Update Draft76Handler.cs hacktoberfest-accepted

src/Fleck/Handlers/Draft76Handler.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.Linq;
 using System.Security.Cryptography;
@@ -21,40 +22,56 @@ public static IHandler Create(WebSocketHttpRequest request, Action<string> onMes
                 ReceiveData = data => ReceiveData(onMessage, data)
             };
         }
-        
+
         public static void ReceiveData(Action<string> onMessage, List<byte> data)
         {
             while (data.Count > 0)
             {
                 if (data[0] != Start)
+                {
+                    FleckLog.Error("Invalid frame start.");
                     throw new WebSocketException(WebSocketStatusCodes.InvalidFramePayloadData);
-
+                }
+
                 var endIndex = data.IndexOf(End);
                 if (endIndex < 0)
+                {
+                    FleckLog.Warn("End marker not found, waiting for more data.");
                     return;
-
+                }
+
                 if (endIndex > MaxSize)
+                {
+                    FleckLog.Error("Message too big.");
                     throw new WebSocketException(WebSocketStatusCodes.MessageTooBig);
-
+                }
+
                 var bytes = data.Skip(1).Take(endIndex - 1).ToArray();
-
                 data.RemoveRange(0, endIndex + 1);
-
                 var message = Encoding.UTF8.GetString(bytes);
-
                 onMessage(message);
             }
         }
-
         public static byte[] FrameText(string data)
         {
+            //Utilizing ArrayPool<T> reduces heap allocation
+            //by reusing arrays from a pool. This can improve performance
+            //by reducing the amount and frequency
+            //of garbage collections.
             byte[] bytes = Encoding.UTF8.GetBytes(data);
-            // wrap the array with the wrapper bytes
-            var wrappedBytes = new byte[bytes.Length + 2];
-            wrappedBytes[0] = Start;
-            wrappedBytes[wrappedBytes.Length - 1] = End;
-            Array.Copy(bytes, 0, wrappedBytes, 1, bytes.Length);
-            return wrappedBytes;
+            var wrappedBytes = ArrayPool<byte>.Shared.Rent(bytes.Length + 2);
+
+            try
+            {
+                wrappedBytes[0] = Start;
+                wrappedBytes[wrappedBytes.Length - 1] = End;
+                Array.Copy(bytes, 0, wrappedBytes, 1, bytes.Length);
+                return wrappedBytes;
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(wrappedBytes);
+            }
         }
 
         public static byte[] Handshake(WebSocketHttpRequest request, string subProtocol)
@@ -86,7 +103,6 @@ public static byte[] Handshake(WebSocketHttpRequest request, string subProtocol)
 
             return byteResponse;
         }
-
         public static byte[] CalculateAnswerBytes(string key1, string key2, ArraySegment<byte> challenge)
         {
             byte[] result1Bytes = ParseKey(key1);
@@ -96,10 +112,12 @@ public static byte[] CalculateAnswerBytes(string key1, string key2, ArraySegment
             Array.Copy(result1Bytes, 0, rawAnswer, 0, 4);
             Array.Copy(result2Bytes, 0, rawAnswer, 4, 4);
             Array.Copy(challenge.Array, challenge.Offset, rawAnswer, 8, 8);
-
-            return MD5.Create().ComputeHash(rawAnswer);
+            //Replaced MD5 with more secure SHA-256, since MD5 is considered cryptographically unsuitable
+            using (var sha256 = SHA256.Create())
+            {
+                return sha256.ComputeHash(rawAnswer);
+            }
         }
-
         private static byte[] ParseKey(string key)
         {
             int spaces = key.Count(x => x == ' ');