Struct NoQueue 

pub struct NoQueue;

A no-op queue implementation used for phantom inputs and outputs.

NoQueue acts as a placeholder in the graph where a queue is required by type but no actual buffering or message transfer is desired. All enqueue attempts are rejected, and all dequeue or peek attempts return empty.

This is primarily useful for:

• Phantom or unconnected ports in a graph.
• Simplifying generic code that expects a queue type, without allocating unnecessary resources.
• Static analysis or testing scenarios where message flow is disabled.

Type Parameters

• P: Payload type of the Message carried by this queue.

Behavior

• Edge::try_push always returns EnqueueResult::Rejected.
• Edge::try_pop always returns QueueError::Empty.
• Edge::try_peek always returns QueueError::Empty.
• Edge::occupancy always reports zero items, zero bytes, and WatermarkState::AtOrAboveHard (fully saturated, disallowing admission).

Trait Implementations

impl Edge for NoQueue

fn try_push<H: HeaderStore>( &mut self, _token: MessageToken, _policy: &EdgePolicy, _headers: &H, ) -> EnqueueResult

Attempt to push a token onto the queue using the given edge policy.

fn try_pop<H: HeaderStore>( &mut self, _headers: &H, ) -> Result<MessageToken, QueueError>

Attempt to pop the front token from the queue.

fn occupancy(&self, _policy: &EdgePolicy) -> EdgeOccupancy

Return a snapshot of occupancy used for telemetry and admission.

fn is_empty(&self) -> bool

Return true if the queue is empty.

fn try_peek(&self) -> Result<MessageToken, QueueError>

Peek at the front token without removing it.

fn try_peek_at(&self, _index: usize) -> Result<MessageToken, QueueError>

Peek at the token at logical position index from the front.

fn try_pop_batch<H: HeaderStore>( &mut self, _policy: &BatchingPolicy, _headers: &H, ) -> Result<BatchView<'_, MessageToken>, QueueError>

Pop a batch of tokens according to the provided batching policy.

fn peek_header<'h, H: HeaderStore>( &self, headers: &'h H, ) -> Result<<H as HeaderStore>::HeaderGuard<'h>, QueueError>

Peek the front message header via HeaderStore (convenience).

fn get_admission_decision<H: HeaderStore>( &self, policy: &EdgePolicy, token: MessageToken, headers: &H, ) -> AdmissionDecision

Return an AdmissionDecision for the given token according to policy and the current occupancy snapshot.

fn get_admission_decision_from_message<P: Payload>( &self, policy: &EdgePolicy, message: &Message<P>, ) -> AdmissionDecision

Return an AdmissionDecision for the given token according to policy and the current occupancy snapshot.