//******************************************************************************************************//  CommandParser.cs - Gbtc////  Copyright © 2020, Grid Protection Alliance.  All Rights Reserved.////  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See//  the NOTICE file distributed with this work for additional information regarding copyright ownership.//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may not use this//  file except in compliance with the License. You may obtain a copy of the License at:////      http://opensource.org/licenses/MIT////  Unless agreed to in writing, the subject software distributed under the License is distributed on an//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the//  License for the specific language governing permissions and limitations.////  Code Modification History://  ----------------------------------------------------------------------------------------------------//  05/12/2020 - J. Ritchie Carroll//       Generated original version of source code.////****************************************************************************************************** #region [ Contributor License Agreements ] //*******************************************************************************************************////   Code based on the following project://        https://github.com/Callisto82/tftp.net//  //   Copyright © 2011, Michael Baer////******************************************************************************************************* #endregion using System;using System.Collections.Generic;using System.IO;using System.Text; namespace GSF.Net.TFtp.Commands{    /// <summary>    /// Parses a ITFtpCommand.    /// </summary>    internal class CommandParser    {        /// <summary>        /// Parses an ITFtpCommand from the given byte array. If the byte array cannot be parsed for some reason, a TFtpParserException is thrown.        /// </summary>        public ITFtpCommand Parse(byte[] message)        {            try            {                return ParseInternal(message);            }            catch (TFtpParserException)            {                throw;            }            catch (Exception ex)            {                throw new TFtpParserException(ex);            }        }         private ITFtpCommand ParseInternal(byte[] message)        {            TFtpStreamReader reader = new TFtpStreamReader(new MemoryStream(message));             ushort opcode = reader.ReadUInt16();             switch (opcode)            {                case ReadRequest.OpCode:                    return ParseReadRequest(reader);                 case WriteRequest.OpCode:                    return ParseWriteRequest(reader);                 case Data.OpCode:                    return ParseData(reader);                 case Acknowledgement.OpCode:                    return ParseAcknowledgement(reader);                 case Error.OpCode:                    return ParseError(reader);                 case OptionAcknowledgement.OpCode:                    return ParseOptionAcknowledgement(reader);                 default:                    throw new TFtpParserException("Invalid opcode");            }        }         private OptionAcknowledgement ParseOptionAcknowledgement(TFtpStreamReader reader)        {            IEnumerable<TransferOption> options = ParseTransferOptions(reader);            return new OptionAcknowledgement(options);        }         private Error ParseError(TFtpStreamReader reader)        {            ushort errorCode = reader.ReadUInt16();            string message = ParseNullTerminatedString(reader);            return new Error(errorCode, message);        }         private Acknowledgement ParseAcknowledgement(TFtpStreamReader reader)        {            ushort blockNumber = reader.ReadUInt16();            return new Acknowledgement(blockNumber);        }         private Data ParseData(TFtpStreamReader reader)        {            ushort blockNumber = reader.ReadUInt16();            byte[] data = reader.ReadBytes(10000);            return new Data(blockNumber, data);        }         private WriteRequest ParseWriteRequest(TFtpStreamReader reader)        {            string filename = ParseNullTerminatedString(reader);            TFtpTransferMode mode = ParseModeType(ParseNullTerminatedString(reader));            IEnumerable<TransferOption> options = ParseTransferOptions(reader);            return new WriteRequest(filename, mode, options);        }         private ReadRequest ParseReadRequest(TFtpStreamReader reader)        {            string filename = ParseNullTerminatedString(reader);            TFtpTransferMode mode = ParseModeType(ParseNullTerminatedString(reader));            IEnumerable<TransferOption> options = ParseTransferOptions(reader);            return new ReadRequest(filename, mode, options);        }         private List<TransferOption> ParseTransferOptions(TFtpStreamReader reader)        {            List<TransferOption> options = new List<TransferOption>();             while (true)            {                string name;                 try                {                    name = ParseNullTerminatedString(reader);                }                catch (IOException)                {                    name = "";                }                 if (string.IsNullOrEmpty(name))                    break;                 string value = ParseNullTerminatedString(reader);                options.Add(new TransferOption(name, value));            }            return options;        }         private static TFtpTransferMode ParseModeType(string mode)        {            if (Enum.TryParse(mode, true, out TFtpTransferMode result))                return result;                         throw new TFtpParserException($"Unknown mode type: {mode}");        }         private static string ParseNullTerminatedString(TFtpStreamReader reader)        {            byte b;            StringBuilder str = new StringBuilder();             while ((b = reader.ReadByte()) > 0)                str.Append((char)b);             return str.ToString();        }    }     [Serializable]    internal class TFtpParserException : Exception    {        public TFtpParserException(string message)            : base(message) { }         public TFtpParserException(Exception e)            : base("Error while parsing message.", e) { }    }}