Quack.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / System.Activities / System / Activities / Quack.cs / 1305376 / Quack.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------------------------

namespace System.Activities 
{
    using System; 
    using System.Runtime; 

    // A mostly output-restricted double-ended queue. You can add an item to both ends 
    // and it is optimized for removing from the front.  The list can be scanned and
    // items can be removed from any location at the cost of performance.
    class Quack
    { 
        T[] items;
 
        // First element when items is not empty 
        int head;
        // Next vacancy when items are not full 
        int tail;
        // Number of elements.
        int count;
 
        public Quack()
        { 
            this.items = new T[4]; 
        }
 
        public Quack(T[] items)
        {
            Fx.Assert(items != null, "This shouldn't get called with null");
            Fx.Assert(items.Length > 0, "This shouldn't be called with a zero length array."); 

            this.items = items; 
 
            // The default value of 0 is correct for both
            // head and tail. 

            this.count = this.items.Length;
        }
 
        public int Count
        { 
            get { return this.count; } 
        }
 
        public T this[int index]
        {
            get
            { 
                Fx.Assert(index < this.count, "Index out of range.");
 
                int realIndex = (this.head + index) % this.items.Length; 

                return this.items[realIndex]; 
            }
        }

        public T[] ToArray() 
        {
            Fx.Assert(this.count > 0, "We should only call this when we have items."); 
 
            T[] compressedItems = new T[this.count];
 
            for (int i = 0; i < this.count; i++)
            {
                compressedItems[i] = this.items[(this.head + i) % this.items.Length];
            } 

            return compressedItems; 
        } 

        public void PushFront(T item) 
        {
            if (this.count == this.items.Length)
            {
                Enlarge(); 
            }
 
            if (--this.head == -1) 
            {
                this.head = this.items.Length - 1; 
            }
            this.items[this.head] = item;

            ++this.count; 
        }
 
        public void Enqueue(T item) 
        {
            if (this.count == this.items.Length) 
            {
                Enlarge();
            }
 
            this.items[this.tail] = item;
            if (++this.tail == this.items.Length) 
            { 
                this.tail = 0;
            } 

            ++this.count;
        }
 
        public T Dequeue()
        { 
            Fx.Assert(this.count > 0, "Quack is empty"); 

            T removed = this.items[this.head]; 
            this.items[this.head] = default(T);
            if (++this.head == this.items.Length)
            {
                this.head = 0; 
            }
 
            --this.count; 

            return removed; 
        }

        public bool Remove(T item)
        { 
            int found = -1;
 
            for (int i = 0; i < this.count; i++) 
            {
                int realIndex = (this.head + i) % this.items.Length; 
                if (object.Equals(this.items[realIndex], item))
                {
                    found = i;
                    break; 
                }
            } 
 
            if (found == -1)
            { 
                return false;
            }
            else
            { 
                Remove(found);
                return true; 
            } 
        }
 
        public void Remove(int index)
        {
            Fx.Assert(index < this.count, "Index out of range");
 
            for (int i = index - 1; i >= 0; i--)
            { 
                int sourceIndex = (this.head + i) % this.items.Length; 
                int targetIndex = sourceIndex + 1;
 
                if (targetIndex == this.items.Length)
                {
                    targetIndex = 0;
                } 

                this.items[targetIndex] = this.items[sourceIndex]; 
            } 

            --this.count; 
            ++this.head;

            if (this.head == this.items.Length)
            { 
                this.head = 0;
            } 
        } 

        void Enlarge() 
        {
            Fx.Assert(this.items.Length > 0, "Quack is empty");

            int capacity = this.items.Length * 2; 
            this.SetCapacity(capacity);
        } 
 
        void SetCapacity(int capacity)
        { 
            Fx.Assert(capacity >= this.count, "Capacity is set to a smaller value");

            T[] newArray = new T[capacity];
            if (this.count > 0) 
            {
                if (this.head < this.tail) 
                { 
                    Array.Copy(this.items, this.head, newArray, 0, this.count);
                } 
                else
                {
                    Array.Copy(this.items, this.head, newArray, 0, this.items.Length - this.head);
                    Array.Copy(this.items, 0, newArray, this.items.Length - this.head, this.tail); 
                }
            } 
 
            this.items = newArray;
            this.head = 0; 
            this.tail = (this.count == capacity) ? 0 : this.count;
        }
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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Quack.cs source code in C# .NET

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