PIBIO_STORAGE_DETACH_FN callback function (winbio_adapter.h)

Article
07/27/2022

Called by the Windows Biometric Framework immediately before a storage adapter is removed from the processing pipeline of the biometric unit. The purpose of this function is to release adapter specific resources attached to the pipeline.

Syntax

PIBIO_STORAGE_DETACH_FN PibioStorageDetachFn;

HRESULT PibioStorageDetachFn(
  [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.
WINBIO_E_INVALID_DEVICE_STATE	The StorageContext field of the WINBIO_PIPELINE structure cannot be NULL.

Remarks

To prevent memory leaks, your implementation of the StorageAdapterDetach function must release the private WINBIO_STORAGE_CONTEXT structure pointed to by the StorageContext member of the pipeline along with any other resources attached to the storage context.

If the StorageContext field in the pipeline object is NULL when this function is called, the pipeline was not properly initialized and you must return WINBIO_E_INVALID_DEVICE_STATE to notify the Windows Biometric Framework of the problem.

Before returning S_OK, this function must set the StorageContext field of the WINBIO_PIPELINE structure to NULL and the StorageHandle field to INVALID_HANDLE_VALUE.

Examples

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

/////////////////////////////////////////////////////////////////////////////////////////
//
// StorageAdapterDetach
//
// Purpose:
//      Release adapter specific resources attached to the pipeline.
//
// Parameters:
//      Pipeline -  Pointer to a WINBIO_PIPELINE structure associated with 
//                  the biometric unit performing the operation.
//
static HRESULT
WINAPI
StorageAdapterDetach(
    __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_STORAGE_CONTEXT storageContext = 
           (PWINBIO_STORAGE_CONTEXT)Pipeline->StorageContext;

    // Verify the pipeline state.
    if (storageContext == NULL)
    {
        // The pipeline state is not valid. This function should never
        // be called if the storage context in the pipeline is already
        // closed.
        hr = WINBIO_E_INVALID_DEVICE_STATE;
        goto cleanup;
    }

    // Release any structures attached to the context block.
    StorageAdapterClearContext(Pipeline);

    // Close the database.
    StorageAdapterCloseDatabase(Pipeline);

    // Remove the context from the pipeline.
    Pipeline->StorageContext = NULL;
    Pipeline->StorageHandle = INVALID_HANDLE_VALUE;

    // Clear the result set. Depending on your implementation, this action
    // can be performed by the StorageAdapterClearContext function called
    // earlier.
    ResultSetCleanup(&storageContext->ResultSet);

    // Release the adapter context.
    _AdapterRelease( storageContext );
    storageContext = NULL;

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)

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