code: function ContentRange(unit, range, length) {
    this.unit = unit;
    this.range = range;
    this.length = length;
    if (this.range.high && this.length && this.length <= this.range.high) {
      throw new Error('Length is less than or equal to the range');
    }
  }
docs: Content-Range HTTP Header class.
  
  @param {String} unit Usually "bytes", but can be any token; http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.12
  @param {RangeSpec|String|'*'} range A RangeSpec instance, a string like '0-49' or '*' if unknown
  @param {Number|'*'} length The total length of the full entity-body or '*' if this length is unknown or difficult to determine
  @constructor
  @throws Error
  @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.16