index.js

/**
 * Export `ModParser`.
 */

exports = module.exports = ModParser;

/**
 * Channel count by identifier table.
 */

var channelCountByIdentifier = exports.channelCountByIdentifier = {
  'TDZ1': 1, '1CHN': 1, 'TDZ2': 2, '2CHN': 2, 'TDZ3': 3, '3CHN': 3,
  'M.K.': 4, 'FLT4': 4, 'M!K!': 4, '4CHN': 4, 'TDZ4': 4, '5CHN': 5, 'TDZ5': 5,
  '6CHN': 6, 'TDZ6': 6, '7CHN': 7, 'TDZ7': 7, '8CHN': 8, 'TDZ8': 8, 'OCTA': 8, 'CD81': 8,
  '9CHN': 9, 'TDZ9': 9,
  '10CH': 10, '11CH': 11, '12CH': 12, '13CH': 13, '14CH': 14, '15CH': 15, '16CH': 16, '17CH': 17,
  '18CH': 18, '19CH': 19, '20CH': 20, '21CH': 21, '22CH': 22, '23CH': 23, '24CH': 24, '25CH': 25,
  '26CH': 26, '27CH': 27, '28CH': 28, '29CH': 29, '30CH': 30, '31CH': 31, '32CH': 32
}

/**
 * ModParser class.
 *
 * @param {String} mod
 * @api public
 */

function ModParser(mod){
  this.data = mod;
  this.samples = [];
  this.sampleData = [];
  this.positions = [];
  this.patternCount = 0;
  this.patterns = [];

  this.title = trimNulls(mod.substr(0, 20))

  this.sampleCount = 31;

  for (var i = 0; i < this.sampleCount; i++) {
    var sampleInfo = mod.substr(20 + i*30, 30);
    var sampleName = trimNulls(sampleInfo.substr(0, 22));
    this.samples[i] = {
      name: sampleName,
      length: getWord(sampleInfo, 22) * 2,
      finetune: sampleInfo.charCodeAt(24),
      volume: sampleInfo.charCodeAt(25),
      repeatOffset: getWord(sampleInfo, 26) * 2,
      repeatLength: getWord(sampleInfo, 28) * 2,
    }
  }

  this.positionCount = mod.charCodeAt(950);
  this.positionLoopPoint = mod.charCodeAt(951);
  for (var i = 0; i < 128; i++) {
    this.positions[i] = mod.charCodeAt(952+i);
    if (this.positions[i] >= this.patternCount) {
      this.patternCount = this.positions[i]+1;
    }
  }

  var identifier = mod.substr(1080, 4);

  this.channelCount = channelCountByIdentifier[identifier];
  if (!this.channelCount) {
    this.channelCount = 4;
  }

  var patternOffset = 1084;
  for (var pat = 0; pat < this.patternCount; pat++) {
    this.patterns[pat] = [];
    for (var row = 0; row < 64; row++) {
      this.patterns[pat][row] = [];
      for (var chan = 0; chan < this.channelCount; chan++) {
        b0 = mod.charCodeAt(patternOffset);
        b1 = mod.charCodeAt(patternOffset + 1);
        b2 = mod.charCodeAt(patternOffset + 2);
        b3 = mod.charCodeAt(patternOffset + 3);
        var eff = b2 & 0x0f;
        this.patterns[pat][row][chan] = {
          sample: (b0 & 0xf0) | (b2 >> 4),
          period: ((b0 & 0x0f) << 8) | b1,
          effect: eff,
          effectParameter: b3
        };
        if (eff == 0x0E) {
          this.patterns[pat][row][chan].extEffect = (b3 & 0xF0) >> 4;
          this.patterns[pat][row][chan].extEffectParameter = (b3 & 0x0F);
        }
        patternOffset += 4;
      }
    }
  }

  var sampleOffset = patternOffset;
  for (var s = 0; s < this.sampleCount; s++) {
    this.samples[s].startOffset = sampleOffset;
    this.sampleData[s] = new Uint8Array(this.samples[s].length);
    var i = 0;
    for (var o = sampleOffset, e = sampleOffset + this.samples[s].length; o < e; o++) {
      this.sampleData[s][i] = mod.charCodeAt(o);
      i++;
    }
    sampleOffset += this.samples[s].length;
  }
}

function trimNulls(str){
  return str.replace(/\x00+$/, '');
}

function getWord(str, pos){
  return (str.charCodeAt(pos) << 8) + str.charCodeAt(pos+1);
}