PIBIO_SENSOR_CONTROL_UNIT_FN callback function (winbio_adapter.h)

Called by the Windows Biometric Framework to perform a vendor-defined control operation that does not require elevated privilege. Call the SensorAdapterControlUnitPrivileged function to perform a vendor-defined control operation that requires elevated privilege.

Syntax

PIBIO_SENSOR_CONTROL_UNIT_FN PibioSensorControlUnitFn;

HRESULT PibioSensorControlUnitFn(
  [in, out] PWINBIO_PIPELINE Pipeline,
  [in]      ULONG ControlCode,
  [in]      PUCHAR SendBuffer,
  [in]      SIZE_T SendBufferSize,
  [in]      PUCHAR ReceiveBuffer,
  [in]      SIZE_T ReceiveBufferSize,
  [out]     PSIZE_T ReceiveDataSize,
  [out]     PULONG OperationStatus
)
{...}

Parameters

[in, out] Pipeline

Pointer to a WINBIO_PIPELINE structure associated with the biometric unit performing the operation.

[in] ControlCode

A ULONG value that specifies the vendor-defined operation to perform.

[in] SendBuffer

Pointer to a buffer that contains the control information to be sent to the sensor adapter. The format and content of the buffer is vendor-defined.

[in] SendBufferSize

Size, in bytes, of the buffer specified by the SendBuffer parameter.

[in] ReceiveBuffer

Pointer to a buffer that receives information sent by the sensor adapter. The format of the buffer is vendor-defined.

[in] ReceiveBufferSize

Size, in bytes, of the buffer specified by the ReceiveBuffer parameter.

[out] ReceiveDataSize

Pointer to a variable that receives the size, in bytes, of the data written to the buffer specified by the ReceiveBuffer parameter.

[out] OperationStatus

Pointer to a variable that receives a vendor-defined status code that specifies the outcome of the control operation.

Return value

If the function succeeds, it returns S_OK. If the function fails, it must return one of the following HRESULT values to indicate the error.

Remarks

Your implementation of this function should be identical to your implementation of the SensorAdapterControlUnitPrivileged function except that elevated privileges are not required to perform the operations specified by the ControlCode parameter. You are responsible for defining the operations and deciding which will not require elevated privilege.

This function must check the value of the ReceiveBufferSize parameter to be certain that the buffer specified by the ReceiveBuffer parameter is large enough to hold the data being returned.

Examples

The following pseudocode shows one possible implementation of this function. The example does not compile. You must adapt it to suit your purpose.

//////////////////////////////////////////////////////////////////////////////////////////
//
// SensorAdapterControlUnit
//
// Purpose:
//      Performs a vendor-defined control operation that does not require 
//      elevated privilege.
//
// Parameters:
//      Pipeline            - Pointer to a WINBIO_PIPELINE structure associated 
//                            with the biometric unit performing the operation.
//      ControlCode         - Specifies the vendor-defined operation to perform.
//      SendBuffer          - Contains the control information sent to the 
//                            sensor adapter.
//      SendBufferSize      - Size, in bytes, of the buffer specified by the 
//                            SendBuffer parameter.
//      ReceiveBuffer       - Receives information returned by the sensor adapter
//                            in response to the control operation.
//      ReceiveBufferSize   - Size, in bytes, of the buffer specified by the 
//                            ReceiveBuffer parameter.
//      ReceiveDataSize     - Receives the size, in bytes, of the data written to 
//                            the buffer specified by the ReceiveBuffer parameter.
//      OperationStatus     - Receives a vendor-defined status code that specifies 
//                            the outcome of the control operation.
//
static HRESULT
WINAPI
SensorAdapterControlUnit(
    __inout PWINBIO_PIPELINE Pipeline,
    __in ULONG ControlCode,
    __in_bcount(SendBufferSize) PUCHAR SendBuffer,
    __in SIZE_T SendBufferSize,
    __in_bcount(ReceiveBufferSize) PUCHAR ReceiveBuffer,
    __in SIZE_T ReceiveBufferSize,
    __out SIZE_T *ReceiveDataSize,
    __out ULONG *OperationStatus
    )
{
    HRESULT hr = S_OK;
    BOOL result = TRUE;

