kontainer-js/Matroska/EBMLElement/Element.js

A media file format generator/parser that exposes a React-like API.

'use strict';

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

var _slicedToArray2 = require('babel-runtime/helpers/slicedToArray');

var _slicedToArray3 = _interopRequireDefault(_slicedToArray2);

var _getPrototypeOf = require('babel-runtime/core-js/object/get-prototype-of');

var _getPrototypeOf2 = _interopRequireDefault(_getPrototypeOf);

var _classCallCheck2 = require('babel-runtime/helpers/classCallCheck');

var _classCallCheck3 = _interopRequireDefault(_classCallCheck2);

var _createClass2 = require('babel-runtime/helpers/createClass');

var _createClass3 = _interopRequireDefault(_createClass2);

var _possibleConstructorReturn2 = require('babel-runtime/helpers/possibleConstructorReturn');

var _possibleConstructorReturn3 = _interopRequireDefault(_possibleConstructorReturn2);

var _inherits2 = require('babel-runtime/helpers/inherits');

var _inherits3 = _interopRequireDefault(_inherits2);

var _Component2 = require('../../core/Component');

var _Component3 = _interopRequireDefault(_Component2);

var _Writer = require('../../core/Writer');

var _Writer2 = _interopRequireDefault(_Writer);

var _Reader = require('../../core/Reader');

var _Reader2 = _interopRequireDefault(_Reader);

var _Util = require('../../core/Util');

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function getElementIdLength(buffer, offset) {
  var firstByte = buffer[offset];
  for (var i = 1; i < 5; i++) {
    if (firstByte >>> 8 - i & 0x01) {
      return i;
    }
  }
  (0, _Util.throwException)('Invalid Element id');
}

function writeMaskedSize(size, buffer, offset, sizeLen, len) {
  var msb = size >>> (len - 1) * 8;

  msb &= 0xFF >>> sizeLen;
  msb |= 0x01 << 8 - sizeLen;
  var maskedSize = 0;
  for (var i = 1; i <= len; i++) {
    if (i === 1) {
      maskedSize = msb;
    } else {
      maskedSize <<= 8;
      maskedSize |= size >>> (len - i) * 8 & 0xFF;
    }
  }
  return _Writer2.default.writeNumber(maskedSize, buffer, offset, len);
}

function checkUnknownSize(buffer, offset, length) {
  for (var i = 0; i < length; i++) {
    var byte = buffer[offset + i];

    if (i === 0) {
      if (byte !== (~(0xFF << 8 - length) & 0xFF)) {
        return false;
      }
    } else {
      if (byte !== 0xFF) {
        return false;
      }
    }
  }
  return true;
}

var Element = function (_Component) {
  (0, _inherits3.default)(Element, _Component);

  function Element(id, name, props) {
    (0, _classCallCheck3.default)(this, Element);

    var _this = (0, _possibleConstructorReturn3.default)(this, (0, _getPrototypeOf2.default)(Element).call(this, name, props));

    _this.id = id;
    _this.size = 0;
    _this.sizeLen = props.initialSizeLen || 0;
    return _this;
  }

  (0, _createClass3.default)(Element, [{
    key: 'serialize',
    value: function serialize(buffer) {
      var offset = arguments.length <= 1 || arguments[1] === undefined ? 0 : arguments[1];

      //console.log(`--- Element.serialize enter. type=${this.type}`);
      var elementId = this.id;

      var base = offset;
      var writtenBytesNum = void 0;

      if (buffer) {
        for (var i = 0; i < elementId.length; i++) {
          buffer[base + i] = elementId[i];
        }
      }

      base += elementId.length;

      var sizeLen = this.sizeLen;
      var size = this.size - elementId.length - sizeLen;

      base += Element.writeElementSize(size, buffer, base, sizeLen);

      //console.log(`--- Element.serialize exit. type=${this.type}, size=${base - offset}`);
      return base - offset;
    }
  }, {
    key: 'getSize',
    value: function getSize() {
      return this.size;
    }
  }, {
    key: 'setSize',
    value: function setSize(size) {
      if (this.size === 0) {
        // For master elements.
        this.size = size;
      }
    }
  }, {
    key: 'setElementSize',
    value: function setElementSize(size) {
      this.sizeLen = Element.getNecessaryBytesNumForSize(size);
      this.size = size + this.id.length + this.sizeLen;
    }

    // Parses buffer and returns props.

