+package Tie::Hash::Sorted::XS;
+
+use 5.014000;
+use strict;
+use warnings;
+
+use Tree::SizeBalanced;
+
+our $VERSION = '0.000_001';
+
+sub TIEHASH {
+ my ($class, $tree) = @_;
+ $tree //= Tree::SizeBalanced::str_any->new;
+ bless \$tree, $class
+}
+
+sub FETCH {
+ my ($self, $key) = @_;
+ my ($k, $v) = $$self->find($key);
+ $v
+}
+
+sub STORE {
+ my ($self, $key, $value) = @_;
+ $$self->delete($key);
+ $$self->insert($key, $value);
+}
+
+sub DELETE {
+ my ($self, $key) = @_;
+ $$self->delete($key);
+}
+
+# sub CLEAR unimplemented
+
+sub EXISTS {
+ my ($self, $key) = @_;
+ my @list = $$self->find($key);
+ @list > 0;
+}
+
+sub FIRSTKEY {
+ my ($self) = @_;
+ $$self->find_min
+}
+
+sub NEXTKEY {
+ my ($self, $lastkey) = @_;
+ $$self->find_gt($lastkey);
+}
+
+sub SCALAR {
+ my ($self) = @_;
+ $$self->size
+}
+
+1;
+__END__
+
+=encoding utf-8
+
+=head1 NAME
+
+Tie::Hash::Sorted::XS - hash with ordered keys backed by binary search tree
+
+=head1 SYNOPSIS
+
+ use Tie::Hash::Sorted::XS;
+
+ tie my %hash, 'Tie::Hash::Sorted::XS';
+
+ $hash{Jim} = 5;
+ $hash{Bob} = 3;
+ $hash{Anna} = 7;
+
+ my $keys = join ' ', keys %hash;
+
+ is $keys, 'Anna Bob Jim', 'keys are ordered';
+ is $hash{Bob}, 3, 'retrieval works';
+
+=head1 DESCRIPTION
+
+This module is not yet fully implemented. Current limitations include
+the CLEAR function not being implemented (meaning it is impossible to
+assign a list to a tied hash) and iteration being slow (O(n log n) to
+iterate over the whole hash). The latter is due to lack of suitable
+methods in the underlying L<Tree::SizeBalanced>.
+
+L<Tree::SizeBalanced> is an implementation of a size-balanced tree, a
+kind of self-balanced binary search tree. This is a data structure
+similar to a Perl hash that permits O(log n) insertion, deletion, and
+random access while keeping the keys sorted.
+
+This module is a C<tie> interface to L<Tree::SizeBalanced>. It allows
+one to create a hash that is implemented by a L<Tree::SizeBalanced>.
+These hashes should work similarly to regular Perl hashes except that
+keys will be ordered, keys can be any objects (not just strings), and
+they have different performance characteristics.
+
+The module is used by calling the tie function:
+
+=over
+
+=item B<tie> my %hash, 'Tie::Hash::Sorted::XS'[, I<$tree>]
+
+This ties a brand new hash to a given L<Tree::SizeBalanced> object (or
+if none is given, C<< Tree::SizeBalanced::str_any->new >> is used).
+
+Whenever this hash is iterated, the keys will come ordered.
+
+=back
+
+=head1 SEE ALSO
+
+L<Tree::SizeBalanced>, L<http://wcipeg.com/wiki/Size_Balanced_Tree>
+
+=head1 AUTHOR
+
+Marius Gavrilescu, E<lt>marius@ieval.roE<gt>
+
+=head1 COPYRIGHT AND LICENSE
+
+Copyright (C) 2018 by Marius Gavrilescu
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself, either Perl version 5.24.3 or,
+at your option, any later version of Perl 5 you may have available.
+
+
+=cut
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