Re: Bitwise ops in RPG (was: Re: Determining *DS4 support)

[Buck Calabro <buck.calabro@xxxxxxxxxxxxxxxxx>]

Mark Lazarus wrote:

>Buck said:
>>I work with telephone switch data.  Because the switch needs to store many
>>millions of call records, the switch stores many attributes as single bits
>>to save space.  Extracting these status bits was not pleasant in RPG
III...

Mark wondered:
>  RPG has several bit twiddling operations.  What couldn't you handle?

It isn't really a matter of "can't handle" .  Obviously we got it done - we
can read these call records :-)  If you want a mild challenge, decode these
fields from a two byte string:

bits 16-08 Call start date value
bits 07-04 Answer type value
bit  03    Time change flag
bit  02    Operator Assistance flag
bit  01    International call flag

Bit 16 is the most significant (leftmost) bit.  The value fields are used as
actual numbers, while the flag fields are indicators.  For a real challenge,
compile your code in S/36 mode, like the original code had to.  Oh yeah, the
field layouts change with each switch upgrade.

Ease of coding and run time performance have both improved significantly by
rewriting this in RPG IV.  

Buck Calabro
Aptis; Albany, NY
"Nothing is so firmly believed as
 that which we least know" -- Michel Montaigne
Visit the Midrange archives at http://www.midrange.com
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