INFO: Direct Drive Access Under Win32 |
The information in this article applies to:
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Microsoft Win32 Application Programming Interface (API), used with:
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The Microsoft Windows NT operating system, versions 3.1, 3.5, 3.51, 4.0
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The Microsoft Windows 2000 operating system
SUMMARY
To open a physical hard drive for direct disk access (raw I/O) in a
Win32-based application, use a device name of the form
\\.\PhysicalDriveN
where N is 0, 1, 2, and so forth, representing each of the physical drives
in the system.
To open a logical drive, direct access is of the form
\\.\X:
where X: is a hard-drive partition letter, floppy disk drive, or CD-ROM
drive.
MORE INFORMATION
You can open a physical or logical drive using the CreateFile() application
programming interface (API) with these device names provided that you have
the appropriate access rights to the drive (that is, you must be an
administrator). You must use both the CreateFile() FILE_SHARE_READ and
FILE_SHARE_WRITE flags to gain access to the drive.
Once the logical or physical drive has been opened, you can then perform
direct I/O to the data on the entire drive. When performing direct disk
I/O, you must seek, read, and write in multiples of sector sizes of the
device and on sector boundaries. Call DeviceIoControl() using
IOCTL_DISK_GET_DRIVE_GEOMETRY to get the bytes per sector, number of
sectors, sectors per track, and so forth, so that you can compute the size
of the buffer that you will need.
Note that a Win32-based application cannot open a file by using internal
Windows NT object names; for example, attempting to open a CD-ROM drive by
opening
\Device\CdRom0
does not work because this is not a valid Win32 device name. An application
can use the QueryDosDevice() API to get a list of all valid Win32 device
names and see the mapping between a particular Win32 device name and an
internal Windows NT object name. An application running at a sufficient
privilege level can define, redefine, or delete Win32 device mappings by
calling the DefineDosDevice() API.
Additional query words:
Keywords : kbAPI kbFileIO kbKernBase kbOSWin2000 kbDSupport kbGrpKernBase
Issue type : kbinfo
Technology : kbOSWinNT kbOSWinSearch
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