpdateQueuedSong(pc, GetQueuedSong());
+
+	idle_add(IDLE_OPTIONS);
+}
+
+static void
+playlist_order(playlist &playlist)
+{
+	if (playlist.current >= 0)
+		/* update playlist.current, order==position now */
+		playlist.current = playlist.queue.OrderToPosition(playlist.current);
+
+	playlist.queue.RestoreOrder();
+}
+
+void
+playlist::SetSingle(PlayerControl &pc, bool status)
+{
+	if (status == queue.single)
+		return;
+
+	queue.single = status;
+
+	pc.SetBorderPause(queue.single && !queue.repeat);
+
+	/* if the last song is currently being played, the "next song"
+	   might change when single mode is toggled */
+	UpdateQueuedSong(pc, GetQueuedSong());
+
+	idle_add(IDLE_OPTIONS);
+}
+
+void
+playlist::SetConsume(bool status)
+{
+	if (status == queue.consume)
+		return;
+
+	queue.consume = status;
+	idle_add(IDLE_OPTIONS);
+}
+
+void
+playlist::SetRandom(PlayerControl &pc, bool status)
+{
+	if (status == queue.random)
+		return;
+
+	const DetachedSong *const queued_song = GetQueuedSong();
+
+	queue.random = status;
+
+	if (queue.random) {
+		/* shuffle the queue order, but preserve current */
+
+		const int current_position = GetCurrentPosition();
+
+		queue.ShuffleOrder();
+
+		if (current_position >= 0) {
+			/* make sure the current song is the first in
+			   the order list, so the whole rest of the
+			   playlist is played after that */
+			unsigned current_order =
+				queue.PositionToOrder(current_position);
+			queue.SwapOrders(0, current_order);
+			current = 0;
+		} else
+			current = -1;
+	} else
+		playlist_order(*this);
+
+	UpdateQueuedSong(pc, queued_song);
+
+	idle_add(IDLE_OPTIONS);
+}
+
+int
+playlist::GetCurrentPosition() const
+{
+	return current >= 0
+		? queue.OrderToPosition(current)
+		: -1;
+}
+
+int
+playlist::GetNextPosition() const
+{
+	if (current < 0)
+		return -1;
+
+	if (queue.single && queue.repeat)
+		return queue.OrderToPosition(current);
+	else if (queue.IsValidOrder(current + 1))
+		return queue.OrderToPosition(current + 1);
+	else if (queue.repeat)
+		return queue.OrderToPosition(0);
+
+	return -1;
+}

src/queue/Playlist.hxx

@@ -0,0 +1,264 @@
+/*
+ * 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_PLAYLIST_HXX
+#define MPD_PLAYLIST_HXX
+
+#include "queue/Queue.hxx"
+#include "PlaylistError.hxx"
+
+enum TagType : uint8_t;
+struct PlayerControl;
+class DetachedSong;
+class Database;
+class Error;
+class SongLoader;
+
+struct playlist {
+	/**
+	 * The song queue - it contains the "real" playlist.
+	 */
+	struct Queue queue;
+
+	/**
+	 * This value is true if the player is currently playing (or
+	 * should be playing).
+	 */
+	bool playing;
+
+	/**
+	 * If true, then any error is fatal; if false, MPD will
+	 * attempt to play the next song on non-fatal errors.  During
+	 * seeking, this flag is set.
+	 */
+	bool stop_on_error;
+
+	/**
+	 * Number of errors since playback was started.  If this
+	 * number exceeds the length of the playlist, MPD gives up,
+	 * because all songs have been tried.
+	 */
+	unsigned error_count;
+
+	/**
+	 * The "current song pointer".  This is the song which is
+	 * played when we get the "play" command.  It is also the song
+	 * which is currently being played.
+	 */
+	int current;
+
+	/**
+	 * The "next" song to be played, when the current one
+	 * finishes.  The decoder thread may start decoding and
+	 * buffering it, while the "current" song is still playing.
+	 *
+	 * This variable is only valid if #playing is true.
+	 */
+	int queued;
+
+	playlist(unsigned max_length)
+		:queue(max_length), playing(false), current(-1), queued(-1) {
+	}
+
+	~playlist() {
+	}
+
+	uint32_t GetVersion() const {
+		return queue.version;
+	}
+
+	unsigned GetLength() const {
+		return queue.GetLength();
+	}
+
+	unsigned PositionToId(unsigned position) const {
+		return queue.PositionToId(position);
+	}
+
+	gcc_pure
+	int GetCurrentPosition() const;
+
+	gcc_pure
+	int GetNextPosition() const;
+
+	/**
+	 * Returns the song object which is currently queued.  Returns
+	 * none if there is none (yet?) or if MPD isn't playing.
+	 */
+	gcc_pure
+	const DetachedSong *GetQueuedSong() const;
+
+	/**
+	 * This is the "PLAYLIST" event handler.  It is invoked by the
+	 * player thread whenever it requests a new queued song, or
+	 * when it exits.
+	 */
+	void SyncWithPlayer(PlayerControl &pc);
+
+protected:
+	/**
+	 * Called by all editing methods after a modification.
+	 * Updates the queue version and emits #IDLE_PLAYLIST.
