vc弹出USB的方法. 附试验通过的代码！

vc弹出USB的方法. 附试验通过的代码！

http://blog.sina.com.cn/s/blog_4fcd1ea30100qrzn.html

(2011-04-15 10:09:48)

bool CUsbSwitchDlg::UnInstallUsb(char szDriveName) //参数是要弹出的盘符如：G，F

{

DWORD accessMode = 0, shareMode = 0;

HANDLE   hDevice;

ULONG returned = 0,bResult = 0;

DWORD   dwError;

shareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;  // default

accessMode = GENERIC_WRITE | GENERIC_READ;       // default

if (szDriveName == 0)

{

return FALSE;

}

CString vol_string = \\\\.\\G:;

vol_string.SetAt(4, szDriveName);

hDevice = CreateFile(vol_string,

accessMode,   shareMode,     NULL, OPEN_EXISTING, 0,       NULL);

if (hDevice == INVALID_HANDLE_VALUE)

{

CString debugInfo;

dwError   =   GetLastError();

debugInfo.Format("error = %d ", dwError);

TRACE("IOCTL_STORAGE_EJECT_MEDIA  errorcode = %d \n", dwError);

return FALSE;

}

bResult   =   DeviceIoControl(hDevice,

IOCTL_STORAGE_EJECT_MEDIA, //弹出U盘的具体命令。

NULL, 0, NULL, 0,&returned,      NULL);

if   (!bResult)   //   IOCTL   failed     //经实验，有时虽然失败了，U盘还是能弹出

{

CString debugInfo;

dwError   =   GetLastError();

debugInfo.Format("error = %d ", dwError);

TRACE("IOCTL_STORAGE_EJECT_MEDIA  errorcode = %d \n", dwError);

}

bResult   =   CloseHandle(hDevice);

if   (!bResult)

{

CString debugInfo;

dwError   =   GetLastError();

debugInfo.Format("error = %d ", dwError);

TRACE("IOCTL_STORAGE_EJECT_MEDIA  errorcode = %d \n", dwError);

return FALSE;

}

return TRUE;

}

关于U盘盘符的问题：

添加WM_DEVICECHANGE的消息处理函数OnDeviceChange,

在该函数中捕获DBT_DEVICEARRIVAL事件(当U盘插入时,OS会发WM_DEVICECHANGE广播消息,该消息的wParam中会包含DBT_DEVICEARRIVAL事件),

同时得到DEV_BROADCAST_VOLUME结构的数据,DEV_BROADCAST_VOLUME结构的dbch_devicetype 成员是DBT_DEVTYP_VOLUME代表是磁盘。

dbcv_unitmask成员是一个Mask变量,最低位对应A,其次是B,...,根据它可就可以得到当前U盘的盘符了.    比如0x1代表A盘。0x10代表B盘。当然同理你可以得到系统上刚插入的串口设备。要学会举一反三。

BOOL CUsbSwitchDlg::OnDeviceChange( UINT nEventType, DWORD dwData )

{

if (nEventType == DBT_DEVICEARRIVAL)

{

DEV_BROADCAST_HDR* dev_hdr = (DEV_BROADCAST_HDR*)dwData;

if (dev_hdr->dbch_devicetype == DBT_DEVTYP_VOLUME)

{

DEV_BROADCAST_VOLUME* pdev_vol = (DEV_BROADCAST_VOLUME*)dwData;;

int vol_char = 0;

int vol_int = pdev_vol->dbcv_unitmask;

// calculate the vol_num

for (;vol_int;)

{

vol_int = vol_int/2;

vol_char++;

}

m_USBvolNum = vol_char + 'A' - 1;//m_USBvolNum即为盘符，如G或者I

}

}

return FALSE;

}