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unknown.cpp
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Upload User: xhy777
Upload Date: 2007-02-14
Package Size: 24088k
Code Size: 3k
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Windows Kernel

Development Platform:

Visual C++

unknown.cpp：Code Content
  1. /*----------------------------------------------------------------------------
  2. / Title;
  3. /   unknown.cpp
  4. /
  5. / Authors;
  6. /   David De Vorchik (daviddv)
  7. /
  8. / Notes;
  9. /   Helper functions for handling IUnknown
  10. /----------------------------------------------------------------------------*/
  11. #include "precomp.hxx"
  12. #pragma hdrstop
  15. /*-----------------------------------------------------------------------------
  16. / CUnknown
  17. /   Helper functions to aid the implementation of IUnknown within objects,
  18. /   handles not only AddRef and Release, but also QueryInterface.
  19. /----------------------------------------------------------------------------*/
  21. LONG g_cRefCount = 0;          // global reference count
  23. CUnknown::CUnknown()
  24. {
  25.     m_cRefCount = 0;
  26.     InterlockedIncrement(&g_cRefCount);
  27. }
  29. CUnknown::~CUnknown()
  30. {
  31.     MDTraceAssert( m_cRefCount == 0 || m_cRefCount == 1000);    // 1000 is for agretation term case
  32.     InterlockedDecrement(&g_cRefCount);
  33. }
  36. /*-----------------------------------------------------------------------------
  37. / CUnknown::HandleQueryInterface
  38. / ------------------------------
  39. /   A table driven implementation of QueryInterface that scans through trying
  40. /   to find a suitable match for the object.
  41. /
  42. / In:
  43. /   riid = interface being requested
  44. /   ppvObject -> receives a pointer to the object
  45. /   aIntefaces = array of interface descriptions
  46. /   cif = number of interfaces in array
  47. /
  48. / Out:
  49. /   -
  50. /----------------------------------------------------------------------------*/
  51. STDMETHODIMP CUnknown::HandleQueryInterface(REFIID riid, LPVOID* ppvObject, LPINTERFACES aInterfaces, int cif)
  52. {
  53.     HRESULT hr = S_OK;
  54.     int i;
  56.     MDTraceAssert(ppvObject);
  57.     MDTraceAssert(aInterfaces);
  58.     MDTraceAssert(cif);
  60.     *ppvObject = NULL;          // no interface yet
  62.     for ( i = 0; i != cif; i++ )
  63.     {
  64.         if ( IsEqualIID(riid, *aInterfaces[i].piid) || IsEqualIID(riid, IID_IUnknown) )
  65.         {
  66.             *ppvObject = aInterfaces[i].pvObject;
  67.             goto exit_gracefully;
  68.         }
  69.     }
  71.     hr = E_NOINTERFACE;         // failed.
  73. exit_gracefully:
  75.     if ( SUCCEEDED(hr) )
  76.         ((LPUNKNOWN)*ppvObject)->AddRef();
  78.     return hr;
  79. }
  82. /*-----------------------------------------------------------------------------
  83. / CUnknown::HandleAddRef
  84. / ----------------------
  85. /   Increase the objects reference count.  Global reference count increase
  86. /   by the constructor.
  87. /
  88. / In:
  89. /   -
  90. / Out:
  91. /   current reference count
  92. /----------------------------------------------------------------------------*/
  93. STDMETHODIMP_(ULONG) CUnknown::HandleAddRef()
  94. {
  95.     return InterlockedIncrement(&m_cRefCount);
  97. }
  100. /*-----------------------------------------------------------------------------
  101. / CUnknown::HandleRelease
  102. / -----------------------
  103. /   Decrease the reference counts, when the objects reaches zero then
  104. /   destroy it (which inturn will decrease the global reference count).
  105. /
  106. / In:
  107. /   -
  108. / Out:
  109. /   current reference count == 0 if destroyed
  110. /----------------------------------------------------------------------------*/
  111. STDMETHODIMP_(ULONG) CUnknown::HandleRelease()
  112. {
  113.     ULONG cRefCount;
  115.     cRefCount = InterlockedDecrement(&m_cRefCount);
  117.     if ( cRefCount )
  118.         return cRefCount;
  120.     delete this;
  121.     return 0;
  122. }