+	 */
+	void OnModified();
+
+	/**
+	 * Updates the "queued song".  Calculates the next song
+	 * according to the current one (if MPD isn't playing, it
+	 * takes the first song), and queues this song.  Clears the
+	 * old queued song if there was one.
+	 *
+	 * @param prev the song which was previously queued, as
+	 * determined by playlist_get_queued_song()
+	 */
+	void UpdateQueuedSong(PlayerControl &pc, const DetachedSong *prev);
+
+public:
+	void Clear(PlayerControl &pc);
+
+	/**
+	 * A tag in the play queue has been modified by the player
+	 * thread.  Apply the given song's tag to the current song if
+	 * the song matches.
+	 */
+	void TagModified(DetachedSong &&song);
+
+#ifdef ENABLE_DATABASE
+	/**
+	 * The database has been modified.  Pull all updates.
+	 */
+	void DatabaseModified(const Database &db);
+#endif
+
+	PlaylistResult AppendSong(PlayerControl &pc,
+				  DetachedSong &&song,
+				  unsigned *added_id=nullptr);
+
+	PlaylistResult AppendURI(PlayerControl &pc,
+				 const SongLoader &loader,
+				 const char *uri_utf8,
+				 unsigned *added_id=nullptr);
+
+protected:
+	void DeleteInternal(PlayerControl &pc,
+			    unsigned song, const DetachedSong **queued_p);
+
+public:
+	PlaylistResult DeletePosition(PlayerControl &pc,
+				      unsigned position);
+
+	PlaylistResult DeleteOrder(PlayerControl &pc,
+				   unsigned order) {
+		return DeletePosition(pc, queue.OrderToPosition(order));
+	}
+
+	PlaylistResult DeleteId(PlayerControl &pc, unsigned id);
+
+	/**
+	 * Deletes a range of songs from the playlist.
+	 *
+	 * @param start the position of the first song to delete
+	 * @param end the position after the last song to delete
+	 */
+	PlaylistResult DeleteRange(PlayerControl &pc,
+				   unsigned start, unsigned end);
+
+	void DeleteSong(PlayerControl &pc, const char *uri);
+
+	void Shuffle(PlayerControl &pc, unsigned start, unsigned end);
+
+	PlaylistResult MoveRange(PlayerControl &pc,
+				 unsigned start, unsigned end, int to);
+
+	PlaylistResult MoveId(PlayerControl &pc, unsigned id, int to);
+
+	PlaylistResult SwapPositions(PlayerControl &pc,
+				     unsigned song1, unsigned song2);
+
+	PlaylistResult SwapIds(PlayerControl &pc,
+			       unsigned id1, unsigned id2);
+
+	PlaylistResult SetPriorityRange(PlayerControl &pc,
+					unsigned start_position,
+					unsigned end_position,
+					uint8_t priority);
+
+	PlaylistResult SetPriorityId(PlayerControl &pc,
+				     unsigned song_id, uint8_t priority);
+
+	bool AddSongIdTag(unsigned id, TagType tag_type, const char *value,
+			  Error &error);
+	bool ClearSongIdTag(unsigned id, TagType tag_type, Error &error);
+
+	void Stop(PlayerControl &pc);
+
+	PlaylistResult PlayPosition(PlayerControl &pc, int position);
+
+	void PlayOrder(PlayerControl &pc, int order);
+
+	PlaylistResult PlayId(PlayerControl &pc, int id);
+
+	void PlayNext(PlayerControl &pc);
+
+	void PlayPrevious(PlayerControl &pc);
+
+	PlaylistResult SeekSongPosition(PlayerControl &pc,
+					unsigned song_position,
+					float seek_time);
+
+	PlaylistResult SeekSongId(PlayerControl &pc,
+				  unsigned song_id, float seek_time);
+
+	/**
+	 * Seek within the current song.  Fails if MPD is not currently
+	 * playing.
+	 *
+	 * @param time the time in seconds
+	 * @param relative if true, then the specified time is relative to the
+	 * current position
+	 */
+	PlaylistResult SeekCurrent(PlayerControl &pc,
+				   float seek_time, bool relative);
+
+	bool GetRepeat() const {
+		return queue.repeat;
+	}
+
+	void SetRepeat(PlayerControl &pc, bool new_value);
+
+	bool GetRandom() const {
+		return queue.random;
+	}
+
+	void SetRandom(PlayerControl &pc, bool new_value);
+
+	bool GetSingle() const {
+		return queue.single;
+	}
+
+	void SetSingle(PlayerControl &pc, bool new_value);
+
+	bool GetConsume() const {
+		return queue.consume;
+	}
+
+	void SetConsume(bool new_value);
+};
+
+#endif

src/queue/PlaylistControl.cxx

@@ -0,0 +1,260 @@
+/*
+ * 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.
+ */
+
+/*
+ * Functions for controlling playback on the playlist level.
