Initial commit

Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/ViewStateCollection.cs

@@ -0,0 +1,58 @@
+#if UNITY_EDITOR
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace UnityEngine.InputSystem.Editor
+{
+    /// <summary>
+    /// A caching enumerator that will save all enumerated values on the first iteration, and when
+    /// subsequently iterated, return the saved values instead.
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    internal class ViewStateCollection<T> : IViewStateCollection, IEnumerable<T>
+    {
+        private readonly IEnumerable<T> m_Collection;
+        private readonly IEqualityComparer<T> m_Comparer;
+        private IList<T> m_CachedCollection;
+
+        public ViewStateCollection(IEnumerable<T> collection, IEqualityComparer<T> comparer = null)
+        {
+            m_Collection = collection;
+            m_Comparer = comparer;
+        }
+
+        public bool SequenceEqual(IViewStateCollection other)
+        {
+            return other is ViewStateCollection<T> otherCollection && this.SequenceEqual(otherCollection, m_Comparer);
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            if (m_CachedCollection == null)
+            {
+                m_CachedCollection = new List<T>();
+                using (var enumerator = m_Collection.GetEnumerator())
+                {
+                    while (enumerator.MoveNext())
+                    {
+                        m_CachedCollection.Add(enumerator.Current);
+                    }
+                }
+            }
+
+            using (var enumerator = m_CachedCollection.GetEnumerator())
+            {
+                while (enumerator.MoveNext())
+                    yield return enumerator.Current;
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+    }
+}
+
+#endif