自学教程：C++ CheckShutdown函数代码示例

HRESULT HDMediaSource::SetRate(BOOL fThin,float flRate){	DbgLogPrintf(L"%s::SetRate... (Thin:%d, Rate:%.2f)",L"HDMediaSource",fThin,flRate);	CritSec::AutoLock lock(_cs);	HRESULT hr = CheckShutdown();	if (FAILED(hr))		return hr;	if (fThin)		return MF_E_THINNING_UNSUPPORTED;	if (flRate < MIN_MFSOURCE_RATE_SUPPORT ||		flRate > MAX_MFSOURCE_RATE_SUPPORT)		return MF_E_UNSUPPORTED_RATE;	if (flRate == _currentRate)		return _pEventQueue->QueueEventParamVar(MESourceRateChanged,GUID_NULL,S_OK,nullptr);	ComPtr<SourceOperation> op;	hr = SourceOperation::CreateSetRateOperation(fThin,flRate,op.GetAddressOf());	if (FAILED(hr))		return hr;	DbgLogPrintf(L"%s::SetRate OK.",L"HDMediaSource");	return QueueOperation(op.Get());}

HRESULT FlvStream::GetEvent(DWORD dwFlags, IMFMediaEvent** ppEvent){  HRESULT hr = S_OK;  IMFMediaEventQueuePtr pQueue;  { // scope for lock    SourceLock lock(source);    // Check shutdown    hr = CheckShutdown();    // Cache a local pointer to the queue.    if (SUCCEEDED(hr))    {      pQueue = event_queue;    }  }   // release lock  // Use the local pointer to call GetEvent.  if (SUCCEEDED(hr))  {    hr = pQueue->GetEvent(dwFlags, ppEvent);  }  return hr;}

HRESULT PpboxStream::GetMediaSource(IMFMediaSource** ppMediaSource){    SourceLock lock(m_pSource);    if (ppMediaSource == NULL)    {        return E_POINTER;    }    if (m_pSource == NULL)    {        return E_UNEXPECTED;    }    HRESULT hr = S_OK;    hr = CheckShutdown();    // QI the source for IMFMediaSource.    // (Does not hold the source's critical section.)    if (SUCCEEDED(hr))    {        hr = m_pSource->QueryInterface(IID_PPV_ARGS(ppMediaSource));    }    return hr;}

HRESULT CMPEG1Stream::GetMediaSource(IMFMediaSource **ppMediaSource){    SourceLock lock(m_spSource.Get());    if (ppMediaSource == nullptr)    {        return E_POINTER;    }    if (m_spSource == nullptr)    {        return E_UNEXPECTED;    }    HRESULT hr = S_OK;    hr = CheckShutdown();    // QI the source for IMFMediaSource.    // (Does not hold the source's critical section.)    if (SUCCEEDED(hr))    {        hr = m_spSource.CopyTo(IID_PPV_ARGS(ppMediaSource));    }    return hr;}

__override HRESULT CGeometricMediaSource::DispatchOperation(CSourceOperation *pOp){	AutoLock lock(_critSec);    HRESULT hr = CheckShutdown();    if (SUCCEEDED(hr))    {        switch(pOp->GetOperationType())        {        case CSourceOperation::Operation_Start:            hr = DoStart(static_cast<CStartOperation *>(pOp));            break;        case CSourceOperation::Operation_Stop:            hr = DoStop(pOp);            break;        case CSourceOperation::Operation_SetRate:            hr = DoSetRate(static_cast<CSetRateOperation *>(pOp));            break;        default:            hr = E_UNEXPECTED;            break;        }    }    return hr;}

HRESULT WavStream::GetStreamDescriptor(IMFStreamDescriptor** ppStreamDescriptor){    if (ppStreamDescriptor == NULL)    {        return E_POINTER;    }    if (m_pStreamDescriptor == NULL)    {        return E_UNEXPECTED;    }    EnterCriticalSection(&m_critSec);    HRESULT hr = S_OK;        hr = CheckShutdown();    if (SUCCEEDED(hr))    {           *ppStreamDescriptor = m_pStreamDescriptor;        (*ppStreamDescriptor)->AddRef();    }    LeaveCriticalSection(&m_critSec);    return hr;}

