Ensure that CALL3.TXT is not deleted while updating the file

This is necessary so that symlinks that may be used to share CALL3.TXT
between WSJT-X  instances and with  and MAP65  do not get  broken when
adding new entries in either application.

map65/mainwindow.cpp

@@ -1970,16 +1970,16 @@ void MainWindow::on_addButton_clicked()                       //Add button
         << endl
 #endif
       ;
-    f1.close();
+    f1.seek (0);
-    f1.open(QIODevice::ReadOnly | QIODevice::Text);
   }
 
   QString tmpFile = m_appDir + "/CALL3.TMP";
   QFile f2(tmpFile);
-  if(!f2.open(QIODevice::WriteOnly | QIODevice::Text)) {
+  if(!f2.open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text)) {
     msgBox("Cannot open " + tmpFile);
     return;
   }
+  {
     QTextStream in(&f1);
     QTextStream out(&f2);
     QString hc=hiscall;
@@ -2012,16 +2012,19 @@ void MainWindow::on_addButton_clicked()                       //Add button
         }
       }
     } while(!s.isNull());
-
-  f1.close();
     if(hc>hc1 && !m_call3Modified) out << newEntry + "\n";
+  }
+  
   if(m_call3Modified) {
-    QFile f0(m_appDir + "/CALL3.OLD");
+    auto const& old_path = m_appDir + "/CALL3.OLD";
+    QFile f0 {old_path};
     if (f0.exists ()) f0.remove ();
-    QFile f1(m_appDir + "/CALL3.TXT");
+    f1.copy (old_path);         // copying as we want to preserve
-    f1.rename(m_appDir + "/CALL3.OLD");
+                                // symlinks
-    f2.rename(m_appDir + "/CALL3.TXT");
+    f1.open (QFile::WriteOnly | QFile::Text); // truncates
-    f2.close();
+    f2.seek (0);
+    f1.write (f2.readAll ());   // copy contents
+    f2.remove ();
   }
 }
 

widgets/mainwindow.cpp

@@ -5670,16 +5670,16 @@ void MainWindow::on_addButton_clicked()                       //Add button
         << endl
 #endif
       ;
-    f1.close();
+    f1.seek (0);
-    f1.open(QIODevice::ReadOnly | QIODevice::Text);
   }
   QFile f2 {m_config.writeable_data_dir ().absoluteFilePath ("CALL3.TMP")};
-  if(!f2.open(QIODevice::WriteOnly | QIODevice::Text)) {
+  if(!f2.open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text)) {
     MessageBox::warning_message (this, tr ("Add to CALL3.TXT")
                                  , tr ("Cannot open \"%1\" for writing: %2")
                                  .arg (f2.fileName ()).arg (f2.errorString ()));
     return;
   }
+  {
     QTextStream in(&f1);          //Read from CALL3.TXT
     QTextStream out(&f2);         //Copy into CALL3.TMP
     QString hc=hisCall;
@@ -5711,16 +5711,19 @@ void MainWindow::on_addButton_clicked()                       //Add button
         }
       }
     } while(!s.isNull());
-
-  f1.close();
     if(hc>hc1 && !m_call3Modified) out << newEntry + QChar::LineFeed;
+  }
+
   if(m_call3Modified) {
-    QFile f0 {m_config.writeable_data_dir ().absoluteFilePath ("CALL3.OLD")};
+    auto const& old_path = m_config.writeable_data_dir ().absoluteFilePath ("CALL3.OLD");
+    QFile f0 {old_path};
     if (f0.exists ()) f0.remove ();
-    QFile f1 {m_config.writeable_data_dir ().absoluteFilePath ("CALL3.TXT")};
+    f1.copy (old_path);                       // copying as we want to
-    f1.rename(m_config.writeable_data_dir ().absoluteFilePath ("CALL3.OLD"));
+                                              // preserve symlinks
-    f2.rename(m_config.writeable_data_dir ().absoluteFilePath ("CALL3.TXT"));
+    f1.open (QFile::WriteOnly | QFile::Text); // truncates
-    f2.close();
+    f2.seek (0);
+    f1.write (f2.readAll ());                 // copy contents
+    f2.remove ();
   }
 }