  }], [{
    key: 'readElementId',
    value: function readElementId(buffer, offset) {
      var len = getElementIdLength(buffer, offset);
      _Reader2.default.ASSERT(buffer, offset, len);
      var elementId = [];
      for (var i = 0; i < len; i++) {
        elementId.push(buffer[offset + i]);
      }
      return [len, elementId];
    }
  }, {
    key: 'readElementSize',
    value: function readElementSize(buffer, offset) {
      var msb = buffer[offset];
      for (var i = 1; i <= 8; i++) {
        if (msb >>> 8 - i & 0x01) {
          // search the most left 1 bit
          _Reader2.default.ASSERT(buffer, offset, i);

          buffer[offset] &= 0xFF >>> i; // drop left i bits

          if (checkUnknownSize(buffer, offset, i)) {
            // the size is encoded to all 1's, which indicates that the size of the Element is unknown
            buffer[offset] = msb; // restore
            return [i, -1];
          }

          var _Reader$readNumber = _Reader2.default.readNumber(buffer, offset, i);

          var _Reader$readNumber2 = (0, _slicedToArray3.default)(_Reader$readNumber, 2);

          var readBytesNum = _Reader$readNumber2[0];
          var size = _Reader$readNumber2[1];

          buffer[offset] = msb; // restore
          return [readBytesNum, size];
        }
      }
      (0, _Util.throwException)('Invalid Element size');
    }
  }, {
    key: 'writeElementSize',
    value: function writeElementSize(size, buffer, offset, sizeLen) {
      var base = offset;

      if (sizeLen > 4) {
        var left = size / 4294967296;
        var right = size % 4294967296;

        base += writeMaskedSize(left, buffer, base, sizeLen, sizeLen - 4);
        base += _Writer2.default.writeNumber(right, buffer, base, 4);
      } else {
        base += writeMaskedSize(size, buffer, base, sizeLen, sizeLen);
      }
      return base - offset;
    }
  }, {
    key: 'getNecessaryBytesNumForSize',
    value: function getNecessaryBytesNumForSize(value) {
      var bytesNum = 0;

      if (value < (1 << 7) - 1) {
        bytesNum = 1;
      } else if (value < (1 << 14) - 1) {
        bytesNum = 2;
      } else if (value < (1 << 21) - 1) {
        bytesNum = 3;
      } else if (value < (1 << 28) - 1) {
        bytesNum = 4;
      } else if (value < (1 << 35) - 1) {
        bytesNum = 5;
      } else if (value < (1 << 42) - 1) {
        bytesNum = 6;
      } else if (value < (1 << 49) - 1) {
        bytesNum = 7;
      } else if (value <= Math.MAX_SAFE_INTEGER) {
        bytesNum = 8;
      } else {
        (0, _Util.throwException)('Matroska.Element.serialize(' + value + '): largesize(>=2^53) is not supported.');
      }
      return bytesNum;
    }
  }, {
    key: 'parse',
    value: function parse(buffer) {
      var offset = arguments.length <= 1 || arguments[1] === undefined ? 0 : arguments[1];

      var size = void 0;
      var elementId = void 0;
      var base = offset;
      var readBytesNum = void 0;

      var _Element$readElementI = Element.readElementId(buffer, base);

      var _Element$readElementI2 = (0, _slicedToArray3.default)(_Element$readElementI, 2);

      readBytesNum = _Element$readElementI2[0];
      elementId = _Element$readElementI2[1];

      base += readBytesNum;

      var _Element$readElementS = Element.readElementSize(buffer, base);

      var _Element$readElementS2 = (0, _slicedToArray3.default)(_Element$readElementS, 2);

      readBytesNum = _Element$readElementS2[0];
      size = _Element$readElementS2[1];

      base += readBytesNum;

      return [base - offset, {
        size: size,
        elementId: elementId
      }];
    }
  }, {
    key: 'getMimeType',
    value: function getMimeType(element) {
      var results = element.querySelectorAll('TrackType');
      var audioOnly = results.every(function (trackType) {
        return trackType.props.kind === 'audio';
      });
      if (audioOnly) {
        return 'audio/webm';
      }
      return 'video/webm';
    }
  }]);
  return Element;
}(_Component3.default);

exports.default = Element;