Variable document structure

Question

Hello,

I have a file encoded for AS400(IBM870). File contains x structures, structures can be in file more than one (n), but the order and count is not known. The file always contain at least one structure defined in grammar. 

File content sample Axxxxxxxxxx..........Czzzzz...............Bxxxxxaa.............Aznmopaaas...........Cxxddd...............

File structure example	Grammar
--bof-- Record A      ID = A     Value 1 = xxxxx     Value 2 = xxxxx     Filler 10 Record C     ID = C     Value 1 = zzzzz     Filler 15 Record B     ID = B     Value 1 = xxxxx     Value 2 = aa     Filler 13 Record A     ID = A     Value 1 = znmop     Value 2 = aaas     Filler 11 Record C     ID = C     Value 1 = xxddd     Filler 15 --eof--	Records have a fixed length 21 ID is always present  Values are different  Record order is unknown  Record repeat is unknown Grammar contains definition for  record ID (A,B,C,D,E ,F ...) The the file may not contain  all the records

How to automatically parse a file based on existing grammar definition ?

Answer 1

This looks very similar to how the PNG grammar works.

You create a (separate) "parent" structure that contains only one field for ID with "must match" checked.

Then you create (separate) structures that inherit from the parent structure and contain the record specific fields. For the ID field you add one fixed value with the record specific ID.

In the main structure (named like the file) you create a structure with variable element order, then add references to all the record structures.