Last list in a request

Requests have a length field. The x11 protocol takes advantage of this in many requests which have a list as the final property.

Typically lists have a length expression which can be based on other fields in the object or a fixed value. In a reply, since there is a length field, the last list does not need a length expression.

If the size of each property is known the count of read bytes can be tracked as each property is read from the server with a local variable. Before reading the final list the length of the list can be calculated by subtracting the variable from the request length.