question: public static long [ ] interpose ( long [ ] vector , int vectorLen , int offset , int len ) { long [ ] updated = create ( vectorLen + len ) ; int idx = offset > > 6 ; System . arraycopy ( vector , 0 , updated , 0 , idx ) ; if ( idx < vector . length ) { int delta = offset & 63 ; updated [ idx ] |= vector [ idx ] & maskBelow ( delta ) ; } copy ( vector , offset , updated , offset + len , vectorLen - offset ) ; return updated ; }
target:  Returns a copy of the vector, with an empty bit range inserted at the specified location.