jimmcslim / lrucache

An implementation of a cache with a maximum size and a least recently used eviction policy.

LRUCache

Overview

It is an implementation of a cache that implements a Least Recently Used (LRU) eviction policy. The policy is only enforced when the cache is updated via the AddOrUpdate method; i.e. there are no background threads periodically sweeping out data that hasn't been recently accessed.

The solution LRUCache.sln contains two projects:

• DataStructures.csproj: this contains the ICache interface as specified by the coding challenge, and a Cache class that implements this interface using the LRU policy. Both classes are in the FoneDynamics.DataStructures namespace.
• DataStructures.Tests.csproj: the unit test suite for this project. Code coverage is measured at 100% using JetBrains dotCover. The tests are implemented using NUnit 3.

Both projects use .NET Framework 4.7.1 as their target framework.

All operations on this cache have O(1) time complexity; i.e. the time taken to perform an operation is not influenced by the number of items in the cache.

ICache<TKey, TValue> Interface

The following interface is implemented:

public interface ICache<TKey, TValue>
{
    /// <summary>
    /// Adds the value to the cache against the specified key.
    /// If the key already exists, its value is updated.
    /// </summary>
    void AddOrUpdate(TKey key, TValue value);

    /// <summary>
    /// Attempts to get the value from the cache against the specified key
    /// and returns true if the key exists in the cache.
    /// </summary>
    bool TryGetValue(TKey key, out TValue value);
}

Both calls on this interface make key the most recently used of all the keys stored by the cache.