异步设备IO 《windows核心编程》第10章学习

异步IO操作与同步操作区别：

1. 在CreateFile里的FILE_FLAG_OVERLAPPED标志
2. 异步操作函数LPOVERLAPPED参数

接收IO请求完成通知

1. 触发设备内核对象
   缺点：同一个设备内核对象有可能进行多次读写操作，这样第一个完成这个设备内核对象就会被触发，所以这种方式不可以使用于这种情形

   void Test1()
   {
       HANDLE hFile = ::CreateFile(_T("aaa.txt"),
           GENERIC_READ,
           FILE_SHARE_READ,
           NULL,
           OPEN_EXISTING,
           FILE_FLAG_OVERLAPPED,
           NULL);
       if(!hFile)
       {
           wcout<<L"CreateFile Failed ErroCode:"<<::GetLastError()<<endl;
           return ;
       }
       DWORD dwFileSize = ::GetFileSize(hFile,);
       wcout<<L"FileSize:"<<dwFileSize<<endl;
       char * pFileContent = new char[];
       DWORD dwReaded = ;
       OVERLAPPED o_Read = {};
       DWORD bReadDone = ::ReadFile(hFile,
           pFileContent,
           ,
           &dwReaded,
           &o_Read);
       DWORD dwError = ::GetLastError();
       if(!bReadDone && (dwError == ERROR_IO_PENDING))
       {
           WaitForSingleObject(hFile,INFINITE);
           bReadDone = TRUE;
       }
   
       if(bReadDone)
           wcout<<L"I/O Code:"<<o_Read.Internal<<" TransedBytes:"<<o_Read.InternalHigh<<endl;
       else
           wcout<<"Error:"<<::GetLastError()<<endl;
       ::CloseHandle(hFile);
       delete [] pFileContent;
   }

2. 触发事件内核对象

   void Test2()
   {
       HANDLE hFile = ::CreateFile(_T("aaa.txt"),
           GENERIC_WRITE,
           FILE_SHARE_READ,
           NULL,
           OPEN_EXISTING,
           FILE_FLAG_OVERLAPPED,
           NULL);
       if(!hFile)
       {
           wcout<<L"CreateFile Failed ErroCode:"<<::GetLastError()<<endl;
           return ;
       }
       DWORD dwFileSize = ::GetFileSize(hFile,);
       wcout<<L"FileSize:"<<dwFileSize<<endl;
       LARGE_INTEGER liDis = {};
       LARGE_INTEGER liRet = {};
       ::SetFilePointerEx(hFile,liDis,&liRet,FILE_END);
       wcout<<L"PreWrite File Pos:"<<liRet.LowPart<<endl;
       char * pFileContent = new char[];
       memset(pFileContent,'z',);
       DWORD dwReaded = ;
       OVERLAPPED o_Write = {};
       o_Write.Offset = liRet.LowPart;
       o_Write.hEvent = ::CreateEvent(NULL,FALSE,FALSE,NULL);
       DWORD bReadDone = ::WriteFile(hFile,
           pFileContent,
           ,
           &dwReaded,
           &o_Write);
       DWORD dwError = ::GetLastError();
       if(!bReadDone && (dwError == ERROR_IO_PENDING))
       {
           WaitForSingleObject(o_Write.hEvent,INFINITE);
           bReadDone = TRUE;
       }
   
       if(bReadDone)
           wcout<<L"I/O Code:"<<o_Write.Internal<<" TransedBytes:"<<o_Write.InternalHigh<<endl;
       else
           wcout<<"Error:"<<::GetLastError()<<endl;
       ::CloseHandle(hFile);
       delete [] pFileContent;
   }

3. 可提醒IO

   void Test3()
   {
       //可提醒IO
       HANDLE hFile = ::CreateFile(_T("aaa.txt"),
           GENERIC_WRITE,
           FILE_SHARE_READ,
           NULL,
           OPEN_EXISTING,
           FILE_FLAG_OVERLAPPED,
           NULL);
       if(!hFile)
       {
           wcout<<L"CreateFile Failed ErroCode:"<<::GetLastError()<<endl;
           return ;
       }
       DWORD dwFileSize = ::GetFileSize(hFile,);
       wcout<<L"FileSize:"<<dwFileSize<<endl;
       LARGE_INTEGER liDis = {};
       LARGE_INTEGER liRet = {};
       ::SetFilePointerEx(hFile,liDis,&liRet,FILE_END);
       wcout<<L"PreWrite File Pos:"<<liRet.LowPart<<endl;
       char * pFileContent = new char[];
       memset(pFileContent,'g',);
       DWORD dwReaded = ;
       OVERLAPPED o_Write = {};
       o_Write.Offset = liRet.LowPart;
       DWORD bReadDone = ::WriteFileEx(hFile,
           pFileContent,
           ,
           &o_Write,
           FileIOCompletionRoutine);
   
