Nuclex.Support/Source/Collections/Pool.cs

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#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2014 Nuclex Development Labs
This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.
You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion
using System;
using System.Collections.Generic;
using System.Text;
namespace Nuclex.Support.Collections {
/// <summary>Pool that recycles objects in order to avoid garbage build-up</summary>
/// <typeparam name="TItem">Type of objects being pooled</typeparam>
/// <remarks>
/// <para>
/// Use this class to recycle objects instead of letting them become garbage,
/// creating new instances each time. The Pool class is designed to either be
/// used on its own or as a building block for a static class that wraps it.
/// </para>
/// <para>
/// Special care has to be taken to revert the entire state of a recycled
/// object when it is returned to the pool. For example, events will need to
/// have their subscriber lists emptied to avoid sending out events to the
/// wrong subscribers and accumulating more and more subscribers each time
/// they are reused.
/// </para>
/// <para>
/// To simplify such cleanup, pooled objects can implement the IRecyclable
/// interface. When an object is returned to the pool, the pool will
/// automatically call its IRecyclable.Recycle() method.
/// </para>
/// </remarks>
public class Pool<TItem> {
/// <summary>Default number of recyclable objects the pool will store</summary>
public const int DefaultPoolSize = 64;
/// <summary>Initializes a new pool using the default capacity</summary>
public Pool() : this(DefaultPoolSize, null, null) { }
/// <summary>Initializes a new pool using the default capacity</summary>
/// <param name="createNewDelegate">Delegate that will be used to create new items</param>
public Pool(Func<TItem> createNewDelegate) :
this(DefaultPoolSize, createNewDelegate, null) { }
/// <summary>Initializes a new pool using the default capacity</summary>
/// <param name="createNewDelegate">Delegate that will be used to create new items</param>
/// <param name="recycleDelegate">Delegate that will be used to recycle items</param>
public Pool(Func<TItem> createNewDelegate, Action<TItem> recycleDelegate) :
this(DefaultPoolSize, createNewDelegate, recycleDelegate) { }
/// <summary>Initializes a new pool using a user-specified capacity</summary>
/// <param name="capacity">Capacity of the pool</param>
public Pool(int capacity) :
this(capacity, null, null) { }
/// <summary>Initializes a new pool using a user-specified capacity</summary>
/// <param name="capacity">Capacity of the pool</param>
/// <param name="createNewDelegate">Delegate that will be used to create new items</param>
public Pool(int capacity, Func<TItem> createNewDelegate) :
this(capacity, createNewDelegate, null) { }
/// <summary>Initializes a new pool using a user-specified capacity</summary>
/// <param name="capacity">Capacity of the pool</param>
/// <param name="createNewDelegate">Delegate that will be used to create new items</param>
/// <param name="recycleDelegate">Delegate that will be used to recycle items</param>
public Pool(int capacity, Func<TItem> createNewDelegate, Action<TItem> recycleDelegate) {
Capacity = capacity;
if(createNewDelegate == null) {
if(!typeof(TItem).HasDefaultConstructor()) {
throw new ArgumentException(
"Type " + typeof(TItem).Name + " has no default constructor and " +
"requires a custom 'create instance' delegate"
);
}
createNewDelegate = new Func<TItem>(Activator.CreateInstance<TItem>);
}
if(recycleDelegate == null) {
recycleDelegate = new Action<TItem>(callRecycleIfSupported);
}
this.createNewDelegate = createNewDelegate;
this.recycleDelegate = recycleDelegate;
}
/// <summary>
/// Returns a new or recycled instance of the types managed by the pool
/// </summary>
/// <returns>A new or recycled instance</returns>
public TItem Get() {
lock(this) {
if(this.items.Count > 0) {
return this.items.Dequeue();
} else {
return this.createNewDelegate();
}
}
}
/// <summary>
/// Redeems an instance that is no longer used to be recycled by the pool
/// </summary>
/// <param name="item">The instance that will be redeemed</param>
public void Redeem(TItem item) {
// Call Recycle() when the object is redeemed (instead of when it leaves
// the pool again) in order to eliminate any references the object may hold
// to other objects.
this.recycleDelegate(item);
lock(this) {
if(this.items.Count < this.capacity) {
this.items.Enqueue(item);
}
}
}
/// <summary>Number of objects the pool can retain</summary>
/// <remarks>
/// Changing this value causes the pool to be emtpied. It is recommended that
/// you only read the pool's capacity, never change it.
/// </remarks>
public int Capacity {
get { return this.capacity; }
set {
this.capacity = value;
this.items = new Queue<TItem>(value);
}
}
/// <summary>
/// Calls the Recycle() method on an objects if it implements
/// the IRecyclable interface
/// </summary>
/// <param name="item">
/// Object whose Recycle() method will be called if supported by the object
/// </param>
private static void callRecycleIfSupported(TItem item) {
IRecyclable recycleable = item as IRecyclable;
if(recycleable != null) {
recycleable.Recycle();
}
}
/// <summary>Objects being retained for recycling</summary>
private Queue<TItem> items;
/// <summary>Capacity of the pool</summary>
/// <remarks>
/// Required because the Queue class doesn't allow this value to be retrieved
/// </remarks>
private int capacity;
/// <summary>Delegate used to create new instances of the pool's type</summary>
private Func<TItem> createNewDelegate;
/// <summary>Delegate used to recycle instances</summary>
private Action<TItem> recycleDelegate;
}
} // namespace Nuclex.Support.Collections