peekable

Capable of being peeked at or into.

Her fourteen dollhouses range in sophistication from a child-made primitive (1887) to an electrified manse set on a low table and peekable from all sides.

Of a stream or other sequence: from which the next value can be retrieved without advancing the pointer from its current position.

Peekable streams also have an internal record of their current position and can look ahead in the stream for information.