浅谈 MFC 的子类化机制和该机制的一个应用（2）

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。