qambi/dist/midi_stream.js

MIDI sequencer, loads MIDI files, can record and playback MIDI, uses WebMIDI and WebAudio

/*
  Wrapper for accessing bytes through sequential reads

  based on: https://github.com/gasman/jasmid
  adapted to work with ArrayBuffer -> Uint8Array
*/

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var fcc = String.fromCharCode;

var MIDIStream = function () {

  // buffer is Uint8Array
  function MIDIStream(buffer) {
    _classCallCheck(this, MIDIStream);

    this.buffer = buffer;
    this.position = 0;
  }

  /* read string or any number of bytes */


  _createClass(MIDIStream, [{
    key: 'read',
    value: function read(length) {
      var toString = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : true;

      var result = void 0;

      if (toString) {
        result = '';
        for (var i = 0; i < length; i++, this.position++) {
          result += fcc(this.buffer[this.position]);
        }
        return result;
      } else {
        result = [];
        for (var _i = 0; _i < length; _i++, this.position++) {
          result.push(this.buffer[this.position]);
        }
        return result;
      }
    }

    /* read a big-endian 32-bit integer */

  }, {
    key: 'readInt32',
    value: function readInt32() {
      var result = (this.buffer[this.position] << 24) + (this.buffer[this.position + 1] << 16) + (this.buffer[this.position + 2] << 8) + this.buffer[this.position + 3];
      this.position += 4;
      return result;
    }

    /* read a big-endian 16-bit integer */

  }, {
    key: 'readInt16',
    value: function readInt16() {
      var result = (this.buffer[this.position] << 8) + this.buffer[this.position + 1];
      this.position += 2;
      return result;
    }

    /* read an 8-bit integer */

  }, {
    key: 'readInt8',
    value: function readInt8(signed) {
      var result = this.buffer[this.position];
      if (signed && result > 127) {
        result -= 256;
      }
      this.position += 1;
      return result;
    }
  }, {
    key: 'eof',
    value: function eof() {
      return this.position >= this.buffer.length;
    }

    /* read a MIDI-style letiable-length integer
      (big-endian value in groups of 7 bits,
      with top bit set to signify that another byte follows)
    */

  }, {
    key: 'readVarInt',
    value: function readVarInt() {
      var result = 0;
      while (true) {
        var b = this.readInt8();
        if (b & 0x80) {
          result += b & 0x7f;
          result <<= 7;
        } else {
          /* b is the last byte */
          return result + b;
        }
      }
    }
  }, {
    key: 'reset',
    value: function reset() {
      this.position = 0;
    }
  }, {
    key: 'setPosition',
    value: function setPosition(p) {
      this.position = p;
    }
  }]);

  return MIDIStream;
}();

exports.default = MIDIStream;