question: starts the clock . does nothing if the clock is already started . concode_field_sep long deltaUs concode_elem_sep long positionUs concode_elem_sep boolean started concode_field_sep long elapsedRealtimeMinus concode_elem_sep void stop concode_elem_sep long getPositionUs concode_elem_sep void setPositionUs
target: void function ( ) { if ( ! started ) { started = true ; deltaUs = elapsedRealtimeMinus ( positionUs ) ; } }