//#define DISABLE_POOL
using System;
using System.Collections.Generic;
using System.Text;
namespace ObjectPool {
public interface IObjectPoolMethods : IDisposable {
/// <summary>
/// This method is used to setup an instance of
/// an object.
/// </summary>
/// <remarks>
/// Use an empty constructor in the class and
/// entirely rely on this method to setup and
/// initialize the object if the class is going
/// to be used for object pooling. Do not call this
/// method from the constructor or it will be called
/// twice and will affect performace.
/// </remarks>
/// <param name="setupParameters"></param>
void SetupObject(params object[] setupParameters);
/// <summary>
/// This event must be fired when dispose is called
/// or the Object Pool will not be able to work
/// </summary>
event EventHandler Disposing;
}
/// <summary>
/// A generic class that provide object pooling functionality
/// to classes that implement the IObjectPoolMethods interface
/// </summary>
/// <remarks>
/// As long as the lock(this) statements remain this class is thread
/// </remarks>
/// <typeparam name="T">
/// The type of the object that should be pooled
/// </typeparam>
public class ObjectPool<T> where T : IObjectPoolMethods, new() {
/// <summary>
/// The MAX_POOL does not restrict the maximum
/// number of objects in the object pool
/// instead it restricts the number of
/// disposed objects that the pool will maintain
/// a reference too and attempt to pool. This
/// number should be set based on a memory and
/// usage anaylsis based on the types of objects
/// being pooled. I have found the best results
/// by setting this number to average peak objects
/// in use at one time.
/// </summary>
/// <value>100</value>
private const int MAX_POOL = 2000;
/// <summary>
/// The static instance of the object pool. Thankfully the
/// use of generics eliminates the need for a hash for each
/// different pool type
/// </summary>
private static ObjectPool<T> me = new ObjectPool<T>();
/// <summary>
/// Using a member for the max pool count allows different
/// types to have a different value based on usage analysis
/// </summary>
private int mMaxPool = ObjectPool<T>.MAX_POOL;
/// <summary>
/// A Linked List of the WeakReferences to the objects in the pool
/// When the count of the list goes beyond the max pool count
/// items are removed from the end of the list. The objects at the
/// end of the list are also most likely to have already been collected
/// by the garbage collector.
/// </summary>
private LinkedList<WeakReference> objectPool = new LinkedList<WeakReference>();
/// <summary>
/// Return the singleton instance
/// </summary>
/// <returns>
/// The single instance allowed for the given type
/// </returns>
public static ObjectPool<T> GetInstance() {
return me;
}
/// <summary>
/// This method gets called on the object disposing
/// event for objects created from this object pool class.
/// If the implementing class does not fire this event on
/// dispose the object pooling will not work
/// </summary>
/// <param name="sender">
/// The class instance that is pooled
/// </param>
/// <param name="e">
/// An empty event args parameters
/// </param>
/// <exception cref="System.ArgumentException">
/// Thrown if the type of the object in the weak reference does not match
/// the type of this generic instance
/// </exception>
private void Object_Disposing(object sender, EventArgs e) {
//The lock is required here because this method may
//be called from events on different threads
lock (this) {
Add(new WeakReference(sender));
}
}
/// <summary>
/// This method will add a new instance to be tracked by
/// this object pooling class. This should be a reference
/// to an object that was just disposed otherwise it makes no
/// sense and will likely cause some serious problems.
/// </summary>
/// <param name="weak">
/// WeakReference to the object that was disposed
/// </param>
/// <exception cref="System.ArgumentException">
/// Thrown if the type of the object in the weak reference does not match
/// the type of this generic instance
/// </exception>
private void Add(WeakReference weak) {
objectPool.AddFirst(weak);
if (objectPool.Count >= mMaxPool) {
objectPool.RemoveLast();
}
}
/// <summary>
/// Remove the reference from the pool. This should
/// only be called when the object in the pool
/// is being reactivated or if the weak reference has
/// been determined to be expired.
/// </summary>
/// <param name="weak">
/// A reference to remove
/// </param>
/// <exception cref="System.ArgumentException">
/// Thrown if the type of the object in the weak reference does not match
/// the type of this generic instance
/// </exception>
private void Remove(WeakReference weak) {
objectPool.Remove(weak);
}
///<summary>
/// This method will verify that the type of the weak
/// reference is valid for this generic instance. I haven't
/// figured out a way do it automagically yet
/// </summary>
/// <exception cref="System.ArgumentException">
/// Thrown if the type of the object in the weak reference does not match
/// the type of this generic instance
/// </exception>
private void TypeCheck(WeakReference weak) {
if (weak.Target != null && weak.Target.GetType() != typeof(T)) {
throw new ArgumentException("Target type does not match pool type", "weak");
}
}
/// <summary>
/// This method will return an object reference that is fully
/// setup. It will either retrieve the object from the object
/// pool if there is a disposed object available or it will
/// create a new instance.
/// </summary>
/// <param name="setupParameters">
/// The setup parameters required for the
/// IObjectPoolMethods.SetupObject method. Need to find a
/// way to check for all of the types efficiently and at
/// compile time.
/// </param>
/// <returns>
/// The reference to the object
/// </returns>
public T GetObjectFromPool(params object[] setupParameters) {
T result = default(T);
#if DISABLE_POOL
result = new T();
result.SetupObject(setupParameters);
return result;
#else
lock (this) {
WeakReference remove = null;
foreach (WeakReference weak in objectPool) {
object o = weak.Target;
if (o != null) {
remove = weak;
result = (T)o;
GC.ReRegisterForFinalize(result);
break;
}
}
if (remove != null) {
objectPool.Remove(remove);
}
}
if (result == null) {
result = new T();
result.Disposing += new EventHandler(Object_Disposing);
}
result.SetupObject(setupParameters);
return result;
#endif
}
}
}
ObjectPool