WinBioUnlockUnit function (winbio.h)

Article
10/13/2021

Releases the session lock on the specified biometric unit.

Syntax

HRESULT WinBioUnlockUnit(
  [in] WINBIO_SESSION_HANDLE SessionHandle,
  [in] WINBIO_UNIT_ID        UnitId
);

Parameters

[in] SessionHandle

A WINBIO_SESSION_HANDLE value that identifies an open biometric session. Open a synchronous session handle by calling WinBioOpenSession. Open an asynchronous session handle by calling WinBioAsyncOpenSession.

[in] UnitId

A WINBIO_UNIT_ID value that specifies the biometric unit to unlock.

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.

Return code	Description
E_HANDLE	The session handle is not valid.
E_INVALIDARG	The UnitId parameter cannot contain zero.
WINBIO_E_LOCK_VIOLATION	The biometric unit specified by the UnitId parameter is not currently locked by the session.

Remarks

Calling WinBioUnlockUnit automatically releases any locks held by the session. This function will fail if the biometric unit specified by the UnitId has not been previously locked by calling the WinBioLockUnit function.

To use WinBioUnlockUnit synchronously, call the function with a session handle created by calling WinBioOpenSession. The function blocks until the operation completes or an error is encountered.

To use WinBioUnlockUnit asynchronously, call the function with a session handle created by calling WinBioAsyncOpenSession. The framework allocates a WINBIO_ASYNC_RESULT structure and uses it to return information about operation success or failure. The WINBIO_ASYNC_RESULT structure is returned to the application callback or to the application message queue, depending on the value you set in the NotificationMethod parameter of the WinBioAsyncOpenSession function:

If you choose to receive completion notices by using a callback, you must implement a PWINBIO_ASYNC_COMPLETION_CALLBACK function and set the NotificationMethod parameter to WINBIO_ASYNC_NOTIFY_CALLBACK.
If you choose to receive completion notices by using the application message queue, you must set the NotificationMethod parameter to WINBIO_ASYNC_NOTIFY_MESSAGE. The framework returns a WINBIO_ASYNC_RESULT pointer to the LPARAM field of the window message.

To prevent memory leaks, you must call WinBioFree to release the WINBIO_ASYNC_RESULT structure after you have finished using it.

Examples

The following function calls WinBioLockUnit to lock the biometric unit before calling WinBioIdentify to identify the user. It calls WinBioUnlockUnit to unlock the biometric union before closing the open session. Link to the Winbio.lib static library and include the following header files:

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

HRESULT LockUnlock( )
{
    // Declare variables.
    HRESULT hr = S_OK;
    WINBIO_IDENTITY identity = {0};
    WINBIO_SESSION_HANDLE sessionHandle = NULL;
    WINBIO_UNIT_ID unitId = 0;
    WINBIO_REJECT_DETAIL rejectDetail = 0;
    WINBIO_BIOMETRIC_SUBTYPE subFactor = WINBIO_SUBTYPE_NO_INFORMATION;
    BOOL lockAcquired = FALSE;

    // 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
            NULL,                       // Database ID
            &sessionHandle              // [out] Session handle
            );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioEnumBiometricUnits failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }

    // Lock the session. The Biometric unit ID (1) is hard coded in
    // this example.
    hr = WinBioLockUnit( sessionHandle, 1 );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioLockUnit failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }
    wprintf_s(L"\n Biometric unit #1 is locked.\n");
    lockAcquired = TRUE;


    // Locate the biometric sensor and retrieve a WINBIO_IDENTITY object.
    // You must swipe your finger on the sensor.
    wprintf_s(L"\n Calling WinBioIdentify - Swipe finger on sensor...\n");
    hr = WinBioIdentify( 
            sessionHandle, 
            &unitId, 
            &identity, 
            &subFactor, 
            &rejectDetail
            );
    wprintf_s(L"\n Swipe processed - Unit ID: %d\n", unitId);
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioIdentify failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }


e_Exit:

    // Unlock the biometric unit if it is locked.
    if (lockAcquired == TRUE)
    {
        hr = WinBioUnlockUnit( sessionHandle, 1 );
        if (FAILED(hr))
        {
            wprintf_s(L"\n WinBioUnlockUnit failed. hr = 0x%x\n", hr);
        }
        wprintf_s(L"\n Biometric unit #1 is unlocked.\n");
        lockAcquired = FALSE;
    }

    if (sessionHandle != NULL)
    {
        WinBioCloseSession(sessionHandle);
        sessionHandle = NULL;
    }

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

    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.h (include Winbio.h)
Library	Winbio.lib
DLL	Winbio.dll

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