+ *
+ */
+
+#include "config.h"
+#include "Playlist.hxx"
+#include "PlaylistError.hxx"
+#include "PlayerControl.hxx"
+#include "DetachedSong.hxx"
+#include "Log.hxx"
+
+void
+playlist::Stop(PlayerControl &pc)
+{
+	if (!playing)
+		return;
+
+	assert(current >= 0);
+
+	FormatDebug(playlist_domain, "stop");
+	pc.Stop();
+	queued = -1;
+	playing = false;
+
+	if (queue.random) {
+		/* shuffle the playlist, so the next playback will
+		   result in a new random order */
+
+		unsigned current_position = queue.OrderToPosition(current);
+
+		queue.ShuffleOrder();
+
+		/* make sure that "current" stays valid, and the next
+		   "play" command plays the same song again */
+		current = queue.PositionToOrder(current_position);
+	}
+}
+
+PlaylistResult
+playlist::PlayPosition(PlayerControl &pc, int song)
+{
+	pc.ClearError();
+
+	unsigned i = song;
+	if (song == -1) {
+		/* play any song ("current" song, or the first song */
+
+		if (queue.IsEmpty())
+			return PlaylistResult::SUCCESS;
+
+		if (playing) {
+			/* already playing: unpause playback, just in
+			   case it was paused, and return */
+			pc.SetPause(false);
+			return PlaylistResult::SUCCESS;
+		}
+
+		/* select a song: "current" song, or the first one */
+		i = current >= 0
+			? current
+			: 0;
+	} else if (!queue.IsValidPosition(song))
+		return PlaylistResult::BAD_RANGE;
+
+	if (queue.random) {
+		if (song >= 0)
+			/* "i" is currently the song position (which
+			   would be equal to the order number in
+			   no-random mode); convert it to a order
+			   number, because random mode is enabled */
+			i = queue.PositionToOrder(song);
+
+		if (!playing)
+			current = 0;
+
+		/* swap the new song with the previous "current" one,
+		   so playback continues as planned */
+		queue.SwapOrders(i, current);
+		i = current;
+	}
+
+	stop_on_error = false;
+	error_count = 0;
+
+	PlayOrder(pc, i);
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::PlayId(PlayerControl &pc, int id)
+{
+	if (id == -1)
+		return PlayPosition(pc, id);
+
+	int song = queue.IdToPosition(id);
+	if (song < 0)
+		return PlaylistResult::NO_SUCH_SONG;
+
+	return PlayPosition(pc, song);
+}
+
+void
+playlist::PlayNext(PlayerControl &pc)
+{
+	if (!playing)
+		return;
+
+	assert(!queue.IsEmpty());
+	assert(queue.IsValidOrder(current));
+
+	const int old_current = current;
+	stop_on_error = false;
+
+	/* determine the next song from the queue's order list */
+
+	const int next_order = queue.GetNextOrder(current);
+	if (next_order < 0) {
+		/* no song after this one: stop playback */
+		Stop(pc);
+
+		/* reset "current song" */
+		current = -1;
+	}
+	else
+	{
+		if (next_order == 0 && queue.random) {
+			/* The queue told us that the next song is the first
+			   song.  This means we are in repeat mode.  Shuffle
+			   the queue order, so this time, the user hears the
+			   songs in a different than before */
+			assert(queue.repeat);
+
+			queue.ShuffleOrder();
+
+			/* note that current and queued are
+			   now invalid, but playlist_play_order() will
+			   discard them anyway */
+		}
+
+		PlayOrder(pc, next_order);
+	}
+
+	/* Consume mode removes each played songs. */
+	if (queue.consume)
+		DeleteOrder(pc, old_current);
+}
+
+void
+playlist::PlayPrevious(PlayerControl &pc)
+{
+	if (!playing)
+		return;
+
+	assert(!queue.IsEmpty());
+
+	int order;
+	if (current > 0) {
+		/* play the preceding song */
+		order = current - 1;
+	} else if (queue.repeat) {
+		/* play the last song in "repeat" mode */
+		order = queue.GetLength() - 1;
+	} else {
+		/* re-start playing the current song if it's
+		   the first one */
+		order = current;
+	}
+
+	PlayOrder(pc, order);
+}
+
+PlaylistResult
+playlist::SeekSongPosition(PlayerControl &pc, unsigned song, float seek_time)
+{
+	if (!queue.IsValidPosition(song))
+		return PlaylistResult::BAD_RANGE;
+
+	const DetachedSong *queued_song = GetQueuedSong();
+
+	unsigned i = queue.random
+		? queue.PositionToOrder(song)
+		: song;
+
+	pc.ClearError();
+	stop_on_error = true;
+	error_count = 0;
+
+	if (!playing || (unsigned)current != i) {
+		/* seeking is not within the current song - prepare
+		   song change */
+
+		playing = true;
+		current = i;
+
+		queued_song = nullptr;
+	}
+
+	if (!pc.Seek(new DetachedSong(queue.GetOrder(i)), seek_time)) {
+		UpdateQueuedSong(pc, queued_song);
+
+		return PlaylistResult::NOT_PLAYING;
+	}
+
+	queued = -1;
+	UpdateQueuedSong(pc, nullptr);
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::SeekSongId(PlayerControl &pc, unsigned id, float seek_time)
+{
+	int song = queue.IdToPosition(id);
+	if (song < 0)
+		return PlaylistResult::NO_SUCH_SONG;
+
+	return SeekSongPosition(pc, song, seek_time);
+}
+
+PlaylistResult
+playlist::SeekCurrent(PlayerControl &pc, float seek_time, bool relative)
+{
+	if (!playing)
+		return PlaylistResult::NOT_PLAYING;
+
+	if (relative) {
+		const auto status = pc.GetStatus();
+
+		if (status.state != PlayerState::PLAY &&
+		    status.state != PlayerState::PAUSE)
+			return PlaylistResult::NOT_PLAYING;
+
+		seek_time += (int)status.elapsed_time;
+	}
+
+	if (seek_time < 0)
+		seek_time = 0;
+
+	return SeekSongPosition(pc, current, seek_time);
+}

src/queue/PlaylistEdit.cxx

@@ -0,0 +1,410 @@
+/*
+ * 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.
