ISensorDriver::OnClientDisconnect method (sensorsclassextension.h)

Artikel
02/22/2024

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.

You can use this call as a signal to update lists and reference counts of connected applications.

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

Requirement	Value
Minimum supported client	Windows 7,Available in Windows 7.
Minimum supported server	None supported
Target Platform	Desktop
Header	sensorsclassextension.h
Library	SensorsClassExtension.lib

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