Initial Commit

database/perl/vendor/lib/DBM/Deep/Storage.pm

@@ -0,0 +1,70 @@
+package DBM::Deep::Storage;
+
+use 5.008_004;
+
+use strict;
+use warnings FATAL => 'all';
+
+=head1 NAME
+
+DBM::Deep::Storage - abstract base class for storage
+
+=head2 flush()
+
+This flushes the filehandle. This takes no parameters and returns nothing.
+
+=cut
+
+sub flush { die "flush must be implemented in a child class" }
+
+=head2 is_writable()
+
+This takes no parameters. It returns a boolean saying if this filehandle is
+writable.
+
+Taken from L<http://www.perlmonks.org/?node_id=691054/>.
+
+=cut
+
+sub is_writable { die "is_writable must be implemented in a child class" }
+
+=head1 LOCKING
+
+This is where the actual locking of the storage medium is performed.
+Nested locking is supported.
+
+B<NOTE>: It is unclear what will happen if a read lock is taken, then
+a write lock is taken as a nested lock, then the write lock is released.
+
+Currently, the only locking method supported is flock(1). This is a
+whole-file lock. In the future, more granular locking may be supported.
+The API for that is unclear right now.
+
+The following methods manage the locking status. In all cases, they take
+a L<DBM::Deep> object and returns nothing.
+
+=over 4
+
+=item * lock_exclusive( $obj )
+
+Take a lock usable for writing.
+
+=item * lock_shared( $obj )
+
+Take a lock usable for reading.
+
+=item * unlock( $obj )
+
+Releases the last lock taken. If this is the outermost lock, then the
+object is actually unlocked.
+
+=back
+
+=cut
+
+sub lock_exclusive { die "lock_exclusive must be implemented in a child class" }
+sub lock_shared { die "lock_shared must be implemented in a child class" }
+sub unlock { die "unlock must be implemented in a child class" }
+
+1;
+__END__