In
<77142d37c0c3c34da0d7b1da7d7ca343135ce...@nwt-s-mbx1.rocketsoftware.com>,
on 07/13/2011
at 07:12 PM, Bill Fairchild <[email protected]> said:
>If you know the record IDs are "regular format" (meaning the CCHH
>part always equals the CCHH of the track on which the records are
>stored and the R part is monotonically increasing), then you can
>easily read the records on the track backwards by doing direct reads
>of R(n), R(n-1), ..., R(1).
It will require 256 revolutions unless you know the highest record
number. You can avoid that by chaining 256 Read Count CCW's first.
>Otherwise you will first have to scan forward through the track
>buffer, find the beginning of each record, save its offset in a
>table, and then process the records in reverse order starting with
>the last entry in the table.
Which is no more code than other approaches and has the side effect of
handling non-standard CCHHR assignments.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT
ISO position; see <http://patriot.net/~shmuel/resume/brief.html>
We don't care. We don't have to care, we're Congress.
(S877: The Shut up and Eat Your spam act of 2003)
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