MidiFileWriter.java

package org.herac.tuxguitar.io.midi;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import org.herac.tuxguitar.io.midi.base.MidiEvent;
import org.herac.tuxguitar.io.midi.base.MidiMessage;
import org.herac.tuxguitar.io.midi.base.MidiSequence;
import org.herac.tuxguitar.io.midi.base.MidiTrack;

public class MidiFileWriter implements MidiFileHeader {

  private static int writeEvent(MidiEvent event, MidiEvent previous,
      OutputStream out) throws IOException {
    int length = writeVariableLengthQuantity(((previous != null) ? (event
        .getTick() - previous.getTick()) : 0), out);
    MidiMessage message = event.getMessage();
    if (message.getType() == MidiMessage.TYPE_SHORT) {
      length += writeShortMessage(message, out);
    } else if (message.getType() == MidiMessage.TYPE_META) {
      length += writeMetaMessage(message, out);
    }

    return length;
  }

  private static int writeMetaMessage(MidiMessage message, OutputStream out)
      throws IOException {
    int length = 0;
    byte[] data = message.getData();
    if (out != null) {
      out.write(0xFF);
      out.write(message.getCommand());
    }
    length += 2;
    length += writeVariableLengthQuantity(data.length, out);
    if (out != null) {
      out.write(data);
    }
    length += data.length;
    return length;
  }

  private static int writeShortMessage(MidiMessage message, OutputStream out)
      throws IOException {
    byte[] data = message.getData();
    int length = data.length;
    if (out != null) {
      out.write(message.getData(), 0, length);
    }
    return length;
  }

  private static int writeTrack(MidiTrack track, DataOutputStream out)
      throws IOException {
    int length = 0;
    if (out != null) {
      out.writeInt(TRACK_MAGIC);
    }
    if (out != null) {
      out.writeInt(writeTrack(track, null));
    }
    MidiEvent previous = null;
    for (int i = 0; i < track.size(); i++) {
      MidiEvent event = track.get(i);
      length += writeEvent(event, previous, out);
      previous = event;
    }
    return length;
  }

  private static int writeVariableLengthQuantity(long value, OutputStream out)
      throws IOException {
    boolean started = false;
    int length = 0;
    int data = (int) ((value >> 21) & 0x7f);
    if (data != 0) {
      if (out != null) {
        out.write(data | 0x80);
      }
      length++;
      started = true;
    }
    data = (int) ((value >> 14) & 0x7f);
    if (data != 0 || started) {
      if (out != null) {
        out.write(data | 0x80);
      }
      length++;
      started = true;
    }
    data = (int) ((value >> 7) & 0x7f);
    if (data != 0 || started) {
      if (out != null) {
        out.write(data | 0x80);
      }
      length++;
    }
    data = (int) (value & 0x7f);
    if (out != null) {
      out.write(data);
    }
    length++;
    return length;
  }

  public void write(MidiSequence sequence, int type, OutputStream stream)
      throws IOException {
    DataOutputStream out = new DataOutputStream(stream);
    out.writeInt(HEADER_MAGIC);
    out.writeInt(HEADER_LENGTH);
    out.writeShort(type);
    out.writeShort(sequence.countTracks());
    out.writeShort((sequence.getDivisionType() == MidiSequence.PPQ) ? (sequence
        .getResolution() & 0x7fff) : 0);
    for (int i = 0; i < sequence.countTracks(); i++) {
      writeTrack(sequence.getTrack(i), out);
    }
    out.flush();
    out.close();
  }
}