/*
* Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package javax.sound.midi;
import java.util.ArrayList;
import java.util.HashSet;
import com.sun.media.sound.MidiUtils;
A MIDI track is an independent stream of MIDI events (time-stamped MIDI data)
that can be stored along with other tracks in a standard MIDI file. The MIDI
specification allows only 16 channels of MIDI data, but tracks are a way to
get around this limitation. A MIDI file can contain any number of tracks,
each containing its own stream of up to 16 channels of MIDI data.
A Track occupies a middle level in the hierarchy of data played by a Sequencer: sequencers play sequences, which contain tracks, which contain MIDI events. A sequencer may provide controls that mute or solo individual tracks.
The timing information and resolution for a track is controlled by and stored in the sequence containing the track. A given Track is considered to belong to the particular Sequence that maintains its timing. For this reason, a new (empty) track is created by calling the Sequence.createTrack method, rather than by directly invoking a Track constructor.
The Track class provides methods to edit the track by adding or removing MidiEvent objects from it. These operations keep the event list in the correct time order. Methods are also included to obtain the track's size, in terms of either the number of events it contains or its duration in ticks.
Author: Kara Kytle, Florian Bomers See Also:
/**
* A MIDI track is an independent stream of MIDI events (time-stamped MIDI data)
* that can be stored along with other tracks in a standard MIDI file. The MIDI
* specification allows only 16 channels of MIDI data, but tracks are a way to
* get around this limitation. A MIDI file can contain any number of tracks,
* each containing its own stream of up to 16 channels of MIDI data.
* <p>
* A {@code Track} occupies a middle level in the hierarchy of data played by a
* {@link Sequencer}: sequencers play sequences, which contain tracks, which
* contain MIDI events. A sequencer may provide controls that mute or solo
* individual tracks.
* <p>
* The timing information and resolution for a track is controlled by and stored
* in the sequence containing the track. A given {@code Track} is considered to
* belong to the particular {@link Sequence} that maintains its timing. For this
* reason, a new (empty) track is created by calling the
* {@link Sequence#createTrack} method, rather than by directly invoking a
* {@code Track} constructor.
* <p>
* The {@code Track} class provides methods to edit the track by adding or
* removing {@code MidiEvent} objects from it. These operations keep the event
* list in the correct time order. Methods are also included to obtain the
* track's size, in terms of either the number of events it contains or its
* duration in ticks.
*
* @author Kara Kytle
* @author Florian Bomers
* @see Sequencer#setTrackMute
* @see Sequencer#setTrackSolo
*/
public class Track {
// TODO: use arrays for faster access
The list containing the events.
/**
* The list containing the events.
*/
private final ArrayList<MidiEvent> eventsList = new ArrayList<>();
Use a hashset to detect duplicate events in add(MidiEvent).
/**
* Use a hashset to detect duplicate events in add(MidiEvent).
*/
private final HashSet<MidiEvent> set = new HashSet<>();
private final MidiEvent eotEvent;
Package-private constructor. Constructs a new, empty Track object, which
initially contains one event, the meta-event End of Track.
/**
* Package-private constructor. Constructs a new, empty Track object, which
* initially contains one event, the meta-event End of Track.
*/
Track() {
// start with the end of track event
MetaMessage eot = new ImmutableEndOfTrack();
eotEvent = new MidiEvent(eot, 0);
eventsList.add(eotEvent);
set.add(eotEvent);
}
Adds a new event to the track. However, if the event is already contained
in the track, it is not added again. The list of events is kept in time
order, meaning that this event inserted at the appropriate place in the
list, not necessarily at the end.
Params: - event – the event to add
Returns: true if the event did not already exist in the track and was added, otherwise false
/**
* Adds a new event to the track. However, if the event is already contained
* in the track, it is not added again. The list of events is kept in time
* order, meaning that this event inserted at the appropriate place in the
* list, not necessarily at the end.
*
* @param event the event to add
* @return {@code true} if the event did not already exist in the track and
* was added, otherwise {@code false}
*/
public boolean add(MidiEvent event) {
if (event == null) {
return false;
}
synchronized(eventsList) {
if (!set.contains(event)) {
int eventsCount = eventsList.size();
// get the last event
MidiEvent lastEvent = null;
if (eventsCount > 0) {
lastEvent = eventsList.get(eventsCount - 1);
}
// sanity check that we have a correct end-of-track
if (lastEvent != eotEvent) {
// if there is no eot event, add our immutable instance again
if (lastEvent != null) {
// set eotEvent's tick to the last tick of the track
eotEvent.setTick(lastEvent.getTick());
} else {
// if the events list is empty, just set the tick to 0
eotEvent.setTick(0);
}
// we needn't check for a duplicate of eotEvent in "eventsList",
// since then it would appear in the set.
eventsList.add(eotEvent);
set.add(eotEvent);
eventsCount = eventsList.size();
}
// first see if we are trying to add
// and endoftrack event.
if (MidiUtils.isMetaEndOfTrack(event.getMessage())) {
// since end of track event is useful
// for delays at the end of a track, we want to keep
// the tick value requested here if it is greater
// than the one on the eot we are maintaining.
