有时候程序总是会发生意想不到的情况，为了方便排查错误的情况，还是写日志比较方便。这里自己写了一个简单的函数，能实现基本的功能。

BOOL WriteLog(char * DataBuffer){    CString strTempPath;    ::GetTempPath(MAX_PATH, strTempPath.GetBuffer(MAX_PATH));    CString strLogFile = strTempPath + L"Log.txt";    HANDLE hFile = INVALID_HANDLE_VALUE;    DWORD dwBytesWritten = 0;    BOOL bErrorFlag = FALSE;    OVERLAPPED strOverlapped = {};    strOverlapped.Offset = 0xFFFFFFFF;    strOverlapped.OffsetHigh= 0xFFFFFFFF;    hFile = CreateFile(strLogFile, GENERIC_READ| GENERIC_WRITE, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);    if (hFile== INVALID_HANDLE_VALUE)    {        return false;    }    char TimeMessage[MAX_PATH] = { 0 };    SYSTEMTIME st;    ::GetLocalTime(&st);    char szTime[26] = { 0 };    sprintf_s(szTime, "%04d-%02d-%02d %02d:%02d:%02d %d ", st.wYear, st.wMonth, st.wDay, st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);    sprintf_s(TimeMessage, "%s: %s\n", szTime,DataBuffer);    DWORD dwBytesToWrite = (DWORD)strlen(TimeMessage);    bErrorFlag = WriteFile(hFile, TimeMessage, dwBytesToWrite, NULL, &strOverlapped);    if (bErrorFlag==FALSE)    {        return false;    }    CloseHandle(hFile);    return true;}

这里用到CreateFile和WriteFile函数：

CreateFile 函数创建或打开下列对象，并返回一个可以用来访问这些对象的句柄。 

  文件 

  pipes

  邮槽 

  通信资源 

  磁盘驱动器（仅适用于 windowsNT ） 

  控制台 

  文件夹（仅用于打开）

HANDLE CreateFile( LPCTSTR lpFileName,    // 指向文件名的指针  DWORD dwDesiredAccess,    // 访问模式（写 / 读）  DWORD dwShareMode,    // 共享模式  LPSECURITY_ATTRIBUTES lpSecurityAttributes, // 指向安全属性的指针  DWORD dwCreationDisposition,   // 如何创建  DWORD dwFlagsAndAttributes,   // 文件属性  HANDLE hTemplateFile    // 用于复制文件句柄 );BOOL WriteFile(  HANDLE       hFile,  LPCVOID      lpBuffer,  DWORD        nNumberOfBytesToWrite,  LPDWORD      lpNumberOfBytesWritten,  LPOVERLAPPED lpOverlapped);

 

这里有一点需要说明的，要写让文件能追加改写，一定要定义一个 OVERLAPPED 结构体，并把offset,offsethigh设成0xFFFFFFFF，并把这个结构体的地址传给WriteFile的最后一个参数。不然每次都会重头写，

 OVERLAPPED strOverlapped = {}; strOverlapped.Offset = 0xFFFFFFFF; strOverlapped.OffsetHigh= 0xFFFFFFFF; bErrorFlag = WriteFile(hFile, TimeMessage, dwBytesToWrite, NULL, &strOverlapped);

 

这里有一个获得time的函数，也值得关注。

 SYSTEMTIME st; ::GetLocalTime(&st); char szTime[26] = { 0 }; sprintf_s(szTime, "%04d-%02d-%02d %02d:%02d:%02d %d ", st.wYear, st.wMonth, st.wDay, st.wHour, st.wMinute, st.wSecond, st.wMilliseconds)

 

最后的结果类似这样的：