OBJECT3.CPP

/* 
 * OBJECT3.CPP 
 * 
 * Object implementation using multiple inheritance. 
 * 
 * Copyright (c)1993-1995 Microsoft Corporation, All Rights Reserved 
 * 
 * Kraig Brockschmidt, Microsoft 
 * Internet  :  kraigb@microsoft.com 
 * Compuserve:  >INTERNET:kraigb@microsoft.com 
 */ 
 
#include <windows.h> 
#include "query.h" 
 
 
//Message strings for the interface functions 
static TCHAR szMessage[]=TEXT("Message from ISampleOne::GetMessage"); 
static TCHAR szString[] =TEXT("Message from ISampleTwo::GetString"); 
 
 
/* 
 * CreateObject3 
 * 
 * Purpose: 
 *  Creates an instance of Object2 returning an IUnknown 
 *  interface. 
 * 
 * Parameters: 
 *  ppUnk           IUnknown ** in which to return the 
 *                  interface pointer. 
 * 
 * Return Value: 
 *  BOOL            TRUE if the function is successful, 
 *                  FALSE otherwise. 
 */ 
 
BOOL CreateObject3(IUnknown **ppUnk) 
    { 
    HRESULT     hr; 
    CObject3   *pObj; 
 
    if (NULL==ppUnk) 
        return FALSE; 
 
    //Create the new object, which gives us a C++ object pointer 
    pObj=new CObject3(); 
 
    if (NULL==pObj) 
        return FALSE; 
 
    /* 
     * Now get the IUnknown interface to this object and make 
     * sure that it's reference count is correct.  We could either 
     * typecast pObj to IUnknown and call AddRef explicitly, or 
     * we can simply call pObj->QueryInterface and let it do the 
     * typecast and the AddRef for us. 
     */ 
    hr=pObj->QueryInterface(IID_IUnknown, (PPVOID)ppUnk); 
    return SUCCEEDED(hr); 
    } 
 
 
 
 
 
/* 
 * CObject3::CObject3 
 * CObject3::~CObject3 
 * 
 * Constructor Parameters: 
 *  None 
 */ 
 
CObject3::CObject3(void) 
    { 
    m_cRef=0; 
    return; 
    } 
 
CObject3::~CObject3(void) 
    { 
    return; 
    } 
 
 
 
 
 
/* 
 * CObject3::QueryInterface 
 * 
 * Purpose: 
 *  Manages the interfaces for this object which supports the 
 *  IUnknown, ISampleOne, and ISampleTwo interfaces. 
 * 
 * Parameters: 
 *  riid            REFIID of the interface to return. 
 *  ppv             PPVOID in which to store the pointer. 
 * 
 * Return Value: 
 *  HRESULT         NOERROR on success, E_NOINTERFACE if the 
 *                  interface is not supported. 
 */ 
 
STDMETHODIMP CObject3::QueryInterface(REFIID riid, PPVOID ppv) 
    { 
    //Always NULL the out-parameters 
    *ppv=NULL; 
 
    /* 
     * Since all the interfaces are part of this same object, 
     * we *must* use typecasts to set up the right vtables from 
     * the 'this' pointer.  Casting to an interface will give 
     * us a pointer that points to exactly that interface vtable. 
     * 
     * Note that since we don't have an explicit IUnknown base, 
     * responding to IUnknown here simply return ISampleOne, which 
     * has the right IUnknown vtable anyway. 
     */ 
    if (IID_IUnknown==riid || IID_ISampleOne==riid) 
        *ppv=(ISampleOne *)this; 
 
    if (IID_ISampleTwo==riid) 
        *ppv=(ISampleTwo *)this; 
 
    if (NULL==*ppv) 
        return ResultFromScode(E_NOINTERFACE); 
 
    //AddRef any interface we'll return. 
    ((LPUNKNOWN)*ppv)->AddRef(); 
    return NOERROR; 
    } 
 
 
 
/* 
 * CObject3::AddRef 
 * CObject3::Release 
 * 
 * Reference counting members.  When Release sees a zero count 
 * the object destroys itself. 
 */ 
 
DWORD CObject3::AddRef(void) 
    { 
    return ++m_cRef; 
    } 
 
DWORD CObject3::Release(void) 
    { 
    if (0!=--m_cRef) 
        return m_cRef; 
 
    delete this; 
    return 0; 
    } 
 
 
 
 
/* 
 * CObject3::GetMessage 
 * 
 * Purpose: 
 *  Returns a string to the caller.  This is the implementation 
 *  of ISampleOne::GetMessage. 
 * 
 * Parameters: 
 *  psz             LPTSTR in which to store the string. 
 *  cch             UINT size of psz. 
 * 
 * Return Value: 
 *  HRESULT         NOERROR if the string is stored, E_OUTOFMEMORY 
 *                  if the buffer is too small. 
 */ 
 
STDMETHODIMP CObject3::GetMessage(LPTSTR psz, UINT cch) 
    { 
    if (NULL==psz) 
        return ResultFromScode(E_POINTER); 
 
    if (cch < (UINT)lstrlen(szMessage)) 
        return ResultFromScode(E_OUTOFMEMORY); 
 
    lstrcpy(psz, szMessage); 
    return NOERROR; 
    } 
 
 
/* 
 * CObject3::GetString 
 * 
 * Purpose: 
 *  Returns a string to the caller.  This is the implementation 
 *  of ISampleTwo::GetString. 
 * 
 * Parameters: 
 *  psz             LPTSTR in which to store the string. 
 *  cch             UINT size of psz. 
 * 
 * Return Value: 
 *  HRESULT         NOERROR if the string is stored, E_OUTOFMEMORY 
 *                  if the buffer is too small. 
 */ 
 
STDMETHODIMP CObject3::GetString(LPTSTR psz, UINT cch) 
    { 
    if (NULL==psz) 
        return ResultFromScode(E_POINTER); 
 
    if (cch < (UINT)lstrlen(szString)) 
        return ResultFromScode(E_OUTOFMEMORY); 
 
    lstrcpy(psz, szString); 
    return NOERROR; 
    }