Eliminate temporary array.

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -679,8 +679,7 @@ private async Task<PayloadData> SwitchAuthenticationAsync(ConnectionSettings cs,
 				}
 
 				// send the password as a NULL-terminated UTF-8 string
-				var passwordBytes = Encoding.UTF8.GetBytes(password);
-				Array.Resize(ref passwordBytes, passwordBytes.Length + 1);
+				var passwordBytes = AuthenticationUtility.GetNullTerminatedPasswordBytes(password);
 				payload = new(passwordBytes);
 				await SendReplyAsync(payload, ioBehavior, cancellationToken).ConfigureAwait(false);
 				return await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
@@ -736,8 +735,7 @@ private async Task<PayloadData> SwitchAuthenticationAsync(ConnectionSettings cs,
 	private async Task<PayloadData> SendClearPasswordAsync(string password, IOBehavior ioBehavior, CancellationToken cancellationToken)
 	{
 		// add NUL terminator to password
-		var passwordBytes = Encoding.UTF8.GetBytes(password);
-		Array.Resize(ref passwordBytes, passwordBytes.Length + 1);
+		var passwordBytes = AuthenticationUtility.GetNullTerminatedPasswordBytes(password);
 
 		// send plaintext password
 		var payload = new PayloadData(passwordBytes);
@@ -780,8 +778,7 @@ private async Task<PayloadData> SendEncryptedPasswordAsync(
 #endif
 
 		// add NUL terminator to password
-		var passwordBytes = Encoding.UTF8.GetBytes(password);
-		Array.Resize(ref passwordBytes, passwordBytes.Length + 1);
+		var passwordBytes = AuthenticationUtility.GetNullTerminatedPasswordBytes(password);
 
 		// XOR the password bytes with the challenge
 		AuthPluginData = Utility.TrimZeroByte(switchRequestData);

src/MySqlConnector/Protocol/Serialization/AuthenticationUtility.cs

@@ -9,6 +9,17 @@ namespace MySqlConnector.Protocol.Serialization;
 
 internal static class AuthenticationUtility
 {
+	/// <summary>
+	/// Returns the UTF-8 bytes for <paramref name="password"/>, followed by a null byte.
+	/// </summary>
+	public static byte[] GetNullTerminatedPasswordBytes(string password)
+	{
+		var passwordByteCount = Encoding.UTF8.GetByteCount(password);
+		var passwordBytes = new byte[passwordByteCount + 1];
+		Encoding.UTF8.GetBytes(password.AsSpan(), passwordBytes);
+		return passwordBytes;
+	}
+
 	public static byte[] CreateAuthenticationResponse(ReadOnlySpan<byte> challenge, string password) =>
 		string.IsNullOrEmpty(password) ? [] : HashPassword(challenge, password);