collections -是否限制.NET中队列的大小?

Translate

我有一个初始化为2的Queue <T>对象,但是显然,这只是该容量,并且在添加项目时一直在扩展。是否已经有一个对象,当达到限制时,该对象会自动使项目出队,还是创建我自己的继承类的最佳解决方案?

This question and all comments follow the "Attribution Required."

所有的回答

Translate

我已经找到了所需的基本版本,虽然它不是完美的,但是它会一直起作用,直到出现更好的情况为止。

public class LimitedQueue<T> : Queue<T>
{
    public int Limit { get; set; }

    public LimitedQueue(int limit) : base(limit)
    {
        Limit = limit;
    }

    public new void Enqueue(T item)
    {
        while (Count >= Limit)
        {
            Dequeue();
        }
        base.Enqueue(item);
    }
}
来源
Translate

我建议您拉起C5库。与SCG(System.Collections.Generic)不同,C5被编程为接口并被设计为子类。大多数公共方法是虚拟的,没有一个类是密封的。这样,您将不必使用那个讨厌的“新”关键字,如果您的LimitedQueue<T>被铸成一个SCG.Queue<T>。使用C5并使用与以前几乎相同的代码,您将从CircularQueue<T>。的CircularQueue<T>实际上实现了一个堆栈和一个队列,因此您几乎可以免费获得两个带有限制的选项。我在下面用一些3.5结构重写了它:

using C5;

public class LimitedQueue<T> : CircularQueue<T>
{
    public int Limit { get; set; }

    public LimitedQueue(int limit) : base(limit)
    {
        this.Limit = limit;
    }

    public override void Push(T item)
    {
        CheckLimit(false);
        base.Push(item);
    }

    public override void Enqueue(T item)
    {
        CheckLimit(true);
        base.Enqueue(item);
    }

    protected virtual void CheckLimit(bool enqueue)
    {
        while (this.Count >= this.Limit)
        {
            if (enqueue)
            {
                this.Dequeue();
            }
            else
            {
                this.Pop();
            }
        }
    }
}

我认为这段代码应该完全符合您的期望。

来源
Translate

您应该创建自己的类,环形缓冲区可能会满足您的需求。

.NET中的数据结构允许您指定容量(数组除外),该数据结构用于构建用于保存内部数据的内部数据结构。

例如,对于列表,容量用于确定内部阵列的大小。当您开始向列表中添加元素时,它将开始从索引0开始填充该数组,当其达到您的容量时,它将容量增加到新的更高容量,并继续进行填充。

来源
Translate

您为什么不只使用大小为2的数组?队列应该能够动态增长和收缩。

或围绕的实例创建包装器类Queue<T>实例,并且每次进入一个队列<T>对象,请检查队列的大小。如果大于2,则使第一个项目出队。

来源
Translate

好吧,我希望这堂课对您有帮助:
在内部,循环FIFO缓冲区使用具有指定大小的Queue <T>。一旦达到缓冲区的大小,它将用新的替换旧的项目。

注意:您不能随机删除项目。我将方法Remove(T item)设置为返回false。如果您愿意,可以修改以随机删除项目

public class CircularFIFO<T> : ICollection<T> , IDisposable
{
    public Queue<T> CircularBuffer;

    /// <summary>
    /// The default initial capacity.
    /// </summary>
    private int capacity = 32;

    /// <summary>
    /// Gets the actual capacity of the FIFO.
    /// </summary>
    public int Capacity
    {
        get { return capacity; }          
    }

    /// <summary>
    ///  Initialize a new instance of FIFO class that is empty and has the default initial capacity.
    /// </summary>
    public CircularFIFO()
    {            
        CircularBuffer = new Queue<T>();
    }

    /// <summary>
    /// Initialize a new instance of FIFO class that is empty and has the specified initial capacity.
    /// </summary>
    /// <param name="size"> Initial capacity of the FIFO. </param>
    public CircularFIFO(int size)
    {
        capacity = size;
        CircularBuffer = new Queue<T>(capacity);
    }

    /// <summary>
    /// Adds an item to the end of the FIFO.
    /// </summary>
    /// <param name="item"> The item to add to the end of the FIFO. </param>
    public void Add(T item)
    {
        if (this.Count >= this.Capacity)
            Remove();

        CircularBuffer.Enqueue(item);
    }

    /// <summary>
    /// Adds array of items to the end of the FIFO.
    /// </summary>
    /// <param name="item"> The array of items to add to the end of the FIFO. </param>
     public void Add(T[] item)
    { 
        int enqueuedSize = 0;
        int remainEnqueueSize = this.Capacity - this.Count;

        for (; (enqueuedSize < item.Length && enqueuedSize < remainEnqueueSize); enqueuedSize++)
            CircularBuffer.Enqueue(item[enqueuedSize]);

        if ((item.Length - enqueuedSize) != 0)
        {
            Remove((item.Length - enqueuedSize));//remaining item size

            for (; enqueuedSize < item.Length; enqueuedSize++)
                CircularBuffer.Enqueue(item[enqueuedSize]);
        }           
    }

