Returns the length of a data object specified by the tag and reference number.
Return value
Returns the length of data element if found and FAIL (or -1) otherwise.
Description
Hlength calls Hstartread, HQuerylength, and Hendaccess to determine the length of a data element. Hlength uses Hstartread to obtain an access identifier for the specified data object.
Hlength will return the correct data length for linked-block elements, however it is important to remember that the data in linked-block elements is not stored contiguously.