Initial check in rtl

src.rtl/dpgrtl.inputbuffer.pas

@@ -0,0 +1,123 @@
+unit dpgrtl.inputbuffer;
+
+interface
+uses
+   dpgrtl.types;
+
+type
+   TInputBuffer = class( TInterfacedObject, IInputBuffer)
+      protected
+         fMarkerCount   : integer;
+         fMarkerOffset  : integer;
+         fNumToConsume  : integer;
+
+      protected
+         procedure   Remove( Num: integer); virtual; abstract;
+         procedure   SyncConsume; inline;
+
+      protected
+         function    GetMarked: boolean; inline;
+
+         procedure   Consume; inline;
+         procedure   Commit;  inline;
+
+         function    Mark: integer;
+         procedure   Rewind( Value: integer);
+   end;
+
+
+implementation
+
+{ TInputBuffer }
+
+// @@@: IInputBuffer implementation +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+//
+//                                  IInputBuffer implementation
+//
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ================================================================================================
+// Mark
+//
+//    Returns an integer marker theh can be used to rewind the buffer to its current state.
+// ================================================================================================
+function TInputBuffer.Mark: integer;
+begin
+   SyncConsume;
+   INC( fMarkerCount);
+
+   result := fMarkerOffset
+end;
+
+// ================================================================================================
+// Consume
+//
+//    Mark another input item for deferred consumption.
+// ================================================================================================
+procedure TInputBuffer.Consume;
+begin
+   INC( fNumToConsume);
+end;
+
+// ================================================================================================
+// Commit
+//
+//    This method updates the state of the input buffer so that the text matched since the most
+//    recent Mark() is no longer held by the buffer. So, you either do a mark/rewind for failed
+//    predicate or mark/commit to keep on parsing without rewinding the input.
+// ================================================================================================
+procedure TInputBuffer.Commit;
+begin
+   if fMarkerCount > 0 then
+      DEC( fMarkerCount)
+end;
+
+// ================================================================================================
+// Rewind
+//
+// Rewind the character buffer to a marker. 'Value' marker returned previously from mark.
+// ================================================================================================
+procedure TInputBuffer.Rewind(Value: integer);
+begin
+   SyncConsume;
+
+   fMarkerOffset := Value;
+   DEC( fMarkerCount)
+end;
+
+// ================================================================================================
+// GetMarked
+// ================================================================================================
+function TInputBuffer.GetMarked: boolean;
+begin
+   result := fMarkerCount <> 0
+end;
+
+// @@@: Internals +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+//
+//                                           Internals
+//
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+// ================================================================================================
+// Sync Consume
+// ================================================================================================
+procedure TInputBuffer.SyncConsume;
+begin
+   if fNumToConsume > 0 then
+   begin
+      if fMarkerCount > 0
+         then INC( fMarkerOffset, fNumToConsume)
+         else Remove( fNumToConsume);
+
+      fNumToConsume := 0
+   end
+end;
+
+end.