Struct MulticastBuffer 

pub struct MulticastBuffer<T> { /* private fields */ }

Pre-allocated SPMC multicast buffer with reference-counted slots.

Provides zero-allocation publish/consume on the hot path. The buffer is constructed in Ring 2 and used in Ring 0.

Type Parameters

• T - The event type. Must be Clone for consumers (typically Arc<RecordBatch> where clone is an O(1) atomic increment).

Performance Targets

Operation	Target
publish()	< 100ns
consume()	< 50ns

Implementations

impl<T> MulticastBuffer<T>

pub fn new(capacity: usize, consumer_count: usize) -> Self

Creates a new multicast buffer.

Allocates all slots up front (Ring 2). The hot path (publish/consume) is allocation-free.

Arguments

• capacity - Number of slots (must be a power of 2, > 0)
• consumer_count - Number of downstream consumers

Panics

Panics if capacity is not a power of 2 or is 0.

pub fn publish(&self, value: T) -> Result<(), DagError>

Publishes a value to all consumers.

Writes the value into the next available slot and sets the refcount to consumer_count. All consumers will be able to read this value via consume().

Errors

Returns DagError::BackpressureFull if the target slot is still in use by a slow consumer (backpressure).

Safety Contract

Must be called from a single writer thread only. The DAG executor enforces this by assigning exactly one producer per shared stage.

pub fn consume(&self, consumer_idx: usize) -> Option<T>

where T: Clone,

Consumes the next value for a given consumer.

Returns None if no new data is available. Each consumer maintains its own read position and will receive every published value in order.

Arguments

• consumer_idx - The consumer’s index (0-based, must be < consumer_count)

Panics

Panics in debug mode if consumer_idx >= consumer_count.

pub fn capacity(&self) -> usize

Returns the buffer capacity (number of slots).

pub fn consumer_count(&self) -> u32

Returns the number of consumers.

pub fn write_position(&self) -> u64

Returns the current write position (total number of publishes).

pub fn read_position(&self, consumer_idx: usize) -> u64

Returns the current read position for a consumer.

Panics

Panics if consumer_idx is out of bounds.

Trait Implementations

impl<T> Debug for MulticastBuffer<T>

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

Formats the value using the given formatter.

impl<T: Send> Send for MulticastBuffer<T>

impl<T: Send> Sync for MulticastBuffer<T>