code: func NewArena(size uint32) *Arena {
  	// Don't store data at position 0 in order to reserve offset=0 as a kind
  	// of nil pointer.
  	out := &Arena{
  		n:   1,
  		buf: make([]byte, size),
  	}
  
  	return out
  }
docs: // NewArena allocates a new arena of the specified size and returns it.