[win32] CLog: Do not use FlushFileBuffers after each write to file wh…

…ich causes unnecessary performance penalties. Instead of using FlushFileBuffers specify FILE_FLAG_WRITE_THROUGH flag on the creation which causes any writes made to that handle to be written directly to the file without being buffered.

xbmc/utils/win32/Win32InterfaceForCLog.cpp

@@ -60,13 +60,15 @@ bool CWin32InterfaceForCLog::OpenLogFile(const std::string& logFilename, const s
   }
 
   m_hFile = CreateFileW(strLogFileW.c_str(), GENERIC_WRITE, FILE_SHARE_READ, NULL,
-                                  CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+                                  CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_WRITE_THROUGH, NULL);
+
   if (m_hFile == INVALID_HANDLE_VALUE)
     return false;
 
   static const unsigned char BOM[3] = { 0xEF, 0xBB, 0xBF };
   DWORD written;
   (void)WriteFile(m_hFile, BOM, sizeof(BOM), &written, NULL); // write BOM, ignore possible errors
+  (void)FlushFileBuffers(m_hFile);
 
   return true;
 }
@@ -91,7 +93,6 @@ bool CWin32InterfaceForCLog::WriteStringToLog(const std::string& logString)
 
   DWORD written;
   const bool ret = (WriteFile(m_hFile, strData.c_str(), strData.length(), &written, NULL) != 0) && written == strData.length();
-  (void)FlushFileBuffers(m_hFile);
 
   return ret;
 }