+ */
+
+/*
+ * Functions for editing the playlist (adding, removing, reordering
+ * songs in the queue).
+ *
+ */
+
+#include "config.h"
+#include "Playlist.hxx"
+#include "PlaylistError.hxx"
+#include "PlayerControl.hxx"
+#include "util/UriUtil.hxx"
+#include "util/Error.hxx"
+#include "DetachedSong.hxx"
+#include "SongLoader.hxx"
+#include "Idle.hxx"
+#include "Log.hxx"
+
+#include <stdlib.h>
+
+void
+playlist::OnModified()
+{
+	queue.IncrementVersion();
+
+	idle_add(IDLE_PLAYLIST);
+}
+
+void
+playlist::Clear(PlayerControl &pc)
+{
+	Stop(pc);
+
+	queue.Clear();
+	current = -1;
+
+	OnModified();
+}
+
+PlaylistResult
+playlist::AppendSong(PlayerControl &pc,
+		     DetachedSong &&song, unsigned *added_id)
+{
+	unsigned id;
+
+	if (queue.IsFull())
+		return PlaylistResult::TOO_LARGE;
+
+	const DetachedSong *const queued_song = GetQueuedSong();
+
+	id = queue.Append(std::move(song), 0);
+
+	if (queue.random) {
+		/* shuffle the new song into the list of remaning
+		   songs to play */
+
+		unsigned start;
+		if (queued >= 0)
+			start = queued + 1;
+		else
+			start = current + 1;
+		if (start < queue.GetLength())
+			queue.ShuffleOrderLast(start, queue.GetLength());
+	}
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+
+	if (added_id)
+		*added_id = id;
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::AppendURI(PlayerControl &pc,
+		    const SongLoader &loader,
+		    const char *uri, unsigned *added_id)
+{
+	FormatDebug(playlist_domain, "add to playlist: %s", uri);
+
+	Error error;
+	DetachedSong *song = loader.LoadSong(uri, error);
+	if (song == nullptr) {
+		// TODO: return the Error
+		LogError(error);
+		return error.IsDomain(playlist_domain)
+			? PlaylistResult(error.GetCode())
+			: PlaylistResult::NO_SUCH_SONG;
+	}
+
+	PlaylistResult result = AppendSong(pc, std::move(*song), added_id);
+	delete song;
+
+	return result;
+}
+
+PlaylistResult
+playlist::SwapPositions(PlayerControl &pc, unsigned song1, unsigned song2)
+{
+	if (!queue.IsValidPosition(song1) || !queue.IsValidPosition(song2))
+		return PlaylistResult::BAD_RANGE;
+
+	const DetachedSong *const queued_song = GetQueuedSong();
+
+	queue.SwapPositions(song1, song2);
+
+	if (queue.random) {
+		/* update the queue order, so that current
+		   still points to the current song order */
+
+		queue.SwapOrders(queue.PositionToOrder(song1),
+				 queue.PositionToOrder(song2));
+	} else {
+		/* correct the "current" song order */
+
+		if (current == (int)song1)
+			current = song2;
+		else if (current == (int)song2)
+			current = song1;
+	}
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::SwapIds(PlayerControl &pc, unsigned id1, unsigned id2)
+{
+	int song1 = queue.IdToPosition(id1);
+	int song2 = queue.IdToPosition(id2);
+
+	if (song1 < 0 || song2 < 0)
+		return PlaylistResult::NO_SUCH_SONG;
+
+	return SwapPositions(pc, song1, song2);
+}
+
+PlaylistResult
+playlist::SetPriorityRange(PlayerControl &pc,
+			   unsigned start, unsigned end,
+			   uint8_t priority)
+{
+	if (start >= GetLength())
+		return PlaylistResult::BAD_RANGE;
+
+	if (end > GetLength())
+		end = GetLength();
+
+	if (start >= end)
+		return PlaylistResult::SUCCESS;
+
+	/* remember "current" and "queued" */
+
+	const int current_position = GetCurrentPosition();
+	const DetachedSong *const queued_song = GetQueuedSong();
+
+	/* apply the priority changes */
+
+	queue.SetPriorityRange(start, end, priority, current);
+
+	/* restore "current" and choose a new "queued" */
+
+	if (current_position >= 0)
+		current = queue.PositionToOrder(current_position);
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::SetPriorityId(PlayerControl &pc,
+			unsigned song_id, uint8_t priority)
+{
+	int song_position = queue.IdToPosition(song_id);
+	if (song_position < 0)
+		return PlaylistResult::NO_SUCH_SONG;
+
+	return SetPriorityRange(pc, song_position, song_position + 1,
+				priority);
+
+}
+
+void
+playlist::DeleteInternal(PlayerControl &pc,
+			 unsigned song, const DetachedSong **queued_p)
+{
+	assert(song < GetLength());
+
+	unsigned songOrder = queue.PositionToOrder(song);
+
+	if (playing && current == (int)songOrder) {
+		const bool paused = pc.GetState() == PlayerState::PAUSE;
+
+		/* the current song is going to be deleted: stop the player */
+
+		pc.Stop();
+		playing = false;
+
+		/* see which song is going to be played instead */
+
+		current = queue.GetNextOrder(current);
+		if (current == (int)songOrder)
