A hydraulic machine comprising a rotary toroidal piston chamber with two or more stationary pistons, which are provided to operate in such chamber, and having input and output ports for each piston provides a bidirectional motor or pump operable with high constant torque and high efficiency. Radially movable gates provide closed sections of the piston chamber and open to allow continuous rotation in one direction without reciprocating pistons or cranking mechanism. Rotation of the chamber is achieved by reaction to the force of hydraulic pressure on the pistons. A rotary piston chamber with four stationary pistons, operating as a four piston hydraulic motor simultaneously driving itself as a two piston pump functions as a pressure multiplier providing output pressure higher than the input pressure. Uses include sump pump, pumped energy storage and hydroelectric power generation.