WinBioIdentifyWithCallback function (winbio.h)

Asynchronously captures a biometric sample and determines whether it matches an existing biometric template. The function returns immediately to the caller, performs capture and identification on a separate thread, and calls into an application-defined callback function to update operation status.

Syntax

HRESULT WinBioIdentifyWithCallback(
  [in]           WINBIO_SESSION_HANDLE     SessionHandle,
  [in]           PWINBIO_IDENTIFY_CALLBACK IdentifyCallback,
  [in, optional] PVOID                     IdentifyCallbackContext
);

Parameters

[in] SessionHandle

A WINBIO_SESSION_HANDLE value that identifies an open biometric session.

[in] IdentifyCallback

Address of a callback function that will be called by the WinBioIdentifyWithCallback function when identification succeeds or fails. You must create the callback.

[in, optional] IdentifyCallbackContext

Pointer to an application-defined data structure that is passed to the callback function in its IdentifyCallbackContext parameter. This structure can contain any data that the custom callback function is designed to handle.

Return value

If the function succeeds, it returns S_OK. If the function fails, it returns an HRESULT value that indicates the error. Possible values include, but are not limited to, those in the following table. For a list of common error codes, see Common HRESULT Values.

Remarks

The callback routine must have the following signature:

VOID CALLBACK IdentifyCallback(
__in_opt PVOID IdentifyCallbackContext,
__in HRESULT OperationStatus,
__in WINBIO_UNIT_ID UnitId,
__in WINBIO_IDENTITY *Identity,
__in WINBIO_BIOMETRIC_SUBTYPE SubFactor,
__in WINBIO_REJECT_DETAIL RejectDetail
);

Examples

The following code example calls WinBioIdentifyWithCallback to identify a user from a biometric scan. WinBioIdentifyWithCallback is an asynchronous function that configures the biometric subsystem to process biometric input on another thread. Output from the biometric subsystem is then sent to a custom callback function named IdentifyCallback. Link to the Winbio.lib static library and include the following header files:

• Windows.h
• Stdio.h
• Conio.h
• Winbio.h

HRESULT IdentifyWithCallback(BOOL bCancel)
{
    // Declare variables.
    HRESULT hr = S_OK;
    WINBIO_SESSION_HANDLE sessionHandle = NULL;

    // Connect to the system pool. 
    hr = WinBioOpenSession( 
            WINBIO_TYPE_FINGERPRINT,    // Service provider
            WINBIO_POOL_SYSTEM,         // Pool type 
            WINBIO_FLAG_DEFAULT,        // Configuration and access 
            NULL,                       // Array of biometric unit IDs 
            0,                          // Count of biometric unit IDs 
            WINBIO_DB_DEFAULT,          // Database ID 
            &sessionHandle              // [out] Session handle
            );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioOpenSession failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }

    // Call WinBioIdentifyWithCallback. The method is asynchronous
    // and returns immediately.
    wprintf_s(L"\n Calling WinBioIdentifyWithCallback");
    wprintf_s(L"\n Swipe the sensor ...\n");
    hr = WinBioIdentifyWithCallback( 
            sessionHandle,              // Open biometric session
            IdentifyCallback,           // Callback function
            NULL                        // Optional context
            );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioIdentifyWithCallback failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }

    // Cancel user identification if the bCancel flag is set.
    if (bCancel)
    {
        wprintf_s(L"\n Starting CANCEL timer...\n");
        Sleep( 7000 );

        wprintf_s(L"\n Calling WinBioCancel\n");
        hr = WinBioCancel( sessionHandle );
        if (FAILED(hr))
        {
            wprintf_s(L"\n WinBioCancel failed. hr = 0x%x\n", hr);
            goto e_Exit;
        }
    }

    // Wait for the asynchronous identification process to complete 
    // or be canceled.
    hr = WinBioWait( sessionHandle );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioWait failed. hr = 0x%x\n", hr);
    }

e_Exit:

    if (sessionHandle != NULL)
    {
       wprintf_s(L"\n Closing the session.\n");

        hr = WinBioCloseSession(sessionHandle);
        if (FAILED(hr))
        {
            wprintf_s(L"\n WinBioCloseSession failed. hr = 0x%x\n", hr);
        }
        sessionHandle = NULL;
    }

    wprintf_s(L"\n Hit any key to exit...");
    _getch();

    return hr;
}

//------------------------------------------------------------------------
// The following function is the callback for WinBioIdentifyWithCallback.
// The function filters the response from the biometric subsystem and 
// writes a result to the console window.
// 
VOID CALLBACK IdentifyCallback(
    __in_opt PVOID IdentifyCallbackContext,
    __in HRESULT OperationStatus,
    __in WINBIO_UNIT_ID UnitId,
    __in WINBIO_IDENTITY *Identity,
    __in WINBIO_BIOMETRIC_SUBTYPE SubFactor,
    __in WINBIO_REJECT_DETAIL RejectDetail
    )
{
    UNREFERENCED_PARAMETER(IdentifyCallbackContext);
    UNREFERENCED_PARAMETER(Identity);

    wprintf_s(L"\n IdentifyCallback executing");
    wprintf_s(L"\n Swipe processed for unit ID %d\n", UnitId);

    // The attempt to process the fingerprint failed.
    if (FAILED(OperationStatus))
    {
        if (OperationStatus == WINBIO_E_UNKNOWN_ID)
        {
            wprintf_s(L"\n Unknown identity.\n");
        }
        else if (OperationStatus == WINBIO_E_BAD_CAPTURE)
        {
            wprintf_s(L"\n Bad capture; reason: %d\n", RejectDetail);
        }
        else
        {
            wprintf_s(L"IdentifyCallback failed.");
            wprintf_s(L"OperationStatus = 0x%x\n", OperationStatus); 
        }
    }
    // Processing succeeded and the finger swiped is written
    // to the console window.
    else
    {
        wprintf_s(L"\n The following finger was used:");
        switch (SubFactor)
        {
            case WINBIO_SUBTYPE_NO_INFORMATION:
                wprintf_s(L"\n No information\n");
                break;
            case WINBIO_ANSI_381_POS_RH_THUMB:
                wprintf_s(L"\n RH thumb\n");
                break;
            case WINBIO_ANSI_381_POS_RH_INDEX_FINGER:
                wprintf_s(L"\n RH index finger\n");
                break;
            case WINBIO_ANSI_381_POS_RH_MIDDLE_FINGER:
                wprintf_s(L"\n RH middle finger\n");
                break;
            case WINBIO_ANSI_381_POS_RH_RING_FINGER:
                wprintf_s(L"\n RH ring finger\n");
                break;
            case WINBIO_ANSI_381_POS_RH_LITTLE_FINGER:
                wprintf_s(L"\n RH little finger\n");
                break;
            case WINBIO_ANSI_381_POS_LH_THUMB:
                wprintf_s(L"\n LH thumb\n");
                break;
            case WINBIO_ANSI_381_POS_LH_INDEX_FINGER:
                wprintf_s(L"\n LH index finger\n");
                break;
            case WINBIO_ANSI_381_POS_LH_MIDDLE_FINGER:
                wprintf_s(L"\n LH middle finger\n");
                break;
            case WINBIO_ANSI_381_POS_LH_RING_FINGER:
                wprintf_s(L"\n LH ring finger\n");
                break;
            case WINBIO_ANSI_381_POS_LH_LITTLE_FINGER:
                wprintf_s(L"\n LH little finger\n");
                break;
            case WINBIO_SUBTYPE_ANY:
                wprintf_s(L"\n Any finger\n");
                break;
            default:
                break;
        }
    }
}

Requirements

See also

WinBioIdentify