README.md

C++ Cache implementation

This project implements a simple thread-safe cache with several page replacement policies:

• Least Recently Used
• First-In/First-Out
• Least Frequently Used

More about cache algorithms and policy you could read on Wikipedia

Usage

Using this library is simple. It is necessary to include header with the cache implementation (cache.hpp file) and appropriate header with the cache policy if it is needed. If not then the non-special algorithm will be used (it removes the last element which key is the last in the internal container).

Currently, there is only three of them:

• fifo_cache_policy.hpp
• lfu_cache_policy.hpp
• lru_cache_policy.hpp

Example for the LRU policy:

#include <string>
#include "cache.hpp"
#include "lru_cache_policy.hpp"

// alias for an easy class typing
template <typename Key, typename Value>
using lru_cache_t = typename caches::fixed_sized_cache<Key, Value, caches::LRUCachePolicy>;

void foo() {
  constexpr std::size_t CACHE_SIZE = 256;
  lru_cache_t<std::string, int> cache(CACHE_SIZE);

  cache.Put("Hello", 1);
  cache.Put("world", 2);
  
  const auto hello_value = cache.Get("Hello");
  const auto world_value = cache.Get("world");

  std::cout << *hello_value << *world_value << '\n';
  // "12"
}

Custom hashmap usage

You can use a custom hashmap implementation for the caches::fixed_sized_cache class which has the same interface std::unordered_map has.

For example, you can declare LRU cache type like that:

template <typename Key, typename Value>
using lru_cache_t = typename caches::fixed_sized_cache<Key, Value, caches::LRUCachePolicy,
                                                       phmap::node_hash_map<Key, Value>>;
// ...
lru_cache_t<std::string, std::size_t> cache{16};
cache.Put("Hello", 1);
std::cout << *cache.Get("Hello") << '\n';

See test implementation which uses parallel-hashmap.

Requirements

The only requirement is a compatible C++11 compiler.

This project was tested in the environments listed below:

• MinGW64 (MSYS2 project)
  • Clang 13.0+
  • GCC 7+
• MSVC (VS 2015)

If you have any issues with the library building, please let me know.

Contributing

Please fork this repository and contribute back using pull requests. Features can be requested using issues. All code, comments, and critiques are greatly appreciated.