reduce allocations by SessionId hex conversion

generate the hex string once instead of every log
call and optimize ToHex().

Author: mus65

src/Renci.SshNet/Security/KeyExchange.cs

@@ -198,7 +198,7 @@ public Cipher CreateServerCipher(out bool isAead)
             serverKey = GenerateSessionKey(SharedKey, ExchangeHash, serverKey, _serverCipherInfo.KeySize / 8);
 
             _logger.LogInformation("[{SessionId}] Creating {ServerEncryption} server cipher.",
-                                                    Session.ToHex(Session.SessionId),
+                                                    Session.SessionIdHex,
                                                     Session.ConnectionInfo.CurrentServerEncryption);
 
             // Create server cipher
@@ -226,7 +226,7 @@ public Cipher CreateClientCipher(out bool isAead)
             clientKey = GenerateSessionKey(SharedKey, ExchangeHash, clientKey, _clientCipherInfo.KeySize / 8);
 
             _logger.LogInformation("[{SessionId}] Creating {ClientEncryption} client cipher.",
-                                                    Session.ToHex(Session.SessionId),
+                                                    Session.SessionIdHex,
                                                     Session.ConnectionInfo.CurrentClientEncryption);
 
             // Create client cipher
@@ -259,7 +259,7 @@ public HashAlgorithm CreateServerHash(out bool isEncryptThenMAC)
                                                _serverHashInfo.KeySize / 8);
 
             _logger.LogInformation("[{SessionId}] Creating {ServerHmacAlgorithm} server hmac algorithm.",
-                                                    Session.ToHex(Session.SessionId),
+                                                    Session.SessionIdHex,
                                                     Session.ConnectionInfo.CurrentServerHmacAlgorithm);
 
             return _serverHashInfo.HashAlgorithm(serverKey);
@@ -291,7 +291,7 @@ public HashAlgorithm CreateClientHash(out bool isEncryptThenMAC)
                                                _clientHashInfo.KeySize / 8);
 
             _logger.LogInformation("[{SessionId}] Creating {ClientHmacAlgorithm} client hmac algorithm.",
-                                                    Session.ToHex(Session.SessionId),
+                                                    Session.SessionIdHex,
                                                     Session.ConnectionInfo.CurrentClientHmacAlgorithm);
 
             return _clientHashInfo.HashAlgorithm(clientKey);
@@ -311,7 +311,7 @@ public Compressor CreateCompressor()
             }
 
             _logger.LogInformation("[{SessionId}] Creating {CompressionAlgorithm} client compressor.",
-                                                    Session.ToHex(Session.SessionId),
+                                                    Session.SessionIdHex,
                                                     Session.ConnectionInfo.CurrentClientCompressionAlgorithm);
 
             var compressor = _compressorFactory();
@@ -335,7 +335,7 @@ public Compressor CreateDecompressor()
             }
 
             _logger.LogInformation("[{SessionId}] Creating {ServerCompressionAlgorithm} server decompressor.",
-                                                    Session.ToHex(Session.SessionId),
+                                                    Session.SessionIdHex,
                                                     Session.ConnectionInfo.CurrentServerCompressionAlgorithm);
 
             var decompressor = _decompressorFactory();

src/Renci.SshNet/Session.cs

@@ -5,7 +5,9 @@
 using System.Linq;
 using System.Net.Sockets;
 using System.Security.Cryptography;
+#if !NET
 using System.Text;
+#endif
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -291,13 +293,28 @@ public bool IsConnected
             }
         }
 
+        private byte[] _sessionId;
+
         /// <summary>
         /// Gets the session id.
         /// </summary>
         /// <value>
         /// The session id, or <see langword="null"/> if the client has not been authenticated.
         /// </value>
-        public byte[] SessionId { get; private set; }
+        public byte[] SessionId
+        {
+            get
+            {
+                return _sessionId;
+            }
+            private set
+            {
+                _sessionId = value;
+                SessionIdHex = ToHex(value);
+            }
+        }
+
+        internal string SessionIdHex { get; private set; }
 
         /// <summary>
         /// Gets the client init message.
@@ -800,7 +817,7 @@ public async Task ConnectAsync(CancellationToken cancellationToken)
         /// </remarks>
         public void Disconnect()
         {
-            _logger.LogInformation("[{SessionId}] Disconnecting session.", ToHex(SessionId));
+            _logger.LogInformation("[{SessionId}] Disconnecting session.", SessionIdHex);
 
             // send SSH_MSG_DISCONNECT message, clear socket read buffer and dispose it
             Disconnect(DisconnectReason.ByApplication, "Connection terminated by the client.");
@@ -1030,7 +1047,7 @@ internal void SendMessage(Message message)
                 WaitOnHandle(_keyExchangeCompletedWaitHandle.WaitHandle);
             }
 
-            _logger.LogInformation("[{SessionId}] Sending message '{MessageType}' to server: '{Message}'.", ToHex(SessionId), message.GetType().Name, message);
+            _logger.LogInformation("[{SessionId}] Sending message '{MessageType}' to server: '{Message}'.", SessionIdHex, message.GetType().Name, message);
 
             var paddingMultiplier = _clientCipher is null ? (byte)8 : Math.Max((byte)8, _clientCipher.MinimumSize);
             var packetData = message.GetPacket(paddingMultiplier, _clientCompression, _clientEtm || _clientAead);
@@ -1384,7 +1401,7 @@ private void TrySendDisconnect(DisconnectReason reasonCode, string message)
         /// <param name="message"><see cref="DisconnectMessage"/> message.</param>
         internal void OnDisconnectReceived(DisconnectMessage message)
         {
-            _logger.LogInformation("[{SessionId}] Disconnect received: {ReasonCode} {MessageDescription}.", ToHex(SessionId), message.ReasonCode, message.Description);
+            _logger.LogInformation("[{SessionId}] Disconnect received: {ReasonCode} {MessageDescription}.", SessionIdHex, message.ReasonCode, message.Description);
 
