#!/usr/bin/perl -w
#

#####
# Provides fuctions for bencoding/decoding
###

# Decodes a bencoded string to a hash/array reference
sub bDecode {
    my $dictref = $_[0];
    my $retref = undef;
    
    if (substr(${$dictref},0,1) eq "d") {
#        print Dumper($dictref);
        $retref = {};
        ${$dictref} = substr(${$dictref},1);
        PROCDICTHASH: while (substr(${$dictref},0,1) ne 'e') {
            my ($key, $value);
            
            ${$dictref} =~ /^(-?[\d]+)/;
            $key = substr(${$dictref}, length($1)+1, $1);
            ${$dictref} = substr(${$dictref}, length($1)+$1+1);
            if (${$dictref} =~ /^[ldi\d]/) {
                $value = bDecode(\${$dictref});
                if (!defined($value)) {
                    return undef;
                }
            } else {
                return undef;
            }
            
            $retref->{$key} = $value;
        }
        ${$dictref} = substr(${$dictref},1);
    } elsif (substr(${$dictref},0,1) eq "l") {
#        print Dumper($dictref);
        $retref = [];
        ${$dictref} = substr(${$dictref},1);
        PROCDICTARR: while (substr(${$dictref},0,1) ne 'e') {
            if (${$dictref} =~ /^[ldi\d]/) {
                my $value = bDecode(\${$dictref});
                if (!defined($value)) {
                    return undef;
                }
                push (@$retref, $value);
            } else {
                return undef;
            }
        }
        ${$dictref} = substr(${$dictref},1);
    } elsif (${$dictref} =~ /^i(-?[\d]+)e/) {
        ${$dictref} = substr(${$dictref}, length($1)+2);
        return $1;
    } elsif (${$dictref} =~ /^([\d]+):/) {
        $retref = substr(${$dictref}, length($1)+1, $1);
        ${$dictref} = substr(${$dictref}, length($1)+$1+1);
        return $retref;
    } else {
        return undef;
    }

    return $retref;
}

#Encodes a hash/array ref to a bencoded string
sub bEncode {
    my $dictref = $_[0];
    my $retval = '';
    if (ref($dictref) eq 'HASH') {
        $retval = 'd';
        for my $key (sort keys %$dictref) {
            $retval .= length($key).':'.$key;
            $retval .= bEncode($dictref->{$key});
        }
        $retval .= 'e';
    } elsif (ref($dictref) eq 'ARRAY') {
        $retval = 'l';
        for (my $i = 0; $i <= $#{$dictref}; $i++) {
            $retval .= bEncode($dictref->[$i]);
        }
        $retval .= 'e';
    } elsif ($dictref =~ /^-?[\d]+$/) {
        $retval = 'i'.$dictref.'e';
    } else {
        $retval = length($dictref).':'.$dictref;
    }
    return $retval;
};
[download]

---

---

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! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

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:
	&		&
	<		&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.