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#!/usr/bin/env perl
#
# $Id: filesack,v 1.7 2004/10/23 18:51:49 alex Exp $

use Algorithm::Knapsack;

use strict;

my $capacity = shift;
$capacity =   665_600 if $capacity eq '-c';
$capacity = 4_589_843 if $capacity eq '-d';
die "Usage: filesack { size | -c | -d } file ...\n" unless $capacity;

my @files = @ARGV;

die "$capacity\n" unless @files;

#TODO: rewrite du -sk in perl
my @weights = map { int(`du -sk "$_"`) or die "$_, ($!)" } @files;

my $knapsack = Algorithm::Knapsack->new(
    capacity => $capacity,
    weights  => \@weights,
);
$knapsack->compute();
foreach my $solution ($knapsack->solutions()) {
    print join("\n\t", $capacity - $knapsack->{emptiness},
                       map { $files[$_] } @{$solution}),
          "\n";
}

__END__

=head1 NAME

B<filesack> - pack a medium with files to the maximum

=head1 SYNOPSIS

B<filesack> { size | B<-c> | B<-d> } F<file> ...

=head1 DESCRIPTION

The B<filesack> program finds one or more subsets of files or directories
with the maximum total size not exceeding a given size. Its output looks
as follows:

    size
        file
        file
        file
    size
        file
        file
    ...

The total size of files under each size adds up to the size printed
immediately before the file names, and all sizes are the same and as large
as possible, yet no larger than the maximum total size.

=head1 OPTIONS

=over 7

=item B<size>

Maximum total size (in kilobytes).

=item B<-c>

Use the size of a CD, which is 665600 Kb (which equals 650 Mb).

=item B<-d>

Use the size of a DVD, which is 4589843 Kb. This value is the closest to
4,700,000,000 bytes, which is close to the actual capacity of a 4.7 GB
DVD media.

=back

=head1 EXAMPLES

Suppose you have a collection of MP3 albums, and you want to burn them to a
CD, and you want to fill up the CD as much as possible. 

    filesack -c Albums/*

But if you have a 700 Mb CD-R:

    filesack 716800 Albums/*

=head1 REQUIRES

The du(1) utility.

=head1 AUTHOR

Alexander Anderson E<lt>a.anderson@utoronto.caE<gt>

=head1 COPYRIGHT

 Copyright (c) 2004 Alexander Anderson. All rights reserved.
 This program is free software; you can redistribute it and/or
 modify it under the same terms as Perl itself.