Samples/multimedia/directshow/baseclasses/schedule.h

//------------------------------------------------------------------------------
// File: Schedule.h
//
// Desc: DirectShow base classes.
//
// Copyright (c) 1996-2001 Microsoft Corporation.  All rights reserved.
//------------------------------------------------------------------------------


#ifndef __CAMSchedule__
#define __CAMSchedule__

class CAMSchedule : private CBaseObject
{
public:
    virtual ~CAMSchedule();
    // ev is the event we should fire if the advise time needs re-evaluating
    CAMSchedule( HANDLE ev );

    DWORD GetAdviseCount();
    REFERENCE_TIME GetNextAdviseTime();

    // We need a method for derived classes to add advise packets, we return the cookie
    DWORD_PTR AddAdvisePacket( const REFERENCE_TIME & time1, const REFERENCE_TIME & time2, HANDLE h, BOOL periodic );
    // And a way to cancel
    HRESULT Unadvise(DWORD_PTR dwAdviseCookie);

    // Tell us the time please, and we'll dispatch the expired events.  We return the time of the next event.
    // NB: The time returned will be "useless" if you start adding extra Advises.  But that's the problem of
    // whoever is using this helper class (typically a clock).
    REFERENCE_TIME Advise( const REFERENCE_TIME & rtTime );

    // Get the event handle which will be set if advise time requires re-evaluation.
    HANDLE GetEvent() const { return m_ev; }

private:
    // We define the nodes that will be used in our singly linked list
    // of advise packets.  The list is ordered by time, with the
    // elements that will expire first at the front.
    class CAdvisePacket
    {
    public:
        CAdvisePacket()
        {}

        CAdvisePacket * m_next;
        DWORD_PTR       m_dwAdviseCookie;
        REFERENCE_TIME  m_rtEventTime;      // Time at which event should be set
        REFERENCE_TIME  m_rtPeriod;         // Periodic time
        HANDLE          m_hNotify;          // Handle to event or semephore
        BOOL            m_bPeriodic;        // TRUE => Periodic event

        CAdvisePacket( __inout_opt CAdvisePacket * next, LONGLONG time ) : m_next(next), m_rtEventTime(time)
        {}

        void InsertAfter( __inout CAdvisePacket * p )
        {
            p->m_next = m_next;
            m_next    = p;
        }

        int IsZ() const // That is, is it the node that represents the end of the list
        { return m_next == 0; }

        CAdvisePacket * RemoveNext()
        {
            CAdvisePacket *const next = m_next;
            CAdvisePacket *const new_next = next->m_next;
            m_next = new_next;
            return next;
        }

        void DeleteNext()
        {
            delete RemoveNext();
        }

        CAdvisePacket * Next() const
        {
            CAdvisePacket * result = m_next;
            if (result->IsZ()) result = 0;
            return result;
        }

        DWORD_PTR Cookie() const
        { return m_dwAdviseCookie; }
    };

    // Structure is:
    // head -> elmt1 -> elmt2 -> z -> null
    // So an empty list is:       head -> z -> null
    // Having head & z as links makes insertaion,
    // deletion and shunting much easier.
    CAdvisePacket   head, z;            // z is both a tail and a sentry

    volatile DWORD_PTR  m_dwNextCookie;     // Strictly increasing
    volatile DWORD  m_dwAdviseCount;    // Number of elements on list

    CCritSec        m_Serialize;

    // AddAdvisePacket: adds the packet, returns the cookie (0 if failed)
    DWORD_PTR AddAdvisePacket( __inout CAdvisePacket * pPacket );
    // Event that we should set if the packed added above will be the next to fire.
    const HANDLE m_ev;

    // A Shunt is where we have changed the first element in the
    // list and want it re-evaluating (i.e. repositioned) in
    // the list.
    void ShuntHead();

    // Rather than delete advise packets, we cache them for future use
    CAdvisePacket * m_pAdviseCache;
    DWORD           m_dwCacheCount;
    enum { dwCacheMax = 5 };             // Don't bother caching more than five

    void Delete( __inout CAdvisePacket * pLink );// This "Delete" will cache the Link

// Attributes and methods for debugging
public:
#ifdef DEBUG
    void DumpLinkedList();
#else
    void DumpLinkedList() {}
#endif

};

#endif // __CAMSchedule__