非同步裝置IO 《windows核心編程》第10章學習<待續>

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非同步IO操作與同步操作區別：

1. 在CreateFile裡的FILE_FLAG_OVERLAPPED標誌
2. 非同步作業函數LPOVERLAPPED參數

接收IO請求完成通知

1. 觸發裝置核心對象
   缺點：同一個裝置核心對象有可能進行多次讀寫操作，這樣第一個完成這個裝置核心對象就會被觸發，所以這種方式不可以使用於這種情形
   

   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,0);    wcout<<L"FileSize:"<<dwFileSize<<endl;    char * pFileContent = new char[10000000];    DWORD dwReaded = 0;    OVERLAPPED o_Read = {0};    DWORD bReadDone = ::ReadFile(hFile,        pFileContent,        10000000,        &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. 觸發事件核心對象
   

   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,0);    wcout<<L"FileSize:"<<dwFileSize<<endl;    LARGE_INTEGER liDis = {0};    LARGE_INTEGER liRet = {0};    ::SetFilePointerEx(hFile,liDis,&liRet,FILE_END);    wcout<<L"PreWrite File Pos:"<<liRet.LowPart<<endl;    char * pFileContent = new char[10000000];    memset(pFileContent,‘z‘,10000000);    DWORD dwReaded = 0;    OVERLAPPED o_Write = {0};    o_Write.Offset = liRet.LowPart;    o_Write.hEvent = ::CreateEvent(NULL,FALSE,FALSE,NULL);    DWORD bReadDone = ::WriteFile(hFile,        pFileContent,        10000000,        &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,0);    wcout<<L"FileSize:"<<dwFileSize<<endl;    LARGE_INTEGER liDis = {0};    LARGE_INTEGER liRet = {0};    ::SetFilePointerEx(hFile,liDis,&liRet,FILE_END);    wcout<<L"PreWrite File Pos:"<<liRet.LowPart<<endl;    char * pFileContent = new char[10000000];    memset(pFileContent,‘g‘,10000000);    DWORD dwReaded = 0;    OVERLAPPED o_Write = {0};    o_Write.Offset = liRet.LowPart;    DWORD bReadDone = ::WriteFileEx(hFile,        pFileContent,        10000000,        &o_Write,        FileIOCompletionRoutine);    ::CloseHandle(hFile);    SleepEx(10000,TRUE);    delete [] pFileContent;}

   
   可提醒IO的優劣：
   （1）由於回呼函數的原因，最終不得不把大量資訊放在全域變數中。使代碼變的更加複雜
   （2）發出請求線程和完成處理必須是同一線程，沒有達到線程負載平衡
   可提醒IO相關函數
   （1）QueueUserAPC函數
        a.這個函數允許我們手動增加APC項。
        b.可以強制線程退出等待狀態比如WaitForSingleObjectEx 以下是範例程式碼
   

   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 0;    }    else if(dw == WAIT_IO_COMPLETION)    {        wcout<<L"QueueUserApc Forced us out of a wait state"<<endl;        return 0;    }    return 0;}void Test4(){    //利用QueueUserApc來停止線程等待    HANDLE hEvent = ::CreateEvent(NULL,FALSE,FALSE,NULL);    HANDLE hThread = (HANDLE) _beginthreadex(NULL,0,ThreadFunc,hEvent,0,NULL);    Sleep(5000);    QueueUserAPC(APCFunc,hThread,NULL);    WaitForSingleObject(hThread,INFINITE);    CloseHandle(hThread);    CloseHandle(hEvent);}

4. I/O完成連接埠
   待續

非同步裝置IO 《windows核心編程》第10章學習<待續>