question: public static void overwrite ( long [ ] vector , long val , int offset , int len ) { int idx = offset > > 6 ; int bitIdx = offset & 63 ; int truncatedValLen = Math . min ( len , 64 - bitIdx ) ; vector [ idx ] &= ~ ( maskBelow ( truncatedValLen ) << bitIdx ) ; vector [ idx ] |= val << bitIdx ; if ( len != truncatedValLen ) { long mask = maskBelow ( len - truncatedValLen ) ; vector [ idx + 1 ] &= ~ mask ; vector [ idx + 1 ] |= ( val > > > truncatedValLen ) ; } }
target:  Overwrites a bit range within the vector.