SPSCQueue

The SPSCQueue is a lock-free, single-producer single-consumer queue optimized for high-throughput, low-latency communication.

Purpose

To provide efficient inter-thread message passing without dynamic memory allocation or locks.

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Template Parameters

template <typename T, size_t Capacity>
class SPSCQueue;

• T: Type of element (must be nothrow destructible)
• Capacity: Power-of-two queue size

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Interface Summary

bool push(const T &item);
bool emplace(T &&item);
template <typename... Args> bool try_emplace(Args&&...);
bool pop(T &out);
T* try_pop();
std::optional<std::reference_wrapper<T>> try_pop_ref();
bool empty() const;
bool full() const;
size_t size() const;

Responsibilities

• Store a bounded ring buffer of T
• Allow single-producer push and single-consumer pop without contention
• Maintain high cache locality and eliminate allocations

Internals

• Based on a circular buffer
• _head and _tail are padded to avoid false sharing
• Uses std::aligned_storage_t to store elements without constructing them prematurely

Notes

• Capacity must be a power of two
• Used internally in MarketDataBus to deliver events to each subscriber
• Destructs all remaining elements on shutdown

Example Use

SPSCQueue<int, 1024> queue;
queue.push(42);
int x;
if (queue.pop(x)) { /* use x */ }