Supply.decode implementation

gistfile1.txt

        supply {
            my $decoder = Encoding::Registry.find($encoding).decoder;
            my $chars;
            whenever self -> \bytes {
                $decoder.add-bytes(bytes);
                $chars := $decoder.consume-available-chars;
                emit $chars if $chars;

                LAST {
                    $chars := $decoder.consume-all-chars;
                    emit $chars if $chars;
                }
            }
        }