User-supplied Compression Routines

User-supplied compression routines must be stored in modules called USRDCnnn, where nnn is within the range 128 to 255.

To call a user-supplied routine, use the same syntax as for calling a Micro Focus routine, but use the filename USRDCnnn instead of CBLDCnnn where nnn must be a value in the range 128 through 255.

To make your compression routine available to your system, you must create a callable shared object that can be called when needed.

You can map calls to data compression routines in programs from previous UNIX COBOL systems to the new calls using the cob option:

-m CBL_DATA_COMPRESS_nnn=CBLDCnnn

Note: Your compression routines must not make any calls to the File Handler, as this would result in a loop. If you need file access, use byte-stream file I/O.

Once you have enabled data compression for a file, you must always subsequently specify the same type of compression for that file. If you do not, you receive a run-time system error when you open the file.

Data compression has no effect on files other than those in indexed or record sequential format and is ignored at compile time for files that do not support it.

If you want to read a fixed-length sequential file that has had its data compressed, you must specify that the file is compressed in your program. You do this by specifying the DATACOMPRESS Compiler directive.