Struct Sack 

pub struct Sack {
    pub largest_acked: u32,
    pub ack_delay_us: u32,
    /* private fields */
}

Available on crate feature std only.

A selective acknowledgement over a per-stream u32 sequence space.

ranges are inclusive (low, high) runs of acknowledged sequences, sorted descending (highest first), non-overlapping and non-adjacent. ranges[0].1 == largest_acked. An empty ranges slice is invalid — a Sack always ACKs at least one sequence.

Fields

largest_acked: u32

The highest sequence number covered by this ACK.

ack_delay_us: u32

Sender-measured delay between receiving the data packet and generating this ACK, in microseconds. Used by the BBR / RTT estimator.

Implementations

impl Sack

pub fn from_received(received: &[u32], ack_delay_us: u32) -> Option<Sack>

Build a Sack from an unordered slice of received sequence numbers.

Coalesces adjacent or overlapping sequences into the minimal set of inclusive (low, high) ranges sorted descending (highest first).

Returns None if received is empty (there is nothing to ACK).

pub fn from_inclusive_ranges( ranges: Vec<(u32, u32)>, ack_delay_us: u32, ) -> Option<Sack>

Build a Sack from explicit inclusive (low, high) ranges in any order (each must have low <= high). Ranges are sorted ascending, coalesced (adjacent/overlapping merged), reversed to descending, and capped to the highest MAX_SACK_RANGES so the encoded SACK always decodes at the peer (from_wire rejects range_count > MAX_SACK_RANGES). Dropping the lowest ranges is safe: those sequences are recovered by cumulative re-ACK as holes fill, or by RTO. Returns None if ranges is empty.

pub fn ranges(&self) -> &[(u32, u32)]

Returns the inclusive (low, high) ranges, sorted descending (highest first), non-overlapping and non-adjacent. Always non-empty.

pub fn to_wire(&self) -> Vec<u8>

Serialise to wire bytes.

Panics are structurally impossible: ranges is always non-empty (the invariant is enforced by the private field — every constructor (from_received, from_inclusive_ranges, from_wire) guarantees at least one range), and the arithmetic cannot overflow because all fields fit in u32.

pub fn from_wire(buf: &[u8]) -> Result<Sack, SackError>

Decode a Sack from wire bytes produced by Sack::to_wire.

Errors

See SackError for the full error table.

pub fn acks(&self, seq: u32) -> bool

Returns true if seq is covered by any range in this SACK.

Trait Implementations

impl Clone for Sack

fn clone(&self) -> Sack

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Sack

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

Formats the value using the given formatter.

impl Eq for Sack

impl PartialEq for Sack

fn eq(&self, other: &Sack) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Sack