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.