Enumerating Services
The WpdServicesApiSample application includes code that demonstrates how an application can enumerate all of the Contacts services found on any of the devices currently connected to a computer.
When the user chooses option "0" at the command line, the application invokes the EnumerateContactsServices method that is found in the ServiceEnumeration.cpp module. This method displays a list of all connected devices that support the Contacts service.
For example, if the WpdServiceSampleDriver is the only installed device, the application returns three fields of data: a Friendly Name ("Sample Device"), a Manufacturer ("Windows Portable Devices Group"), and, a Description ("Contacts Service Device 2000").
The EnumerateContactsServices method accomplishes the following tasks:
- Creates an IPortableDeviceManager interface to handle enumeration of installed devices.
- Creates an IPortableDeviceServiceManager interface to handle enumeration of the services on each device.
- Iterates through the installed devices, searching for the Contacts service, and displays the device information for any device that supports this service.
The following code illustrates the EnumerateContactsServices method.
// Enumerates all Contacts Services, displaying the associated device of each service.
void EumerateContactsServices(CAtlArray<PWSTR>& ContactsServicePnpIDs)
{
HRESULT hr = S_OK;
DWORD cPnpDeviceIDs = 0;
PWSTR* pPnpDeviceIDs = NULL;
CComPtr<IPortableDeviceManager> pPortableDeviceManager;
CComPtr<IPortableDeviceServiceManager> pServiceManager;
// CoCreate the IPortableDeviceManager interface to enumerate
// portable devices and to get information about them.
hr = CoCreateInstance(CLSID_PortableDeviceManager,
NULL,
CLSCTX_INPROC_SERVER,
IID_PPV_ARGS(&pPortableDeviceManager));
if (FAILED(hr))
{
printf("! Failed to CoCreateInstance CLSID_PortableDeviceManager, hr = 0x%lx\n",hr);
}
// Retrieve the IPortableDeviceServiceManager interface to enumerate device services.
if (SUCCEEDED(hr))
{
hr = pPortableDeviceManager->QueryInterface(IID_PPV_ARGS(&pServiceManager));
if (FAILED(hr))
{
printf("! Failed to QueryInterface IID_IPortableDeviceServiceManager, hr = 0x%lx\n",hr);
}
}
if (SUCCEEDED(hr))
{
// First, pass NULL as the PWSTR array pointer to get the total number
// of devices found on the system.
hr = pPortableDeviceManager->GetDevices(NULL, &cPnpDeviceIDs);
if (FAILED(hr))
{
printf("! Failed to get number of devices on the system, hr = 0x%lx\n",hr);
}
if (SUCCEEDED(hr) && (cPnpDeviceIDs > 0))
{
// Second, allocate an array to hold the PnPDeviceID strings returned from
// the IPortableDeviceManager::GetDevices method
pPnpDeviceIDs = new (std::nothrow) PWSTR[cPnpDeviceIDs];
if (pPnpDeviceIDs != NULL)
{
DWORD dwIndex = 0;
hr = pPortableDeviceManager->GetDevices(pPnpDeviceIDs, &cPnpDeviceIDs);
if (SUCCEEDED(hr))
{
// For each device found, find the contacts service
for (dwIndex = 0; dwIndex < cPnpDeviceIDs; dwIndex++)
{
DWORD cPnpServiceIDs = 0;
PWSTR pPnpServiceID = NULL;
// First, pass NULL as the PWSTR array pointer to get the total number
// of contacts services (SERVICE_Contacts) found on the device.
// To find the total number of all services on the device, use GUID_DEVINTERFACE_WPD_SERVICE.
hr = pServiceManager->GetDeviceServices(pPnpDeviceIDs[dwIndex], SERVICE_Contacts, NULL, &cPnpServiceIDs);
if (SUCCEEDED(hr) && (cPnpServiceIDs > 0))
{
// For simplicity, we are only using the first contacts service on each device
cPnpServiceIDs = 1;
hr = pServiceManager->GetDeviceServices(pPnpDeviceIDs[dwIndex], SERVICE_Contacts, &pPnpServiceID, &cPnpServiceIDs);
if (SUCCEEDED(hr))
{
// We've found the service, display it and save its PnP Identifier
ContactsServicePnpIDs.Add(pPnpServiceID);
printf("[%d] ", static_cast<DWORD>(ContactsServicePnpIDs.GetCount()-1));
// Display information about the device that contains this service.
DisplayDeviceInformation(pServiceManager, pPnpServiceID);
// ContactsServicePnpIDs now owns the memory for this string
pPnpServiceID = NULL;
}
else
{
printf("! Failed to get the first contacts service from '%ws, hr = 0x%lx\n",pPnpDeviceIDs[dwIndex],hr);
}
}
}
}
// Free all returned PnPDeviceID strings
FreePortableDevicePnPIDs(pPnpDeviceIDs, cPnpDeviceIDs);
// Delete the array of PWSTR pointers
delete [] pPnpDeviceIDs;
pPnpDeviceIDs = NULL;
}
else
{
printf("! Failed to allocate memory for PWSTR array\n");
}
}
}
printf("\n%d Contacts Device Service(s) found on the system\n\n", static_cast<DWORD>(ContactsServicePnpIDs.GetCount()));
}
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