    /// <summary>
    /// Removes and Returns an item from the FIFO.
    /// </summary>
    /// <returns> Item removed. </returns>
    public T Remove()
    {
        T removedItem = CircularBuffer.Peek();
        CircularBuffer.Dequeue();

        return removedItem;
    }

    /// <summary>
    /// Removes and Returns the array of items form the FIFO.
    /// </summary>
    /// <param name="size"> The size of item to be removed from the FIFO. </param>
    /// <returns> Removed array of items </returns>
    public T[] Remove(int size)
    {
        if (size > CircularBuffer.Count)
            size = CircularBuffer.Count;

        T[] removedItems = new T[size];

        for (int i = 0; i < size; i++)
        {
            removedItems[i] = CircularBuffer.Peek();
            CircularBuffer.Dequeue();
        }

        return removedItems;
    }

    /// <summary>
    /// Returns the item at the beginning of the FIFO with out removing it.
    /// </summary>
    /// <returns> Item Peeked. </returns>
    public T Peek()
    {
        return CircularBuffer.Peek();
    }

    /// <summary>
    /// Returns the array of item at the beginning of the FIFO with out removing it.
    /// </summary>
    /// <param name="size"> The size of the array items. </param>
    /// <returns> Array of peeked items. </returns>
    public T[] Peek(int size)
    {
        T[] arrayItems = new T[CircularBuffer.Count];
        CircularBuffer.CopyTo(arrayItems, 0);

        if (size > CircularBuffer.Count)
            size = CircularBuffer.Count;

        T[] peekedItems = new T[size];

        Array.Copy(arrayItems, 0, peekedItems, 0, size);

        return peekedItems;
    }

    /// <summary>
    /// Gets the actual number of items presented in the FIFO.
    /// </summary>
    public int Count
    {
        get
        {
            return CircularBuffer.Count;
        }
    }

    /// <summary>
    /// Removes all the contents of the FIFO.
    /// </summary>
    public void Clear()
    {
        CircularBuffer.Clear();
    }

    /// <summary>
    /// Resets and Initialize the instance of FIFO class that is empty and has the default initial capacity.
    /// </summary>
    public void Reset()
    {
        Dispose();
        CircularBuffer = new Queue<T>(capacity);
    }

    #region ICollection<T> Members

    /// <summary>
    /// Determines whether an element is in the FIFO.
    /// </summary>
    /// <param name="item"> The item to locate in the FIFO. </param>
    /// <returns></returns>
    public bool Contains(T item)
    {
        return CircularBuffer.Contains(item);
    }

    /// <summary>
    /// Copies the FIFO elements to an existing one-dimensional array. 
    /// </summary>
    /// <param name="array"> The one-dimensional array that have at list a size of the FIFO </param>
    /// <param name="arrayIndex"></param>
    public void CopyTo(T[] array, int arrayIndex)
    {
        if (array.Length >= CircularBuffer.Count)
            CircularBuffer.CopyTo(array, 0);           
    }

    public bool IsReadOnly
    {
        get { return false; }
    }

    public bool Remove(T item)
    {
        return false; 
    }

    #endregion

    #region IEnumerable<T> Members

    public IEnumerator<T> GetEnumerator()
    {
       return CircularBuffer.GetEnumerator();
    }

    #endregion

    #region IEnumerable Members

    IEnumerator IEnumerable.GetEnumerator()
    {
        return CircularBuffer.GetEnumerator();
    }

    #endregion

    #region IDisposable Members

    /// <summary>
    /// Releases all the resource used by the FIFO.
    /// </summary>
    public void Dispose()
    {          
        CircularBuffer.Clear();
        CircularBuffer = null;
        GC.Collect();
    }

    #endregion
}
来源
Translate

并发解决方案

public class LimitedConcurrentQueue<ELEMENT> : ConcurrentQueue<ELEMENT>
{
    public readonly int Limit;

    public LimitedConcurrentQueue(int limit)
    {
        Limit = limit;
    }

    public new void Enqueue(ELEMENT element)
    {
        base.Enqueue(element);
        if (Count > Limit)
        {
            TryDequeue(out ELEMENT discard);
        }
    }
}

注意:Enqueue控制元素的添加,并且一次执行一次,因此无需执行while对于TryDequeue.

来源
Translate

如果对任何人有用,我做了LimitedStack<T>.

public class LimitedStack<T>
{
    public readonly int Limit;
    private readonly List<T> _stack;

    public LimitedStack(int limit = 32)
    {
        Limit = limit;
        _stack = new List<T>(limit);
    }

    public void Push(T item)
    {
        if (_stack.Count == Limit) _stack.RemoveAt(0);
        _stack.Add(item);
    }

    public T Peek()
    {
        return _stack[_stack.Count - 1];
    }

    public void Pop()
    {
        _stack.RemoveAt(_stack.Count - 1);
    }

    public int Count
    {
        get { return _stack.Count; }
    }
}

太大时,它将删除最旧的项目(堆栈底部)。

(此问题是“ C#限制堆栈大小”的Google排名最高的结果)

来源