浅谈 MFC 的子类化机制和该机制的一个应用（2）

作者： In355Hz

续: 浅谈MFC的子类化机制和该机制的一个应用（1）:

BOOL CDumpMsgBox::OnDumpOut(LPSTR pszDumpBuffer, UINT nBufferSize)

{

       ASSERT(pszDumpBuffer != NULL && nBufferSize != 0);

       ASSERT(AfxIsValidString(pszDumpBuffer, nBufferSize));

       // calculate ´\n´ occur times in buffer.

       int nPosition, nLine = 0;

       for(nPosition = 0; nPosition < (int)nBufferSize; nPosition ++)

       {

        if (pszDumpBuffer[nPosition] == ´\0´)

               break;

        if (pszDumpBuffer[nPosition] == ´\n´)

               nLine ++;

       }

       // alloc enough memory for convert.

       TCHAR *pszBuffer = (TCHAR*)malloc(sizeof(TCHAR) * (nPosition + nLine + 64));

       // convert all ´\n´ ´\r´ or ´\n\r´ to ´\r\n´:

       TCHAR *pszConvert = pszBuffer;

       for (nPosition = 0; nPosition < (int)nBufferSize; nPosition ++)

       {

        if (pszDumpBuffer[nPosition] == ´\0´)

               break;

        if (pszDumpBuffer[nPosition] == ´\r´)

               continue;

        if (pszDumpBuffer[nPosition] == ´\n´)

        {

               *pszConvert = _T(´\r´);

               pszConvert ++;

        }

        *pszConvert = (TCHAR)pszDumpBuffer[nPosition];

        pszConvert ++;

       }

       // set end of string.

       *pszConvert = ´\0´;

       // set converted dump buffer to the edit control.

       m_editDump.AssertValid();

       m_editDump.SetWindowText(pszBuffer);

       free(pszBuffer);

       return TRUE;

}

int CDumpMsgBox::DoMessageBox(UINT nIDPrompt, UINT nType, UINT nIDHelp)

{

       CString string;

       if (!string.LoadString(nIDPrompt))

       {

        TRACE1("CDumpMsgBox::DoMessageBox error: failed to load message box prompt string 0x%04x.\n",

               nIDPrompt);

        ASSERT(FALSE);

       }

       if (nIDHelp == (UINT)-1)

        nIDHelp = nIDPrompt;

       return DoMessageBox(string, nType, nIDHelp);

}

int CDumpMsgBox::DoMessageBox(LPCTSTR lpszText, UINT nType, UINT nIDHelp)

{

       int nRetCode;

       // not call PreCreateWindow to initialize CREATESTRUCT data.

       AfxHookWindowCreate(this);

       nRetCode = AfxMessageBox(lpszText, nType, nIDHelp);



       if (!AfxUnhookWindowCreate())

        PostNcDestroy();

       return nRetCode;

}

void CDumpMsgBox::DoDumpObject(CObject* pDumpObject)

{

       m_fileDump.AssertValid();      // dump target must exist.

       ASSERT(pDumpObject != NULL);

       CRuntimeClass* pClass = pDumpObject->GetRuntimeClass();

       if (pClass == NULL)

        return;            // unexpect runtime-class value.

       if (AfxIsValidAddress(pDumpObject, pClass->m_nObjectSize, TRUE))

       {

#ifdef _DEBUG

        pDumpObject->Dump(m_dumpContext);

#else // ! _DEBUG

        m_dumpContext << "a " << pClass->m_lpszClassName <<

               " at " << (void*)pDumpObject;

        m_dumpContext << "\nHex Dumps: " << pClass->m_nObjectSize <<" bytes long.\n";

        m_dumpContext.HexDump(_T("HEX"), (BYTE*)pDumpObject, pClass->m_nObjectSize, 8);

#endif      // _DEBUG

       }

}

#ifdef _DEBUG

void CDumpMsgBox::AssertValid() const

{

       CWnd::AssertValid();

       if (m_editDump.GetSafeHwnd())

        m_editDump.AssertValid();

       ASSERT(AfxIsValidAddress(&m_dumpContext, sizeof(CDumpContext), TRUE));

       m_fileDump.AssertValid();

}

void CDumpMsgBox::Dump(CDumpContext& dc) const

{

       if (m_hWnd == NULL)

       {

        CObject::Dump(dc);

        dc << "m_hWnd = NULL\n";

       }

       else

        CWnd::Dump(dc);

       if (0 < dc.GetDepth())

       {

        dc << "include ";

        if (NULL == m_editDump.GetSafeHwnd())

        {

               m_editDump.CObject::Dump(dc);

               dc << "m_hWnd = NULL\n";

        }

        else

               m_editDump.Dump(dc);

        dc << "include ";

        m_fileDump.Dump(dc);

       }

}

#endif      // _DEBUG

代码较为简单，为 MessageBox 增加了一个 Edit Control ，属性为 ES_MULTILINE ，ES_READONLY， ES_AUTOVSCROLL，并且拥有 WS_EX_CLIENTEDGE 属性。

该 Edit Control 的内容通过 CMemFile 和 CDumpContext 生成。构造函数 CDumpContext( CFile* pFile ) 可以生成一个以 CMemFile 为目标的 CDumpContext 实例，然后调用 CObject::Dump，最后通过 CMemFile::Detach 得到包含输出字符串的缓冲区。

以下是 CDumpMsgBox 的应用示例：

CDumpMsgBox msgBox;       // declare intsance

msgBox.DoDumpObject(&msgBox);     // dump itself

msgBox.DoMessageBox(_T("This message box used class CDumpMsgBox."), MB_OKCANCEL); // display

以上代码在 MS Visual C++ 6.0, Win98 下调试通过。

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