Initial commit

Library/PackageCache/com.unity.shadergraph@c8830f61858d/Editor/Data/Util/PooledHashSet.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using UnityEngine.Assertions;
+
+namespace UnityEditor.ShaderGraph
+{
+    class PooledHashSet<T> : HashSet<T>, IDisposable
+    {
+        static Stack<PooledHashSet<T>> s_Pool = new Stack<PooledHashSet<T>>();
+        bool m_Active;
+
+        PooledHashSet() { }
+
+        public static PooledHashSet<T> Get()
+        {
+            if (s_Pool.Count == 0)
+            {
+                return new PooledHashSet<T> { m_Active = true };
+            }
+
+            var list = s_Pool.Pop();
+            list.m_Active = true;
+#if DEBUG
+            GC.ReRegisterForFinalize(list);
+#endif
+            return list;
+        }
+
+        public void Dispose()
+        {
+            Assert.IsTrue(m_Active);
+            m_Active = false;
+            Clear();
+            s_Pool.Push(this);
+#if DEBUG
+            GC.SuppressFinalize(this);
+#endif
+        }
+
+        // Destructor causes some GC alloc so only do this sanity check in debug build
+#if DEBUG
+        ~PooledHashSet()
+        {
+            throw new InvalidOperationException($"{nameof(PooledHashSet<T>)} must be disposed manually.");
+        }
+
+#endif
+    }
+}