What is the differential inverse kinematics algorithm used in the ROS Twist_Controller included in the Universal_Robots_ROS_controllers_cartesian package?

Hi,
I would like to use the ROS Twist_Controller to control the UR manipulator in velocity mode, but I cannot understand what type of differential inverse kinematics algorithm is used by the package, specifically whether a simple inverse Jacobian or a damped inverse is used to calculate the joint velocities required to move the end effector in velocity. I would also be satisfied with just finding the code file where the algorithm is defined.