    // Verify that pointer arguments are not NULL.
    if (!ARGUMENT_PRESENT(Pipeline) ||
        !ARGUMENT_PRESENT(SendBuffer) ||
        !ARGUMENT_PRESENT(ReceiveBuffer) ||
        !ARGUMENT_PRESENT(ReceiveDataSize) ||
        !ARGUMENT_PRESENT(OperationStatus))
    {
        hr = E_POINTER;
        goto cleanup;
    }

    // Retrieve the context from the pipeline.
    PWINBIO_SENSOR_CONTEXT sensorContext = 
                 (PWINBIO_SENSOR_CONTEXT)Pipeline->SensorContext;

    // Verify the state of the pipeline.
    if (sensorContext == NULL || 
        Pipeline->SensorHandle == INVALID_HANDLE_VALUE)
    {
        hr = WINBIO_E_INVALID_DEVICE_STATE;
        goto cleanup;
    }

    switch (ControlCode)
    {
    case MY_NONPRIVILEGED_CTRL_CODE_NP1:
        {
            CTRL_CODE_NP1_SEND_BUFFER *sendBuffer = (CTRL_CODE_NP1_SEND_BUFFER*)SendBuffer;

            // Verify the size of the send buffer.
            if (SendBufferSize < sizeof(CTRL_CODE_NP1_SEND_BUFFER))
            {
                hr = E_INVALIDARG;
                break;
            }

            // Perform any other checks that may be required on the buffer 
            // contents. Return E_INVALIDARG if any of the checks fail.
            if (sendBuffer->SomeField != SomeSpecialValue ||
                sendBuffer->SomeOtherField != SomeOtherSpecialValue)
            {
                hr = E_INVALIDARG;
                break;
            }

            if (ReceiveBufferSize < sizeof(CTRL_CODE_NP1_RECEIVE_BUFFER))
            {
                hr = E_NOT_SUFFICIENT_BUFFER;
                break;
            }
        }

        // Fall through and perform the control operation after the switch
        // statement. Alternatively, depending on your requirements, you can 
        // perform the control operation here.
        break;

    case MY_NONPRIVILEGED_CTRL_CODE_NP2:
        // Continue testing for other non-privileged control codes that your
        // adapter supports.
        {
            CTRL_CODE_NP2_SEND_BUFFER *sendBuffer = (CTRL_CODE_NP2_SEND_BUFFER*)SendBuffer;

            // Verify the size of the send buffer.
            if (SendBufferSize < sizeof(CTRL_CODE_NP2_SEND_BUFFER))
            {
                hr = E_INVALIDARG;
                break;
            }

            // Perform any other checks that may be required on the buffer 
            // contents. Return E_INVALIDARG if any of the checks fail.
            if (sendBuffer->SomeField != SomeSpecialValue ||
                sendBuffer->SomeOtherField != SomeOtherSpecialValue)
            {
                hr = E_INVALIDARG;
                break;
            }

            if (ReceiveBufferSize < sizeof(CTRL_CODE_NP2_RECEIVE_BUFFER))
            {
                hr = E_NOT_SUFFICIENT_BUFFER;
                break;
            }
        }
        break;

    default:
        // All unrecognized control code values should return an error.
        hr = WINBIO_E_INVALID_CONTROL_CODE;
        break;
    }
    if (FAILED(hr))
    {
        goto cleanup;
    }

    // If control code validation succeeds, perform the control operation. This
    // example assumes that the driver performs overlapped I/O and that a properly 
    // initialized OVERLAPPED structure is contained in the sensor context.
    result = DeviceIoControl(
                Pipeline->SensorHandle,
                ControlCode,
                SendBuffer,
                (DWORD)SendBufferSize,
                ReceiveBuffer,
                (DWORD)ReceiveBufferSize,
                (LPDWORD)ReceiveDataSize,
                &sensorContext->Overlapped
                );
    if (result == FALSE && GetLastError() == ERROR_IO_PENDING)
    {
        SetLastError(ERROR_SUCCESS);

        result = GetOverlappedResult(
                    Pipeline->SensorHandle,
                    &sensorContext->Overlapped,
                    (LPDWORD)ReceiveDataSize,
                    TRUE
                    );
    }
    *OperationStatus = GetLastError();

    if (!result)
    {
        hr = _AdapterGetHresultFromWin32(*OperationStatus);
    }

cleanup:

    return hr;
}

Requirements

See also

Plug-in Functions

SensorAdapterControlUnitPrivileged

WinBioControlUnit