using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Collections;

namespace MyTest
{
    class ManagedThreadPoolcs
    {
        public class Semaphore
        {
            #region Member Variables
            /// <summary>The number of units alloted by this semaphore.</summary> 
            private int _count;
            /// <summary>Lock for the semaphore.</summary> 
            private object _semLock = new object();
            #endregion

            #region Construction
            /// <summary> Initialize the semaphore as a binary semaphore.</summary> 
            public Semaphore()
                : this(1)
            {
            }

            /// <summary> Initialize the semaphore as a counting semaphore.</summary> 
            /// <param name="count">Initial number of threads that can take out units from this semaphore.</param> 
            /// <exception cref="ArgumentException">Throws if the count argument is less than 0.</exception> 
            public Semaphore(int count)
            {
                if (count < 0) throw new ArgumentException("Semaphore must have a count of at least 0.", "count");
                _count = count;
            }
            #endregion

            #region Synchronization Operations
            /// <summary>V the semaphore (add 1 unit to it).</summary> 
            public void AddOne() { V(); }

            /// <summary>P the semaphore (take out 1 unit from it).</summary> 
            public void WaitOne() { P(); }

            /// <summary>P the semaphore (take out 1 unit from it).</summary> 
            public void P()
            {
                // Lock so we can work in peace.  This works because lock is actually 
                // built around Monitor. 
                lock (_semLock)
                {
                    // Wait until a unit becomes available.  We need to wait 
                    // in a loop in case someone else wakes up before us.  This could 
                    // happen if the Monitor.Pulse statements were changed to Monitor.PulseAll 
                    // statements in order to introduce some randomness into the order 
                    // in which threads are woken. 
                    while (_count <= 0) Monitor.Wait(_semLock, Timeout.Infinite);
                    _count--;
                }
            }

            /// <summary>V the semaphore (add 1 unit to it).</summary> 
            public void V()
            {
                // Lock so we can work in peace.  This works because lock is actually 
                // built around Monitor. 
                lock (_semLock)
                {
                    // Release our hold on the unit of control.  Then tell everyone 
                    // waiting on this object that there is a unit available. 
                    _count++;
                    Monitor.Pulse(_semLock);
                }
            }

            /// <summary>Resets the semaphore to the specified count.  Should be used cautiously.</summary> 
            public void Reset(int count)
            {
                lock (_semLock) { _count = count; }
            }
            #endregion
        }

        /// <summary>Managed thread pool.</summary> 
        public class ManagedThreadPool
        {
            #region Constants
            /// <summary>Maximum number of threads the thread pool has at its disposal.</summary> 
            private const int _maxWorkerThreads = 80;
            #endregion

            #region Member Variables
            /// <summary>Queue of all the callbacks waiting to be executed.</summary> 
            private static Queue _waitingCallbacks;
            /// <summary> 
            /// Used to signal that a worker thread is needed for processing.  Note that multiple 
            /// threads may be needed simultaneously and as such we use a semaphore instead of 
            /// an auto reset event. 
            /// </summary> 
            private static Semaphore _workerThreadNeeded;
            /// <summary>List of all worker threads at the disposal of the thread pool.</summary> 
            private static ArrayList _workerThreads;
            /// <summary>Number of threads currently active.</summary> 
            private static int _inUseThreads;
            /// <summary>Lockable object for the pool.</summary> 
            private static object _poolLock = new object();
            #endregion

            #region Construction and Finalization
            /// <summary>Initialize the thread pool.</summary> 
            static ManagedThreadPool() { Initialize(); }

            /// <summary>Initializes the thread pool.</summary> 
            private static void Initialize()
            {
                // Create our thread stores; we handle synchronization ourself 
                // as we may run into situtations where multiple operations need to be atomic. 
                // We keep track of the threads we've created just for good measure; not actually 
                // needed for any core functionality. 
                _waitingCallbacks = new Queue();
                _workerThreads = new ArrayList();
                _inUseThreads = 0;

                // Create our "thread needed" event 
                _workerThreadNeeded = new Semaphore(0);

                // Create all of the worker threads 
                for (int i = 0; i < _maxWorkerThreads; i++)
                {
                    // Create a new thread and add it to the list of threads. 
                    Thread newThread = new Thread(new ThreadStart(ProcessQueuedItems));
                    _workerThreads.Add(newThread);

                    // Configure the new thread and start it 
                    newThread.Name = "ManagedPoolThread #" + i.ToString();
                    newThread.IsBackground = true;
                    newThread.Start();

                }
            }
            #endregion

            #region Public Methods
            /// <summary>Queues a user work item to the thread pool.</summary> 
            /// <param name="callback"> 
            /// A WaitCallback representing the delegate to invoke when the thread in the  
            /// thread pool picks up the work item. 
            ///  {
            /*  "caption": "销售查询",
              "children": [
                       {
                           "caption": "店铺货品销售明细",
                           "url": 'frame?url=http://www.lfx1848.com/ERP/ReportView/Store_Sale.aspx',
                       }
                 ]
               },
               {
              "caption": "库存查询",
              "children": [
                       {
                           "caption": "实时库存查询",
                           "url": 'frame?url=http://www.lfx1848.com/ERP/ReportView/Store_Stock.aspx',
                       }
                 ]
               }*/
            /// </param> 
            public static void QueueUserWorkItem(WaitCallback callback)
            {
                // Queue the delegate with no state 
                QueueUserWorkItem(callback, null);
            }

