From 54da341e2a17f064c13d238697eff8d036305c3c Mon Sep 17 00:00:00 2001
From: Bergmann89 <info@bergmann89.de>
Date: Fri, 1 May 2015 16:37:46 +0200
Subject: [PATCH] * implemented reverse enumerator

---
 uutlGenerics.pas | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/uutlGenerics.pas b/uutlGenerics.pas
index 0e8f47b..2abc795 100644
--- a/uutlGenerics.pas
+++ b/uutlGenerics.pas
@@ -84,13 +84,15 @@ type
   public type
     TEnumerator = class(TObject)
     private
+      fReverse: Boolean;
       fList: TFPList;
       fPosition: Integer;
       function GetCurrent: T;
     public
       property Current: T read GetCurrent;
+      function GetEnumerator: TEnumerator;
       function MoveNext: Boolean;
-      constructor Create(const aList: TFPList);
+      constructor Create(const aList: TFPList; const aReverse: Boolean = false);
     end;
 
   private
@@ -111,9 +113,10 @@ type
     procedure DeleteIntern(const aIndex: Integer; const aFreeItem: Boolean = true);
 
   public
-    property OwnsObjects: Boolean read fOwnsObjects write fOwnsObjects;
+    property OwnsObjects:       Boolean read fOwnsObjects       write fOwnsObjects;
 
     function GetEnumerator: TEnumerator;
+    function GetReverseEnumerator: TEnumerator;
     procedure Clear;
 
     constructor Create(const aOwnsObjects: Boolean = true);
@@ -703,19 +706,34 @@ begin
   result := PListItem(fList[fPosition])^.data;
 end;
 
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+function TutlListBase.TEnumerator.GetEnumerator: TEnumerator;
+begin
+  result := self;
+end;
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 function TutlListBase.TEnumerator.MoveNext: Boolean;
 begin
-  inc(fPosition);
-  result := (fPosition < fList.Count)
+  if fReverse then begin
+    dec(fPosition);
+    result := (fPosition >= 0);
+  end else begin
+    inc(fPosition);
+    result := (fPosition < fList.Count)
+  end;
 end;
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
-constructor TutlListBase.TEnumerator.Create(const aList: TFPList);
+constructor TutlListBase.TEnumerator.Create(const aList: TFPList; const aReverse: Boolean);
 begin
   inherited Create;
   fList     := aList;
-  fPosition := -1;
+  fReverse  := aReverse;
+  if fReverse then
+    fPosition := fList.Count
+  else
+    fPosition := -1;
 end;
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -808,7 +826,13 @@ end;
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 function TutlListBase.GetEnumerator: TEnumerator;
 begin
-  result := TEnumerator.Create(fList);
+  result := TEnumerator.Create(fList, false);
+end;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+function TutlListBase.GetReverseEnumerator: TEnumerator;
+begin
+  result := TEnumerator.Create(fList, true);
 end;
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////