Avoid creating substrings when parsing server version.

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -304,7 +304,7 @@ public async Task ConnectAsync(ConnectionSettings cs, ILoadBalancer loadBalancer
 						throw new NotSupportedException("Authentication method '{0}' is not supported.".FormatInvariant(initialHandshake.AuthPluginName));
 					}
 
-					ServerVersion = new ServerVersion(Encoding.ASCII.GetString(initialHandshake.ServerVersion));
+					ServerVersion = new ServerVersion(initialHandshake.ServerVersion);
 					ConnectionId = initialHandshake.ConnectionId;
 					AuthPluginData = initialHandshake.AuthPluginData;
 					m_useCompression = cs.UseCompression && (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Compress) != 0;
@@ -1152,13 +1152,13 @@ private async Task GetRealServerDetailsAsync(IOBehavior ioBehavior, Cancellation
 
 				// first (and only) row
 				payload = await ReceiveReplyAsync(ioBehavior, CancellationToken.None).ConfigureAwait(false);
-				void ReadRow(ReadOnlySpan<byte> span, out int? connectionId_, out string serverVersion_)
+				void ReadRow(ReadOnlySpan<byte> span, out int? connectionId_, out byte[] serverVersion_)
 				{
 					var reader = new ByteArrayReader(span);
 					var length = reader.ReadLengthEncodedIntegerOrNull();
 					connectionId_ = (length != -1 && Utf8Parser.TryParse(reader.ReadByteString(length), out int id, out _)) ? id : default(int?);
 					length = reader.ReadLengthEncodedIntegerOrNull();
-					serverVersion_ = length != -1 ? Encoding.UTF8.GetString(reader.ReadByteString(length)) : null;
+					serverVersion_ = length != -1 ? reader.ReadByteString(length).ToArray() : null;
 				}
 				ReadRow(payload.AsSpan(), out var connectionId, out var serverVersion);
 
@@ -1171,9 +1171,10 @@ void ReadRow(ReadOnlySpan<byte> span, out int? connectionId_, out string serverV
 
 				if (connectionId.HasValue && serverVersion != null)
 				{
-					Log.Info("Session{0} changing ConnectionIdOld {1} to ConnectionId {2} and ServerVersionOld {3} to ServerVersion {4}", m_logArguments[0], ConnectionId, connectionId.Value, ServerVersion.OriginalString, serverVersion);
+					var newServerVersion = new ServerVersion(serverVersion);
+					Log.Info("Session{0} changing ConnectionIdOld {1} to ConnectionId {2} and ServerVersionOld {3} to ServerVersion {4}", m_logArguments[0], ConnectionId, connectionId.Value, ServerVersion.OriginalString, newServerVersion.OriginalString);
 					ConnectionId = connectionId.Value;
-					ServerVersion = new ServerVersion(serverVersion);
+					ServerVersion = newServerVersion;
 				}
 			}
 			catch (MySqlException ex)

src/MySqlConnector/Core/ServerVersion.cs

@@ -1,28 +1,24 @@
 using System;
-using System.Globalization;
+using System.Buffers.Text;
+using System.Text;
+using MySqlConnector.Utilities;
 
 namespace MySqlConnector.Core
 {
 	internal sealed class ServerVersion
 	{
-		public ServerVersion(string versionString)
+		public ServerVersion(ReadOnlySpan<byte> versionString)
 		{
-			OriginalString = versionString;
+			OriginalString = Encoding.ASCII.GetString(versionString);
 
-			var last = 0;
-			var index = versionString.IndexOf('.', last);
-			var major = int.Parse(versionString.Substring(last, index - last), CultureInfo.InvariantCulture);
-			last = index + 1;
-
-			index = versionString.IndexOf('.', last);
-			var minor = int.Parse(versionString.Substring(last, index - last), CultureInfo.InvariantCulture);
-			last = index + 1;
-
-			do
-			{
-				index++;
-			} while (index < versionString.Length && versionString[index] >= '0' && versionString[index] <= '9');
-			var build = int.Parse(versionString.Substring(last, index - last), CultureInfo.InvariantCulture);
+			if (!Utf8Parser.TryParse(versionString, out int major, out var bytesConsumed) || versionString[bytesConsumed] != 0x2E)
+				throw new InvalidOperationException("Error parsing " + OriginalString);
+			versionString = versionString.Slice(bytesConsumed + 1);
+			if (!Utf8Parser.TryParse(versionString, out int minor, out bytesConsumed) || versionString[bytesConsumed] != 0x2E)
+				throw new InvalidOperationException("Error parsing " + OriginalString);
+			versionString = versionString.Slice(bytesConsumed + 1);
+			if (!Utf8Parser.TryParse(versionString, out int build, out bytesConsumed))
+				throw new InvalidOperationException("Error parsing " + OriginalString);
 
 			Version = new Version(major, minor, build);
 		}

tests/MySqlConnector.Tests/ServerVersionTests.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Text;
 using MySqlConnector.Core;
 using Xunit;
 
@@ -16,7 +17,7 @@ public class ServerVersionTests
 		public void ParseServerVersion(string serverVersion, string expectedString)
 		{
 			var expected = Version.Parse(expectedString);
-			Assert.Equal(expected, new ServerVersion(serverVersion).Version);
+			Assert.Equal(expected, new ServerVersion(Encoding.UTF8.GetBytes(serverVersion)).Version);
 		}
 	}
 }