import Coffee.Internal

Runtime/Internal/Utilities/ObjectPool.cs

@@ -0,0 +1,85 @@
+using System;
+using System.Collections.Generic;
+
+namespace Coffee.UIParticleInternal
+{
+    /// <summary>
+    /// Object pool.
+    /// </summary>
+    internal class ObjectPool<T>
+    {
+        private readonly Func<T> _onCreate; // Delegate for creating instances
+        private readonly Action<T> _onReturn; // Delegate for returning instances to the pool
+        private readonly Predicate<T> _onValid; // Delegate for checking if instances are valid
+        private readonly Stack<T> _pool = new Stack<T>(32); // Object pool
+        private int _count; // Total count of created instances
+
+        public ObjectPool(Func<T> onCreate, Predicate<T> onValid, Action<T> onReturn)
+        {
+            _onCreate = onCreate;
+            _onValid = onValid;
+            _onReturn = onReturn;
+        }
+
+        /// <summary>
+        /// Rent an instance from the pool.
+        /// When you no longer need it, return it with <see cref="Return" />.
+        /// </summary>
+        public T Rent()
+        {
+            while (0 < _pool.Count)
+            {
+                var instance = _pool.Pop();
+                if (_onValid(instance))
+                {
+                    return instance;
+                }
+            }
+
+            // If there are no instances in the pool, create a new one.
+            Logging.Log(this, $"A new instance is created (pooled: {_pool.Count}, created: {++_count}).");
+            return _onCreate();
+        }
+
+        /// <summary>
+        /// Return an instance to the pool and assign null.
+        /// Be sure to return the instance obtained with <see cref="Rent" /> with this method.
+        /// </summary>
+        public void Return(ref T instance)
+        {
+            if (instance == null || _pool.Contains(instance)) return; // Ignore if already pooled or null.
+
+            _onReturn(instance); // Return the instance to the pool.
+            _pool.Push(instance);
+            Logging.Log(this, $"An instance is released (pooled: {_pool.Count}, created: {_count}).");
+            instance = default; // Set the reference to null.
+        }
+    }
+
+    /// <summary>
+    /// Object pool for <see cref="List{T}" />.
+    /// </summary>
+    internal static class ListPool<T>
+    {
+        private static readonly ObjectPool<List<T>> s_ListPool =
+            new ObjectPool<List<T>>(() => new List<T>(), _ => true, x => x.Clear());
+
+        /// <summary>
+        /// Rent an instance from the pool.
+        /// When you no longer need it, return it with <see cref="Return" />.
+        /// </summary>
+        public static List<T> Rent()
+        {
+            return s_ListPool.Rent();
+        }
+
+        /// <summary>
+        /// Return an instance to the pool and assign null.
+        /// Be sure to return the instance obtained with <see cref="Rent" /> with this method.
+        /// </summary>
+        public static void Return(ref List<T> toRelease)
+        {
+            s_ListPool.Return(ref toRelease);
+        }
+    }
+}