+			current = -1;
+
+		if (current >= 0 && !paused)
+			/* play the song after the deleted one */
+			PlayOrder(pc, current);
+		else
+			/* no songs left to play, stop playback
+			   completely */
+			Stop(pc);
+
+		*queued_p = nullptr;
+	} else if (current == (int)songOrder)
+		/* there's a "current song" but we're not playing
+		   currently - clear "current" */
+		current = -1;
+
+	/* now do it: remove the song */
+
+	queue.DeletePosition(song);
+
+	/* update the "current" and "queued" variables */
+
+	if (current > (int)songOrder)
+		current--;
+}
+
+PlaylistResult
+playlist::DeletePosition(PlayerControl &pc, unsigned song)
+{
+	if (song >= queue.GetLength())
+		return PlaylistResult::BAD_RANGE;
+
+	const DetachedSong *queued_song = GetQueuedSong();
+
+	DeleteInternal(pc, song, &queued_song);
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::DeleteRange(PlayerControl &pc, unsigned start, unsigned end)
+{
+	if (start >= queue.GetLength())
+		return PlaylistResult::BAD_RANGE;
+
+	if (end > queue.GetLength())
+		end = queue.GetLength();
+
+	if (start >= end)
+		return PlaylistResult::SUCCESS;
+
+	const DetachedSong *queued_song = GetQueuedSong();
+
+	do {
+		DeleteInternal(pc, --end, &queued_song);
+	} while (end != start);
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::DeleteId(PlayerControl &pc, unsigned id)
+{
+	int song = queue.IdToPosition(id);
+	if (song < 0)
+		return PlaylistResult::NO_SUCH_SONG;
+
+	return DeletePosition(pc, song);
+}
+
+void
+playlist::DeleteSong(PlayerControl &pc, const char *uri)
+{
+	for (int i = queue.GetLength() - 1; i >= 0; --i)
+		if (queue.Get(i).IsURI(uri))
+			DeletePosition(pc, i);
+}
+
+PlaylistResult
+playlist::MoveRange(PlayerControl &pc, unsigned start, unsigned end, int to)
+{
+	if (!queue.IsValidPosition(start) || !queue.IsValidPosition(end - 1))
+		return PlaylistResult::BAD_RANGE;
+
+	if ((to >= 0 && to + end - start - 1 >= GetLength()) ||
+	    (to < 0 && unsigned(abs(to)) > GetLength()))
+		return PlaylistResult::BAD_RANGE;
+
+	if ((int)start == to)
+		/* nothing happens */
+		return PlaylistResult::SUCCESS;
+
+	const DetachedSong *const queued_song = GetQueuedSong();
+
+	/*
+	 * (to < 0) => move to offset from current song
+	 * (-playlist.length == to) => move to position BEFORE current song
+	 */
+	const int currentSong = GetCurrentPosition();
+	if (to < 0) {
+		if (currentSong < 0)
+			/* can't move relative to current song,
+			   because there is no current song */
+			return PlaylistResult::BAD_RANGE;
+
+		if (start <= (unsigned)currentSong && (unsigned)currentSong < end)
+			/* no-op, can't be moved to offset of itself */
+			return PlaylistResult::SUCCESS;
+		to = (currentSong + abs(to)) % GetLength();
+		if (start < (unsigned)to)
+			to--;
+	}
+
+	queue.MoveRange(start, end, to);
+
+	if (!queue.random) {
+		/* update current/queued */
+		if ((int)start <= current && (unsigned)current < end)
+			current += to - start;
+		else if (current >= (int)end && current <= to)
+			current -= end - start;
+		else if (current >= to && current < (int)start)
+			current += end - start;
+	}
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+
+	return PlaylistResult::SUCCESS;
+}
+
+PlaylistResult
+playlist::MoveId(PlayerControl &pc, unsigned id1, int to)
+{
+	int song = queue.IdToPosition(id1);
+	if (song < 0)
+		return PlaylistResult::NO_SUCH_SONG;
+
+	return MoveRange(pc, song, song + 1, to);
+}
+
+void
+playlist::Shuffle(PlayerControl &pc, unsigned start, unsigned end)
+{
+	if (end > GetLength())
+		/* correct the "end" offset */
+		end = GetLength();
+
+	if (start + 1 >= end)
+		/* needs at least two entries. */
+		return;
+
+	const DetachedSong *const queued_song = GetQueuedSong();
+	if (playing && current >= 0) {
+		unsigned current_position = queue.OrderToPosition(current);
+
+		if (current_position >= start && current_position < end) {
+			/* put current playing song first */
+			queue.SwapPositions(start, current_position);
+
+			if (queue.random) {
+				current = queue.PositionToOrder(start);
+			} else
+				current = start;
+
+			/* start shuffle after the current song */
+			start++;
+		}
+	} else {
+		/* no playback currently: reset current */
+
+		current = -1;
+	}
+
+	queue.ShuffleRange(start, end);
+
+	UpdateQueuedSong(pc, queued_song);
+	OnModified();
+}

src/queue/PlaylistState.cxx

@@ -0,0 +1,245 @@
+/*
+ * 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.
