I am currently thinking of porting some of my Delphi / Turbo Pascal utilities over to Perl. But I have met with a design problem which I want to post for discussion here :

Pascal has the notion of records, that is, a user defined compound type, more or less like the struc{} thing in C AFAIK. My utilities will parse many of such records to extract information from the files. My current idea to handle this stuff is to map each record to a hash which contains name->value pairs from the file, this can be done in a number of beautiful ways, currently I favor a generic "ReadRecord" routine that gets passed a string suitable for a call to unpack() and a list with the names for each unpacked value. Another, maybe less error prone approach would be to pass in a list of type->name pairs, which would make adding and moving record members easier.

Now where is the problem ? The problem comes with finding the binary size of such a record. Before I can parse a record into a hash, I have to read enough bytes from the disk. Turbo Pascal has the SizeOf() pseudo-function, but Perl dosen't seem to have this. I _could_ hack it up and write my own unpack()-string parser that looks at such a string and tells me how many bytes it most likely would want to unpack correctly, but I would like to know if there is a better way before hacking up such an ugly kludge ...

In reply to How to organize file records by Corion

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