code: func (c *Container) size() int {
  	if c.isArray() {
  		return len(c.array()) * 2 // sizeof(uint16)
  	} else if c.isRun() {
  		return len(c.runs())*interval16Size + runCountHeaderSize
  	} else {
  		return len(c.bitmap()) * 8 // sizeof(uint64)
  	}
  }
docs: // size returns the encoded size of the container, in bytes.