loon – High-Performance, Header-Only Modern C++ Library

loon is a lightweight, header-only C++ library designed for low memory footprint, low latency, and maximum performance. It provides optimized data structures that outperform standard STL counterparts while maintaining familiar interfaces.

Perfect for HFT, gaming, embedded systems, and real-time processing.

Key Features

Feature	Description
Zero-Cost Abstractions	Header-only, no external dependencies
STL-Compliant	Drop-in replacements with familiar APIs
Cache-Efficient	Optimized memory layout, contiguous storage
Low Latency	No dynamic allocation on critical paths
High Performance	Up to 3-4x faster than std:: alternatives

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Data Structures

Structure	Header	Description	Performance
RingBuffer	loon/ring_buffer.hpp	Fixed-size circular queue	3.2x faster than std::queue
SpscQueue	loon/spsc.hpp	Lock-free single-producer single-consumer queue	18.7x faster than mutex queue
LRU Cache	loon/lru.hpp	Least Recently Used cache	O(1) get/put
RedisList	loon/redis_list.hpp	Redis-style doubly-linked list	O(1) push/pop

Complexity Summary

Structure	push	pop	get	put	front/back
RingBuffer	O(1)	O(1)	-	-	O(1)
SpscQueue	O(1)	O(1)	-	-	-
LRU Cache	-	-	O(1)	O(1)	-
RedisList	O(1)	O(1)	-	-	O(1)

Benchmark Highlights

Benchmark	loon	std/mutex	Speedup
RingBuffer round-trip (16B)	1.9 ns	6.1 ns	3.2x
SpscQueue interleaved	2.40 ns	44.9 ns	18.7x
SpscQueue producer/consumer	485M ops/s	26M ops/s	19.5x
LRU Cache get (hit)	15 ns	-	67M ops/s
LRU Cache exists	7.8 ns	-	130M ops/s
RedisList push/pop	3.6 ns	78.5 ns	22x vs std::list

See full benchmarks for detailed results.

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Installation

Using Conan (recommended)

# conanfile.txt
[requires]
loon/0.2.0

# conanfile.py
def requirements(self):
    self.requires("loon/0.2.0")

Header-only (manual)

Copy the include/loon directory to your project and add it to your include path.

CMake

find_package(loon REQUIRED)
target_link_libraries(your_target PRIVATE loon::loon)

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Quick Start

RingBuffer

#include <loon/ring_buffer.hpp>

loon::RingBuffer<int, 1024> buffer;       // fixed capacity, reject when full
loon::RingBuffer<int, 1024> ring(true);   // override oldest when full

buffer.push(42);
auto val = buffer.pop();    // std::optional<int>
buffer.front();             // peek without removing

SPSC Queue

#include <loon/spsc.hpp>

loon::SpscQueue<int, 1024> queue;

// Producer thread
queue.push(42);

// Consumer thread
int value;
if (queue.pop(value)) {
    // use value
}

LRU Cache

#include <loon/lru.hpp>

loon::LRU<int, std::string> cache(100);  // capacity of 100

cache.put(1, "hello");
auto val = cache.get(1);  // std::optional<std::reference_wrapper<V>>
if (val) {
    std::cout << val->get();  // "hello"
}

RedisList

#include <loon/redis_list.hpp>

loon::RedisList<int> list;

list.lpush(1);                    // push front
list.rpush(2);                    // push back
auto val = list.lpop();           // pop front
auto range = list.lrange(0, -1);  // get all (supports negative indices)

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Building from Source

Prerequisites

• C++23 compatible compiler (GCC 13+, Clang 14+)
• CMake 3.20+
• Conan 2.x

Build & Test

make conan-setup    # one-time setup
make deps           # install dependencies
make build          # build and run tests
make package        # create Conan package

Other Targets

make help           # show all targets
make bench          # run benchmarks
make coverage       # generate coverage report
make docs-serve     # serve documentation locally
make format         # apply clang-format

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Documentation

Full documentation available at jsrivaya.github.io/loon

• Getting Started
• API Reference
• Benchmarks

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License

MIT License - see LICENSE for details.