+ */
+
+/*
+ * Saving and loading the playlist to/from the state file.
+ *
+ */
+
+#include "config.h"
+#include "PlaylistState.hxx"
+#include "PlaylistError.hxx"
+#include "Playlist.hxx"
+#include "queue/QueueSave.hxx"
+#include "fs/TextFile.hxx"
+#include "PlayerControl.hxx"
+#include "config/ConfigGlobal.hxx"
+#include "config/ConfigOption.hxx"
+#include "fs/Limits.hxx"
+#include "util/CharUtil.hxx"
+#include "util/StringUtil.hxx"
+#include "Log.hxx"
+
+#include <string.h>
+#include <stdlib.h>
+
+#define PLAYLIST_STATE_FILE_STATE		"state: "
+#define PLAYLIST_STATE_FILE_RANDOM		"random: "
+#define PLAYLIST_STATE_FILE_REPEAT		"repeat: "
+#define PLAYLIST_STATE_FILE_SINGLE		"single: "
+#define PLAYLIST_STATE_FILE_CONSUME		"consume: "
+#define PLAYLIST_STATE_FILE_CURRENT		"current: "
+#define PLAYLIST_STATE_FILE_TIME		"time: "
+#define PLAYLIST_STATE_FILE_CROSSFADE		"crossfade: "
+#define PLAYLIST_STATE_FILE_MIXRAMPDB		"mixrampdb: "
+#define PLAYLIST_STATE_FILE_MIXRAMPDELAY	"mixrampdelay: "
+#define PLAYLIST_STATE_FILE_PLAYLIST_BEGIN	"playlist_begin"
+#define PLAYLIST_STATE_FILE_PLAYLIST_END	"playlist_end"
+
+#define PLAYLIST_STATE_FILE_STATE_PLAY		"play"
+#define PLAYLIST_STATE_FILE_STATE_PAUSE		"pause"
+#define PLAYLIST_STATE_FILE_STATE_STOP		"stop"
+
+#define PLAYLIST_BUFFER_SIZE	2*MPD_PATH_MAX
+
+void
+playlist_state_save(FILE *fp, const struct playlist &playlist,
+		    PlayerControl &pc)
+{
+	const auto player_status = pc.GetStatus();
+
+	fputs(PLAYLIST_STATE_FILE_STATE, fp);
+
+	if (playlist.playing) {
+		switch (player_status.state) {
+		case PlayerState::PAUSE:
+			fputs(PLAYLIST_STATE_FILE_STATE_PAUSE "\n", fp);
+			break;
+		default:
+			fputs(PLAYLIST_STATE_FILE_STATE_PLAY "\n", fp);
+		}
+		fprintf(fp, PLAYLIST_STATE_FILE_CURRENT "%i\n",
+			playlist.queue.OrderToPosition(playlist.current));
+		fprintf(fp, PLAYLIST_STATE_FILE_TIME "%i\n",
+			(int)player_status.elapsed_time);
+	} else {
+		fputs(PLAYLIST_STATE_FILE_STATE_STOP "\n", fp);
+
+		if (playlist.current >= 0)
+			fprintf(fp, PLAYLIST_STATE_FILE_CURRENT "%i\n",
+				playlist.queue.OrderToPosition(playlist.current));
+	}
+
+	fprintf(fp, PLAYLIST_STATE_FILE_RANDOM "%i\n", playlist.queue.random);
+	fprintf(fp, PLAYLIST_STATE_FILE_REPEAT "%i\n", playlist.queue.repeat);
+	fprintf(fp, PLAYLIST_STATE_FILE_SINGLE "%i\n", playlist.queue.single);
+	fprintf(fp, PLAYLIST_STATE_FILE_CONSUME "%i\n",
+		playlist.queue.consume);
+	fprintf(fp, PLAYLIST_STATE_FILE_CROSSFADE "%i\n",
+		(int)pc.GetCrossFade());
+	fprintf(fp, PLAYLIST_STATE_FILE_MIXRAMPDB "%f\n",
+		pc.GetMixRampDb());
+	fprintf(fp, PLAYLIST_STATE_FILE_MIXRAMPDELAY "%f\n",
+		pc.GetMixRampDelay());
+	fputs(PLAYLIST_STATE_FILE_PLAYLIST_BEGIN "\n", fp);
+	queue_save(fp, playlist.queue);
+	fputs(PLAYLIST_STATE_FILE_PLAYLIST_END "\n", fp);
+}
+
+static void
+playlist_state_load(TextFile &file, const SongLoader &song_loader,
+		    struct playlist &playlist)
+{
+	const char *line = file.ReadLine();
+	if (line == nullptr) {
+		LogWarning(playlist_domain, "No playlist in state file");
+		return;
+	}
+
+	while (!StringStartsWith(line, PLAYLIST_STATE_FILE_PLAYLIST_END)) {
+		queue_load_song(file, song_loader, line, playlist.queue);
+
+		line = file.ReadLine();
+		if (line == nullptr) {
+			LogWarning(playlist_domain,
+				   "'" PLAYLIST_STATE_FILE_PLAYLIST_END
+				   "' not found in state file");
+			break;
+		}
+	}
+
+	playlist.queue.IncrementVersion();
+}
+
+bool
+playlist_state_restore(const char *line, TextFile &file,
+		       const SongLoader &song_loader,
+		       struct playlist &playlist, PlayerControl &pc)
+{
+	int current = -1;
+	int seek_time = 0;
+	bool random_mode = false;
+
