Struct PendingAckQueue 

pub struct PendingAckQueue { /* private fields */ }

Fixed-capacity circular buffer of pending acks. Decouples TCP receives from journal fsync by allowing up to cap batches to be submitted to the journal stage before any ack is sent. Acks are flushed in FIFO order as the journal cursor advances.

Box<[PendingAck]> rather than Vec<PendingAck>: the capacity is fixed at construction; a slice avoids the Vec’s capacity field on every push/pop. cap is constrained to a power of two so the modulo on head + len lowers to a single AND.

Implementations

impl PendingAckQueue

pub fn new(cap: usize) -> PendingAckQueue

cap must be a power of two and ≥ 1.

pub fn is_full(&self) -> bool

pub fn is_empty(&self) -> bool

pub fn len(&self) -> usize

pub fn push(&mut self, journal_target: u64, acked_sequence: u64)

Record a pending ack. Caller must ensure !is_full().

pub fn pop_ready( &mut self, journal_cursor: &CachePadded<Atomic<u64>>, ) -> Option<u64>

Pop acks for all batches where the journal cursor has caught up. Non-blocking — returns None immediately if the oldest pending batch isn’t durable yet. Returns the highest acked sequence among the flushed entries.

pub fn pop_oldest_blocking( &mut self, journal_cursor: &CachePadded<Atomic<u64>>, busy_spin: bool, ) -> u64

Block until the oldest pending ack is durable, then pop all ready entries. Returns the highest acked sequence.

pub fn pop_all_blocking( &mut self, journal_cursor: &CachePadded<Atomic<u64>>, busy_spin: bool, ) -> Option<u64>

Block until ALL pending acks are durable. Returns the highest acked sequence, or None if the queue was already empty.