IOCP是一种高性能的I/O模型，更多资料可以google下。
在.Net Framework下，没有提供IOCP的类库，我们需要引入Win32 API来建立IOCP Thread Pool。
我们用CreateIOCompletionPort获得一个IOCP对象的句柄，用PostQueuedCompetionStatus把状态对象（Socket编程下一般系传socket）放进队列，开启一定量线程来运行GetQueuedCompletionStatus监听，GetQueuedCompletionStatus函数会阻塞调用线程。
由于与非托管代码打交道，要实现Safe的代码，有几点需要注意。
1.我们要传递一个状态对象地址给非托管代码，由于GC的关系，我们不能直接传递地址，因为GC在回收的过程中，会移动在堆上的对象，造成地址改变。一般来说，GC移动会修改托管代码里面地址指向，但我们现在把地址传递出托管代码范围，GC也无能为力了。情况如图。
针对这种情况，可以用GCHandle类解决，GCHandle类的Alloc方法为对象注册，Alloc方法有两个参数，第二个参数系GCHandleType类型枚举，默认情况系Normal。当我们要GC不移动对象的时候，例如有个byte[]的Buffer需要非托管代码填充，可以使用Pinned。
GCHandle gch = GCHandle.Alloc(obj); PostQueuedCompletionStatus(GetHandle, (uint)Marshal.SizeOf(gch), IntPtr.Zero, (IntPtr)gch); |
2.PostQueuedCompletionStatus函数的第二个参数是要传送数据的长度，直接使用sizeof系unsafe代码，这里使用Marshal.SizeOf方法。
3.还有需要注意的是，传递的对象必须实现[StructLayout(LayoutKind.Sequential)]标签，以保证该对象的成员在内存里连续分配，遵守C++方式。
4.利用SafeFileHandle引用内核对象更安全，这个类能实现引用计数。
至此，已经讲述完实现Safe代码的要点了。
IOCPThreadPool的实现代码：
{
[StructLayout(LayoutKind.Sequential)]
public class MyData
{
private int value;
public int Value
{
get { return value; }
set { this.value = value; }
}
}
// Classes
//============================================
/// <summary> This class provides the ability to create a thread pool to manage work. The
/// class abstracts the Win32 IOCompletionPort API so it requires the use of
/// unmanaged code. Unfortunately the .NET framework does not provide this functionality </summary>
public sealed class SafeIOCPThreadPool
{
// Win32 Function Prototypes
/// <summary> Win32Func: Create an IO Completion Port Thread Pool </summary>
[DllImport("Kernel32", CharSet = CharSet.Auto)]
private static extern SafeFileHandle CreateIoCompletionPort(IntPtr hFile, IntPtr hExistingCompletionPort, IntPtr puiCompletionKey, UInt32 uiNumberOfConcurrentThreads);
/// <summary> Win32Func: Closes an IO Completion Port Thread Pool </summary>
[DllImport("Kernel32", CharSet = CharSet.Auto)]
private static extern Boolean CloseHandle(SafeHandle hObject);
/// <summary> Win32Func: Posts a context based event into an IO Completion Port Thread Pool </summary>
[DllImport("Kernel32", CharSet = CharSet.Auto)]
private static extern Boolean PostQueuedCompletionStatus(SafeFileHandle hCompletionPort, UInt32 uiSizeOfArgument, IntPtr dwCompletionKey, IntPtr pOverlapped);
/// <summary> Win32Func: Waits on a context based event from an IO Completion Port Thread Pool.
