CSSHPB Parsing

[alanlav]

I am working on adding support for CSSHPB to Nitro but running into a significant issue in completing it.

The CSSHPB tag utilizes the DEVVER in the DES Subheader to determine how some fields should be parsed. The current TRECursor does not have access to this field as nitf_TRECursor_getTREPair only has access to the nitf_TRE object.

I am currently thinking of adding to nitf_TRE an optional pointer to a nitf_DESubheader then modifying nitf_TRECursor_getTREPair to lookup subheader fields such as DESVER if it fails to find values in the hash allowing it to be used in NITF_IF cases.

The des sub header would be populated by adding an optional additional argument to nitf_TRE_construct and nitf_TRE_createSkeleton of nitf_DESubheader

So

nitro/modules/c/nitf/source/NitfReader.c

Line 866 in 298536f

subhdr->subheaderFields = nitf_TRE_createSkeleton(desID, error);

Would change to:

subhdr->subheaderFields = nitf_TRE_createSkeleton(desID, subhdr, error);

I would appreciate the communities input on this.