From: Dave Greenwood [greenwoodde@ornl.gov]
Sent: Wednesday, November 07, 2001 10:39 AM
To: Info-VAX@Mvb.Saic.Com
Subject: Re: Reading binary values in RMS Indexed Files via DCL

In a previous article, del.duncan@intel.com (Del Duncan) wrote:
> I'm trying to ready an RMS Index file and most of the fields are fine,
> but there is one field that is a binary value which should be a
> longword representation of a date;  I'm having trouble reading it and
> have been unsuccessful.   I thought I could extract it from the line
> and re-format it with f$fao but this hasn't worked either.

Back in 1990 a challenge of sorts was held in this newsgroup for the best
(most compact) use of DCL to convert a binary time to ascii using DCL.
Here's the winning solution (from Simon Graham of DEC):

 $ Record[  0, 32 ] = %x0CA87960
 $ Record[ 32, 32 ] = %x0094972C
 $!
 $ Write SYS$OUTPUT F$Fao( "Date : !%D", -
   F$CvUI( 32, 32, F$Fao( "!AD", 8, Record ) ) )

The challenge was posed by Nick de Smith (NICK@ncdlab.ulcc.ac.uk) who
posted this explanation:

$! 1.   "Record" is stored by DCL as a string, and is therefore passed by
$!      descriptor to functions.
$!      We use the "!AD" operator of $FAO to extract the descriptor of Record
$!      using
$!              F$Fao( "!AD", 8, Record )
$!      which will return the descriptor as an 8 byte string.
$! 2.   We now use
$!              F$CvUI( 32, 32, descriptor-as-a-string )
$!      to return the real address of the data as a 32 bit binary number in an integer.
$!      This extracts the second 32 bits of the "Record" descriptor, which is
$!      the value of the dsc$a_pointer element of the descriptor, ie the address of
$!      the data element (the time quadword) that we require.
$! 3.   Lastly, we use the address from step 2 as input to $FAO to get the date. As
$!      the "!AD" format requires the address of a VMS time quadword, and integers are
$!      passed by value to DCL lexical functions, this last $FAO returns the completed
$!      string.

Dave
--------------
Dave Greenwood                Email: Greenwoodde@ORNL.GOV
Oak Ridge National Lab        %STD-W-DISCLAIMER, I only speak for myself