PIBIO_ENGINE_CREATE_ENROLLMENT_FN callback function (winbio_adapter.h)

Article
02/22/2024

Called by the Windows Biometric Framework to initialize the enrollment object in the biometric unit pipeline.

Syntax

PIBIO_ENGINE_CREATE_ENROLLMENT_FN PibioEngineCreateEnrollmentFn;

HRESULT PibioEngineCreateEnrollmentFn(
  [in, out] PWINBIO_PIPELINE Pipeline
)
{...}

Parameters

[in, out] Pipeline

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

Return code	Description
E_POINTER	The Pipeline parameter cannot be NULL.
E_OUTOFMEMORY	There is not enough memory to complete the operation.

Remarks

The EngineAdapterCommitEnrollment marks the beginning of an enrollment transaction. If this function succeeds, the Windows Biometric Framework calls EngineAdapterUpdateEnrollment to add one or more feature sets to the enrollment object. The Framework then calls EngineAdapterCommitEnrollment or EngineAdapterDiscardEnrollment to complete the transaction.

Examples

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

//////////////////////////////////////////////////////////////////////////////////////////
//
// EngineAdapterCreateEnrollment
//
// Purpose:
//      Initialize the enrollment object in the biometric unit pipeline.
//
// Parameters:
//      Pipeline    - Pointer to a WINBIO_PIPELINE structure associated 
//                    with the biometric unit performing the operation
//
static HRESULT
WINAPI
EngineAdapterCreateEnrollment(
    __inout PWINBIO_PIPELINE Pipeline
    )
{
    HRESULT hr = S_OK;

    // Verify that the Pipeline parameter is not NULL.
    if (!ARGUMENT_PRESENT(Pipeline))
    {
        hr = E_POINTER;
        goto cleanup;
    }

    // Retrieve the context from the pipeline.
    PWINBIO_ENGINE_CONTEXT context = 
           (PWINBIO_ENGINE_CONTEXT)Pipeline->EngineContext;

    // Return if an enrollment is already in progress. This example assumes that 
    // your engine adapter context contains an enrollment object.
    if (context->Enrollment.InProgress == TRUE)
    {
        hr = WINBIO_E_INVALID_DEVICE_STATE;
        goto cleanup;
    }

    // Call a custom function (_AdapterCreateEnrollmentTemplate) to create a 
    // new enrollment template and attach it to the engine adapter context.
    hr = _AdapterCreateEnrollmentTemplate( 
            context, 
            &context->Enrollment
            );
    if (FAILED(hr))
    {
        goto cleanup;
    }

    // Initialize any Enrollment data members not initialized by  the 
    // _AdapterCreateEnrollmentTemplate function. This example assumes that
    // your enrollment object contains at a minimum a field that specifies 
    // the number of biometric samples and another that specifies whether a
    // new enrollment is in progress.
    context->Enrollment.SampleCount = 0;
    context->Enrollment.InProgress = TRUE;

cleanup:

    return hr;
}

Requirements

Requirement	Value
Minimum supported client	Windows 7 [desktop apps only]
Minimum supported server	Windows Server 2008 R2 [desktop apps only]
Target Platform	Windows
Header	winbio_adapter.h (include Winbio_adapter.h)

Share via