code: func (p *Pool) Get(size int) (interface{}, int) {
  	n := p.size(size)
  	if pool := p.pool[n]; pool != nil {
  		return pool.Get(), n
  	}
  	return nil, size
  }
docs: // Get pulls object whose generic size is at least of given size.
  // It also returns a real size of x for further pass to Put() even if x is nil.
  // Note that size could be ceiled to the next power of two.