+	if (!StringStartsWith(line, PLAYLIST_STATE_FILE_STATE))
+		return false;
+
+	line += sizeof(PLAYLIST_STATE_FILE_STATE) - 1;
+
+	PlayerState state;
+	if (strcmp(line, PLAYLIST_STATE_FILE_STATE_PLAY) == 0)
+		state = PlayerState::PLAY;
+	else if (strcmp(line, PLAYLIST_STATE_FILE_STATE_PAUSE) == 0)
+		state = PlayerState::PAUSE;
+	else
+		state = PlayerState::STOP;
+
+	while ((line = file.ReadLine()) != nullptr) {
+		if (StringStartsWith(line, PLAYLIST_STATE_FILE_TIME)) {
+			seek_time =
+				atoi(&(line[strlen(PLAYLIST_STATE_FILE_TIME)]));
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_REPEAT)) {
+			playlist.SetRepeat(pc,
+					   strcmp(&(line[strlen(PLAYLIST_STATE_FILE_REPEAT)]),
+						  "1") == 0);
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_SINGLE)) {
+			playlist.SetSingle(pc,
+					   strcmp(&(line[strlen(PLAYLIST_STATE_FILE_SINGLE)]),
+						  "1") == 0);
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_CONSUME)) {
+			playlist.SetConsume(strcmp(&(line[strlen(PLAYLIST_STATE_FILE_CONSUME)]),
+						   "1") == 0);
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_CROSSFADE)) {
+			pc.SetCrossFade(atoi(line + strlen(PLAYLIST_STATE_FILE_CROSSFADE)));
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_MIXRAMPDB)) {
+			pc.SetMixRampDb(atof(line + strlen(PLAYLIST_STATE_FILE_MIXRAMPDB)));
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_MIXRAMPDELAY)) {
+			const char *p = line + strlen(PLAYLIST_STATE_FILE_MIXRAMPDELAY);
+
+			/* this check discards "nan" which was used
+			   prior to MPD 0.18 */
+			if (IsDigitASCII(*p))
+				pc.SetMixRampDelay(atof(p));
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_RANDOM)) {
+			random_mode =
+				strcmp(line + strlen(PLAYLIST_STATE_FILE_RANDOM),
+				       "1") == 0;
+		} else if (StringStartsWith(line, PLAYLIST_STATE_FILE_CURRENT)) {
+			current = atoi(&(line
+					 [strlen
+					  (PLAYLIST_STATE_FILE_CURRENT)]));
+		} else if (StringStartsWith(line,
+					    PLAYLIST_STATE_FILE_PLAYLIST_BEGIN)) {
+			playlist_state_load(file, song_loader, playlist);
+		}
+	}
+
+	playlist.SetRandom(pc, random_mode);
+
+	if (!playlist.queue.IsEmpty()) {
+		if (!playlist.queue.IsValidPosition(current))
+			current = 0;
+
+		if (state == PlayerState::PLAY &&
+		    config_get_bool(CONF_RESTORE_PAUSED, false))
+			/* the user doesn't want MPD to auto-start
+			   playback after startup; fall back to
+			   "pause" */
+			state = PlayerState::PAUSE;
+
+		/* enable all devices for the first time; this must be
+		   called here, after the audio output states were
+		   restored, before playback begins */
+		if (state != PlayerState::STOP)
+			pc.UpdateAudio();
+
+		if (state == PlayerState::STOP /* && config_option */)
+			playlist.current = current;
+		else if (seek_time == 0)
+			playlist.PlayPosition(pc, current);
+		else
+			playlist.SeekSongPosition(pc, current, seek_time);
+
+		if (state == PlayerState::PAUSE)
+			pc.Pause();
+	}
+
+	return true;
+}
+
+unsigned
+playlist_state_get_hash(const playlist &playlist,
+			PlayerControl &pc)
+{
+	const auto player_status = pc.GetStatus();
+
+	return playlist.queue.version ^
+		(player_status.state != PlayerState::STOP
+		 ? ((int)player_status.elapsed_time << 8)
+		 : 0) ^
+		(playlist.current >= 0
+		 ? (playlist.queue.OrderToPosition(playlist.current) << 16)
+		 : 0) ^
+		((int)pc.GetCrossFade() << 20) ^
+		(unsigned(player_status.state) << 24) ^
+		(playlist.queue.random << 27) ^
+		(playlist.queue.repeat << 28) ^
+		(playlist.queue.single << 29) ^
+		(playlist.queue.consume << 30) ^
+		(playlist.queue.random << 31);
+}

src/queue/PlaylistState.hxx

@@ -0,0 +1,54 @@
+/*
+ * 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.
