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DeviceIoControl

The DeviceIoControl function sends a control code directly to a specified device driver, causing the corresponding device to perform the corresponding operation.

VB4-32,5,6
Declare Function DeviceIoControl Lib "kernel32" (ByVal hDevice As Long, ByVal dwIoControlCode As Long, lpInBuffer As Any, ByVal nInBufferSize As Long, lpOutBuffer As Any, ByVal nOutBufferSize As Long, lpBytesReturned As Long, lpOverlapped As Any) As Long

Operating Systems Supported
Requires Windows NT 3.1 or later; Requires Windows 95 or later

Library
Kernel32

Parameter Information
hDevice
[in] Handle to the device on which to perform the operation, typically a volume, directory, file, or alternate stream. To retrieve a device handle, use the function.

dwIoControlCode
[in] Specifies 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 and a short description of each control code, see Device Input and Output Control Codes .

For more detailed information on each control code, see its documentation. In particular, the documentation provides details on the usage of the lpInBuffer, nInBufferSize, lpOutBuffer, nOutBufferSize, and lpBytesReturned parameters.

lpInBuffer
[in] Pointer to a buffer that contains the data required to perform the operation.
This parameter can be NULL if the dwIoControlCode parameter specifies an operation that does not require input data.

nInBufferSize
[in] Specifies the size, in bytes, of the buffer pointed to by lpInBuffer.

lpOutBuffer
[out] Pointer to a buffer that receives the operation's output data.
This parameter can be NULL if the dwIoControlCode parameter specifies an operation that does not produce output data.

nOutBufferSize
[in] Specifies the size, in bytes, of the buffer pointed to by lpOutBuffer.

lpBytesReturned
[out] Pointer to a variable that receives the size, in bytes, of the data stored into the buffer pointed to by lpOutBuffer.
If the output buffer is too small to return any data, then the call fails, returns the error code ERROR_INSUFFICIENT_BUFFER, and the returned byte count is zero.
If the output buffer is too small to hold all of the data but can hold some entries, then the operating system returns as much as fits, the call fails, GetLastError returns the error code ERROR_MORE_DATA, and lpBytesReturned indicates the amount of data returned. 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 produces no output data, and lpOutBuffer can be NULL, DeviceIoControl makes use of the variable pointed to by lpBytesReturned. After such an operation, the value of the variable is without meaning.
If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this is an overlapped operation, you can get the number of bytes returned by calling . If hDevice is associated with an I/O completion port, you can get the number of bytes returned by calling .

lpOverlapped
[in] Pointer to an structure.
If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, lpOverlapped must point to a valid OVERLAPPED structure. In this case, the operation is performed as an overlapped (asynchronous) operation. If the device was opened with FILE_FLAG_OVERLAPPED and lpOverlapped is NULL, the function fails in unpredictable ways.
If hDevice was opened without specifying the FILE_FLAG_OVERLAPPED flag, lpOverlapped is ignored and DeviceIoControl does not return until the operation has been completed, or an error occurs.

Return Values
If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Examples

Related Functions

 

 


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