code: public synchronized void attach(SlabRef slab) {
          // Assume ownership of the caller's ref.  No need to call slab.addRef().
          checkState(!isAttached());
  
          _slab = slab;
          _slabConsumed = 0;
          _slabBytesConsumed = 0;
          _slabExpiresAt = System.currentTimeMillis() + Constants.SLAB_ROTATE_TTL.toMillis();
      }
docs: Attaches a new slab to the channel with the specified capacity.