write shit

Core/Util.cs

@@ -1,4 +1,5 @@
 using BallanceTASEditor.Core.TASStruct;
+using BallanceTASEditor.UI;
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
@@ -18,5 +19,67 @@ namespace BallanceTASEditor.Core {
         //    if (index + count > list.Count) count = list.Count - index;
         //    for (int i = 0; i < count; i++) list.RemoveAt(index);
         //}
+        public static IEnumerable<LinkedListNode<FrameData>> IterateFull(this LinkedList<FrameData> ls) {
+            var pos = ls.First;
+            
+            while(pos != null) {
+                yield return pos;
+                pos = pos.Next;
+            }
+        }
+
+
+        public static IEnumerable<LinkedListNode<FrameData>> IterateWithSelectionRange(this LinkedList<FrameData> ls, SelectionRange relativeRange, LinkedListNode<FrameData> current) {
+            if (current == null) goto end;
+
+            // goto header first
+            long counter;
+            var cache = current.TryShiftTo(relativeRange.start, out counter);
+
+            while (counter <= relativeRange.end && cache != null) {
+                yield return cache;
+                cache = cache.Next;
+                counter++;
+            }
+            
+            end:;
+        }
+
+        public static void RemoveWithSelectionRange(this LinkedList<FrameData> ls, SelectionRange relativeRange, LinkedListNode<FrameData> current) {
+            if (current == null) goto end;
+
+            // goto header first
+            long counter;
+            var cache = current.TryShiftTo(relativeRange.start, out counter);
+
+            LinkedListNode<FrameData> cacheNextNode;
+            while (counter <= relativeRange.end && cache != null) {
+                cacheNextNode = cache.Next;
+                ls.Remove(cache);
+                cache = cacheNextNode;
+                counter++;
+            }
+
+            end:;
+        }
+
+        public static LinkedListNode<FrameData> TryShiftTo(this LinkedListNode<FrameData> node, long offset, out long realShifted) {
+            var cache = node;
+
+            realShifted = 0;
+            if (offset < 0) {
+                while (realShifted != offset && cache.Previous != null) {
+                    cache = cache.Previous;
+                    realShifted--;
+                }
+            } else if (offset > 0) {
+                while (realShifted != offset && cache.Next != null) {
+                    cache = cache.Next;
+                    realShifted++;
+                }
+            }
+
+            return cache;
+        }
     }
 }