2007年6月7日

磁带机 TAPEx

其中，物理驱动器不包括软驱和光驱。逻辑驱动器可以是IDE/SCSI/PCMCIA/USB接口的硬盘分区（卷）、光驱、MO、CF卡等，甚至是虚拟盘。x=0，1，2 ……

其它的设备名称需通过驱动接口的GUID调用设备管理函数族取得，这里暂不讨论。

Q 请举一个简单的例子说明如何通过DeviceIoControl访问设备驱动程序。

A 这里有一个从MSDN上摘抄来的demo程序，演示在NT/2000/XP中如何通过DeviceIoControl获取硬盘的基本参数。

/* The code of interest is in the subroutine GetDriveGeometry. The
   code in main shows how to interpret the results of the IOCTL call. */
  
#include 
#include 
  
BOOL GetDriveGeometry(DISK_GEOMETRY *pdg)
{
    HANDLE hDevice;               // handle to the drive to be examined
    BOOL bResult;                 // results flag
    DWORD junk;                   // discard results
  
    hDevice = CreateFile("\\\\.\\PhysicalDrive0",  // drive to open
                    0,                // no access to the drive
                    FILE_SHARE_READ | // share mode
                    FILE_SHARE_WRITE,
                    NULL,             // default security attributes
                    OPEN_EXISTING,    // disposition
                    0,                // file attributes
                    NULL);            // do not copy file attributes
  
    if (hDevice == INVALID_HANDLE_VALUE) // cannot open the drive
    {
        return (FALSE);
    }
  
    bResult = DeviceIoControl(hDevice,     // device to be queried
        IOCTL_DISK_GET_DRIVE_GEOMETRY,     // operation to perform
                    NULL, 0,               // no input buffer
                    pdg, sizeof(*pdg),     // output buffer
                    &junk,                 // # bytes returned
                    (LPOVERLAPPED) NULL);  // synchronous I/O
  
    CloseHandle(hDevice);
  
    return (bResult);
}
  
int main(int argc, char *argv[])
{
    DISK_GEOMETRY pdg;            // disk drive geometry structure
    BOOL bResult;                 // generic results flag
    ULONGLONG DiskSize;           // size of the drive, in bytes
  
    bResult = GetDriveGeometry (&pdg);
  
    if (bResult)
    {
        printf("Cylinders = %I64d\n", pdg.Cylinders);
        printf("Tracks per cylinder = %ld\n", (ULONG) pdg.TracksPerCylinder);
        printf("Sectors per track = %ld\n", (ULONG) pdg.SectorsPerTrack);
        printf("Bytes per sector = %ld\n", (ULONG) pdg.BytesPerSector);
  
        DiskSize = pdg.Cylinders.QuadPart * (ULONG)pdg.TracksPerCylinder *
            (ULONG)pdg.SectorsPerTrack * (ULONG)pdg.BytesPerSector;
        printf("Disk size = %I64d (Bytes) = %I64d (Mb)\n", DiskSize,
            DiskSize / (1024 * 1024));
    }
    else
    {
        printf("GetDriveGeometry failed. Error %ld.\n", GetLastError());
    }
  
    return ((int)bResult);
}

Q 如果将设备名换成“A:”就可以取A盘参数，换成“CDROM0”就可以取CDROM参数，是这样吗？

A 这个问题暂不做回答。请动手试一下。

现在我们总结一下通过DeviceIoControl访问设备驱动程序的“三步曲”：首先用CreateFile取得设备句柄，然后用DeviceIoControl与设备进行I/O，最后别忘记用CloseHandle关闭设备句柄。

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