ugeSaver.js

'use strict';

function saveUge(song) {
  var buffer = new ArrayBuffer(1024 * 1024);
  var idx = 0;
  var view = new DataView(buffer);

  function addUint8(value) {
    view.setUint8(idx, value);
    idx += 1;
  }
  function addUint32(value) {
    view.setUint32(idx, value, true);
    idx += 4;
  }
  function addShortString(s) {
    view.setUint8(idx, s.length);
    idx += 1;
    var te = new TextEncoder();
    te.encodeInto(s, new Uint8Array(buffer, idx, idx + 255));
    idx += 255;
  }
  function addInstrument(type, i) {
    addUint32(type);
    if (!i) i = {};
    addShortString(i.name || '');
    addUint32(i.length ? i.length : 0);
    addUint8(i.length === null ? 0 : 1);
    addUint8(i.initial_volume);
    addUint32(i.volume_sweep_change < 0 ? 1 : 0);
    addUint8(i.volume_sweep_change != 0 ? 8 - Math.abs(i.volume_sweep_change) : 0);

    addUint32(i.frequency_sweep_time);
    addUint32(i.frequency_sweep_shift < 0 ? 1 : 0);
    addUint32(i.frequency_sweep_shift);

    addUint8(i.duty_cycle);

    addUint32(i.volume);
    addUint32(i.wave_index);

    addUint32(i.noise_shift_clock_frequency);
    addUint32(i.dividing_ratio);
    addUint32(i.bit_count == 7 ? 1 : 0);
  }

  addUint32(3); // version
  addShortString(song.name);
  addShortString(song.artist);
  addShortString(song.comment);

  for (var n = 0; n < 15; n++) addInstrument(0, song.duty_instruments[n]);
  for (var n = 0; n < 15; n++) addInstrument(1, song.wave_instruments[n]);
  for (var n = 0; n < 15; n++) addInstrument(2, song.noise_instruments[n]);
  for (var n = 0; n < 16; n++) {
    for (var m = 0; m < 32; m++) addUint8(song.waves[n] ? song.waves[n][m] : 0);
  }
  addUint32(song.ticks_per_row);

  addUint32(song.patterns.length * 4);
  for (var pattern of song.patterns) {
    for (var track = 0; track < 4; track++) {
      for (var m = 0; m < 64; m++) {
        addUint32(pattern[m][track].note === null ? 90 : pattern[m][track].note);
        addUint32(pattern[m][track].instrument === null ? 0 : pattern[m][track].instrument + 1);
        addUint32(pattern[m][track].effectcode === null ? 0 : pattern[m][track].effectcode);
        addUint8(pattern[m][track].effectparam === null ? 0 : pattern[m][track].effectparam);
      }
    }
  }
  for (var track = 0; track < 4; track++) {
    addUint32(song.sequence.length + 1); //amount of "orders" in a uge file has an off-by-one
    for (var i of song.sequence) addUint32(i * 4 + track);
    addUint32(0); // add the off-by-one error
  }
  for (var n = 0; n < 16; n++) addUint32(0); //Add empty routines

  downloadBlob(new Blob([buffer.slice(0, idx)]), 'song.uge');
}