ReadFileEx方法读文件,为何回调函数没被触发?

Question

不知道为什么FileIOCompletionRoutine函数没进去,代码如下:#include<iostream>
#include<string>
#include<Windows.h>
using namespace std;VOID CALLBACK FileIOCompletionRoutine(DWORD dwErrorCode,DWORD dwNumberOfBytesTransfered,LPOVERLAPPED lpOverlapped)
{ cout<<"enter call back"<<endl;
}int main(void)
{
HANDLE hEvent=NULL;
HANDLE hFile=NULL;
const int buffSize=512;
      char *dataBuffer=new  char[buffSize];        hFile = CreateFile(
TEXT("a.txt"),     
GENERIC_READ,        
0,                 
NULL,               
OPEN_EXISTING,          
FILE_FLAG_OVERLAPPED,  
NULL
  );

  if(hFile==INVALID_HANDLE_VALUE)   return 0;  hEvent=CreateEvent(NULL,true,false,NULL);  if(hEvent==NULL) return 0;
   
    OVERLAPPED ovlap;
    ZeroMemory(&ovlap,sizeof(ovlap));
    ovlap.hEvent=hEvent;       bool  fNotEnd=ReadFileEx
            (
                hFile,           
                dataBuffer,     
                buffSize,  
                &ovlap,
               (LPOVERLAPPED_COMPLETION_ROUTINE)  FileIOCompletionRoutine
            );
       while(true)
       {
       cout<<"loop"<<endl;
Sleep(1000);
       }
   return 0;
}
请教高手,不知道哪里写的不对?还是我对ReadFileEx用法理解有误?

Answer 1

Sleep(1000);
-->
SleepEx(1000, TRUE);