Micosoft.Extension.ObjectPool
源码架构、模式分析：
三大基本对象：
- ObjectPool抽象类
- ObjectPoolProvider抽象类
- IPooledObjectPolicy接口
ObjectPool的默认实现是DefaultPool,对象池的创建由ObjectPoolProvider抽象类的默认实现DefaultObjectPoolProvider类实现。
代码语言：javascript复制public class DefaultObjectPoolProvider : ObjectPoolProvider
{
/// <summary>
/// The maximum number of objects to retain in the pool.
/// </summary>
public int MaximumRetained { get; set; } = Environment.ProcessorCount * 2;
/// <inheritdoc/>
public override ObjectPool<T> Create<T>(IPooledObjectPolicy<T> policy)
{
if (policy == null)
{
throw new ArgumentNullException(nameof(policy));
}
if (typeof(IDisposable).IsAssignableFrom(typeof(T)))
{
return new DisposableObjectPool<T>(policy, MaximumRetained);
}
return new DefaultObjectPool<T>(policy, MaximumRetained);
}
}IPooledObjectPolicy接口有对应的抽象类及默认实现，对象池中的对象(也就是池对象)的创建或返回由此策略类来控制。
代码语言：javascript复制public override T Get()
{
var item = _firstItem;
if (item == null || Interlocked.CompareExchange(ref _firstItem, null, item) != item)
{
var items = _items;
for (var i = 0; i < items.Length; i )
{
item = items[i].Element;
if (item != null && Interlocked.CompareExchange(ref items[i].Element, null, item) == item)
{
return item;
}
}
item = Create();
}
return item;
}
// Non-inline to improve its code quality as uncommon path
[MethodImpl(MethodImplOptions.NoInlining)]
private T Create() => _fastPolicy?.Create() ?? _policy.Create();
public override void Return(T obj)
{
if (_isDefaultPolicy || (_fastPolicy?.Return(obj) ?? _policy.Return(obj)))
{
if (_firstItem != null || Interlocked.CompareExchange(ref _firstItem, obj, null) != null)
{
var items = _items;
for (var i = 0; i < items.Length && Interlocked.CompareExchange(ref items[i].Element, obj, null) != null; i)
{
}
}
}
}从整体的设计思路来说，提供者Provider用来提供具体的对象池，传入的参数也是策略类，而策略类则把控池对象的具体处理。dotnet core中很多源码的开发模式都是这种：通过Policy构建Provider，通过Provider创建最终的类。也就是说，只通过策略类来实现自定义扩展，这种架构可以借鉴和思考。
