Pack decimal possibility

[mikeward61]

We create files on our Linux servers that are NDM'd and processed on our mainframes. We need the ability to create a trailer record that contains a packed field indicating the number of records that should be in the file (i.e. 240 records would be x'0000240C'). Is this possible in Perl?

[ReturnOfThelonious]

Specifically,

my $packed = pack "H*", sprintf "%07dC",  $num_records;

would give you a PIC S9(7) COMP-3 packed decimal (positive only).

Perl can count the records and add the trailer record, too, but I don't know what record format you're using.

[mikeward61]

Thanks, this worked perfectly...

[BrowserUk]

pack doesn't support this directly. This will do the job, though it can probably be made significantly more efficient:

sub toComp3{ 
    my $num = shift; 
    my @digits = split'',abs $num; 
    unshift @digits, 0 unless @digits & 1;
    push @digits, $num < 0 ? 13: 12; 
    my $comp3 = ''; $comp3 .= chr( shift( @digits ) * 16 + shift( @dig
+its ) ) 
        while @digits; 
    return $comp3 
}

print unpack 'H*', toComp3( 240 );;
240c

It also doesn't cover unsigned numbers. Though a flag to indicate signed-ness could be added.

[chuckbutler]

There is a module, Convert::IBM390, that supports various conversion functions for data to/from a mainframe. One is packeb:

use Convert::IBM390 qw(packeb);
my $comp3 = packeb( 'p4', 240 );  #77 A  PIC S9(7) COMP-3.
print $comp3;
__END__
~~output~~
0x0000240c  (of course, in binary)

It works well, and handles negative values.

Good luck. -c

[Corion]

You didn't do much research, did you?

pack, print, sprintf %04x, 123;