CODEWITHSUNDEEP
perl
USTD
USTD

Reputation: 23

Perl pack and unpack binary data in a variable

I have some binary data that comes to me from a library function which I store in a variable called: $data

If I hexify this binary data with: $hexstring = unpack "H*", $data;

It performs this hex transformation correctly, I verified my results against the unix commands: od -c and xxd -p :-)

My question is how to I do the reverse operation to pack this data back into a $newdata variable from the hex data ?

if I do a ref($data), it returns a blank result, so I don't understand what format this binary data is originally formated in the $data variable. The library author tells me it is a string, but my experience trying to pack a string, it does not produce the correct result.

I have tried various attempts to "pack" but I don't seem to know how to pack this correctly. I am stumbling on something. :-)

Please help me to understand my packing errors ;-)

Thanks!

Upvotes: 2

Views: 1645

Answers (1)

Borodin
Borodin

Reputation: 126772

Well it's pretty straightforward in this case. The inverse operation of unpack 'H*' is pack 'H*'

Here's a program demonstrating

use strict;
use warnings 'all';
use 5.10.1;

my $data = "\x01\x23\x45\x67\x89\xAB\xCD\xEF";

my $hex = unpack "H*", $data;
say $hex;

my $newdata = pack "H*", $hex;
say $newdata eq $data ? 'OK' : 'FAIL';

output

0123456789abcdef
OK

Upvotes: 3

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