text: //------------------------------------------------------------------------------
  // File: SysClock.cpp
  //
  // Desc: DirectShow base classes - implements a system clock based on 
  //       IReferenceClock.
  //
  // Copyright (c) 1992-2001 Microsoft Corporation.  All rights reserved.
  //------------------------------------------------------------------------------
  
  
  #include <streams.h>
  #include <limits.h>
  
  
  //#ifdef FILTER_DLL
  
  /* List of class IDs and creator functions for the class factory. This
     provides the link between the OLE entry point in the DLL and an object
     being created. The class factory will call the static CreateInstance
     function when it is asked to create a CLSID_SystemClock object */
  
  CFactoryTemplate g_Templates[1];// = {
  //    {&CLSID_SystemClock, CSystemClock::CreateInstance}
  //};
  
  int g_cTemplates = sizeof(g_Templates) / sizeof(g_Templates[0]);
  //#endif
  
  /* This goes in the factory template table to create new instances */
  CUnknown * WINAPI CSystemClock::CreateInstance(__inout_opt LPUNKNOWN pUnk, __inout HRESULT *phr)
  {
      return new CSystemClock(NAME("System reference clock"),pUnk, phr);
  }
  
  
  CSystemClock::CSystemClock(__in_opt LPCTSTR pName, __inout_opt LPUNKNOWN pUnk, __inout HRESULT *phr) :
      CBaseReferenceClock(pName, pUnk, phr)
  {
  }
  
  STDMETHODIMP CSystemClock::NonDelegatingQueryInterface(
      REFIID riid,
      __deref_out void ** ppv)
  {
      if (riid == IID_IPersist)
      {
          return GetInterface(static_cast<IPersist *>(this), ppv);
      }
      else if (riid == IID_IAMClockAdjust)
      {
          return GetInterface(static_cast<IAMClockAdjust *>(this), ppv);
      }
      else
      {
          return CBaseReferenceClock::NonDelegatingQueryInterface(riid, ppv);
      }
  }
  
  /* Return the clock's clsid */
  STDMETHODIMP
  CSystemClock::GetClassID(__out CLSID *pClsID)
  {
      CheckPointer(pClsID,E_POINTER);
      ValidateReadWritePtr(pClsID,sizeof(CLSID));
      *pClsID = CLSID_SystemClock;
      return NOERROR;
  }
  
  
  STDMETHODIMP 
  CSystemClock::SetClockDelta(REFERENCE_TIME rtDelta)
  {
      return SetTimeDelta(rtDelta);
  }
  