Add AutoPooled buffer example

src/System.Buffers.Experimental/System/Buffers/AutoBufferPool.cs

@@ -0,0 +1,62 @@
+using System.Collections.Concurrent;
+
+namespace System.Buffers
+{
+    public class AutoBufferPool
+    {
+        private readonly static AutoBufferPool s_shared = new AutoBufferPool();
+        public static AutoBufferPool Shared => s_shared;
+
+        private ConcurrentQueue<AutoPooledMemory> _pool = new ConcurrentQueue<AutoPooledMemory>();
+
+        public OwnedMemory<byte> Rent(int minimumBufferSize)
+        {
+            var array = ArrayPool<byte>.Shared.Rent(minimumBufferSize);
+
+            AutoPooledMemory memory;
+            if (!_pool.TryDequeue(out memory))
+            {
+                memory = new AutoPooledMemory(array, this);
+            }
+            else
+            {
+                memory.Initalize(array);
+            }
+
+            return memory;
+        }
+
+        private void Return(AutoPooledMemory memory)
+        {
+            _pool.Enqueue(memory);
+        }
+
+        private class AutoPooledMemory : OwnedMemory<byte>
+        {
+            private AutoBufferPool _pool;
+
+            public AutoPooledMemory(byte[] array, AutoBufferPool pool) : base(array, 0, array.Length)
+            {
+                _pool = pool;
+            }
+
+            public void Initalize(byte[] array)
+            {
+                base.Initialize(array, 0, array.Length);
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                // Return Array to pool before clear
+                ArrayPool<byte>.Shared.Return(Array);
+                base.Dispose(disposing);
+            }
+
+            protected override void DisposeComplete()
+            {
+                // Disposal complete, no init/clear race - return AutoPooledMemory to pool
+                _pool.Return(this);
+            }
+        }
+    }
+}

src/System.Buffers.Experimental/project.json

@@ -27,7 +27,8 @@
     "System.Slices": { "target": "project" },
     "System.Text.Primitives": { "target": "project" },
     "System.Threading": "4.0.11",
-    "System.Runtime.InteropServices": "4.1.0"
+    "System.Runtime.InteropServices": "4.1.0",
+    "System.Collections.Concurrent": "4.0.12"
   },
   "frameworks": {
     "netstandard1.1": {