Simplify some ArraySegment and Span code.

Author: bgrainger

src/MySqlConnector/Core/BatchedCommandPayloadCreator.cs

@@ -25,7 +25,7 @@ public bool WriteQueryCommand(ref CommandListPosition commandListPosition, IDict
 
 			// write command length
 			var commandLength = writer.Position - position - padding.Length;
-			var span = writer.ArraySegment.AsSpan().Slice(position);
+			var span = writer.ArraySegment.AsSpan(position);
 			span[0] = 0xFE;
 			BinaryPrimitives.WriteUInt64LittleEndian(span[1..], (ulong) commandLength);
 		} while (wroteCommand);

src/MySqlConnector/Core/ResultSet.cs

@@ -140,7 +140,7 @@ static int ReadColumnCount(ReadOnlySpan<byte> span)
 						// 'Session.ReceiveReplyAsync' reuses a shared buffer; make a copy so that the column definitions can always be safely read at any future point
 						if (m_columnDefinitionPayloadUsedBytes + payloadLength > m_columnDefinitionPayloads.Count)
 							Utility.Resize(ref m_columnDefinitionPayloads, m_columnDefinitionPayloadUsedBytes + payloadLength);
-						payload.Span.CopyTo(m_columnDefinitionPayloads.Array.AsSpan().Slice(m_columnDefinitionPayloadUsedBytes));
+						payload.Span.CopyTo(m_columnDefinitionPayloads.AsSpan(m_columnDefinitionPayloadUsedBytes));
 
 						var columnDefinition = ColumnDefinitionPayload.Create(new ResizableArraySegment<byte>(m_columnDefinitionPayloads, m_columnDefinitionPayloadUsedBytes, payloadLength));
 						ColumnDefinitions[column] = columnDefinition;

src/MySqlConnector/Core/Row.cs

@@ -135,7 +135,7 @@ public long GetBytes(int ordinal, long dataOffset, byte[]? buffer, int bufferOff
 		var offset = (int) dataOffset;
 		var lengthToCopy = Math.Max(0, Math.Min(m_dataLengths[ordinal] - offset, length));
 		if (lengthToCopy > 0)
-			m_data.Slice(m_dataOffsets[ordinal] + offset, lengthToCopy).Span.CopyTo(buffer.AsSpan()[bufferOffset..]);
+			m_data.Slice(m_dataOffsets[ordinal] + offset, lengthToCopy).Span.CopyTo(buffer.AsSpan(bufferOffset));
 		return lengthToCopy;
 	}
 

src/MySqlConnector/Core/ServerSession.cs

@@ -238,7 +238,7 @@ public async Task PrepareAsync(IMySqlCommand command, IOBehavior ioBehavior, Can
 					payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 					var payloadLength = payload.Span.Length;
 					Utility.Resize(ref columnsAndParameters, columnsAndParametersSize + payloadLength);
-					payload.Span.CopyTo(columnsAndParameters.Array.AsSpan()[columnsAndParametersSize..]);
+					payload.Span.CopyTo(columnsAndParameters.AsSpan(columnsAndParametersSize));
 					parameters[i] = ColumnDefinitionPayload.Create(new(columnsAndParameters, columnsAndParametersSize, payloadLength));
 					columnsAndParametersSize += payloadLength;
 				}
@@ -258,7 +258,7 @@ public async Task PrepareAsync(IMySqlCommand command, IOBehavior ioBehavior, Can
 					payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 					var payloadLength = payload.Span.Length;
 					Utility.Resize(ref columnsAndParameters, columnsAndParametersSize + payloadLength);
-					payload.Span.CopyTo(columnsAndParameters.Array.AsSpan()[columnsAndParametersSize..]);
+					payload.Span.CopyTo(columnsAndParameters.AsSpan(columnsAndParametersSize));
 					columns[i] = ColumnDefinitionPayload.Create(new(columnsAndParameters, columnsAndParametersSize, payloadLength));
 					columnsAndParametersSize += payloadLength;
 				}

src/MySqlConnector/Core/StatementPreparer.cs

@@ -23,7 +23,11 @@ public ParsedStatements SplitStatements()
 		var parser = new PreparedCommandSqlParser(this, statements, statementStartEndIndexes, writer);
 		parser.Parse(m_commandText);
 		for (var i = 0; i < statements.Count; i++)
+#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP3_1_OR_GREATER
+			statements[i].StatementBytes = writer.ArraySegment[statementStartEndIndexes[i * 2]..statementStartEndIndexes[i * 2 + 1]];
+#else
 			statements[i].StatementBytes = writer.ArraySegment.Slice(statementStartEndIndexes[i * 2], statementStartEndIndexes[i * 2 + 1] - statementStartEndIndexes[i * 2]);
+#endif
 		return new ParsedStatements(statements, writer.ToPayloadData());
 	}
 

