C#——I/O完成端口的类定义和测试实例

王朝c#·作者佚名 2008-05-19

我们采用的是I/O Complete Port（以下简称IOCP）处理机制。

简单的讲，当服务应用程序初始化时，它应该先创建一个I/O CP。我们在请求到来后，将得到的数据打包用PostQueuedCompletionStatus发送到IOCP中。这时需要创建一些个线程(7个线程/每CPU，再多就没有意义了)来处理发送到IOCP端口的消息。实现步骤大致如下：

1先在主线程中调用CreateIoCompletionPort创建IOCP。

CreateIoCompletionPort的前三个参数只在把设备同Complete Port相关联时才有用。

此时我们只需传递INVALID_HANDLE_VALUE,NULL和0即可。

第四个参数告诉端口同时能运行的最多线程数，这里设置为0，表示默认为当前计算机的CPU数目。

2我们的ThreadFun线程函数执行一些初始化之后，将进入一个循环，该循环会在服务进程终止时才结束。

在循环中，调用GetQueuedCompletionStatus，这样就把当前线程的ID放入一个等待线程队列中，I/O CP内核对象就总能知道哪个线程在等待处理完成的I/O请求。

如果在IDLE_THREAD_TIMEOUT规定的时间内I/O CP上还没有出现一个Completion Packet，则转入下一次循环。在这里我们设置的IDLE_THREAD_TIMEOUT为1秒。

当端口的I/O完成队列中出现一项时，完成端口就唤醒等待线程队列中的这个线程，该线程将得到完成的I/O项中的信息：

传输的字节数、完成键和OVERLAPPED结构的地址。

在我们的程序中可以用智能指针或者BSTR或者int来接受这个OVERLAPPED结构的地址的值，从而得到消息；然后在这个线程中处理消息。

GetQueuedCompletionStatus的第一个参数hCompletionPort指出了要监视哪一个端口，这里我们传送先前从CreateIoCompletionPort返回的端口句柄。

需要注意的是：

第一，

线程池的数目是有限制的，和CPU数目有关系。

第二，

IOCP是一种较为完美的睡眠/唤醒线程机制；线程当前没有任务要处理时，就进入睡眠状态，从而不占用CPU资源，直到被内核唤醒；

第三，

最近一次刚执行完的线程，下次任务来的时候还会唤醒它；所以有可能比较少被调用的线程以后被调用的几率也少。

测试代码：

using System;

using System.Threading;

// Included for the Thread.Sleep call

using Continuum.Threading;

using System.Runtime.InteropServices;

namespace IOCPDemo

{

//=============================================================================

/**//// Sample class for the threading class

public class UtilThreadingSample

{

//*****************************************************************************

/**//// Test Method

static void Main()

{

// Create the MSSQL IOCP Thread Pool

IOCPThreadPool pThreadPool = new IOCPThreadPool(0, 10, 20, new IOCPThreadPool.USER_FUNCTION(IOCPThreadFunction));

//for(int i =1;i

{

pThreadPool.PostEvent(1234);

}

Thread.Sleep(100);

pThreadPool.Dispose();

}

//********************************************************************

/**//// Function to be called by the IOCP thread pool.

Called when

///

a command is posted for processing by the SocketManager

/// The value provided by the thread posting the event

static public void IOCPThreadFunction(int iValue)

{

try

{

Console.WriteLine("Value: {0}", iValue.ToString());

Thread.Sleep(3000);

}

catch (Exception pException)

{

Console.WriteLine(pException.Message);

}

类代码：

using System;

using System.Threading;

using System.Runtime.InteropServices;

namespace IOCPThreading

{

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]

public sealed class IOCPThreadPool

{

[DllImport("Kernel32", CharSet=CharSet.Auto)]

private unsafe static extern UInt32 CreateIoCompletionPort(UInt32 hFile, UInt32 hExistingCompletionPort, UInt32* puiCompletionKey, UInt32 uiNumberOfConcurrentThreads);

[DllImport("Kernel32", CharSet=CharSet.Auto)]

private unsafe static extern Boolean CloseHandle(UInt32 hObject);

[DllImport("Kernel32", CharSet=CharSet.Auto)]

private unsafe static extern Boolean PostQueuedCompletionStatus(UInt32 hCompletionPort, UInt32 uiSizeOfArgument, UInt32* puiUserArg, System.Threading.NativeOverlapped* pOverlapped);

[DllImport("Kernel32", CharSet=CharSet.Auto)]

private unsafe static extern Boolean GetQueuedCompletionStatus(UInt32 hCompletionPort, UInt32* pSizeOfArgument, UInt32* puiUserArg, System.Threading.NativeOverlapped** ppOverlapped, UInt32 uiMilliseconds);

private const UInt32 INVALID_HANDLE_VALUE = 0xffffffff;

private const UInt32 INIFINITE = 0xffffffff;

private const Int32 SHUTDOWN_IOCPTHREAD = 0x7fffffff;

public delegate void USER_FUNCTION(int iValue);

private UInt32 m_hHandle;

private UInt32 GetHandle { get { return m_hHandle; } set { m_hHandle = value; } }

private Int32 m_uiMaxConcurrency;

private Int32 GetMaxConcurrency { get { return m_uiMaxConcurrency; } set { m_uiMaxConcurrency = value; } }

private Int32 m_iMinThreadsInPool;

private Int32 GetMinThreadsInPool { get { return m_iMinThreadsInPool; } set { m_iMinThreadsInPool = value; } }

private Int32 m_iMaxThreadsInPool;

private Int32 GetMaxThreadsInPool { get { return m_iMaxThreadsInPool; } set { m_iMaxThreadsInPool = value; } }

private Object m_pCriticalSection;

private Object GetCriticalSection { get { return m_pCriticalSection; } set { m_pCriticalSection = value; } }

private USER_FUNCTION m_pfnUserFunction;

private USER_FUNCTION GetUserFunction { get { return m_pfnUserFunction; } set { m_pfnUserFunction = value; } }

private Boolean m_bDisposeFlag;

/**//// SimType: Flag to indicate if the class is disposing

private Boolean IsDisposed { get { return m_bDisposeFlag; } set { m_bDisposeFlag = value; } }

private Int32 m_iCurThreadsInPool;

/**//// SimType: The current number of threads in the thread pool

public Int32 GetCurThreadsInPool { get { return m_iCurThreadsInPool; } set { m_iCurThreadsInPool = value; } }

/**//// SimType: Increment current number of threads in the thread pool

private Int32 IncCurThreadsInPool() { return Interlocked.Increment(ref m_iCurThreadsInPool); }

/**//// SimType: Decrement current number of threads in the thread pool

private Int32 DecCurThreadsInPool() { return Interlocked.Decrement(ref m_iCurThreadsInPool); }

private Int32 m_iActThreadsInPool;

/**//// SimType: The current number of active threads in the thread pool

public Int32 GetActThreadsInPool { get { return m_iActThreadsInPool; } set { m_iActThreadsInPool = value; } }

/**//// SimType: Increment current number of active threads in the thread pool