Ship authenticated remote transports in Unity package

src/GameCult.Networking.WebSockets/CultNetWebSocketMessageIO.cs

@@ -0,0 +1,46 @@
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace GameCult.Networking.WebSockets;
+
+internal static class CultNetWebSocketMessageIO
+{
+    public static Task SendAsync(WebSocket socket, byte[] payload, CancellationToken cancellationToken) =>
+        socket.SendAsync(new ArraySegment<byte>(payload), WebSocketMessageType.Binary, true, cancellationToken);
+
+    public static async Task<byte[]?> ReceiveAsync(
+        WebSocket socket,
+        int maxMessageBytes,
+        CancellationToken cancellationToken)
+    {
+        var segment = new byte[Math.Min(16 * 1024, maxMessageBytes)];
+        using var message = new MemoryStream();
+        while (true)
+        {
+            var result = await socket.ReceiveAsync(new ArraySegment<byte>(segment), cancellationToken)
+                .ConfigureAwait(false);
+            if (result.MessageType == WebSocketMessageType.Close) return null;
+            if (result.MessageType != WebSocketMessageType.Binary)
+            {
+                await socket.CloseAsync(
+                    WebSocketCloseStatus.InvalidMessageType,
+                    "CultNet requires binary MessagePack WebSocket messages.",
+                    cancellationToken).ConfigureAwait(false);
+                return null;
+            }
+            if (message.Length + result.Count > maxMessageBytes)
+            {
+                await socket.CloseAsync(
+                    WebSocketCloseStatus.MessageTooBig,
+                    "CultNet message exceeds the configured maximum.",
+                    cancellationToken).ConfigureAwait(false);
+                return null;
+            }
+            message.Write(segment, 0, result.Count);
+            if (result.EndOfMessage) return message.ToArray();
+        }
+    }
+}