Struct CausalLink 

pub struct CausalLink {
    pub origin_hash: u64,
    pub horizon_encoded: u64,
    pub sequence: u64,
    pub parent_hash: u64,
}

Causal link — 32 bytes prepended to each event in causal-framed EventFrames.

Wire format (32 bytes, no padding):

origin_hash:      8 bytes (u64) — entity identity
horizon_encoded:  8 bytes (u64) — compressed observed horizon
sequence:         8 bytes (u64) — monotonic per-entity
parent_hash:      8 bytes (u64) — xxh3 of (prev link ++ prev payload)

Fields are ordered with the smallest first; serialization uses explicit to_bytes/from_bytes, not transmute, so any in-memory padding the compiler chooses doesn’t leak to the wire.

Fields

origin_hash: u64

Entity identity. The low 32 bits match NetHeader::origin_hash (still u32 on the per-packet wire); the full u64 is used for chain integrity and cross-channel accounting where the wider tag avoids the ~65k peer birthday-collision floor a u32 truncation would produce.

horizon_encoded: u64

Compressed observed horizon (64-bit bloom sketch).

Approximate, with documented FPR-vs-cardinality table on HorizonEncoder — see state/horizon.rs. Tuned for ≲ 16 active origins per event; callers needing exact horizons at higher cardinalities must fall back to the out-of-band full-ObservedHorizon path (ObservedHorizon::has_observed).

sequence: u64

Monotonic sequence number from entity’s reference frame.

parent_hash: u64

xxh3 hash of the previous event’s (CausalLink bytes ++ payload bytes).

Implementations

impl CausalLink

pub fn genesis(origin_hash: u64, horizon_encoded: u64) -> CausalLink

Create the genesis link for a new entity (no parent).

pub fn next(&self, payload: &[u8], horizon_encoded: u64) -> Option<CausalLink>

Create the next link in a chain given the previous link and payload.

Returns None if the sequence number would overflow u64::MAX.

pub fn to_bytes(&self) -> [u8; 32]

Serialize to 32 bytes.

pub fn from_bytes(data: &[u8]) -> Option<CausalLink>

Deserialize from bytes. Returns None if too short.

pub fn is_genesis(&self) -> bool

Check if this is a genesis link (sequence 0, no parent).

Trait Implementations

impl Clone for CausalLink

fn clone(&self) -> CausalLink

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CausalLink

impl Debug for CausalLink

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

Formats the value using the given formatter.

impl Eq for CausalLink

impl PartialEq for CausalLink

fn eq(&self, other: &CausalLink) -> 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 CausalLink