Returns the amount of extended data (xdata) space that is available for an object (entity)
(xdroom ename)
Because there is a limit (currently, 16 kilobytes) on the amount of extended data that can be assigned to an entity definition, and because multiple applications can append extended data to the same entity, this function is provided so an application can verify there is room for the extended data that it will append. It can be called in conjunction with xdsize, which returns the size of an extended data list.
An integer reflecting the number of bytes of available space. If unsuccessful, xdroom returns nil.
The following example looks up the available space for extended data of a viewport object:
Command: (xdroom vpname)
16162
In this example, 16,162 bytes of the original 16,383 bytes of extended data space are available, meaning that 221 bytes are used.