<record> Element Reference

The <record> element is used to group one or more elements together. By default, the record's children have their own scope.

Attributes

Name	Format	Description
import	bool	If set to true, the record's children will not have their own scope. Rather, they will be in the scope of the record itself.
name	string

Detail

%record elements provide a way to group several elements together. the <record> can then be used in expressions as a single element.

import

We can use the import attribute to import the children of the <record> into the same scope as the <record> element itself. This way, subsequent expressions can reference named elements in the <record>.

The following example divides a message into two sections, a header and a body (similar to IP). Since the header record is imported, the Data field in the body can reference it.

    <xddl>
     <structure>
      <record name="Header" import="true">
       <field name="Length" length="8"/>
      </record>
      <record name="Body">
       <field name="Data" length="8 * Length"/>
      </record>
     </structure>
    </xddl>


    import.xddl

If we did not import the header, the Length reference in the Data field would cause an error when the file is loaded.

length

We can restrict the length of a record with the length attribute. The length will be force to be this value even if the lengths of the child elements are not the same.

This can be used for frame-based messages or for forward compatibility.