RE: [MI400] Generate hash code for a source member?

["Bob Crothers" <Bob2@xxxxxxxxxxxxxx>]

Good points.

And what Leif was suggesting looks simple also.  Most likely a much
better way to go.

Bob

-----Original Message-----
From: mi400-admin@midrange.com [mailto:mi400-admin@midrange.com]On
Behalf Of Dan Bale
Sent: Thursday, May 09, 2002 11:05 AM
To: mi400@midrange.com
Subject: RE: [MI400] Generate hash code for a source member?

A simple XFOOT solution, I'm thinking, will not catch changes where
characters are switched, or where records are switched.  I realize I
could
introduce some logic to multiply each element in a record by a
different
value, and do something similar by RRN, and then have to deal with
overflow,
etc., etc.  By the time I've figured that all out, I could turn out
using
just a simple hash.

As it turns out, I think I may have found the answer in Leif's ebook,
as
I've provided in my previous post.  Just have to implement it now.

Dan Bale
SAMSA, Inc.
989-790-0507
DBale@SAMSA.com <mailto:DBale@SAMSA.com>
  Quiquid latine dictum sit altum viditur.
  (Whatever is said in Latin seems profound.)


-----Original Message-----
From: mi400-admin@midrange.com [mailto:mi400-admin@midrange.com]On
Behalf Of Bob Crothers
Sent: Thursday, May 09, 2002 11:14 AM
To: mi400@midrange.com
Subject: RE: [MI400] Generate hash code for a source member?


Dan,

First, you don't really need any of the "official" hash algorithms.
That keeps things simple.  Read the source record in as an array of 32
bit integers.  Crossfoot the array. Add to the total for the member.
Repeat for each record.  Final value is your hash.

Also, keep track of how many times your total overflows.  Eg: If new
total is less than old total, you over flowed.  Keep the count.  When
doing the other side, the "total" and the overflow should match.

This is not an elegant solution by any means, but it would be very easy
to do and would work.  Probably easiest to do out of RPG actually.
Just zero the array before reading records.  That way you don't even
care what the record length is.

Bob

_______________________________________________
This is the MI Programming on the AS400 / iSeries (MI400) mailing list
To post a message email: MI400@midrange.com
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/cgi-bin/listinfo/mi400
or email: MI400-request@midrange.com
Before posting, please take a moment to review the archives
at http://archive.midrange.com/mi400.