I think that I am trying to do something in a relatively portable way.

I have a data set where I have a single file containing different types of records. Each record type has a strictly defined format of fixed length fields. The first four fields are common to all record types, withthe third field defining the type of record. (first is a date, second is a sequence within that date, fourth is a sequence within the record type. none of which is relevent, which is why this comment is parenthetical) I need to be able to both read and write these records.

I have this code 

my      ($RequestYear,$RequestMonth,$RequestDay,$RequestSequence,$Reco
+rdType,$RecordSequence,$Record)        
=unpack("A2           A2            A2          A4               A2   
+       A2              A1486",$_) ;

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To read the header fields. then I read the $RecordType and use a series of elsif to determine how to read the rest of the record, like this(short example, most have more fields): 

 elsif ($RecordType==94){                                     
        my ($Destination, $DestinationType)                   
   =unpack("A8            A40", $Record);

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I would like to split the packing/unpacking function from the data definition so that I can put it all in one place, and reuse it. Something like this: 

@HeaderRecordNames   = qw/$RequestYear $RequestMonth $RequestDay $Requ
+estSequence $RecordType $RecordSequence $Record/;
@HeaderRecordLengths = qw/A2           A2            A2          A4   
+            A2          A2              A1486/;

...

@RecordNames[94]       = qw/$Destination  $DestinationType/;
@RecordLengths[94]     = qw/$A8            A4/;

...

my (@HeaderRecordNames) = unpack(@HeaderRecordLengths, $_);

my (@RecordNames[$Recordtype])=unpack(@RecordLengths[$RecordType]);

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This would eliminate my elsif array and also allow me to keep the data definitions in one place so that I can use them for packing or other purposes. Or change them as needed.

Of course this does not work because I am too novicelike to manage the dreaded symbolic references.

Thoughts?

Skip Huffman

In reply to Dreaded Symbolic References by SkipHuffman

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