0031920: Application Framework - speed up methods of getting label by entry and vice versa

A table for fast access to the labels by entry is implemented in OCAF document. A method TDF_Data::SetAccessByEntries(true) fills-in a table for fast access to the labels. New labels, created later will be added to the table automatically. The method TDF_Tool::Label() will search the entry in the table and then, if not found, will call the old code. Disabling of usage of the table (by calling of TDF_Data::SetAccessByEntries(false)) cleans the internal table of entries - labels. By default, the table is not used.
            This improvement is useful for large documents with a lot of labels, and if the application uses entries to get labels. The application should call TDF_Data::SetAccessByEntries(true) for a document and then, the method TDF_Tool::Label() called inside OCAF and XCAF will use the fast access to the labels and speed-up the application.
            Also, the method TDF_Tool::Entry() is improved (by MPV).

            Modified files:
            - TDF_Data.hxx and cxx: the new methods SetAccessByEntries(bool), IsAccessByEntries() and GetLabel(entry) are implemented. No need to use the method GetLabel() directly. It is called in TDF_Tool::Label().
            - TDF_Label.cxx: adding of a newly created label to the table of entries - labels.
            - TDF_Tool.cxx: the method Entry() is accelerated (by MPV) and Label() is improved to call TDF_Data::GetLabel().
            - DDF_DataCommands.cxx: a new draw-command is added SetAccessByEntry, which sets or unsets usage of the table for fast access to the labels. Usage of the draw-command is illustrated in a new test "bugs caf bug31920".

            Tests:
            - bugs caf bug31920: a new simple test to check TDF_Tool::Label() when fast access to the labels is on.

            Doc:
            - dox\upgrade\upgrade.md is extended for new information

src/TDF/TDF_Data.cxx

@@ -94,7 +94,8 @@ myTransaction           (0),
 myNbTouchedAtt          (0),
 myNotUndoMode           (Standard_True),
 myTime                  (0),
-myAllowModification     (Standard_True)
+myAllowModification     (Standard_True),
+myAccessByEntries       (Standard_False)
 {
   const Handle(NCollection_IncAllocator) anIncAllocator=
     new NCollection_IncAllocator (16000);
@@ -118,6 +119,7 @@ void TDF_Data::Destroy()
     Handle(TDF_Attribute) aFirst = myRoot->FirstAttribute();
     myRoot->RemoveAttribute(anEmpty, aFirst);
   }
+  myAccessByEntriesTable.Clear();
   myRoot->Destroy (myLabelNodeAllocator);
   myRoot = NULL;
 }
@@ -439,7 +441,43 @@ Handle(TDF_Delta) TDF_Data::Undo(const Handle(TDF_Delta)& aDelta,
   return newDelta;
 }
 
+//=======================================================================
+//function : SetAccessByEntries
+//purpose  : 
+//=======================================================================
 
+void TDF_Data::SetAccessByEntries(const Standard_Boolean aSet)
+{
+  myAccessByEntries = aSet;
+
+  myAccessByEntriesTable.Clear();
+  if (myAccessByEntries) {
+    // Add root label.
+    TCollection_AsciiString anEntry;
+    TDF_Tool::Entry (myRoot, anEntry);
+    myAccessByEntriesTable.Bind (anEntry, myRoot);
+
+    // Add all other labels.
+    TDF_ChildIterator itr (myRoot, Standard_True);
+    for (; itr.More(); itr.Next()) {
+      const TDF_Label aLabel = itr.Value();
+      TDF_Tool::Entry (aLabel, anEntry);
+      myAccessByEntriesTable.Bind (anEntry, aLabel);
+    }
+  }
+}
+
+//=======================================================================
+//function : RegisterLabel
+//purpose  : 
+//=======================================================================
+
+void TDF_Data::RegisterLabel(const TDF_Label& aLabel)
+{
+  TCollection_AsciiString anEntry;
+  TDF_Tool::Entry (aLabel, anEntry);
+  myAccessByEntriesTable.Bind (anEntry, aLabel);
+}
 
 //=======================================================================
 //function : Dump