Re: Help with QimgCvtImg

Scott Klement wrote:
> ...
> c) Instead of using from/to notation for the data structures, consider
> using length notation.  I shudder to think of the amount of work it'd take
> to fix one of these structures if it were defined wrong.
> ...

The (sort of) good thing about from/to notation is that you can see that
the subfield is defined starting in the right place.  I find that
defining API structures using only length notation makes it difficult to
debug problems with the structure, especially if it has a lot of
subfields.  But I hate from/to notation because it's hard (for me at
least, because I hate subtracting) to see that the data type is correct.

Using length notation with OVERLAY makes it easy to see that both the
data type and the starting position match the API documentation.

For example

DQIMI0100         DS                     inz
D StructLen                     10I 0    overlay(QIMI0100 :1)
D                                        inz(101)
D StructFmt                      8A      overlay(QIMI0100 :5) 
D                                        inz('IMGI0100')
D ResX00_1                      10A      overlay(QIMI0100 :13) 
D                                        inz(*allx'00')
D ResX00_2                      10A      overlay(QIMI0100 :23) 
D                                        inz(*allx'00')
D DataStrmFmt                   10I 0    overlay(QIMI0100 :33) 
D PhotoI                        10I 0    overlay(QIMI0100 :37) 
D ResUnit                       10I 0    overlay(QIMI0100 :41) 
 ...