Message Board Programming (CFile function and dynamic Assignment)

This is the simplest example of a memory allocation instance that has never been used by itself, which is an instance of itself from an unsaved file, which is an instance of a memory error */ The following code dumps the contents of the file into other files note the following points here: 1. Try to understand capturing open file exceptions and know how to catch exceptions 2. How to dynamically allocate memory space and Release 3 after use. How to correctly use the file dialog box provided by MFC */  / /The following code is: Dump the contents of the file into another specified file Void cmydlg::onsavebutton ()  { // TODO: Add your  Control notification handler code here cfile file; cstring m_path= "D:\ \test.txt ";  if (!file. Open (M_path,cfile::moderead))  {  messagebox ("opening file error1!");   return ; } int len=file. GetLength ();  // char* buffer=new char[len+1];//prone to buffer overflow the problem is that the following uses buffer[len]= ' + '; Have reminded themselves again of  if (!buffer)  {  messagebox ("allocating fail!");   return; } else {//  carefully examine how the program implements exception handling for files   try  {    file. Read (Buffer,len);   }  catch (cfileexception* e)   {    MessageBox ("Reading fiLe error ");    file. Close ();    e->delete ();   return ;  }  //   buffer[len]= ' + ';  } file. Close ();  m_path= "D:\\total.txt";  if (!file. Open (m_path,cfile::modewrite| cfile::modecreate))  {  messagebox ("Opening file error2");  return ;  } file. Seektoend ();//point the file pointer to the end of the file and write  file. Write (Buffer,len);  file. Close ();  delete buffer;}  //open file, read into edit box Void cmydlg::onread ()  { // TODO: Add your control  Notification handler code here cfile file; if (!file. Open ("D:\\test.txt", Cfile::moderead))  {  messagebox ("opening file error!");   return ; }     int len=file. GetLength ();  char* buffer=new char[len+1]; if (!buffer)  {  messagebox (" Allocating fail ");    return ; } else {  try  {   file. Read (Buffer,len);   }  catch (cfileexception* e)   {    MessageBox ("Reading file error");    file. Close ();    e->delete ();    return;  } } buffer[len]= ' + ';  m_note=buffer; delete buffer;   file. Close ();    updatedata (FALSE);} Void cmydlg::onsavepath ()  { // todo: add your control notification  handler code here cstring msg= "File save error";  CFileDialog dlg (True, "TXT", Null,null, "Text file (*.txt) |*. TXT ");  //cfiledialog dlg (true,null,null,null,null);   if (dlg. DoModal () ==idok)   {   m_path=dlg. GetPathName ();   }  else  {   messagebox (msg);   }}

Message Board Programming (CFile function and dynamic Assignment)