deps/encoding/encoding.js
function UTF16Decoder(utf16_be, options) {
  var fatal = options.fatal;
  var /** @type {?number} */ utf16_lead_byte = null,
      /** @type {?number} */ utf16_lead_surrogate = null;
  /**
   * @param {ByteInputStream} byte_pointer The byte stream to decode.
   * @return {?number} The next code point decoded, or null if not enough
   *     data exists in the input stream to decode a complete code point.
   */
  this.decode = function(byte_pointer) {
    var bite = byte_pointer.get();
    if (bite === EOF_byte && utf16_lead_byte === null &&
        utf16_lead_surrogate === null) {
      return EOF_code_point;
    }
    if (bite === EOF_byte && (utf16_lead_byte !== null ||
                              utf16_lead_surrogate !== null)) {
      return decoderError(fatal);
    }
    byte_pointer.offset(1);
    if (utf16_lead_byte === null) {
      utf16_lead_byte = bite;
      return null;
    }
    var code_point;
    if (utf16_be) {
      code_point = (utf16_lead_byte << 8) + bite;
    } else {
      code_point = (bite << 8) + utf16_lead_byte;
    }
    utf16_lead_byte = null;
    if (utf16_lead_surrogate !== null) {
      var lead_surrogate = utf16_lead_surrogate;
      utf16_lead_surrogate = null;
      if (inRange(code_point, 0xDC00, 0xDFFF)) {
        return 0x10000 + (lead_surrogate - 0xD800) * 0x400 +
            (code_point - 0xDC00);
      }
      byte_pointer.offset(-2);
      return decoderError(fatal);
    }
    if (inRange(code_point, 0xD800, 0xDBFF)) {
      utf16_lead_surrogate = code_point;
      return null;
    }
    if (inRange(code_point, 0xDC00, 0xDFFF)) {
      return decoderError(fatal);
    }
    return code_point;
  };
}
function UTF16Decoder(utf16_be, options) {
  var fatal = options.fatal;
  var /** @type {?number} */ utf16_lead_byte = null,
      /** @type {?number} */ utf16_lead_surrogate = null;
  /**
   * @param {ByteInputStream} byte_pointer The byte stream to decode.
   * @return {?number} The next code point decoded, or null if not enough
   *     data exists in the input stream to decode a complete code point.
   */
  this.decode = function(byte_pointer) {
    var bite = byte_pointer.get();
    if (bite === EOF_byte && utf16_lead_byte === null &&
        utf16_lead_surrogate === null) {
      return EOF_code_point;
    }
    if (bite === EOF_byte && (utf16_lead_byte !== null ||
                              utf16_lead_surrogate !== null)) {
      return decoderError(fatal);
    }
    byte_pointer.offset(1);
    if (utf16_lead_byte === null) {
      utf16_lead_byte = bite;
      return null;
    }
    var code_point;
    if (utf16_be) {
      code_point = (utf16_lead_byte << 8) + bite;
    } else {
      code_point = (bite << 8) + utf16_lead_byte;
    }
    utf16_lead_byte = null;
    if (utf16_lead_surrogate !== null) {
      var lead_surrogate = utf16_lead_surrogate;
      utf16_lead_surrogate = null;
      if (inRange(code_point, 0xDC00, 0xDFFF)) {
        return 0x10000 + (lead_surrogate - 0xD800) * 0x400 +
            (code_point - 0xDC00);
      }
      byte_pointer.offset(-2);
      return decoderError(fatal);
    }
    if (inRange(code_point, 0xD800, 0xDBFF)) {
      utf16_lead_surrogate = code_point;
      return null;
    }
    if (inRange(code_point, 0xDC00, 0xDFFF)) {
      return decoderError(fatal);
    }
    return code_point;
  };
}
function UTF16Decoder ( utf16_be , options ) { var fatal = options . fatal ; var /** @type {?number} */ utf16_lead_byte = null , /** @type {?number} */ utf16_lead_surrogate = null ; /**
   * @param {ByteInputStream} byte_pointer The byte stream to decode.
   * @return {?number} The next code point decoded, or null if not enough
   *     data exists in the input stream to decode a complete code point.
   */ this . decode = function ( byte_pointer ) { var bite = byte_pointer . get ( ) ; if ( bite === EOF_byte && utf16_lead_byte === null && utf16_lead_surrogate === null ) { return EOF_code_point ; } if ( bite === EOF_byte && ( utf16_lead_byte !== null || utf16_lead_surrogate !== null ) ) { return decoderError ( fatal ) ; } byte_pointer . offset ( 1 ) ; if ( utf16_lead_byte === null ) { utf16_lead_byte = bite ; return null ; } var code_point ; if ( utf16_be ) { code_point = ( utf16_lead_byte << 8 ) + bite ; } else { code_point = ( bite << 8 ) + utf16_lead_byte ; } utf16_lead_byte = null ; if ( utf16_lead_surrogate !== null ) { var lead_surrogate = utf16_lead_surrogate ; utf16_lead_surrogate = null ; if ( inRange ( code_point , 0xDC00 , 0xDFFF ) ) { return 0x10000 + ( lead_surrogate - 0xD800 ) * 0x400 + ( code_point - 0xDC00 ) ; } byte_pointer . offset ( - 2 ) ; return decoderError ( fatal ) ; } if ( inRange ( code_point , 0xD800 , 0xDBFF ) ) { utf16_lead_surrogate = code_point ; return null ; } if ( inRange ( code_point , 0xDC00 , 0xDFFF ) ) { return decoderError ( fatal ) ; } return code_point ; } ; }
14.2 utf-16 
@constructor
@param {boolean} utf16_be True if big-endian, false if little-endian.
@param {{fatal: boolean}} options
14 . 2 utf - 16