/// <summary>
/// Write a sequence to an output stream in standard midi format.
/// <see cref="gnu.sound.midi.spi.MidiFileWriter#write(Sequence, int, Stream)"/>
/// </summary>
public override int Write(Sequence stream, int fileType, Stream outputStream)
{
var dos = new MidiDataOutputStream(outputStream);
Track[] tracks = stream.Tracks.ToArray();
dos.Write((int)0x4D546864); // MThd
dos.Write((int)6);
dos.Write((Int16)fileType);
dos.Write((Int16)tracks.Length);
float divisionType = stream.DivisionType;
int resolution = stream.Resolution;
// FIXME: division computation is incomplete.
int division = 0;
if (divisionType == Sequence.PPQ)
{
division = resolution & 0x7FFF;
}
dos.Write((Int16)division);
int length = 14;
for (int i = 0; i < tracks.Length; i++)
{
length += WriteTrack(tracks[i], dos);
}
return(length);
}
/// <summary>
/// Write a track to an output stream.
/// <param name="track">the track to write</param>
/// <param name="dos">a MidiDataOutputStream to write to</param>
/// <returns>the number of bytes written</returns>
/// </summary>
private int WriteTrack(Track track, MidiDataOutputStream dos)
{
int i = 0;
int eventCount = track.EventCount();
int trackLength = 0;
MidiEvent previousEvent = null;
dos.Write((int)0x4D54726B); // "MTrk"
trackLength = ComputeTrackLength(track, dos);
dos.Write((int)trackLength);
while (i < eventCount)
{
MidiEvent midiEvent = track.Get(i);
int deltaTime = 0;
if (previousEvent != null)
{
deltaTime = (int)(midiEvent.Tick - previousEvent.Tick);
}
dos.WriteVariableLengthInt(deltaTime);
// FIXME: use running status byte
byte[] msg = midiEvent.Message.GetMessage();
dos.Write(msg);
previousEvent = midiEvent;
i++;
}
// We're done if the last event was an End of Track meta message.
if (previousEvent != null && (previousEvent.Message is MetaMessage))
{
var mm = (MetaMessage)previousEvent.Message;
// End of Track message
if (mm.GetMetaMessageType() == (int)MidiHelper.MetaEventType.EndOfTrack)
{
return(trackLength + 8);
}
}
// Write End of Track meta message
dos.WriteVariableLengthInt(0); // Delta time of 0
dos.Write((byte)MidiHelper.META); // Meta Message
dos.Write((byte)MidiHelper.MetaEventType.EndOfTrack); // End of Track message
dos.WriteVariableLengthInt(0); // Length of 0
return(trackLength + 8 + 4);
}
/// <summary>
/// Compute the length of a track as it will be written to the
/// output stream.
/// <param name="track">the track to measure</param>
/// <param name="dos">a MidiDataOutputStream used for helper method</param>
/// <returns>the length of the track</returns>
/// </summary>
private int ComputeTrackLength(Track track, MidiDataOutputStream dos)
{
int length = 0;
int i = 0;
int eventCount = track.EventCount();
long previousTick = 0;
while (i < eventCount)
{
MidiEvent midiEvent = track.Get(i);
long tick = midiEvent.Tick;
length += MidiDataOutputStream.VariableLengthIntLength((int)(tick - previousTick));
previousTick = tick;
length += midiEvent.Message.Length;
i++;
}
return(length);
}
