无法使用C++中的Windows服务检索可移动设备上的数据

Question

我试图检测可移动设备的插入并使用NT服务检索所述设备的驱动器号.我已经成功检测到设备的插入和移除,但是无法设置一个DEV_BROADCAST_VOLUME允许我从卷中获取驱动器号,GUID等的结构.

case SERVICE_CONTROL_DEVICEEVENT:{
            switch(evtype){
            case DBT_DEVICEARRIVAL:{
                    DEV_BROADCAST_VOLUME *hdr = (DEV_BROADCAST_VOLUME*) evdata;
                    ofstream log ("C:\\log.txt", ios::app);
                    log << hdr->dbcv_devicetype;
                    log.close();
                }
                break;

上面的代码片段编译并正确运行,但是当我插入一个闪存驱动器时,hdr->dbcv_devicetype日志作为55555和DBT_DEVTYP_VOLUME(这是USB驱动器)的值被定义为2(hdr->dbcv_devicetype应该相同,DBT_DEVTYP_VOLUME因为我插入了一个闪存驱动器).由于某种原因要么DBT_DEVTYP_VOLUME没有正确初始化,要么我正在做的其他事情是错误的.我使用Windows 7与Visual Studio 2011 C++.

Answer 1

尝试这个：

  PDEV_BROADCAST_HDR lpdb = (PDEV_BROADCAST_HDR)evdata;
  if (lpdb -> dbch_devicetype == DBT_DEVTYP_VOLUME)
   {
    PDEV_BROADCAST_VOLUME lpdbv = (PDEV_BROADCAST_VOLUME)lpdb;

    if (lpdbv -> dbcv_flags & DBTF_MEDIA)
     {
      StringCchPrintf( szMsg, sizeof(szMsg)/sizeof(szMsg[0]), 
                       TEXT("Drive %c: Media has arrived.\n"), 
                       FirstDriveFromMask(lpdbv ->dbcv_unitmask) );

      MessageBox( hwnd, szMsg, TEXT("WM_DEVICECHANGE"), MB_OK );
     }
   }

   /*------------------------------------------------------------------
      FirstDriveFromMask( unitmask )

      Description
        Finds the first valid drive letter from a mask of drive letters.
        The mask must be in the format bit 0 = A, bit 1 = B, bit 2 = C, 
        and so on. A valid drive letter is defined when the 
        corresponding bit is set to 1.

      Returns the first drive letter that was found.
   --------------------------------------------------------------------*/

   char FirstDriveFromMask( ULONG unitmask )
    {
     char i;

     for (i = 0; i < 26; ++i)
      {
       if (unitmask & 0x1)
         break;
       unitmask = unitmask >> 1;
      }

     return( i + 'A' );
   }

从检测介质插入或移除中提取的代码