Struct ResendSender 

pub struct ResendSender { /* private fields */ }

Go-Back-N sliding-window sender state machine.

Encapsulates sequence allocation, in-flight frame buffering, sliding-window bounds checks, cumulative ACK processing, round-trip time measurement, and timeout retransmission gathering.

Implementations

impl ResendSender

pub fn new(window_size: u8, max_retransmission_attempts: usize) -> Self

Creates a new sender state machine with the specified window size and retransmission limit.

Panics

Panics if window_size == 0 or window_size > 128, or if max_retransmission_attempts == 0.

pub fn base(&self) -> u8

Returns the current base sequence number (oldest unacknowledged frame).

pub fn next_seq(&self) -> u8

Returns the next sequence number to be assigned.

pub fn in_flight(&self) -> u8

Returns the number of frames currently in flight.

pub fn can_send(&self) -> bool

Returns true if another frame can be transmitted within the sliding window.

pub fn is_idle(&self) -> bool

Returns true if there are no in-flight unacknowledged frames.

pub fn retransmission_attempts(&self) -> usize

Returns the number of consecutive retransmission attempts made for the current window.

pub fn enqueue_frame( &mut self, session_id: u32, channel_id: u16, frame_type: FrameType, payload: &[u8], ) -> Result<(u8, Vec<u8>), FrameError>

Enqueues and encodes a new frame to be transmitted.

Note

This method is intended exclusively for sequenced outbound frames (such as FrameType::Data). Pure cumulative acknowledgments (FrameType::Ack) must not be enqueued into the sliding window; emit them directly using encode_frame or coordinate them via [AckTracker].

Errors

Returns FrameError::WindowFull if in_flight() >= window_size. Returns FrameError::PayloadTooLarge if payload.len() > MAX_PAYLOAD_SIZE.

pub fn handle_ack(&mut self, ack_seq: u8) -> AckOutcome

Processes an incoming cumulative acknowledgment.

If ack_seq is within [base, next_seq), all frames from base through ack_seq are removed from the buffer, base is advanced to ack_seq + 1, retransmission attempts are reset to 0, and the elapsed RTT for ack_seq is returned in AckOutcome::Advanced.

pub fn handle_timeout( &mut self, ) -> Result<Vec<Vec<u8>>, RetransmissionLimitExceeded>

Handles a retransmission timer timeout.

Increments retransmission_attempts. If the limit is reached, returns Err(RetransmissionLimitExceeded). Otherwise, gathers and returns clones of all unacknowledged frames from base to next_seq and updates their transmission timestamps.

Errors

Returns RetransmissionLimitExceeded if retransmission_attempts >= max_retransmission_attempts. Callers should call reset() before reusing the sender after exceeding the limit.

pub fn reset(&mut self)

Resets the sender to an empty initial state.

Trait Implementations

impl Debug for ResendSender

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ResendSender

fn default() -> Self

Returns the “default value” for a type.