CHANGED TO MIRROR

Assets/Mirror/Runtime/Batching/Batcher.cs

@@ -0,0 +1,97 @@
+// batching functionality encapsulated into one class.
+// -> less complexity
+// -> easy to test
+//
+// IMPORTANT: we use THRESHOLD batching, not MAXED SIZE batching.
+// see threshold comments below.
+//
+// includes timestamp for tick batching.
+// -> allows NetworkTransform etc. to use timestamp without including it in
+//    every single message
+using System;
+using System.Collections.Generic;
+
+namespace Mirror
+{
+    public class Batcher
+    {
+        // batching threshold instead of max size.
+        // -> small messages are fit into threshold sized batches
+        // -> messages larger than threshold are single batches
+        //
+        // in other words, we fit up to 'threshold' but still allow larger ones
+        // for two reasons:
+        // 1.) data races: skipping batching for larger messages would send a
+        //     large spawn message immediately, while others are batched and
+        //     only flushed at the end of the frame
+        // 2) timestamp batching: if each batch is expected to contain a
+        //    timestamp, then large messages have to be a batch too. otherwise
+        //    they would not contain a timestamp
+        readonly int threshold;
+
+        // TimeStamp header size for those who need it
+        public const int HeaderSize = sizeof(double);
+
+        // batched messages
+        // IMPORTANT: we queue the serialized messages!
+        //            queueing NetworkMessage would box and allocate!
+        Queue<PooledNetworkWriter> messages = new Queue<PooledNetworkWriter>();
+
+        public Batcher(int threshold)
+        {
+            this.threshold = threshold;
+        }
+
+        // add a message for batching
+        // we allow any sized messages.
+        // caller needs to make sure they are within max packet size.
+        public void AddMessage(ArraySegment<byte> message)
+        {
+            // put into a (pooled) writer
+            // -> WriteBytes instead of WriteSegment because the latter
+            //    would add a size header. we want to write directly.
+            // -> will be returned to pool when making the batch!
+            // IMPORTANT: NOT adding a size header / msg saves LOTS of bandwidth
+            PooledNetworkWriter writer = NetworkWriterPool.GetWriter();
+            writer.WriteBytes(message.Array, message.Offset, message.Count);
+            messages.Enqueue(writer);
+        }
+
+        // batch as many messages as possible into writer
+        // returns true if any batch was made.
+        public bool MakeNextBatch(NetworkWriter writer, double timeStamp)
+        {
+            // if we have no messages then there's nothing to do
+            if (messages.Count == 0)
+                return false;
+
+            // make sure the writer is fresh to avoid uncertain situations
+            if (writer.Position != 0)
+                throw new ArgumentException($"MakeNextBatch needs a fresh writer!");
+
+            // write timestamp first
+            // -> double precision for accuracy over long periods of time
+            writer.WriteDouble(timeStamp);
+
+            // do start no matter what
+            do
+            {
+                // add next message no matter what. even if > threshold.
+                // (we do allow > threshold sized messages as single batch)
+                PooledNetworkWriter message = messages.Dequeue();
+                ArraySegment<byte> segment = message.ToArraySegment();
+                writer.WriteBytes(segment.Array, segment.Offset, segment.Count);
+
+                // return the writer to pool
+                NetworkWriterPool.Recycle(message);
+            }
+            // keep going as long as we have more messages,
+            // AND the next one would fit into threshold.
+            while (messages.Count > 0 &&
+                   writer.Position + messages.Peek().Position <= threshold);
+
+            // we had messages, so a batch was made
+            return true;
+        }
+    }
+}