ReferenceCounter.cs

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using System;
 
namespace Tgstation.Server.Host.Utils
{
    abstract class ReferenceCounter<TInstance> : IDisposable
        where TInstance : class
    {
        protected TInstance Instance => actualInstance ?? throw UninitializedOrDisposedException();
 
        readonly object initDisposeLock;
 
        TInstance? actualInstance;
 
        Action? referenceCleanupAction;
 
        bool initialized;
 
        protected ReferenceCounter()
        {
            initDisposeLock = new object();
        }
 
        public void Dispose()
        {
            lock (initDisposeLock)
            {
                referenceCleanupAction?.Invoke();
                referenceCleanupAction = null;
                actualInstance = null;
            }
        }
 
        public void Initialize(TInstance instance, Action referenceCleanupAction)
        {
            ArgumentNullException.ThrowIfNull(instance);
 
            ArgumentNullException.ThrowIfNull(referenceCleanupAction);
 
            lock (initDisposeLock)
            {
                if (initialized)
                    throw new InvalidOperationException($"{nameof(ReferenceCounter<TInstance>)} already initialized!");
 
                actualInstance = instance;
                this.referenceCleanupAction = referenceCleanupAction;
                initialized = true;
            }
        }
 
        protected void DangerousDropReference()
        {
            referenceCleanupAction = null;
        }
 
        InvalidOperationException UninitializedOrDisposedException()
        {
            if (initialized)
                return new ObjectDisposedException(nameof(ReferenceCounter<TInstance>));
 
            return new InvalidOperationException($"{nameof(ReferenceCounter<TInstance>)} not initialized!");
        }
    }
}