Hello monks, I have a problem with perl's pack function and null byte padding. Here's the problem: 
print unpack "H*", pack("H*", "a12");

[download]
This returns a120, because packed data is padded to full byte length at the end, not at the front. This is quite problematic. Possible solution is to do this instead 
my $string = "a12";
print unpack "H*", pack("H*", "0" x (length $string % 2) . $string);

[download]
Of course this is a lot uglier, requires you to actually have a variable declared and is not as explicit as the first version, however it works. My question is: is there a possibility to do the same thing with just pack format string to avoid patching it with length() of the string? Is there a cpan library that takes care of this? I wrote my own helper function for this but I've run into some circullar using of my packages which I want to avoid. Help appreciated!

In reply to Pack uneven length hex by melez

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.