Aaru/SCSI/Modes/0F.cs

// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// Filename       : 0F.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Device structures decoders.
//
// --[ Description ] ----------------------------------------------------------
//
//     Decodes SCSI MODE PAGE 0Fh: Data compression page.
//
// --[ License ] --------------------------------------------------------------
//
//     This library is free software; you can redistribute it and/or modify
//     it under the terms of the GNU Lesser General Public License as
//     published by the Free Software Foundation; either version 2.1 of the
//     License, or (at your option) any later version.
//
//     This library is distributed in the hope that it will be useful, but
//     WITHOUT ANY WARRANTY; without even the implied warranty of
//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
//     Lesser General Public License for more details.
//
//     You should have received a copy of the GNU Lesser General Public
//     License along with this library; if not, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
// Copyright © 2011-2018 Natalia Portillo
// ****************************************************************************/

using System.Text;

namespace DiscImageChef.Decoders.SCSI
{
    public static partial class Modes
    {
        #region Mode Page 0x0F: Data compression page
        /// <summary>
        /// Data compression page
        /// Page code 0x0F
        /// 16 bytes in SSC-1, SSC-2, SSC-3
        /// </summary>
        public struct ModePage_0F
        {
            /// <summary>
            /// Parameters can be saved
            /// </summary>
            public bool PS;
            /// <summary>
            /// Data compression enabled
            /// </summary>
            public bool DCE;
            /// <summary>
            /// Data compression capable
            /// </summary>
            public bool DCC;
            /// <summary>
            /// Data decompression enabled
            /// </summary>
            public bool DDE;
            /// <summary>
            /// Report exception on decompression
            /// </summary>
            public byte RED;
            /// <summary>
            /// Compression algorithm
            /// </summary>
            public uint CompressionAlgo;
            /// <summary>
            /// Decompression algorithm
            /// </summary>
            public uint DecompressionAlgo;
        }

        public static ModePage_0F? DecodeModePage_0F(byte[] pageResponse)
        {
            if((pageResponse?[0] & 0x40) == 0x40) return null;

            if((pageResponse?[0] & 0x3F) != 0x0F) return null;

            if(pageResponse[1] + 2 != pageResponse.Length) return null;

            if(pageResponse.Length < 16) return null;

            ModePage_0F decoded = new ModePage_0F();

            decoded.PS |= (pageResponse[0] & 0x80) == 0x80;

            decoded.DCE |= (pageResponse[2] & 0x80) == 0x80;
            decoded.DCC |= (pageResponse[2] & 0x40) == 0x40;
            decoded.DDE |= (pageResponse[3] & 0x80) == 0x80;
            decoded.RED = (byte)((pageResponse[3] & 0x60) >> 5);

            decoded.CompressionAlgo = (uint)((pageResponse[4] << 24) + (pageResponse[5] << 16) +
                                             (pageResponse[6] << 8) + pageResponse[7]);
            decoded.DecompressionAlgo = (uint)((pageResponse[8] << 24) + (pageResponse[9] << 16) +
                                               (pageResponse[10] << 8) + pageResponse[11]);

            return decoded;
        }

        public static string PrettifyModePage_0F(byte[] pageResponse)
        {
            return PrettifyModePage_0F(DecodeModePage_0F(pageResponse));
        }

        public static string PrettifyModePage_0F(ModePage_0F? modePage)
        {
            if(!modePage.HasValue) return null;

            ModePage_0F page = modePage.Value;
            StringBuilder sb = new StringBuilder();

            sb.AppendLine("SCSI Data compression page:");

            if(page.PS) sb.AppendLine("\tParameters can be saved");

            if(page.DCC)
            {
                sb.AppendLine("\tDrive supports data compression");
                if(page.DCE)
                {
                    sb.Append("\tData compression is enabled with ");
                    switch(page.CompressionAlgo)
                    {
                        case 3:
                            sb.AppendLine("IBM ALDC with 512 byte buffer");
                            break;
                        case 4:
                            sb.AppendLine("IBM ALDC with 1024 byte buffer");
                            break;
                        case 5:
                            sb.AppendLine("IBM ALDC with 2048 byte buffer");
                            break;
                        case 0x10:
                            sb.AppendLine("IBM IDRC");
                            break;
                        case 0x20:
                            sb.AppendLine("DCLZ");
                            break;
                        case 0xFF:
                            sb.AppendLine("an unregistered compression algorithm");
                            break;
                        default:
                            sb.AppendFormat("an unknown algorithm coded {0}", page.CompressionAlgo).AppendLine();
                            break;
                    }
                }

                if(page.DDE)
                {
                    sb.AppendLine("\tData decompression is enabled");
                    if(page.DecompressionAlgo == 0) sb.AppendLine("\tLast data read was uncompressed");
                    else
                    {
                        sb.Append("\tLast data read was compressed with ");
                        switch(page.CompressionAlgo)
                        {
                            case 3:
                                sb.AppendLine("IBM ALDC with 512 byte buffer");
                                break;
                            case 4:
                                sb.AppendLine("IBM ALDC with 1024 byte buffer");
                                break;
                            case 5:
                                sb.AppendLine("IBM ALDC with 2048 byte buffer");
                                break;
                            case 0x10:
                                sb.AppendLine("IBM IDRC");
                                break;
                            case 0x20:
                                sb.AppendLine("DCLZ");
                                break;
                            case 0xFF:
                                sb.AppendLine("an unregistered compression algorithm");
                                break;
                            default:
                                sb.AppendFormat("an unknown algorithm coded {0}", page.CompressionAlgo).AppendLine();
                                break;
                        }
                    }
                }

                sb.AppendFormat("\tReport exception on compression is set to {0}", page.RED).AppendLine();
            }
            else sb.AppendLine("\tDrive does not support data compression");

            return sb.ToString();
        }
        #endregion Mode Page 0x0F: Data compression page
    }
}