            /// <summary>Queues a user work item to the thread pool.</summary> 
            /// <param name="callback"> 
            /// A WaitCallback representing the delegate to invoke when the thread in the  
            /// thread pool picks up the work item. 
            /// </param> 
            /// <param name="state"> 
            /// The object that is passed to the delegate when serviced from the thread pool. 
            /// </param> 
            public static void QueueUserWorkItem(WaitCallback callback, object state)
            {
                // Create a waiting callback that contains the delegate and its state. 
                // At it to the processing queue, and signal that data is waiting. 
                WaitingCallback waiting = new WaitingCallback(callback, state);
                lock (_poolLock) { _waitingCallbacks.Enqueue(waiting); }
                _workerThreadNeeded.AddOne();
            }
            public static void CancellingAWorkItem()
            {
                CancellationTokenSource cts = new CancellationTokenSource();

                // Pass the CancellationToken and the number-to-count-to into the operation
                QueueUserWorkItem(o => Count(cts.Token, 1000));


                cts.Cancel();  // If Count returned already, Cancel has no effect on it
                // Cancel returns immediately, and the method continues running here...


            }
            private static void Count(CancellationToken token, Int32 countTo)
            {
                for (Int32 count = 0; count < countTo; count++)
                {
                    if (token.IsCancellationRequested)
                    {
                        //    Console.WriteLine("Count is cancelled");
                        break; // Exit the loop to stop the operation
                    }

                    Console.WriteLine(count);
                    Thread.Sleep(10);   // For demo, waste some time
                }
                Console.WriteLine("Count is done");
            }
            /// <summary>Empties the work queue of any queued work items.  Resets all threads in the pool.</summary> 
            public static void Reset()
            {
                lock (_poolLock)
                {
                    // Cleanup any waiting callbacks 
                    try
                    {
                        // Try to dispose of all remaining state 
                        foreach (object obj in _waitingCallbacks)
                        {
                            WaitingCallback callback = (WaitingCallback)obj;
                            if (callback.State is IDisposable) ((IDisposable)callback.State).Dispose();
                        }
                    }
                    catch { }

                    // Shutdown all existing threads 
                    try
                    {
                        foreach (Thread thread in _workerThreads)
                        {
                            if (thread != null) thread.Abort("reset");
                        }
                    }
                    catch { }

                    // Reinitialize the pool (create new threads, etc.) 
                    Initialize();
                }
            }
            #endregion

            #region Properties
            /// <summary>Gets the number of threads at the disposal of the thread pool.</summary> 
            public static int MaxThreads { get { return _maxWorkerThreads; } }
            /// <summary>Gets the number of currently active threads in the thread pool.</summary> 
            public static int ActiveThreads { get { return _inUseThreads; } }
            /// <summary>Gets the number of callback delegates currently waiting in the thread pool.</summary> 
            public static int WaitingCallbacks { get { lock (_poolLock) { return _waitingCallbacks.Count; } } }
            #endregion

            #region Thread Processing
            /// <summary>Event raised when there is an exception on a threadpool thread.</summary> 
            public static event UnhandledExceptionEventHandler UnhandledException;

            /// <summary>A thread worker function that processes items from the work queue.</summary> 
            private static void ProcessQueuedItems()
            {
                // Process indefinitely 
                while (true)
                {
                    _workerThreadNeeded.WaitOne();

                    // Get the next item in the queue.  If there is nothing there, go to sleep 
                    // for a while until we're woken up when a callback is waiting. 
                    WaitingCallback callback = null;

                    // Try to get the next callback available.  We need to lock on the  
                    // queue in order to make our count check and retrieval atomic. 
                    lock (_poolLock)
                    {
                        if (_waitingCallbacks.Count > 0)
                        {
                            try { callback = (WaitingCallback)_waitingCallbacks.Dequeue(); }
                            catch { } // make sure not to fail here 
                        }
                    }

                    if (callback != null)
                    {
                        // We now have a callback.  Execute it.  Make sure to accurately 
                        // record how many callbacks are currently executing. 
                        try
                        {
                            Interlocked.Increment(ref _inUseThreads);
                            callback.Callback(callback.State);
                        }
                        catch (Exception exc)
                        {
                            try
                            {
                                UnhandledExceptionEventHandler handler = UnhandledException;
                                if (handler != null) handler(typeof(ManagedThreadPool), new UnhandledExceptionEventArgs(exc, false));
                            }
                            catch { }
                        }
                        finally
                        {
                            Interlocked.Decrement(ref _inUseThreads);
                        }
                    }
                }
            }
            #endregion

            /// <summary>Used to hold a callback delegate and the state for that delegate.</summary> 
            private class WaitingCallback
            {
                #region Member Variables
                /// <summary>Callback delegate for the callback.</summary> 
                private WaitCallback _callback;
                /// <summary>State with which to call the callback delegate.</summary> 
                private object _state;
                #endregion

                #region Construction
                /// <summary>Initialize the callback holding object.</summary> 
                /// <param name="callback">Callback delegate for the callback.</param> 
                /// <param name="state">State with which to call the callback delegate.</param> 
                public WaitingCallback(WaitCallback callback, object state)
                {
                    _callback = callback;
                    _state = state;
                }
                #endregion

                #region Properties
                /// <summary>Gets the callback delegate for the callback.</summary> 
                public WaitCallback Callback { get { return _callback; } }
                /// <summary>Gets the state with which to call the callback delegate.</summary> 
                public object State { get { return _state; } }
                #endregion
            }
        }
    }
}