Issue 720 (#721)

* Implemented a backup scheme for the file writer.

* Also consider backup files when the writer fails.

* Removed test exception

* Added config option for number of backups.

src/laybasic/laybasic/gsiDeclLayLayoutView.cc

@@ -317,14 +317,14 @@ static void delete_layers2 (lay::LayoutView *view, unsigned int index, const std
 
 static void save_as1 (lay::LayoutView *view, unsigned int index, const std::string &filename, const db::SaveLayoutOptions &options)
 {
-  view->save_as (index, filename, tl::OutputStream::OM_Auto, options, true);
+  view->save_as (index, filename, tl::OutputStream::OM_Auto, options, true, 0);
 }
 
 static void save_as2 (lay::LayoutView *view, unsigned int index, const std::string &filename, bool /*gzip*/, const db::SaveLayoutOptions &options)
 {
   //  because set_format_from_name always returns true now, we ignore the gzip option -
   //  it's probably used only in that context.
-  view->save_as (index, filename, tl::OutputStream::OM_Auto, options, true);
+  view->save_as (index, filename, tl::OutputStream::OM_Auto, options, true, 0);
 }
 
 #if defined(HAVE_QTBINDINGS)

src/laybasic/laybasic/layCellView.cc

@@ -297,7 +297,7 @@ LayoutHandle::update_save_options (db::SaveLayoutOptions &options)
 }
 
 void 
-LayoutHandle::save_as (const std::string &fn, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update)
+LayoutHandle::save_as (const std::string &fn, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update, int keep_backups)
 {
   if (update) {
 
@@ -321,8 +321,13 @@ LayoutHandle::save_as (const std::string &fn, tl::OutputStream::OutputStreamMode
     {
       //  The write needs to be finished before the file watcher gets the new modification time
       db::Writer writer (options);
-      tl::OutputStream stream (fn, om);
-      writer.write (*mp_layout, stream);
+      tl::OutputStream stream (fn, om, false, keep_backups);
+      try {
+        writer.write (*mp_layout, stream);
+      } catch (...) {
+        stream.reject ();
+        throw;
+      }
     }
 
     if (update) {

src/laybasic/laybasic/layCellView.h

@@ -212,7 +212,7 @@ public:
    *  Save the layout under the given file name and with the given options.
    *  If update is true, this method updates the cell view's filename, title, save options and dirty flag.
    */
-  void save_as (const std::string &filename, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update = true);
+  void save_as (const std::string &filename, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update = true, int keep_backups = 0);
 
   /**
    *  @brief Sets the save options and a flag indicating whether they are valid

src/laybasic/laybasic/layLayoutView.cc

@@ -2216,12 +2216,12 @@ LayoutView::signal_selection_changed ()
 }
 
 void 
-LayoutView::save_as (unsigned int index, const std::string &filename, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update)
+LayoutView::save_as (unsigned int index, const std::string &filename, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update, int keep_backups)
 {
   tl_assert (index < cellviews ());
 
   tl::SelfTimer timer (tl::verbosity () >= 11, tl::to_string (QObject::tr ("Saving")));
-  cellview (index)->save_as (filename, om, options, update);
+  cellview (index)->save_as (filename, om, options, update, keep_backups);
 
   cellview_changed (index);
 }

src/laybasic/laybasic/layLayoutView.h

@@ -826,7 +826,7 @@ public:
    *  @brief Save the given cellview into the given file (with options)
    *  If "update" is true, the cell view's properties will be updated (options, filename etc.).
    */
-  void save_as (unsigned int index, const std::string &filename, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update);
+  void save_as (unsigned int index, const std::string &filename, tl::OutputStream::OutputStreamMode om, const db::SaveLayoutOptions &options, bool update, int keep_backups);
 
   /**
    *  @brief Implementation of the undo operations