All,
hacker asked in this question how to compress relatively short strings. He had a unique goal in mind with specific requirements. Since the only way I could think to do it likely wouldn't meet his requirements, I provided an intentional obfu solution. The general idea is to use 7 bits to store each character. This gives a 12.5% reduction in size but only supports ASCII 0-127.

This wasn't as straight forward as I had guessed. I asked around in the CB if there was something I was missing which apparently I wasn't. diotalevi indicated that this was one of the first problems he tried solving in Perl. Traditional compression techniques fail because with short strings they end up being bigger than the original. When you can afford the runtime cost but not the disk space (apparently every MB had to be justified during the campaign he was working), 7bit strings start to look appealing.

I mentioned on Monday (today) that I would try to provide a more straight forward solution as well as multiple implementations. One for runtime speed (assuming RAM isn't a factor), one for RAM, and one that balances both.

I didn't do very well. I was hoping others would find the task fun and provide better solutions. Here is my solution optimized for memory. 

sub shrink {
    my $str = '';
    for ( 0 .. length( $_[0] ) - 1 ) {
        my $bit = 7 * $_;
        vec($str, $bit++, 1) = $_ for split //, unpack('b8', substr($_
+[0], $_, 1));
    }
    return $str; 
}

sub grow {
    my ($str, $chr) = ('', '');
    my $end = length( $_[0] ) * 8;
    $end -= ($end % 7) + 1;
    for ( 0 .. $end ) {
        vec($chr, $_ % 7, 1) = vec($_[0], $_, 1);
        if ( $_ % 7 == 6 ) {
            vec($chr, 7, 1) = 0;
            $str .= $chr;
            $chr = '';  
        }
    }
    return $str;
}

[download]

Cheers - L~R

In reply to Efficient 7bit compression by Limbic~Region

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.