Dispose objects properly. Fixes #275

This commit doesn't ensure that an ObjectDisposedException will be thrown
if an object is used after it's disposed; a NullReferenceException or
some other exception may be thrown instead. These are internal types
that should always be used correctly in this code, so tracking incorrect
use of Dispose is a low priority.

Author: bgrainger

src/MySqlConnector/Protocol/Serialization/CompressedPayloadHandler.cs

@@ -7,7 +7,7 @@
 
 namespace MySql.Data.Protocol.Serialization
 {
-	internal class CompressedPayloadHandler : IPayloadHandler
+	internal sealed class CompressedPayloadHandler : IPayloadHandler
 	{
 		public CompressedPayloadHandler(IByteHandler byteHandler)
 		{
@@ -18,6 +18,13 @@ public CompressedPayloadHandler(IByteHandler byteHandler)
 			m_compressedBufferedByteReader = new BufferedByteReader();
 		}
 
+		public void Dispose()
+		{
+			Utility.Dispose(ref m_byteHandler);
+			Utility.Dispose(ref m_uncompressedStreamByteHandler);
+			Utility.Dispose(ref m_uncompressedStream);
+		}
+
 		public void StartNewConversation()
 		{
 			m_compressedSequenceNumber = 0;
@@ -30,8 +37,11 @@ public IByteHandler ByteHandler
 			set => throw new NotSupportedException();
 		}
 
-		public ValueTask<ArraySegment<byte>> ReadPayloadAsync(ArraySegmentHolder<byte> cache, ProtocolErrorBehavior protocolErrorBehavior, IOBehavior ioBehavior) =>
-			ProtocolUtility.ReadPayloadAsync(m_bufferedByteReader, new CompressedByteHandler(this, protocolErrorBehavior), () => -1, cache, protocolErrorBehavior, ioBehavior);
+		public ValueTask<ArraySegment<byte>> ReadPayloadAsync(ArraySegmentHolder<byte> cache, ProtocolErrorBehavior protocolErrorBehavior, IOBehavior ioBehavior)
+		{
+			using (var compressedByteHandler = new CompressedByteHandler(this, protocolErrorBehavior))
+				return ProtocolUtility.ReadPayloadAsync(m_bufferedByteReader, compressedByteHandler, () => -1, cache, protocolErrorBehavior, ioBehavior);
+		}
 
 		public ValueTask<int> WritePayloadAsync(ArraySegment<byte> payload, IOBehavior ioBehavior)
 		{
@@ -232,14 +242,18 @@ private uint ComputeAdler32Checksum(byte[] data, int offset, int length)
 		}
 
 		// CompressedByteHandler implements IByteHandler and delegates reading bytes back to the CompressedPayloadHandler class.
-		private class CompressedByteHandler : IByteHandler
+		private sealed class CompressedByteHandler : IByteHandler
 		{
 			public CompressedByteHandler(CompressedPayloadHandler compressedPayloadHandler, ProtocolErrorBehavior protocolErrorBehavior)
 			{
 				m_compressedPayloadHandler = compressedPayloadHandler;
 				m_protocolErrorBehavior = protocolErrorBehavior;
 			}
 
+			public void Dispose()
+			{
+			}
+
 			public ValueTask<int> ReadBytesAsync(ArraySegment<byte> buffer, IOBehavior ioBehavior) =>
 				m_compressedPayloadHandler.ReadBytesAsync(buffer, m_protocolErrorBehavior, ioBehavior);
 
@@ -249,9 +263,9 @@ public ValueTask<int> ReadBytesAsync(ArraySegment<byte> buffer, IOBehavior ioBeh
 			readonly ProtocolErrorBehavior m_protocolErrorBehavior;
 		}
 
-		readonly MemoryStream m_uncompressedStream;
-		readonly IByteHandler m_uncompressedStreamByteHandler;
-		readonly IByteHandler m_byteHandler;
+		MemoryStream m_uncompressedStream;
+		IByteHandler m_uncompressedStreamByteHandler;
+		IByteHandler m_byteHandler;
 		readonly BufferedByteReader m_bufferedByteReader;
 		readonly BufferedByteReader m_compressedBufferedByteReader;
 		int m_compressedSequenceNumber;

src/MySqlConnector/Protocol/Serialization/IByteHandler.cs

@@ -3,7 +3,7 @@
 
 namespace MySql.Data.Protocol.Serialization
 {
-	internal interface IByteHandler
+	internal interface IByteHandler : IDisposable
 	{
 		/// <summary>
 		/// Reads data from this byte handler.

src/MySqlConnector/Protocol/Serialization/IPayloadHandler.cs

@@ -3,7 +3,7 @@
 
 namespace MySql.Data.Protocol.Serialization
 {
-	internal interface IPayloadHandler
+	internal interface IPayloadHandler : IDisposable
 	{
 		/// <summary>
 		/// Starts a new "conversation" with the MySQL Server. This resets the "<a href="https://dev.mysql.com/doc/internals/en/sequence-id.html">sequence id</a>"

src/MySqlConnector/Protocol/Serialization/SocketByteHandler.cs

@@ -13,6 +13,8 @@ public SocketByteHandler(Socket socket)
 			m_socketAwaitable = new SocketAwaitable(socketEventArgs);
 		}
 
+		public void Dispose() => m_socketAwaitable.EventArgs.Dispose();
+
 		public ValueTask<int> ReadBytesAsync(ArraySegment<byte> buffer, IOBehavior ioBehavior)
 		{
 			return (ioBehavior == IOBehavior.Asynchronous) ?

src/MySqlConnector/Protocol/Serialization/StandardPayloadHandler.cs

@@ -11,6 +11,12 @@ public StandardPayloadHandler(IByteHandler byteHandler)
 			m_getNextSequenceNumber = () => m_sequenceNumber++;
 		}
 
+		public void Dispose()
+		{
+			m_bufferedByteReader = null;
+			Utility.Dispose(ref m_byteHandler);
+		}
+
 		public void StartNewConversation()
 		{
 			m_sequenceNumber = 0;

src/MySqlConnector/Protocol/Serialization/StreamByteHandler.cs

@@ -11,6 +11,8 @@ public StreamByteHandler(Stream stream)
 			m_stream = stream;
 		}
 
+		public void Dispose() => m_stream.Dispose();
+
 		public ValueTask<int> ReadBytesAsync(ArraySegment<byte> buffer, IOBehavior ioBehavior)
 		{
 			return (ioBehavior == IOBehavior.Asynchronous) ?

src/MySqlConnector/Serialization/MySqlSession.cs

@@ -598,6 +598,7 @@ private async Task InitSslAsync(ProtocolCapabilities serverCapabilities, Connect
 			}
 			catch (Exception ex)
 			{
+				sslStream.Dispose();
 				ShutdownSocket();
 				m_hostname = "";
 				lock (m_lock)
@@ -612,7 +613,7 @@ private async Task InitSslAsync(ProtocolCapabilities serverCapabilities, Connect
 
 		private void ShutdownSocket()
 		{
-			m_payloadHandler = null;
+			Utility.Dispose(ref m_payloadHandler);
 			Utility.Dispose(ref m_networkStream);
 			SafeDispose(ref m_tcpClient);
 			SafeDispose(ref m_socket);