SPSCQueue¶

SPSCQueue is a lock-free, bounded-size single-producer/single-consumer queue optimized for HFT workloads. It supports in-place construction, zero allocations, and cache-line isolation.

template <typename T, size_t Capacity>
class SPSCQueue;

Purpose¶

Provide low-latency, zero-contention messaging between one writer and one reader.

Requirements¶

Capacity must be a power of two.
T must be nothrow-destructible.
Only one producer and one consumer may operate concurrently.

Key Features¶

Method	Description
`push(const T&)`	Enqueues a copy of an object.
`emplace(T&&)`	Enqueues an rvalue object (move).
`try_emplace(...)`	Constructs object in-place with arguments.
`pop(T&)`	Pops and moves the front element into `out`.
`try_pop()`	Returns a pointer to the front element, or `nullptr` if empty.
`try_pop_ref()`	Returns `std::optional<std::reference_wrapper<T>>` for inline access.
`empty()` / `full()`	Check queue state.
`clear()`	Destroys and drains all pending elements.
`size()`	Returns current number of elements.

Internal Design¶

Ring buffer implementation with Capacity entries, using modulo MASK = Capacity - 1.
_head and _tail are std::atomic<size_t> and are false-shared-safe via alignas(64).
Uses placement new for in-place construction, avoids heap entirely.

Notes¶

Optimized for predictable, sub-microsecond latency in tight loops.
No memory reclamation or ABA protection — not suitable for multi-producer/multi-consumer setups.
All methods use memory_order_acquire/release to ensure visibility across cores.
Destruction ensures safe draining of remaining elements via ~T() call.