Revert "Revert "perf: faster NetworkWriter pooling (#1616)""

This reverts commit e96b687.

Assets/Mirror/Runtime/NetworkWriterPool.cs

@@ -1,37 +1,44 @@
 using System;
-using System.Collections.Generic;
 
 namespace Mirror
 {
-    // a NetworkWriter that will recycle itself when disposed
     public class PooledNetworkWriter : NetworkWriter, IDisposable
     {
         public void Dispose()
         {
             NetworkWriterPool.Recycle(this);
         }
     }
-
     public static class NetworkWriterPool
     {
-        static readonly Stack<PooledNetworkWriter> pool = new Stack<PooledNetworkWriter>();
+        public const int MaxPoolSize = 10;
+
+        static readonly PooledNetworkWriter[] pool = new PooledNetworkWriter[MaxPoolSize];
+        static int next = -1;
 
         public static PooledNetworkWriter GetWriter()
         {
-            if (pool.Count != 0)
+            if (next == -1)
             {
-                PooledNetworkWriter writer = pool.Pop();
-                // reset cached writer length and position
-                writer.SetLength(0);
-                return writer;
+                return new PooledNetworkWriter();
             }
 
-            return new PooledNetworkWriter();
+            PooledNetworkWriter writer = pool[next];
+            pool[next] = null;
+            next--;
+
+            // reset cached writer length and position
+            writer.SetLength(0);
+            return writer;
         }
 
         public static void Recycle(PooledNetworkWriter writer)
         {
-            pool.Push(writer);
+            if ((next + 1) < MaxPoolSize)
+            {
+                next++;
+                pool[next] = writer;
+            }
         }
     }
 }