       ::CloseHandle(hFile);
       SleepEx(,TRUE);
       delete [] pFileContent;
   }

   可提醒IO的优劣：

   （1）由于回调函数的原因，最终不得不把大量信息放在全局变量中。使代码变的更加复杂

   （2）发出请求线程和完成处理必须是同一线程，没有达到线程负载均衡

   可提醒IO相关函数

   （1）QueueUserAPC函数

   a.这个函数允许我们手动增加APC项。

   b.可以强制线程退出等待状态比如WaitForSingleObjectEx 以下是示例代码

   VOID WINAPI APCFunc(ULONG_PTR pvParam)
   {
       //Nothing To Do
   }
   
   UINT WINAPI ThreadFunc(PVOID pvParam)
   {
       wcout<<L"start Wait...."<<endl;
       DWORD dw = ::WaitForSingleObjectEx(pvParam,INFINITE,TRUE);
       if(dw == WAIT_OBJECT_0)
       {
           wcout<<L"Event signaled"<<endl;
           return ;
       }
       else if(dw == WAIT_IO_COMPLETION)
       {
           wcout<<L"QueueUserApc Forced us out of a wait state"<<endl;
           return ;
       }
       return ;
   }
   void Test4()
   {
       //利用QueueUserApc来停止线程等待
       HANDLE hEvent = ::CreateEvent(NULL,FALSE,FALSE,NULL);
       HANDLE hThread = (HANDLE) _beginthreadex(NULL,,ThreadFunc,hEvent,,NULL);
       Sleep();
       QueueUserAPC(APCFunc,hThread,NULL);
       WaitForSingleObject(hThread,INFINITE);
       CloseHandle(hThread);
       CloseHandle(hEvent);
   }

4. I/O完成端口
   待续

   void Test5()
   {
       //I/O完成端口
       TCHAR SrcFileName[MAXSIZE];
       TCHAR DesFileName[MAXSIZE];
   
       cout<<"请输入源文件名：\n";
       wcin>>SrcFileName;
   
       cout<<"请输入目的文件名：\n";
       wcin>>DesFileName;
   
       HANDLE hSrcFile=CreateFile(SrcFileName,GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_FLAG_OVERLAPPED,NULL);
       if(hSrcFile==INVALID_HANDLE_VALUE)
       {
           printf("文件打开失败！");
       }
       DWORD FileSizeHigh;
       DWORD FileSize=GetFileSize(hSrcFile,&FileSizeHigh);
   
       HANDLE hDstFile=CreateFile(DesFileName,GENERIC_WRITE,,NULL,CREATE_NEW,FILE_FLAG_OVERLAPPED,NULL);
   
       //创建完成端口
       HANDLE hIOCP=CreateIoCompletionPort(INVALID_HANDLE_VALUE,NULL,,);
       if(hIOCP==NULL)
       {
           printf("完成端口创建失败！");
       }
   
       //绑定完成端口
       CreateIoCompletionPort(hSrcFile,hIOCP,READ_KEY,);
       CreateIoCompletionPort(hDstFile,hIOCP,WRITE_KEY,);
   
       OVERLAPPED ov={};
       PostQueuedCompletionStatus(hIOCP,,WRITE_KEY,&ov);
       OVERLAPPED ovSrc={};
       OVERLAPPED ovDes={};
       ULONG_PTR CompletionKey;
       BYTE* pBuffer=new BYTE[BUFFERSIZE];
       int i=;
       int j=;
       while(true)
       {
           DWORD nTransfer;
           OVERLAPPED* o;
   
           GetQueuedCompletionStatus(hIOCP,&nTransfer,&CompletionKey,&o,INFINITE);
           switch(CompletionKey)
           {
           case READ_KEY:
               //代表读取IO操作已经完成，进行下一步写入操作
               WriteFile(hDstFile,pBuffer,o->InternalHigh,NULL,&ovDes);
               cout<<"write:"<<++i<<endl;
               ovDes.Offset+=o->InternalHigh;
               //if(ovDes.Offset== FileSize/1024 )
               //    return 0;
               break;
           case WRITE_KEY:
               //代表写入IO操作已经完成，进行下一步读取操作
               memset(pBuffer,,BUFFERSIZE*sizeof(BYTE));
               if(ovSrc.Offset < FileSize)//文件读取未完成
               {
                   DWORD nBytes;
                   if(ovSrc.Offset+BUFFERSIZE < FileSize)
                       nBytes=BUFFERSIZE;
                   else
                       nBytes=FileSize-ovSrc.Offset;
                   ReadFile(hSrcFile,pBuffer,nBytes,NULL,&ovSrc);
                   cout<<"read:"<<++j<<endl;
   
                   ovSrc.Offset+=nBytes;
               }
               else
                   return ;
               break;
           default:
               break;
   
           }
       }
   
       return ;
   }