sdk/samples/all in on code/Visual Studio 2008/CppDllCOMServer/ClassFactory.cpp

   1 /****************************** Module Header ******************************\
   2 Module Name:  ClassFactory.cpp
   3 Project:      CppDllCOMServer
   4 Copyright (c) Microsoft Corporation.
   5
   6 The file implements the class factory for the SimpleObject COM class. A class
   7 factory (aka a class object) is a component whose main purpose is to create
   8 other components. It provides many controls over the creation process of the
   9 component. When a client uses a CLSID to request the creation of an object
  10 instance, the first step is creation of a class factory, an intermediate
  11 object that contains an implementation of the methods of the IClassFactory
  12 interface. While COM provides several instance creation functions, the first
  13 step in the implementation of these functions is always the creation of a
  14 class factory. For example, CoCreateInstance provides a wrapper over a
  15 CoGetClassObject and CreateInstance method of IClassFactory interface.
  16 CoCreateInstance internally creates class factory for the specified CLSID,
  17 gets the IClassFactory interface pointer, and then creates the component by
  18 calling CreateInstance on IClassFactory interface pointer and then returns
  19 the requested interface pointer to the client by calling QueryInterface
  20 method in the CreateInstance method of IClassFactory.
  21
  22 The class factory implements the IClassFactory interface. The class factory
  23 object must implement these two methods of IClassFactory to support the
  24 object creation.
  25
  26     IFACEMETHODIMP CreateInstance(IUnknown *pUnkOuter, REFIID riid, void **ppv);
  27     IFACEMETHODIMP LockServer(BOOL fLock);
  28
  29 This source is subject to the Microsoft Public License.
  30 See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
  31 All other rights reserved.
  32
  33 THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
  34 EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
  35 WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
  36 \***************************************************************************/
  37
  38 #include "ClassFactory.h"
  39 #include "SimpleObject.h"
  40
  41
  42 extern long g_cDllRef;
  43
  44
  45 ClassFactory::ClassFactory() : m_cRef(1)
  46 {
  47     InterlockedIncrement(&g_cDllRef);
  48 }
  49
  50 ClassFactory::~ClassFactory()
  51 {
  52     InterlockedDecrement(&g_cDllRef);
  53 }
  54
  55
  56 //
  57 // IUnknown
  58 //
  59
  60 IFACEMETHODIMP ClassFactory::QueryInterface(REFIID riid, void **ppv)
  61 {
  62     HRESULT hr = S_OK;
  63
  64     if (IsEqualIID(IID_IUnknown, riid) ||
  65         IsEqualIID(IID_IDispatch, riid) ||  // For implementing IDispatch
  66         IsEqualIID(IID_IClassFactory, riid))
  67     {
  68         *ppv = static_cast<IUnknown *>(this);
  69         AddRef();
  70     }
  71     else
  72     {
  73         hr = E_NOINTERFACE;
  74         *ppv = NULL;
  75     }
  76
  77     return hr;
  78 }
  79
  80 IFACEMETHODIMP_(ULONG) ClassFactory::AddRef()
  81 {
  82     return InterlockedIncrement(&m_cRef);
  83 }
  84
  85 IFACEMETHODIMP_(ULONG) ClassFactory::Release()
  86 {
  87     ULONG cRef = InterlockedDecrement(&m_cRef);
  88     if (0 == cRef)
  89     {
  90         delete this;
  91     }
  92     return cRef;
  93 }
  94
  95
  96 //
  97 // IClassFactory
  98 //
  99
 100 IFACEMETHODIMP ClassFactory::CreateInstance(IUnknown *pUnkOuter, REFIID riid, void **ppv)
 101 {
 102     HRESULT hr = CLASS_E_NOAGGREGATION;
 103
 104     // pUnkOuter is used for aggregation. We do not support it in the sample.
 105     if (pUnkOuter == NULL)
 106     {
 107         hr = E_OUTOFMEMORY;
 108
 109         // Create the COM component.
 110         SimpleObject *pSimpleObj = new SimpleObject();
 111         if (pSimpleObj)
 112         {
 113             // Query the specified interface.
 114             hr = pSimpleObj->QueryInterface(riid, ppv);
 115             pSimpleObj->Release();
 116         }
 117     }
 118
 119     return hr;
 120 }
 121
 122 IFACEMETHODIMP ClassFactory::LockServer(BOOL fLock)
 123 {
 124     if (fLock)
 125     {
 126         InterlockedIncrement(&g_cDllRef);
 127     }
 128     else
 129     {
 130         InterlockedDecrement(&g_cDllRef);
 131     }
 132     return S_OK;
 133 }