Merge pull request #343 from bgrainger/reduce-allocations

Defer string creation in ColumnDefinitionPayload.

Author: bgrainger

src/MySqlConnector/Serialization/ColumnDefinitionPayload.cs

@@ -1,11 +1,19 @@
-using System;
+using System;
 using System.Text;
 
 namespace MySql.Data.Serialization
 {
 	internal class ColumnDefinitionPayload
 	{
-		public string Name { get; private set; }
+		public string Name
+		{
+			get
+			{
+				if (!m_readNames)
+					ReadNames();
+				return m_name;
+			}
+		}
 
 		public CharacterSet CharacterSet { get; private set; }
 
@@ -15,27 +23,67 @@ internal class ColumnDefinitionPayload
 
 		public ColumnFlags ColumnFlags { get; private set; }
 
-		public string SchemaName { get; private set; }
+		public string SchemaName
+		{
+			get
+			{
+				if (!m_readNames)
+					ReadNames();
+				return m_schemaName;
+			}
+		}
 
-		public string CatelogName { get; private set; }
+		public string CatalogName
+		{
+			get
+			{
+				if (!m_readNames)
+					ReadNames();
+				return m_catalogName;
+			}
+		}
 
-		public string Table { get; private set; }
+		public string Table
+		{
+			get
+			{
+				if (!m_readNames)
+					ReadNames();
+				return m_table;
+			}
+		}
 
-		public string PhysicalTable { get; private set; }
+		public string PhysicalTable
+		{
+			get
+			{
+				if (!m_readNames)
+					ReadNames();
+				return m_physicalTable;
+			}
+		}
 
-		public string PhysicalName { get; private set; }
+		public string PhysicalName
+		{
+			get
+			{
+				if (!m_readNames)
+					ReadNames();
+				return m_physicalName;
+			}
+		}
 
 		public byte Decimals { get; private set; }
 
 		public static ColumnDefinitionPayload Create(PayloadData payload)
 		{
 			var reader = new ByteArrayReader(payload.ArraySegment);
-			var catalog = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
-			var schema = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
-			var table = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
-			var physicalTable = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
-			var name = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
-			var physicalName = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			SkipLengthEncodedByteString(ref reader); // catalog
+			SkipLengthEncodedByteString(ref reader); // schema
+			SkipLengthEncodedByteString(ref reader); // table
+			SkipLengthEncodedByteString(ref reader); // physical table
+			SkipLengthEncodedByteString(ref reader); // name
+			SkipLengthEncodedByteString(ref reader); // physical name
 			reader.ReadByte(0x0C); // length of fixed-length fields, always 0x0C
 			var characterSet = (CharacterSet) reader.ReadUInt16();
 			var columnLength = reader.ReadUInt32();
@@ -57,19 +105,41 @@ public static ColumnDefinitionPayload Create(PayloadData payload)
 
 			return new ColumnDefinitionPayload
 			{
-				Name = name,
+				OriginalPayload = payload,
 				CharacterSet = characterSet,
 				ColumnLength = columnLength,
 				ColumnType = columnType,
 				ColumnFlags = columnFlags,
-				SchemaName = schema,
-				CatelogName = catalog,
-				Table = table,
-				PhysicalTable = physicalTable,
-				PhysicalName = physicalName,
 				Decimals = decimals
 			};
+		}
 
+		private static void SkipLengthEncodedByteString(ref ByteArrayReader reader)
+		{
+			var length = checked((int) reader.ReadLengthEncodedInteger());
+			reader.Offset += length;
 		}
+
+		private void ReadNames()
+		{
+			var reader = new ByteArrayReader(OriginalPayload.ArraySegment);
+			m_catalogName = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			m_schemaName = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			m_table = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			m_physicalTable = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			m_name = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			m_physicalName = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+			m_readNames = true;
+		}
+
+		PayloadData OriginalPayload { get; set; }
+
+		bool m_readNames;
+		string m_name;
+		string m_schemaName;
+		string m_catalogName;
+		string m_table;
+		string m_physicalTable;
+		string m_physicalName;
 	}
 }