SHIFT_PER_LONG
dst += dst_idx >> SHIFT_PER_LONG;
src += src_idx >> SHIFT_PER_LONG;
dst += dst_idx >> SHIFT_PER_LONG;
dst += dst_idx >> SHIFT_PER_LONG;
dst += dst_idx >> SHIFT_PER_LONG;
src += src_idx >> SHIFT_PER_LONG;
dst += dst_idx >> SHIFT_PER_LONG;
src += src_idx >> SHIFT_PER_LONG;
dst += dst_idx >> SHIFT_PER_LONG;