/// All threads in the pool wait in this Win32 Function </summary>
[DllImport("Kernel32", CharSet = CharSet.Auto)]
private static extern Boolean GetQueuedCompletionStatus(SafeFileHandle hCompletionPort, out UInt32 pSizeOfArgument, out IntPtr dwCompletionKey, out IntPtr ppOverlapped, UInt32 uiMilliseconds);
// Constants
/// <summary> SimTypeConst: This represents the Win32 Invalid Handle Value Macro </summary>
private readonly IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);
/// <summary> SimTypeConst: This represents the Win32 INFINITE Macro </summary>
private readonly UInt32 INIFINITE = 0xffffffff;
/// <summary> SimTypeConst: This tells the IOCP Function to shutdown </summary>
private readonly IntPtr SHUTDOWN_IOCPTHREAD = new IntPtr(0x7fffffff);
// Delegate Function Types
/// <summary> DelType: This is the type of user function to be supplied for the thread pool </summary>
public delegate void USER_FUNCTION(MyData obj);
// Private Properties
private SafeFileHandle m_hHandle;
/// <summary> SimType: Contains the IO Completion Port Thread Pool handle for this instance </summary>
private SafeFileHandle GetHandle { get { return m_hHandle; } set { m_hHandle = value; } }
private Int32 m_uiMaxConcurrency;
/// <summary> SimType: The maximum number of threads that may be running at the same time </summary>
private Int32 GetMaxConcurrency { get { return m_uiMaxConcurrency; } set { m_uiMaxConcurrency = value; } }
private Int32 m_iMinThreadsInPool;
/// <summary> SimType: The minimal number of threads the thread pool maintains </summary>
private Int32 GetMinThreadsInPool { get { return m_iMinThreadsInPool; } set { m_iMinThreadsInPool = value; } }
private Int32 m_iMaxThreadsInPool;
/// <summary> SimType: The maximum number of threads the thread pool maintains </summary>
private Int32 GetMaxThreadsInPool { get { return m_iMaxThreadsInPool; } set { m_iMaxThreadsInPool = value; } }
private Object m_pCriticalSection;
/// <summary> RefType: A serialization object to protect the class state </summary>
private Object GetCriticalSection { get { return m_pCriticalSection; } set { m_pCriticalSection = value; } }
private USER_FUNCTION m_pfnUserFunction;
/// <summary> DelType: A reference to a user specified function to be call by the thread pool </summary>
private USER_FUNCTION GetUserFunction { get { return m_pfnUserFunction; } set { m_pfnUserFunction = value; } }
private Boolean m_bDisposeFlag;
/// <summary> SimType: Flag to indicate if the class is disposing </summary>
private Boolean IsDisposed { get { return m_bDisposeFlag; } set { m_bDisposeFlag = value; } }
// Public Properties
private Int32 m_iCurThreadsInPool;
/// <summary> SimType: The current number of threads in the thread pool </summary>
public Int32 GetCurThreadsInPool { get { return m_iCurThreadsInPool; } set { m_iCurThreadsInPool = value; } }
/// <summary> SimType: Increment current number of threads in the thread pool </summary>
private Int32 IncCurThreadsInPool() { return Interlocked.Increment(ref m_iCurThreadsInPool); }
/// <summary> SimType: Decrement current number of threads in the thread pool </summary>
private Int32 DecCurThreadsInPool() { return Interlocked.Decrement(ref m_iCurThreadsInPool); }
private Int32 m_iActThreadsInPool;
/// <summary> SimType: The current number of active threads in the thread pool </summary>
public Int32 GetActThreadsInPool { get { return m_iActThreadsInPool; } set { m_iActThreadsInPool = value; } }
/// <summary> SimType: Increment current number of active threads in the thread pool </summary>
private Int32 IncActThreadsInPool() { return Interlocked.Increment(ref m_iActThreadsInPool); }
/// <summary> SimType: Decrement current number of active threads in the thread pool </summary>
private Int32 DecActThreadsInPool() { return Interlocked.Decrement(ref m_iActThreadsInPool); }
private Int32 m_iCurWorkInPool;
/// <summary> SimType: The current number of Work posted in the thread pool </summary>
public Int32 GetCurWorkInPool { get { return m_iCurWorkInPool; } set { m_iCurWorkInPool = value; } }
/// <summary> SimType: Increment current number of Work posted in the thread pool </summary>
private Int32 IncCurWorkInPool() { return Interlocked.Increment(ref m_iCurWorkInPool); }
