[Add] VContainer

Packages/jp.hadashikick.vcontainer/Runtime/Internal/ListPool.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+
+namespace VContainer.Internal
+{
+    internal static class ListPool<T>
+    {
+        const int DefaultCapacity = 32;
+
+        private static readonly Stack<List<T>> _pool = new Stack<List<T>>(4);
+        
+        /// <summary>
+        /// BufferScope supports releasing a buffer with using clause.
+        /// </summary>
+        internal readonly struct BufferScope : IDisposable
+        {
+            private readonly List<T> _buffer;
+
+            public BufferScope(List<T> buffer)
+            {
+                _buffer = buffer;
+            }
+            
+            public void Dispose()
+            {
+                Release(_buffer);
+            }
+        }
+
+        /// <summary>
+        /// Get a buffer from the pool.
+        /// </summary>
+        /// <returns></returns>
+        internal static List<T> Get()
+        {
+            lock (_pool)
+            {
+                if (_pool.Count == 0)
+                {
+                    return new List<T>(DefaultCapacity);
+                }
+
+                return _pool.Pop();
+            }
+        }
+
+        /// <summary>
+        /// Get a buffer from the pool. Returning a disposable struct to support recycling via using clause.
+        /// </summary>
+        /// <param name="buffer"></param>
+        /// <returns></returns>
+        internal static BufferScope Get(out List<T> buffer)
+        {
+            buffer = Get();
+            return new BufferScope(buffer);
+        }
+
+        /// <summary>
+        /// Declare a buffer won't be used anymore and put it back to the pool.  
+        /// </summary>
+        /// <param name="buffer"></param>
+        internal static void Release(List<T> buffer)
+        {
+            buffer.Clear();
+            lock (_pool)
+            {
+                _pool.Push(buffer);
+            }
+        }
+    }
+}