BOOL DeviceIoControl(
[in] HANDLE hDevice,
[in] DWORD dwIoControlCode,
[in, optional] LPVOID lpInBuffer,
[in] DWORD nInBufferSize,
[out, optional] LPVOID lpOutBuffer,
[in] DWORD nOutBufferSize,
[out, optional] LPDWORD lpBytesReturned,
[in, out, optional] LPOVERLAPPED lpOverlapped
Parameters
[in] hDevice
A handle to the device on which the operation is to be performed. The device is typically a volume,
directory, file, or stream. To retrieve a device handle, use the
CreateFile function. For more information, see
Remarks.
[in] dwIoControlCode
The control code for the operation. This value identifies the specific operation to be performed and the
type of device on which to perform it.
For a list of the control codes, see Remarks. The documentation for each control code provides usage details
for the lpInBuffer, nInBufferSize,
lpOutBuffer, and nOutBufferSize parameters.
[in, optional] lpInBuffer
A pointer to the input buffer that contains the data required to perform the operation. The format of this
data depends on the value of the dwIoControlCode parameter.
This parameter can be NULL if dwIoControlCode specifies
an operation that does not require input data.
[in] nInBufferSize
The size of the input buffer, in bytes.
[out, optional] lpOutBuffer
A pointer to the output buffer that is to receive the data returned by the operation. The format of this
data depends on the value of the dwIoControlCode parameter.
This parameter can be NULL if dwIoControlCode specifies
an operation that does not return data.
[in] nOutBufferSize
The size of the output buffer, in bytes.
[out, optional] lpBytesReturned
A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.
If the output buffer is too small to receive any data, the call fails,
GetLastError returns
ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is zero.
If the output buffer is too small to hold all of the data but can hold some entries, some drivers will return
as much data as fits. In this case, the call fails,
GetLastError returns
ERROR_MORE_DATA, and lpBytesReturned indicates the amount
of data received. Your application should call
DeviceIoControl again with the same operation,
specifying a new starting point.
If lpOverlapped is NULL,
lpBytesReturned cannot be NULL. Even when an operation
returns no output data and lpOutBuffer is NULL,
DeviceIoControl makes use of
lpBytesReturned. After such an operation, the value of
lpBytesReturned is meaningless.
If lpOverlapped is not NULL,
lpBytesReturned can be NULL. If this parameter is not
NULL and the operation returns data, lpBytesReturned is
meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call
GetOverlappedResult. If
hDevice is associated with an I/O completion port, you can retrieve the number of
bytes returned by calling
GetQueuedCompletionStatus.
[in, out, optional] lpOverlapped
A pointer to an OVERLAPPED structure.
If hDevice was opened without specifying
FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.
If hDevice was opened with the FILE_FLAG_OVERLAPPED flag,
the operation is performed as an overlapped (asynchronous) operation. In this case,
lpOverlapped must point to a valid
OVERLAPPED structure that contains a handle to an
event object. Otherwise, the function fails in unpredictable ways.
For overlapped operations,
DeviceIoControl returns immediately, and the event
object is signaled when the operation has been completed. Otherwise, the function does not return until the
operation has been completed or an error occurs.
Return value
If the operation completes successfully, the return value is nonzero (TRUE).
If the operation fails or is pending, the return value is zero. To get extended error information, call
GetLastError.
To retrieve a handle to the device, you must call the
CreateFile function with either the name of a device or
the name of the driver associated with a device. To specify a device name, use the following format:
\\.\DeviceName
DeviceIoControl can accept a handle to a specific
device. For example, to open a handle to the logical drive A: with
CreateFile, specify \\.\a:. Alternatively, you can use the
names \\.\PhysicalDrive0, \\.\PhysicalDrive1, and so on, to open handles to the physical drives on a system.
You should specify the FILE_SHARE_READ and
FILE_SHARE_WRITE access flags when calling
CreateFile to open a handle to a device driver. However,
when you open a communications resource, such as a serial port, you must specify exclusive access. Use the other
CreateFile parameters as follows when opening a device
handle:
The fdwCreate parameter must specify
OPEN_EXISTING.
The hTemplateFile parameter must be NULL.
The fdwAttrsAndFlags parameter can specify
FILE_FLAG_OVERLAPPED to indicate that the returned handle can be used in overlapped
(asynchronous) I/O operations.
For lists of supported control codes, see the following topics:
CD-ROM Control Codes
Communications Control Codes
Device Management Control Codes
Directory Management Control Codes
Disk Management Control Codes
File Management Control Codes
Power Management Control Codes
Volume Management Control Codes
Examples
For an example that uses DeviceIoControl, see Calling DeviceIoControl.
Requirements
