// ObjectPool.cs

//

// Copyright (c) 2011 Novell

//

// Authors: 

//      Jérémie "garuma" Laval

//

// Permission is hereby granted, free of charge, to any person obtaining a copy

// of this software and associated documentation files (the "Software"), to deal

// in the Software without restriction, including without limitation the rights

// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the Software is

// furnished to do so, subject to the following conditions:

//

// The above copyright notice and this permission notice shall be included in

// all copies or substantial portions of the Software.

//

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

// THE SOFTWARE.

//

//





#if NET_3_5



using System;

using System.Threading;

using System.Collections;

using System.Collections.Generic;

using System.Runtime.Serialization;



namespace System.Collections.Concurrent

{

    internal abstract class ObjectPool<T> where T : class

    {

        const int capacity = 20;

        const int bit = 0x8000000;



        readonly T[] buffer;

        int addIndex;

        int removeIndex;



        public ObjectPool()

        {

            buffer = new T[capacity];

            for (int i = 0; i < capacity; i++)

                buffer[i] = Creator();

            addIndex = capacity - 1;

        }



        protected abstract T Creator();



        public T Take()

        {

            if ((addIndex & ~bit) - 1 == removeIndex)

                return Creator();



            int i;

            T result;

            int tries = 3;



            do

            {

                i = removeIndex;

                if ((addIndex & ~bit) - 1 == i || tries == 0)

                    return Creator();

                result = buffer[i % capacity];

            } while (Interlocked.CompareExchange(ref removeIndex, i + 1, i) != i && --tries > -1);



            return result;

        }



        public void Release(T obj)

        {

            if (obj == null || addIndex - removeIndex >= capacity - 1)

                return;



            int i;

            int tries = 3;

            do

            {

                do

                {

                    i = addIndex;

                } while ((i & bit) > 0);

                if (i - removeIndex >= capacity - 1)

                    return;

            } while (Interlocked.CompareExchange(ref addIndex, i + 1 + bit, i) != i && --tries > 0);



            buffer[i % capacity] = obj;

            addIndex = addIndex - bit;

        }

    }

}



#endif