// Otherwise, we only want a single eot event, so ignore.
if (event.getTick() > eotEvent.getTick()) {
eotEvent.setTick(event.getTick());
}
return true;
}
// prevent duplicates
set.add(event);
// insert event such that events is sorted in increasing
// tick order
int i = eventsCount;
for ( ; i > 0; i--) {
if (event.getTick() >= (eventsList.get(i-1)).getTick()) {
break;
}
}
if (i == eventsCount) {
// we're adding an event after the
// tick value of our eot, so push the eot out.
// Always add at the end for better performance:
// this saves all the checks and arraycopy when inserting
// overwrite eot with new event
eventsList.set(eventsCount - 1, event);
// set new time of eot, if necessary
if (eotEvent.getTick() < event.getTick()) {
eotEvent.setTick(event.getTick());
}
// add eot again at the end
eventsList.add(eotEvent);
} else {
eventsList.add(i, event);
}
return true;
}
}
return false;
}
Removes the specified event from the track.
Params: - event – the event to remove
Returns: true if the event existed in the track and was removed, otherwise false
/**
* Removes the specified event from the track.
*
* @param event the event to remove
* @return {@code true} if the event existed in the track and was removed,
* otherwise {@code false}
*/
public boolean remove(MidiEvent event) {
// this implementation allows removing the EOT event.
// pretty bad, but would probably be too risky to
// change behavior now, in case someone does tricks like:
//
// while (track.size() > 0) track.remove(track.get(track.size() - 1));
// also, would it make sense to adjust the EOT's time
// to the last event, if the last non-EOT event is removed?
// Or: document that the ticks() length will not be reduced
// by deleting events (unless the EOT event is removed)
synchronized(eventsList) {
if (set.remove(event)) {
int i = eventsList.indexOf(event);
if (i >= 0) {
eventsList.remove(i);
return true;
}
}
}
return false;
}
Obtains the event at the specified index.
Params: - index – the location of the desired event in the event vector
Throws: - ArrayIndexOutOfBoundsException – if the specified index is negative
or not less than the current size of this track
See Also: Returns: the event at the specified index
/**
* Obtains the event at the specified index.
*
* @param index the location of the desired event in the event vector
* @return the event at the specified index
* @throws ArrayIndexOutOfBoundsException if the specified index is negative
* or not less than the current size of this track
* @see #size
*/
public MidiEvent get(int index) throws ArrayIndexOutOfBoundsException {
try {
synchronized(eventsList) {
return eventsList.get(index);
}
} catch (IndexOutOfBoundsException ioobe) {
throw new ArrayIndexOutOfBoundsException(ioobe.getMessage());
}
}
Obtains the number of events in this track.
Returns: the size of the track's event vector
/**
* Obtains the number of events in this track.
*
* @return the size of the track's event vector
*/
public int size() {
synchronized(eventsList) {
return eventsList.size();
}
}
Obtains the length of the track, expressed in MIDI ticks. (The duration of a tick in seconds is determined by the timing resolution of the Sequence containing this track, and also by the tempo of the music as set by the sequencer.) See Also: Returns: the duration, in ticks
/**
* Obtains the length of the track, expressed in MIDI ticks. (The duration
* of a tick in seconds is determined by the timing resolution of the
* {@code Sequence} containing this track, and also by the tempo of the
* music as set by the sequencer.)
*
* @return the duration, in ticks
* @see Sequence#Sequence(float, int)
* @see Sequencer#setTempoInBPM(float)
* @see Sequencer#getTickPosition()
*/
public long ticks() {
long ret = 0;
synchronized (eventsList) {
if (eventsList.size() > 0) {
ret = (eventsList.get(eventsList.size() - 1)).getTick();
}
}
return ret;
}
private static class ImmutableEndOfTrack extends MetaMessage {
private ImmutableEndOfTrack() {
super(new byte[3]);
data[0] = (byte) META;
data[1] = MidiUtils.META_END_OF_TRACK_TYPE;
data[2] = 0;
}
@Override
public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {
throw new InvalidMidiDataException("cannot modify end of track message");
}
}
}