transport

type Codec interface {
	Encode(*capnp.Message) error
	Decode() (*capnp.Message, error)

	// Mark a message previously returned by Decode as no longer needed. The
	// Codec may re-use the space for future messages.
	ReleaseMessage(*capnp.Message)
	Close() error
}

type Transport interface {
	// NewMessage allocates a new message to be sent over the transport.
	// The caller must call the release function when it no longer needs
	// to reference the message. Calling the release function more than once
	// has no effect. Before releasing the message, send may be called at most
	// once to send the mssage.
	//
	// Messages returned by NewMessage must have a nil CapTable.
	// When the returned ReleaseFunc is called, any clients in the message's
	// CapTable will be released.
	//
	// The Arena in the returned message should be fast at allocating new
	// segments.  The returned ReleaseFunc MUST be safe to call concurrently
	// with subsequent calls to NewMessage.
	NewMessage() (_ rpccp.Message, send func() error, _ capnp.ReleaseFunc, _ error)

	// RecvMessage receives the next message sent from the remote vat.
	// The returned message is only valid until the release function is
	// called.  The release function may be called concurrently with
	// RecvMessage or with any other release function returned by RecvMessage.
	//
	// Messages returned by RecvMessage must have a nil CapTable.
	// When the returned ReleaseFunc is called, any clients in the message's
	// CapTable will be released.
	//
	// The Arena in the returned message should not fetch segments lazily;
	// the Arena should be fast to access other segments.
	RecvMessage() (rpccp.Message, capnp.ReleaseFunc, error)

	// Close releases any resources associated with the transport. If there
	// are any outstanding calls to NewMessage, a returned send function,
	// or RecvMessage, they will be interrupted and return errors.
	Close() error
}