+package Onis::Data::Persistent::Dbm;
+
+use strict;
+use warnings;
+
+use Carp qw(carp confess);
+use AnyDBM_File;
+
+use Onis::Config (qw(get_config));
+
+=head1 NAME
+
+Onis::Data::Persistent::Dbm - Storage backend using AnyDBM_File.
+
+=head1 DESCRIPTION
+
+Storage backend that uses DBM files for storing data permanently.
+
+=head1 CONFIGURATION OPTIONS
+
+=over 4
+
+=item B<gdbm_directory>: I<E<lt>dirE<gt>>
+
+Directory in which the GDBM-files are kept.
+
+=back
+
+=cut
+
+our $DBMDirectory = get_config ('gdbm_directory') || 'var';
+$DBMDirectory =~ s#/$##g;
+
+if (!$DBMDirectory or !-d $DBMDirectory)
+{
+ print STDERR <<ERROR;
+The directory ``$DBMDirectory'' does not exist or is not useable. Please
+create it before running onis.
+ERROR
+ exit (1);
+}
+
+our $Alarm = chr (7);
+our %Objects = ();
+
+if ($::DEBUG & 0x0200)
+{
+ require Data::Dumper;
+}
+
+return (1);
+
+sub new
+{
+ my $pkg = shift;
+ my $name = shift;
+ my $key = shift;
+ my @fields = @_;
+ my $caller = caller ();
+ my $obj = {};
+ my %hash;
+ my $i = 0;
+ my $filename;
+
+ my $id = $caller . ':' . $name;
+ $id =~ s#/##g;
+
+ $filename = "$GDBMDirectory/$id.gdbm";
+
+ if (exists ($Objects{$id}))
+ {
+ print STDERR $/, __FILE__, ": Name $name has been used in context $caller before.";
+ return (undef);
+ }
+
+ $Objects{$id} = $obj;
+
+ $obj->{'data'} = tie (%hash, 'AnyDBM_File', $filename, O_CREAT|O_RDWR, 0664);
+ $obj->{'key'} = $key;
+ $obj->{'fields'} = [@fields];
+ $obj->{'num_fields'} = scalar (@fields);
+ $obj->{'field_index'} = {map { $_ => $i++ } (@fields)};
+ $obj->{'id'} = $id;
+ $obj->{'cache'} = {};
+
+ if ($::DEBUG & 0x0200)
+ {
+ my $prefix = __FILE__ . ': ';
+ my $dbg = Data::Dumper->Dump ([$obj], ['obj']);
+ $dbg =~ s/^/$prefix/mg; chomp ($dbg);
+ print STDOUT $/, $dbg;
+ }
+
+ return (bless ($obj, $pkg));
+}
+
+sub put
+{
+ my $obj = shift;
+ my $key = shift;
+ my @fields = @_;
+ my $db = $obj->{'data'};
+
+ if ($obj->{'num_fields'} != scalar (@fields))
+ {
+ my $id = $obj->{'id'};
+ carp ("Number of fields do not match ($id).");
+ return;
+ }
+
+ if ($::DEBUG & 0x0200)
+ {
+ print STDOUT $/, __FILE__, ': PUT(', $obj->{'id'}, ', ', $key, ') = (' . join (', ', @fields) . ')';
+ }
+
+ $obj->{'cache'}{$key} = [@fields];
+}
+
+sub get
+{
+ my $obj = shift;
+ my $key = shift;
+ my $val;
+ my @ret;
+ my $db = $obj->{'data'};
+
+ if (!exists ($obj->{'cache'}{$key}))
+ {
+ if ($db->get ($key, $val))
+ {
+ $obj->{'cache'}{$key} = undef;
+ }
+ else
+ {
+ $obj->{'cache'}{$key} = [split ($Alarm, $val)];
+ }
+ }
+
+ if (!defined ($obj->{'cache'}{$key}))
+ {
+ return (qw());
+ }
+ else
+ {
+ @ret = @{$obj->{'cache'}{$key}};
+ }
+
+ if ($::DEBUG & 0x0200)
+ {
+ print STDOUT $/, __FILE__, ': GET(', $obj->{'id'}, ', ', $key, ') = (' . join (', ', @ret) . ')';
+ }
+
+ return (@ret);
+}
+
+sub keys
+{
+ my $obj = shift;
+ my @fields = @_;
+ my @field_indizes = ();
+ my $db = $obj->{'data'};
+ my $key;
+ my $val;
+
+ for ($db->seq ($key, $val, R_FIRST); $db->seq ($key, $val, R_NEXT) == 0;)
+ {
+ next if (defined ($obj->{'cache'}{$key}));
+ $obj->{'cache'}{$key} = [split ($Alarm, $val)];
+ }
+
+ if (!@fields)
+ {
+ return (keys %{$obj->{'cache'}});
+ }
+
+ for (@fields)
+ {
+ my $field = $_;
+ if (!defined ($obj->{'field_index'}{$field}))
+ {
+ my $id = $obj->{'id'};
+ print STDERR $/, __FILE__, ": $field is not a valid field ($id).";
+ next;
+ }
+ push (@field_indizes, $obj->{'field_index'}{$field});
+ }
+
+ return (sort
+ sub {
+ for (@field_indizes)
+ {
+ my $d = $obj->{'cache'}{$a}[$_] cmp $obj->{'cache'}{$b}[$_];
+ return ($d) if ($d);
+ }
+ }, @keys);
+}
+
+sub del
+{
+ my $obj = shift;
+ my $key = shift;
+ my $db = $obj->{'data'};
+
+ if (exists ($obj->{'cache'}{$key}))
+ {
+ if (defined ($obj->{'cache'}{$key}))
+ {
+ $db->del ($key);
+ $obj->{'cache'}{$key} = undef;
+ }
+ # It's known that the key doesn't exist..
+ }
+ else
+ {
+ $db->del ($key);
+ $obj->{'cache'}{$key} = undef;
+ }
+}
+
+sub sync
+{
+ my $obj = shift;
+ my $db = $obj->{'data'};
+
+ for (keys %{$obj->{'cache'}})
+ {
+ my $key = $_;
+ my $val = join ($Alarm, @{$obj->{'cache'}{$key}});
+
+ $db->put ($key, $val);
+ delete ($obj->{'cache'}{$key});
+ }
+
+ $db->sync ();
+}
+
+END
+{
+ for (keys (%Objects))
+ {
+ my $obj = $_;
+ $obj->sync ();
+ }
+}
+
+=head1 AUTHOR
+
+Florian octo Forster, L<octo at verplant.org>
+
+=cut