/// <summary> SimType: Decrement current number of Work posted in the thread pool </summary>
private Int32 DecCurWorkInPool() { return Interlocked.Decrement(ref m_iCurWorkInPool); }
// Constructor, Finalize, and Dispose
//***********************************************
/// <summary> Constructor </summary>
/// <param name = "iMaxConcurrency"> SimType: Max number of running threads allowed </param>
/// <param name = "iMinThreadsInPool"> SimType: Min number of threads in the pool </param>
/// <param name = "iMaxThreadsInPool"> SimType: Max number of threads in the pool </param>
/// <param name = "pfnUserFunction"> DelType: Reference to a function to call to perform work </param>
/// <exception cref = "Exception"> Unhandled Exception </exception>
public SafeIOCPThreadPool(Int32 iMaxConcurrency, Int32 iMinThreadsInPool, Int32 iMaxThreadsInPool, USER_FUNCTION pfnUserFunction)
{
try
{
// Set initial class state
GetMaxConcurrency = iMaxConcurrency;
GetMinThreadsInPool = iMinThreadsInPool;
GetMaxThreadsInPool = iMaxThreadsInPool;
GetUserFunction = pfnUserFunction;
// Init the thread counters
GetCurThreadsInPool = 0;
GetActThreadsInPool = 0;
GetCurWorkInPool = 0;
// Initialize the Monitor Object
GetCriticalSection = new Object();
// Set the disposing flag to false
IsDisposed = false;
// Create an IO Completion Port for Thread Pool use
GetHandle = CreateIoCompletionPort(INVALID_HANDLE_VALUE, IntPtr.Zero, IntPtr.Zero, (UInt32)GetMaxConcurrency);
// Test to make sure the IO Completion Port was created
if (GetHandle.IsInvalid)
throw new Exception("Unable To Create IO Completion Port");
// Allocate and start the Minimum number of threads specified
Int32 iStartingCount = GetCurThreadsInPool;
ThreadStart tsThread = new ThreadStart(IOCPFunction);
for (Int32 iThread = 0; iThread < GetMinThreadsInPool; ++iThread)
{
// Create a thread and start it
Thread thThread = new Thread(tsThread);
thThread.Name = "IOCP " + thThread.GetHashCode();
thThread.Start();
// Increment the thread pool count
IncCurThreadsInPool();
Console.WriteLine(thThread.Name);
}
}
catch (Exception)
{
throw;
}
}
//***********************************************
/// <summary> Finalize called by the GC </summary>
~SafeIOCPThreadPool()
{
if (!IsDisposed)
Dispose();
}
//**********************************************
/// <summary> Called when the object will be shutdown. This
/// function will wait for all of the work to be completed
/// inside the queue before completing </summary>
public void Dispose()
{
try
{
// Flag that we are disposing this object
IsDisposed = true;
// Get the current number of threads in the pool
Int32 iCurThreadsInPool = GetCurThreadsInPool;
// Shutdown all thread in the pool
for (Int32 iThread = 0; iThread < iCurThreadsInPool; ++iThread)
{
bool bret = PostQueuedCompletionStatus(GetHandle, 4, SHUTDOWN_IOCPTHREAD, IntPtr.Zero);
}
// Wait here until all the threads are gone
while (GetCurThreadsInPool != 0) Thread.Sleep(100);
// Close the IOCP Handle
CloseHandle(GetHandle);
}
catch
{
}
}
// Private Methods
//*******************************************
/// <summary> IOCP Worker Function that calls the specified user function </summary>
private void IOCPFunction()
{
UInt32 uiNumberOfBytes;
IntPtr dwCompletionKey;
IntPtr lpOverlapped;
try
{
while (true)
{
// Wait for an event
GetQueuedCompletionStatus(GetHandle, out uiNumberOfBytes, out dwCompletionKey, out lpOverlapped, INIFINITE);
if(uiNumberOfBytes <= 0)
{
continue;
}
// Decrement the number of events in queue
DecCurWorkInPool();
// Was this thread told to shutdown
if (dwCompletionKey == SHUTDOWN_IOCPTHREAD)
break;
// Increment the number of active threads
IncActThreadsInPool();
try
{
// Call the user function
GCHandle gch = GCHandle.FromIntPtr(lpOverlapped);
MyData obj = (MyData) gch.Target;
GetUserFunction(obj);
}
catch
{
throw;
}
// Get a lock
Monitor.Enter(GetCriticalSection);
try
{
// If we have less than max threads currently in the pool
if (GetCurThreadsInPool < GetMaxThreadsInPool)
{
// Should we add a new thread to the pool
if (GetActThreadsInPool == GetCurThreadsInPool)
{
if (IsDisposed == false)
{
// Create a thread and start it
ThreadStart tsThread = new ThreadStart(IOCPFunction);
Thread thThread = new Thread(tsThread);
thThread.Name = "IOCP " + thThread.GetHashCode();
