Struct PeerEntry 

#[repr(C)]
pub struct PeerEntry {
    pub state: AtomicU32,
    pub epoch: AtomicU32,
    pub last_heartbeat: AtomicU64,
    pub ring_offset: u64,
    pub _reserved: [u8; 40],
}

One 64-byte entry in the peer table.

r[impl shm.peer-table]

Fields

state: AtomicU32

Current peer state (Empty / Attached / Goodbye / Reserved).

epoch: AtomicU32

Incremented on each attach; used as an ABA counter for crash recovery.

last_heartbeat: AtomicU64

Monotonic clock reading (nanoseconds) of the last heartbeat.

ring_offset: u64

Byte offset from the start of the segment to this guest’s BipBuffer pair.

_reserved: [u8; 40]

Implementations

impl PeerEntry

pub unsafe fn init(&mut self, ring_offset: u64)

Write initial values for a new peer entry.

Safety

self must point into exclusively-owned, zeroed memory.

pub fn state(&self) -> PeerState

Read the current peer state.

pub fn epoch(&self) -> u32

Read the current epoch.

pub fn try_attach(&self) -> Result<u32, PeerState>

Attempt to attach: CAS Empty → Attached, increment epoch.

Returns Ok(new_epoch) on success, Err(actual) if the slot is not Empty.

pub fn try_reserve(&self) -> Result<u32, PeerState>

Reserve this slot before spawning a guest: CAS Empty → Reserved, increment epoch.

Returns Ok(new_epoch) on success, Err(actual) if the slot is not Empty.

pub fn try_claim_reserved(&self) -> Result<(), PeerState>

Claim a reserved slot: CAS Reserved → Attached.

Called by a spawned guest to complete the attach handshake. Returns Ok(()) on success, Err(actual) if the slot is not Reserved.

pub fn release_reserved(&self)

Release a reserved slot back to Empty (called by host if spawn fails).

pub fn set_goodbye(&self)

Mark this slot as Goodbye (orderly detach or crash detected by host).

pub fn reset(&self)

Reset to Empty (crash recovery — called by host after reclaiming slots).

pub fn update_heartbeat(&self, timestamp_ns: u64)

Write the current heartbeat timestamp.

timestamp_ns must be a monotonic clock reading in nanoseconds.

r[impl shm.crash.heartbeat-clock]

pub fn last_heartbeat(&self) -> u64

Read the last recorded heartbeat timestamp.

pub fn is_heartbeat_stale(&self, current_time_ns: u64, interval_ns: u64) -> bool

Return true if the heartbeat is stale (peer likely crashed).

A heartbeat is stale when current_time_ns - last_heartbeat > 2 * interval_ns. Always returns false when interval_ns == 0 (heartbeats disabled).