=head1 NAME

Net::FCP::Key::CHK - manage CHK keys.

=head1 SYNOPSIS

 use Net::FCP::Key::CHK;

 my $key = new Net::FCP::Key::CHK;
 my $key = new_from_uri Net::FCP::Key::CHK $uri;
 my $key = new_from_data Net::FCP::Key::CHK $data, $metadata;
 ... more to come


=head1 DESCRIPTION

=back

=head2 THE Net::FCP::Key::CHK CLASS

=over 4

=cut

package Net::FCP::Key::CHK;

use Carp;
use Digest::SHA1;
use Crypt::Twofish2;
use MIME::Base64;

no warnings;

sub log2($$) { # n, minlog
   my ($n, $b) = @_;

   $b++ while 1 << $b < $n;

   $b;
}

sub decode_fbase64 {
   my $s = shift;

   $s =~ y%~\-%+/%;
   decode_base64 "$s======";
}

sub encode_fbase64 {
   my $s = encode_base64 shift, "";
   $s =~ s/=+$//;
   $s =~ y%+/%~\-%;
   $s;
}

=item my $key = new Net::FCP::Key::CHK;

Don't use :)

=cut

sub new {
   my $class = shift;

   bless { }, $class;
}

=item my $key = new_from_date Net::FCP::Key::CHK $data, $metadata;

Generate a CHK from the given data and metadata strings.

=cut

sub new_from_data {
   my ($class, $data, $metadata) = @_;

   $class->new->set_data ($data, $metadata);
}

sub set_data {
   my ($self, $data, $metadata) = @_;

   my $d = new Digest::SHA1;
   $d->add ($metadata);
   $d->add ($data);
   $d = $d->digest;

   # only works for 128 bit keys
   my $k = new Digest::SHA1;
   $k->add ("\x00" x 1);
   $k->add ($d);
}

=item $size = $key->size

Returns the size of the data (in bytes).

=cut

=item $digest = $key->digest

Return the store digest/hash.

=cut

=item $keynum = $key->keynumber

Returns the keynumber (version?)

=cut

=item $chk = $key->chk

Return the full CHK.

=cut

=back

=head1 SEE ALSO

L<Net::FCP>.

=head1 BUGS

Not heavily tested.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

1;