+ */
+
+/*
+ * Saving and loading the playlist to/from the state file.
+ *
+ */
+
+#ifndef MPD_PLAYLIST_STATE_HXX
+#define MPD_PLAYLIST_STATE_HXX
+
+#include <stdio.h>
+
+struct playlist;
+struct PlayerControl;
+class TextFile;
+class SongLoader;
+
+void
+playlist_state_save(FILE *fp, const playlist &playlist,
+		    PlayerControl &pc);
+
+bool
+playlist_state_restore(const char *line, TextFile &file,
+		       const SongLoader &song_loader,
+		       playlist &playlist, PlayerControl &pc);
+
+/**
+ * Generates a hash number for the current state of the playlist and
+ * the playback options.  This is used by timer_save_state_file() to
+ * determine whether the state has changed and the state file should
+ * be saved.
+ */
+unsigned
+playlist_state_get_hash(const playlist &playlist,
+			PlayerControl &c);
+
+#endif

src/queue/PlaylistTag.cxx

@@ -0,0 +1,93 @@
+/*
+ * 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.
+ */
+
+/*
+ * Functions for editing the playlist (adding, removing, reordering
+ * songs in the queue).
+ *
+ */
+
+#include "config.h"
+#include "Playlist.hxx"
+#include "PlaylistError.hxx"
+#include "DetachedSong.hxx"
+#include "tag/Tag.hxx"
+#include "tag/TagBuilder.hxx"
+#include "util/Error.hxx"
+
+bool
+playlist::AddSongIdTag(unsigned id, TagType tag_type, const char *value,
+		       Error &error)
+{
+	const int position = queue.IdToPosition(id);
+	if (position < 0) {
+		error.Set(playlist_domain, int(PlaylistResult::NO_SUCH_SONG),
+			  "No such song");
+		return false;
+	}
+
+	DetachedSong &song = queue.Get(position);
+	if (song.IsFile()) {
+		error.Set(playlist_domain, int(PlaylistResult::DENIED),
+			  "Cannot edit tags of local file");
+		return false;
+	}
+
+	{
+		TagBuilder tag(std::move(song.WritableTag()));
+		tag.AddItem(tag_type, value);
+		song.SetTag(tag.Commit());
+	}
+
+	queue.ModifyAtPosition(position);
+	OnModified();
+	return true;
+}
+
+bool
+playlist::ClearSongIdTag(unsigned id, TagType tag_type,
+			 Error &error)
+{
+	const int position = queue.IdToPosition(id);
+	if (position < 0) {
+		error.Set(playlist_domain, int(PlaylistResult::NO_SUCH_SONG),
+			  "No such song");
+		return false;
+	}
+
+	DetachedSong &song = queue.Get(position);
+	if (song.IsFile()) {
+		error.Set(playlist_domain, int(PlaylistResult::DENIED),
+			  "Cannot edit tags of local file");
+		return false;
+	}
+
+	{
+		TagBuilder tag(std::move(song.WritableTag()));
+		if (tag_type == TAG_NUM_OF_ITEM_TYPES)
+			tag.RemoveAll();
+		else
+			tag.RemoveType(tag_type);
+		song.SetTag(tag.Commit());
+	}
+
+	queue.ModifyAtPosition(position);
+	OnModified();
+	return true;
+}

src/queue/PlaylistUpdate.cxx

@@ -0,0 +1,73 @@
+/*
+ * 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 "Playlist.hxx"
+#include "db/Interface.hxx"
+#include "db/LightSong.hxx"
+#include "DetachedSong.hxx"
+#include "tag/Tag.hxx"
+#include "Idle.hxx"
+#include "util/Error.hxx"
+
+static bool
+UpdatePlaylistSong(const Database &db, DetachedSong &song)
+{
+	if (!song.IsInDatabase() || !song.IsFile())
+		/* only update Songs instances that are "detached"
+		   from the Database */
+		return false;
+
+	const LightSong *original = db.GetSong(song.GetURI(), IgnoreError());
+	if (original == nullptr)
+		/* not found - shouldn't happen, because the update
+		   thread should ensure that all stale Song instances
+		   have been purged */
+		return false;
+
+	if (original->mtime == song.GetLastModified()) {
+		/* not modified */
+		db.ReturnSong(original);
+		return false;
+	}
+
+	song.SetLastModified(original->mtime);
+	song.SetTag(*original->tag);
+
+	db.ReturnSong(original);
+	return true;
+}
+
+void
+playlist::DatabaseModified(const Database &db)
+{
+	bool modified = false;
+
+	for (unsigned i = 0, n = queue.GetLength(); i != n; ++i) {
+		if (UpdatePlaylistSong(db, queue.Get(i))) {
+			queue.ModifyAtPosition(i);
+			modified = true;
+		}
+	}
+
+	if (modified) {
+		queue.IncrementVersion();
+		idle_add(IDLE_PLAYLIST);
+	}
+}