src/MySqlConnector/Protocol/Serialization/ByteBufferWriter.cs

@@ -46,7 +46,7 @@ public void Advance(int count)
 	public void TrimEnd(int byteCount)
 	{
 		Debug.Assert(byteCount <= m_output.Length, "byteCount <= m_output.Length");
-		m_output = m_buffer.AsMemory().Slice(Position - byteCount);
+		m_output = m_buffer.AsMemory(Position - byteCount);
 	}
 
 	public void Write(byte value)

src/MySqlConnector/Protocol/Serialization/CompressedPayloadHandler.cs

@@ -82,9 +82,9 @@ private ValueTask<int> ReadBytesAsync(Memory<byte> buffer, ProtocolErrorBehavior
 						ValueTaskExtensions.FromException<int>(new EndOfStreamException("Wanted to read 7 bytes but only read {0} when reading compressed packet header".FormatInvariant(headerReadBytes.Count)));
 				}
 
-				var payloadLength = (int) SerializationUtility.ReadUInt32(headerReadBytes.Array!, headerReadBytes.Offset, 3);
+				var payloadLength = (int) SerializationUtility.ReadUInt32(headerReadBytes.AsSpan(0, 3));
 				var packetSequenceNumber = headerReadBytes.Array![headerReadBytes.Offset + 3];
-				var uncompressedLength = (int) SerializationUtility.ReadUInt32(headerReadBytes.Array, headerReadBytes.Offset + 4, 3);
+				var uncompressedLength = (int) SerializationUtility.ReadUInt32(headerReadBytes.AsSpan(4, 3));
 
 				// verify the compressed packet sequence number
 				var expectedSequenceNumber = GetNextCompressedSequenceNumber();

src/MySqlConnector/Protocol/Serialization/ProtocolUtility.cs

@@ -417,7 +417,7 @@ private static ValueTask<Packet> ReadPacketAfterHeader(ReadOnlySpan<byte> header
 				ValueTaskExtensions.FromException<Packet>(new EndOfStreamException("Expected to read 4 header bytes but only received {0}.".FormatInvariant(headerBytes.Length)));
 		}
 
-		var payloadLength = (int) SerializationUtility.ReadUInt32(headerBytes.Slice(0, 3));
+		var payloadLength = (int) SerializationUtility.ReadUInt32(headerBytes[..3]);
 		int packetSequenceNumber = headerBytes[3];
 
 		Exception? packetOutOfOrderException = null;
@@ -441,7 +441,11 @@ private static ValueTask<Packet> CreatePacketFromPayload(ArraySegment<byte> payl
 			if (protocolErrorBehavior == ProtocolErrorBehavior.Ignore)
 				return default;
 
+#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP3_1_OR_GREATER
+			if (payloadBytes is [ ErrorPayload.Signature, .. ])
+#else
 			if (payloadBytes.Count > 0 && payloadBytes.AsSpan()[0] == ErrorPayload.Signature)
+#endif
 				return new ValueTask<Packet>(new Packet(payloadBytes));
 
 			return ValueTaskExtensions.FromException<Packet>(exception);

src/MySqlConnector/Protocol/Serialization/SerializationUtility.cs

@@ -2,14 +2,6 @@ namespace MySqlConnector.Protocol.Serialization;
 
 internal static class SerializationUtility
 {
-	public static uint ReadUInt32(byte[] buffer, int offset, int count)
-	{
-		uint value = 0;
-		for (int i = 0; i < count; i++)
-			value |= ((uint) buffer[offset + i]) << (8 * i);
-		return value;
-	}
-
 	public static uint ReadUInt32(ReadOnlySpan<byte> span)
 	{
 		uint value = 0;

src/MySqlConnector/Utilities/ResizableArray.cs

@@ -9,6 +9,8 @@ internal sealed class ResizableArray<T>
 	public T[]? Array => m_array;
 	public int Count => m_array?.Length ?? 0;
 
+	public Span<T> AsSpan(int start) => m_array.AsSpan(start);
+
 	/// <summary>
 	/// Do not call this method directly; use <see cref="Utility.Resize{T}"/>.
 	/// </summary>