ISensorDriver::OnClientDisconnect method (sensorsclassextension.h)

The ISensorDriver::OnClientDisconnect method notifies the sensor driver that a client application has disconnected.

Syntax

HRESULT OnClientDisconnect(
  [in] IWDFFile *pClientFile,
  [in] LPWSTR   pwszSensorID
);

Parameters

[in] pClientFile

Pointer to an IWDFFile interface that represents the file object for the client that disconnected.

[in] pwszSensorID

LPWSTR that contains the ID for the sensor from which the client application is disconnecting.

Return value

If the operation succeeds, this method returns S_OK. Otherwise, this method returns one of the error codes that are defined in Winerror.h.

Remarks

The sensor class extension calls this method in the following instances:

• An application closes normally.
• The user revokes permission for an application to access the device that contains the specified sensor.
• The cleanup work from a call to ISensorClassExtension::CleanupFile has completed.

For more information about how to use this method, see Filtering data.

Examples

The following example code demonstrates an implementation of ISensorDriver::OnClientDisconnect. This function uses an ATL simple map, named Clients, to keep track of connected clients. See ISensorDriver::OnClientConnect for an example of how connected clients are added to the map.

The ClientData structure is defined as follows.

// Struct to keep track of connected client status.
struct ClientData
{
    BOOL bListening;  // Client is listening to events.
    ULONG ulInterval;  // Interval requested by client.
};

The function definition follows.

HRESULT CSensorDdi:: OnClientDisconnect(
        __in IWDFFile* pClientFile,
        __in LPWSTR pwszSensorID
        )
{
    if(NULL == pClientFile ||
       NULL == pwszSensorID)
    {
        return E_POINTER;
    }

    HRESULT hr = S_OK;
    ClientData* pCD = NULL;
    BOOL bRet = FALSE;

    // Find this client in the map.
    pCD = Clients.Lookup(pClientFile);
    if(pCD == NULL)
    {
        hr = E_UNEXPECTED;
    }

    if(SUCCEEDED(hr))
    {
        // Free the client data memory.
        delete pCD;
        pCD = NULL;

        // Remove this client from the array.
        bRet = Clients.Remove(pClientFile);
        if(FALSE == bRet)
        {
            hr = E_UNEXPECTED;
        }
    }

    return hr;
}

Requirements

See also

ISensorDriver

ISensorDriver::OnClientConnect