How to rewrite the function below with ATL?
HRESULT EnumerateVideoInputFilters(void** gottaFilter)
{
// Once again, code stolen from the DX9 SDK.
// Create the System Device Enumerator.
ICreateDevEnum *pSysDevEnum = NULL;
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL,
CLSCTX_INPROC_SERVER, IID_ICreateDevEnum,
(void **)&pSysDevEnum);
if (FAILED(hr))
{
return hr;
}
// Obtain a class enumerator for the audio input category.
IEnumMoniker *pEnumCat = NULL;
hr = pSysDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,
&pEnumCat, 0);
if (hr == S_OK)
{
// Enumerate the monikers.
IMoniker *pMoniker = NULL;
ULONG cFetched;
if (pEnumCat->Next(1, &pMoniker, &cFetched) == S_OK)
{
//开发者_Python百科 Bind the first moniker to an object.
IPropertyBag *pPropBag;
hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag,
(void **)&pPropBag);
if (SUCCEEDED(hr))
{
// To retrieve the filter's friendly name,
// do the following:
VARIANT varName;
VariantInit(&varName);
hr = pPropBag->Read(L"FriendlyName", &varName, 0);
if (SUCCEEDED(hr))
{
wprintf(L"Selecting Audio Input Device: %s\n",
varName.bstrVal);
}
VariantClear(&varName);
// To create an instance of the filter,
// do the following:
// Remember to release gottaFilter later.
hr = pMoniker->BindToObject(NULL, NULL, IID_IBaseFilter,
gottaFilter);
pPropBag->Release();
}
pMoniker->Release();
}
pEnumCat->Release();
}
pSysDevEnum->Release();
return hr;
}
General idea is that you use CComPtr
and other similar things like CComBSTR
, CComVariant
, CComQIPtr
:
ISomeInterface* pointer = 0;
HRESULT hr = whatever->Obtain( &pointer );
if( SUCCEDED( hr ) ) {
hr = pointer-DoSomething();
pointer->Release();
}
return hr;
becomes:
CComPtr<ISomeInterface> pointer;
HRESULT hr = whatever->Obtain( &pointer );
if( FAILED( hr ) ) {
return hr;
}
r = pointer-DoSomething();
return hr;
This makes your code smaller and cleaner - you don't need to call Release()
for each pointer and thus you can reduce nesting by returning early.
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