AMQP10::Protocol::FrameReader

The read buffer is allocated once, sized for max_frame_size (at least MIN_MAX_FRAME_SIZE), and reused for every frame.

The largest frame the buffer can hold; max_frame_size can be lowered to at most this.

Largest frame accepted, header included; never more than the buffer holds.

Lowers the accepted frame size to the negotiated one without reallocating the buffer, so the reader used for the Open handshake can carry on serving the connection.

Resumable: when the IO raises partway through a frame, calling read again continues that frame with the bytes already read.