IO完成端口+线程池的应用（终于有点明白了，大家帮看下哪里写的不合理


/ 异步方式调用.cpp : 定义控制台应用程序的入口点。
//#include "stdafx.h"
#include <windows.h>
#include <iostream>
using namespace std;PTP_WORK hWork = NULL; //定义工作项变量
HANDLE hPort;    //定义I/O完成端口句柄
HANDLE hFile[4] = {0}; 
//enum Key{CK_READ1,CK_READ2,CK_READ3,CK_READ4}//线程池处理函数VOID NTAPI WorkCallback(PTP_CALLBACK_INSTANCE Instance,PVOID Context)
{
    DWORD dwNumBytes;
    ULONG_PTR CompletionKey;
    OVERLAPPED* pOverlapped = NULL;
   
    //不断等待，当有IO请求完成的时候，执行相应的操作
    while(1)
    {
        BOOL bOk = GetQueuedCompletionStatus(hPort,&dwNumBytes,&CompletionKey,&pOverlapped,5000);
        DWORD dwError = GetLastError();        cout<<"完成等待"<<endl;
        if(bOk)
        {
            switch(CompletionKey)
            {
            case 0:
                cout<<"文件1"<<endl;
                //执行与文件1有关的其他操作，操作完成后，关闭句柄
                CloseHandle(hFile[0]);
                
                break;
            case 1:
                cout<<"文件2"<<endl;                CloseHandle(hFile[1]);
                break;
            case 2:
                cout<<"文件3"<<endl;                CloseHandle(hFile[2]);
                break;
            case 3:
                cout<<"文件4"<<endl;                CloseHandle(hFile[3]);
                break;
            default:
                cout<<"出现错误"<<endl;
                break;            }
        }
        else
        {
            if(pOverlapped != NULL)
            {
                cout<<"pOverlapped != NULL"<<endl;
            }
            else if(dwError == WAIT_TIMEOUT)
            {
                cout<<" WAIT_TIMEOUT"<<endl;
            }
            else
            {
                cout<<"未知错误"<<endl;
            }
        }
    }    cout<<"处理工作项"<<endl;}//创建新的I/O完成端口函数
HANDLE CreateNewCompletionPort(DWORD dwNumberOfConcurrentThreads)
{
    return CreateIoCompletionPort(INVALID_HANDLE_VALUE,NULL,0,dwNumberOfConcurrentThreads);
}//设备与I/O完成端口关联函数
BOOL AssociateDeviceWithCompletionPort(HANDLE hCompletionPort,HANDLE hDevice,DWORD dwCompletionKey)
{
    HANDLE h = CreateIoCompletionPort(hDevice,hCompletionPort,dwCompletionKey,0);
    return (h == hCompletionPort);}
int _tmain(int argc, _TCHAR* argv[])
{
    LPCWSTR pszName[] = {_T("a1.txt"),_T("a2.txt"),_T("a3.txt"),_T("a4.txt")};
    OVERLAPPED o = {0};
    o.Offset = 0;
    BYTE bBuffer[100] =  "abcde";
    //打开文件句柄（共4个文件句柄）
    for(int i=0; i<4; ++i)
    {
        hFile[i] = CreateFile(pszName[i],GENERIC_WRITE,0,NULL,OPEN_ALWAYS,FILE_FLAG_OVERLAPPED,NULL);    }    //创建一个I/O完成端口
    hPort = CreateNewCompletionPort(0);
    //将4个文件句柄与完成端口关联
    for(int i=0; i<4;++i)
    {
        if(!AssociateDeviceWithCompletionPort(hPort,hFile[i],i))
        {
            cout<<"完成端口关联失败"<<endl;
        }    }    if(FALSE == TrySubmitThreadpoolCallback(WorkCallback,NULL,NULL))
    {
        cout<<"线程池失败"<<endl;
    }
    //异步模式的4个IO请求，不影响主线程的继续运行    for(int i=0; i<4; ++i)
    {
        WriteFile(hFile[i],bBuffer,100,NULL,&o);
        DWORD dwError = GetLastError();
        if(ERROR_IO_PENDING ==dwError)            cout<<"进入了异步"<<endl;
       
        
    }
        cout<<"继续主线程"<<endl;    for(int i = 0;i<100;++i)
    {
        cout<<i<<endl;
    }    Sleep(5000);    system("pause");
    return 0;
}
这是根据自己的理解写的，不知道对不对，请指教啊