copy
fun copy(src: PackedInts.Reader, srcPos: Int, dest: PackedInts.Mutable, destPos: Int, len: Int, mem: Int)
Copy src[srcPos:srcPos+len] into dest[destPos:destPos+len] using at most mem bytes.
fun copy(src: PackedInts.Reader, srcPos: Int, dest: PackedInts.Mutable, destPos: Int, len: Int, buf: LongArray)
Same as .copy but using a pre-allocated buffer.