107 lines
2.2 KiB
C++
107 lines
2.2 KiB
C++
// Microsoft Windows
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// Copyright (C) Microsoft Corporation, 1997 - 1999
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// File: unknown.cpp
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// Helper functions for handling IUnknown
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#include "pch.h"
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#pragma hdrstop
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/*
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/ CUnknown
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/ Helper functions to aid the implementation of IUnknown within objects,
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/ handles not only AddRef and Release, but also QueryInterface.
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*/
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LONG g_cRefCount = 0;// global reference count
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CUnknown::CUnknown()
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{
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m_cRefCount = 0;
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InterlockedIncrement(&g_cRefCount);
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}
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CUnknown::~CUnknown()
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{
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TraceAssert( m_cRefCount == 0 );
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InterlockedDecrement(&g_cRefCount);
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}
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/*
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/ CUnknown::HandleQueryInterface
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/ A table driven implementation of QueryInterface that scans through trying
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/ to find a suitable match for the object.
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/ In:
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/ riid = interface being requested
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/ ppvObject -> receives a pointer to the object
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/ aIntefaces = array of interface descriptions
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/ cif = number of interfaces in array
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*/
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STDMETHODIMP CUnknown::HandleQueryInterface(REFIID riid, LPVOID* ppvObject, LPINTERFACES aInterfaces, int cif)
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{
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HRESULT hr = S_OK;
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int i;
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TraceAssert(ppvObject);
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TraceAssert(aInterfaces);
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TraceAssert(cif);
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*ppvObject = NULL;// no interface yet
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for ( i = 0; i != cif; i++ )
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{
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if ( IsEqualIID(riid, *aInterfaces[i].piid) || IsEqualIID(riid, IID_IUnknown) )
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{
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*ppvObject = aInterfaces[i].pvObject;
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goto exit_gracefully;
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}
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}
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hr = E_NOINTERFACE;// failed.
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exit_gracefully:
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if ( SUCCEEDED(hr) )
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((LPUNKNOWN)*ppvObject)->AddRef();
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return hr;
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}
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/*
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/ Increase the objects reference count. Global reference count increase
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/ by the constructor.
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/ Out:
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/ current reference count
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*/
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STDMETHODIMP_(ULONG) CUnknown::HandleAddRef()
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{
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return InterlockedIncrement(&m_cRefCount);
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}
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/*
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/ Decrease the reference counts, when the objects reaches zero then
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/ destroy it (which inturn will decrease the global reference count).
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/ Out:
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/ current reference count == 0 if destroyed
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*/
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STDMETHODIMP_(ULONG) CUnknown::HandleRelease()
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{
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ULONG cRefCount;
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cRefCount = InterlockedDecrement(&m_cRefCount);
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if ( cRefCount )
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return cRefCount;
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delete this;
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return 0;
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} |