HRESULT MPEG1Stream::GetMediaSource(IMFMediaSource** ppMediaSource){    SourceLock lock(m_pSource);    if (ppMediaSource == NULL)    {        return E_POINTER;    }    if (m_pSource == NULL)    {        return E_UNEXPECTED;    }    HRESULT hr = S_OK;        CHECK_HR(hr = CheckShutdown());    // QI the source for IMFMediaSource.    // (Does not hold the source's critical section.)    CHECK_HR(hr = m_pSource->QueryInterface(IID_PPV_ARGS(ppMediaSource)));done:    return hr;}

// Called when the rate changes on the presentation clock.HRESULT STDMETHODCALLTYPE EVRCustomPresenter::OnClockSetRate(MFTIME hnsSystemTime, float fRate){  Log("EVRCustomPresenter::OnClockSetRate (rate=%f)", fRate);  HRESULT hr = S_OK;  CAutoLock lock(this);  // We cannot set the rate after shutdown.  hr = CheckShutdown();  CHECK_HR(hr, "EVRCustomPresenter::OnClockRestart cannot set rate after shutdown");  // If the rate is changing from zero (scrubbing) to non-zero, cancel the frame-step operation.  if ((m_fRate == 0.0f) && (fRate != 0.0f))  {    CancelFrameStep();    m_FrameStep.samples.Clear();  }  m_fRate = fRate;  // Tell the scheduler about the new rate.  m_scheduler.SetClockRate(fRate);  return hr;}

// Retrieves the presenter's media type.HRESULT STDMETHODCALLTYPE EVRCustomPresenter::GetCurrentMediaType(IMFVideoMediaType **ppMediaType){  Log("EVRCustomPresenter::GetCurrentMediaType");  HRESULT hr = S_OK;  if (ppMediaType == NULL)  {    return E_POINTER;  }  *ppMediaType = NULL;  CAutoLock lock(this);  hr = CheckShutdown();  CHECK_HR(hr, "EVRCustomPresenter::GetCurrentMediaType presenter is shutdown");  CheckPointer(m_pMediaType, MF_E_NOT_INITIALIZED);  // Get IMFVideoMediaType pointer and store as an IMFMediaType pointer by callin QueryInterface  hr = m_pMediaType->QueryInterface(__uuidof(IMFVideoMediaType), (void**)&ppMediaType);  CHECK_HR(hr, "EVRCustomPresenter::GetCurrentMediaType IMFMediaType::QueryInterface() failed");  return hr;}

STDMETHODIMP CMediaEventGenerator::QueueEvent(    _In_ MediaEventType met,    _In_ REFGUID extendedType,    _In_ HRESULT hrStatus,    _In_opt_ const PROPVARIANT* pvValue    ){    HRESULT hr = S_OK;    //MFWMITRACE(DH_THIS_FILE, TP_NORMAL, __FUNCTION__ " : MultiPinMFT QueueEvent called");    m_critSec.Lock();        hr = CheckShutdown();    if (SUCCEEDED(hr))    {        hr = m_pQueue->QueueEventParamVar(                            met,                             extendedType,                             hrStatus,                             pvValue                            );    }    m_critSec.Unlock();        return hr;}

void CMPEG1Stream::Shutdown(){    if (SUCCEEDED(CheckShutdown()))    {        m_state = STATE_SHUTDOWN;        // Shut down the event queue.        if (m_spEventQueue)        {            m_spEventQueue->Shutdown();        }        // Release objects.        m_Samples.Clear();        m_Requests.Clear();        m_spStreamDescriptor.Reset();        m_spEventQueue.Reset();        // NOTE:        // Do NOT release the source pointer here, because the stream uses        // it to hold the critical section. In particular, the stream must        // hold the critical section when checking the shutdown status,        // which obviously can occur after the stream is shut down.        // It is OK to hold a ref count on the source after shutdown,        // because the source releases its ref count(s) on the streams,        // which breaks the circular ref count.    }}

void CMPEG1Stream::Pause(){    ThrowIfError(CheckShutdown());    m_state = STATE_PAUSED;    ThrowIfError(QueueEvent(MEStreamPaused, GUID_NULL, S_OK, nullptr));}