class CPullPin : public CAMThread
{
    IAsyncReader*       m_pReader;
    REFERENCE_TIME      m_tStart;
    REFERENCE_TIME      m_tStop;
    REFERENCE_TIME      m_tDuration;
    BOOL                m_bSync;

    enum ThreadMsg {
        TM_Pause,       // stop pulling and wait for next message
        TM_Start,       // start pulling
        TM_Exit,        // stop and exit
    };

    ThreadMsg m_State;

    // override pure thread proc from CAMThread
    DWORD ThreadProc(void);

    // running pull method (check m_bSync)
    void Process(void);

    // clean up any cancelled i/o after a flush
    void CleanupCancelled(void);

    // suspend thread from pulling, eg during seek
    HRESULT PauseThread();

    // start thread pulling - create thread if necy
    HRESULT StartThread();

    // stop and close thread
    HRESULT StopThread();

    // called from ProcessAsync to queue and collect requests
    HRESULT QueueSample(
                REFERENCE_TIME& tCurrent,
                REFERENCE_TIME tAlignStop,
                BOOL bDiscontinuity);

    HRESULT CollectAndDeliver(
                REFERENCE_TIME tStart,
                REFERENCE_TIME tStop);

    HRESULT DeliverSample(
                IMediaSample* pSample,
                REFERENCE_TIME tStart,
                REFERENCE_TIME tStop);

protected:
    IMemAllocator *     m_pAlloc;

public:
    CPullPin();
    virtual ~CPullPin();

    // returns S_OK if successfully connected to an IAsyncReader interface
    // from this object
    // Optional allocator should be proposed as a preferred allocator if
    // necessary
    // bSync is TRUE if we are to use sync reads instead of the
    // async methods.
    HRESULT Connect(IUnknown* pUnk, IMemAllocator* pAlloc, BOOL bSync);

    // disconnect any connection made in Connect
    HRESULT Disconnect();

    // agree an allocator using RequestAllocator - optional
    // props param specifies your requirements (non-zero fields).
    // returns an error code if fail to match requirements.
    // optional IMemAllocator interface is offered as a preferred allocator
    // but no error occurs if it can't be met.
    virtual HRESULT DecideAllocator(
                IMemAllocator* pAlloc,
                ALLOCATOR_PROPERTIES * pProps);

    // set start and stop position. if active, will start immediately at
    // the new position. Default is 0 to duration
    HRESULT Seek(REFERENCE_TIME tStart, REFERENCE_TIME tStop);

    // return the total duration
    HRESULT Duration(REFERENCE_TIME* ptDuration);

    // start pulling data
    HRESULT Active(void);

    // stop pulling data
    HRESULT Inactive(void);

    // helper functions
    LONGLONG AlignDown(LONGLONG ll, LONG lAlign) {
        // aligning downwards is just truncation
        return ll & ~(lAlign-1);
    };