code: function typeAtOffset(baseType: any, offsetFieldName: string): any {
    return jBinary.Template({
        baseType: baseType,
        read: function(context) {
          if (+context[offsetFieldName] === 0) {
            return null;
          } else {
            return this.binary.read(this.baseType, +context[offsetFieldName]);
          }
        }
      });
  }
docs: Read a jBinary type at an offset in the buffer specified by another field.