             // transition to disconnecting state to avoid throwing exceptions while cleaning up, and to
             // ensure any exceptions that are raised do not overwrite the SshConnectionException that we
@@ -1479,7 +1496,7 @@ internal void OnKeyExchangeInitReceived(KeyExchangeInitMessage message)
             {
                 _isStrictKex = true;
 
-                _logger.LogInformation("[{SessionId}] Enabling strict key exchange extension.", ToHex(SessionId));
+                _logger.LogInformation("[{SessionId}] Enabling strict key exchange extension.", SessionIdHex);
 
                 if (_inboundPacketSequence != 1)
                 {
@@ -1495,7 +1512,7 @@ internal void OnKeyExchangeInitReceived(KeyExchangeInitMessage message)
 
             ConnectionInfo.CurrentKeyExchangeAlgorithm = _keyExchange.Name;
 
-            _logger.LogInformation("[{SessionId}] Performing {KeyExchangeAlgorithm} key exchange.", ToHex(SessionId), ConnectionInfo.CurrentKeyExchangeAlgorithm);
+            _logger.LogInformation("[{SessionId}] Performing {KeyExchangeAlgorithm} key exchange.", SessionIdHex, ConnectionInfo.CurrentKeyExchangeAlgorithm);
 
             _keyExchange.HostKeyReceived += KeyExchange_HostKeyReceived;
 
@@ -1811,34 +1828,30 @@ private Message LoadMessage(byte[] data, int offset, int count)
             var message = _sshMessageFactory.Create(messageType);
             message.Load(data, offset + 1, count - 1);
 
-            _logger.LogInformation("[{SessionId}] Received message '{MessageType}' from server: '{Message}'.", ToHex(SessionId), message.GetType().Name, message);
+            _logger.LogInformation("[{SessionId}] Received message '{MessageType}' from server: '{Message}'.", SessionIdHex, message.GetType().Name, message);
 
             return message;
         }
 
-        private static string ToHex(byte[] bytes, int offset)
+        private static string ToHex(byte[] bytes)
         {
-            var byteCount = bytes.Length - offset;
-
-            var builder = new StringBuilder(bytes.Length * 2);
-
-            for (var i = offset; i < byteCount; i++)
+            if (bytes is null)
             {
-                var b = bytes[i];
-                _ = builder.Append(b.ToString("X2"));
+                return null;
             }
 
-            return builder.ToString();
-        }
+#if NET
+            return Convert.ToHexString(bytes);
+#else
+            var builder = new StringBuilder(bytes.Length * 2);
 
-        internal static string ToHex(byte[] bytes)
-        {
-            if (bytes is null)
+            foreach (var b in bytes)
             {
-                return null;
+                builder.Append(b.ToString("X2"));
             }
 
-            return ToHex(bytes, 0);
+            return builder.ToString();
+#endif
         }
 
         /// <summary>
@@ -1955,7 +1968,7 @@ private void SocketDisconnectAndDispose()
                         {
                             try
                             {
-                                _logger.LogInformation("[{SessionId}] Shutting down socket.", ToHex(SessionId));
+                                _logger.LogInformation("[{SessionId}] Shutting down socket.", SessionIdHex);
 
                                 // Interrupt any pending reads; should be done outside of socket read lock as we
                                 // actually want shutdown the socket to make sure blocking reads are interrupted.
@@ -1971,9 +1984,9 @@ private void SocketDisconnectAndDispose()
                             }
                         }
 
-                        _logger.LogInformation("[{SessionId}] Disposing socket.", ToHex(SessionId));
+                        _logger.LogInformation("[{SessionId}] Disposing socket.", SessionIdHex);
                         _socket.Dispose();
-                        _logger.LogInformation("[{SessionId}] Disposed socket.", ToHex(SessionId));
+                        _logger.LogInformation("[{SessionId}] Disposed socket.", SessionIdHex);
                         _socket = null;
                     }
                 }
@@ -2057,7 +2070,7 @@ private void RaiseError(Exception exp)
         {
             var connectionException = exp as SshConnectionException;
 
-            _logger.LogInformation(exp, "[{SessionId}] Raised exception", ToHex(SessionId));
+            _logger.LogInformation(exp, "[{SessionId}] Raised exception", SessionIdHex);
 
             if (_isDisconnecting)
             {
@@ -2084,7 +2097,7 @@ private void RaiseError(Exception exp)
 
             if (connectionException != null)
             {
-                _logger.LogInformation(exp, "[{SessionId}] Disconnecting after exception", ToHex(SessionId));
+                _logger.LogInformation(exp, "[{SessionId}] Disconnecting after exception", SessionIdHex);
                 Disconnect(connectionException.DisconnectReason, exp.ToString());
             }
         }
@@ -2157,7 +2170,7 @@ protected virtual void Dispose(bool disposing)
 
             if (disposing)
             {
-                _logger.LogInformation("[{SessionId}] Disposing session.", ToHex(SessionId));
+                _logger.LogInformation("[{SessionId}] Disposing session.", SessionIdHex);
 
                 Disconnect();