thThread.Start();
// Increment the thread pool count
IncCurThreadsInPool();
}
}
}
}
catch
{
}
// Relase the lock
Monitor.Exit(GetCriticalSection);
// Increment the number of active threads
DecActThreadsInPool();
}
}
catch
{
}
// Decrement the thread pool count
DecCurThreadsInPool();
}
// Public Methods
//******************************************
/// <summary> IOCP Worker Function that calls the specified user function </summary>
/// <param name="obj"> SimType: A value to be passed with the event </param>
/// <exception cref = "Exception"> Unhandled Exception </exception>
public void PostEvent(MyData obj)
{
try
{
// Only add work if we are not disposing
if (IsDisposed == false)
{
// Post an event into the IOCP Thread Pool
GCHandle gch = GCHandle.Alloc(obj);
PostQueuedCompletionStatus(GetHandle, (uint)Marshal.SizeOf(gch), IntPtr.Zero, (IntPtr)gch);
// Increment the number of item of work
IncCurWorkInPool();
// Get a lock
Monitor.Enter(GetCriticalSection);
try
{
// If we have less than max threads currently in the pool
if (GetCurThreadsInPool < GetMaxThreadsInPool)
{
// Should we add a new thread to the pool
if (GetActThreadsInPool == GetCurThreadsInPool)
{
if (IsDisposed == false)
{
// Create a thread and start it
ThreadStart tsThread = new ThreadStart(IOCPFunction);
Thread thThread = new Thread(tsThread);
thThread.Name = "IOCP " + thThread.GetHashCode();
thThread.Start();
// Increment the thread pool count
IncCurThreadsInPool();
}
}
}
}
catch
{
}
// Release the lock
Monitor.Exit(GetCriticalSection);
}
}
catch (Exception e)
{
throw e;
}
catch
{
throw new Exception("Unhandled Exception");
}
}
//*****************************************
/// <summary> IOCP Worker Function that calls the specified user function </summary>
/// <exception cref = "Exception"> Unhandled Exception </exception>
public void PostEvent()
{
try
{
// Only add work if we are not disposing
if (IsDisposed == false)
{
// Post an event into the IOCP Thread Pool
PostQueuedCompletionStatus(GetHandle, 0, IntPtr.Zero, IntPtr.Zero);
// Increment the number of item of work
IncCurWorkInPool();
// Get a lock
Monitor.Enter(GetCriticalSection);
try
{
// If we have less than max threads currently in the pool
if (GetCurThreadsInPool < GetMaxThreadsInPool)
{
// Should we add a new thread to the pool
if (GetActThreadsInPool == GetCurThreadsInPool)
{
if (IsDisposed == false)
{
// Create a thread and start it
ThreadStart tsThread = new ThreadStart(IOCPFunction);
Thread thThread = new Thread(tsThread);
thThread.Name = "IOCP " + thThread.GetHashCode();
thThread.Start();
// Increment the thread pool count
IncCurThreadsInPool();
}
}
}
}
catch
{
}
// Release the lock
Monitor.Exit(GetCriticalSection);
}
}
catch (Exception e)
{
throw e;
}
catch
{
throw new Exception("Unhandled Exception");
}
}
}
}
测试代码：
{
//============================================
/// <summary> Sample class for the threading class </summary>
public class UtilThreadingSample
{
//*******************************************
/// <summary> Test Method </summary>
static void Main()
{
// Create the MSSQL IOCP Thread Pool
SafeIOCPThreadPool pThreadPool = new SafeIOCPThreadPool(0, 5, 10, new SafeIOCPThreadPool.USER_FUNCTION(IOCPThreadFunction));
for (int i = 0; i < 100; i++)
{
pThreadPool.PostEvent(new MyData(){Value = i});
}
pThreadPool.Dispose();
Console.WriteLine("Disposed");
Console.ReadLine();
}
private static object syncRoot = new object();
//*****************************************
/// <summary> Function to be called by the IOCP thread pool. Called when
/// a command is posted for processing by the SocketManager </summary>
/// <param name="obj"> The value provided by the thread posting the event </param>
static public void IOCPThreadFunction(MyData obj)
{
try
{
Console.WriteLine("Value: {0},Thread:{1}", obj.Value, Thread.CurrentThread.Name);
}
catch (Exception pException)
{
Console.WriteLine(pException.Message);
}
}
}
}
参考资料：
IOCP Thread Pooling in C# - Part I
http://www.devarticles.com/c/a/C-Sharp/IOCP-Thread-Pooling-in-C-sharp-Part-I/
IOCP Thread Pooling in C# - Part II
http://www.devarticles.com/c/a/C-Sharp/IOCP-Thread-Pooling-in-C-sharp-Part-II/
蛙蛙推荐：在c#使用IOCP（完成端口）的简单示例
http://www.cnblogs.com/onlytiancai/archive/2009/01/05/1241571.html