Aaru/Aaru.Filesystems/MicroDOS.cs

// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : MicroDOS.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : MicroDOS filesystem plugin
//
// --[ Description ] ----------------------------------------------------------
//
//     Identifies the MicroDOS filesystem and shows information.
//
// --[ 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 © 2011-2022 Natalia Portillo
// ****************************************************************************/



// ReSharper disable UnusedType.Local
// ReSharper disable UnusedMember.Local

namespace Aaru.Filesystems;

using System;
using System.Runtime.InteropServices;
using System.Text;
using Aaru.CommonTypes;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Schemas;
using Marshal = Aaru.Helpers.Marshal;

/// <inheritdoc />
/// <summary>
///     Implements detection for the MicroDOS filesystem. Information from http://www.owg.ru/mkt/BK/MKDOS.TXT Thanks
///     to tarlabnor for translating it
/// </summary>
public sealed class MicroDOS : IFilesystem
{
    const ushort MAGIC  = 0xA72E;
    const ushort MAGIC2 = 0x530C;

    /// <inheritdoc />
    public FileSystemType XmlFsType { get; private set; }
    /// <inheritdoc />
    public Encoding Encoding { get; private set; }
    /// <inheritdoc />
    public string Name => "MicroDOS file system";
    /// <inheritdoc />
    public Guid Id => new("9F9A364A-1A27-48A3-B730-7A7122000324");
    /// <inheritdoc />
    public string Author => "Natalia Portillo";

    /// <inheritdoc />
    public bool Identify(IMediaImage imagePlugin, Partition partition)
    {
        if(1 + partition.Start >= partition.End)
            return false;

        if(imagePlugin.Info.SectorSize < 512)
            return false;

        ErrorNumber errno = imagePlugin.ReadSector(0 + partition.Start, out byte[] bk0);

        if(errno != ErrorNumber.NoError)
            return false;

        Block0 block0 = Marshal.ByteArrayToStructureLittleEndian<Block0>(bk0);

        return block0.label == MAGIC && block0.mklabel == MAGIC2;
    }

    /// <inheritdoc />
    public void GetInformation(IMediaImage imagePlugin, Partition partition, out string information, Encoding encoding)
    {
        Encoding    = encoding ?? Encoding.GetEncoding("koi8-r");
        information = "";

        var sb = new StringBuilder();

        ErrorNumber errno = imagePlugin.ReadSector(0 + partition.Start, out byte[] bk0);

        if(errno != ErrorNumber.NoError)
            return;

        Block0 block0 = Marshal.ByteArrayToStructureLittleEndian<Block0>(bk0);

        sb.AppendLine("MicroDOS filesystem");
        sb.AppendFormat("Volume has {0} blocks ({1} bytes)", block0.blocks, block0.blocks * 512).AppendLine();

        sb.AppendFormat("Volume has {0} blocks used ({1} bytes)", block0.usedBlocks, block0.usedBlocks * 512).
           AppendLine();

        sb.AppendFormat("Volume contains {0} files", block0.files).AppendLine();
        sb.AppendFormat("First used block is {0}", block0.firstUsedBlock).AppendLine();

        XmlFsType = new FileSystemType
        {
            Type                  = "MicroDOS",
            ClusterSize           = 512,
            Clusters              = block0.blocks,
            Files                 = block0.files,
            FilesSpecified        = true,
            FreeClusters          = (ulong)(block0.blocks - block0.usedBlocks),
            FreeClustersSpecified = true
        };

        information = sb.ToString();
    }

    // Followed by directory entries
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    readonly struct Block0
    {
        /// <summary>BK starts booting here</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 24)]
        public readonly byte[] bootCode;
        /// <summary>Number of files in directory</summary>
        public readonly ushort files;
        /// <summary>Total number of blocks in files of the directory</summary>
        public readonly ushort usedBlocks;
        /// <summary>Unknown</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 228)]
        public readonly byte[] unknown;
        /// <summary>Ownership label (label that shows it belongs to Micro DOS format)</summary>
        public readonly ushort label;
        /// <summary>MK-DOS directory format label</summary>
        public readonly ushort mklabel;
        /// <summary>Unknown</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 50)]
        public readonly byte[] unknown2;
        /// <summary>
        ///     Disk size in blocks (absolute value for the system unlike NORD, NORTON etc.) that doesn't use two fixed values
        ///     40 or 80 tracks, but i.e. if you drive works with 76 tracks this field will contain an appropriate number of blocks
        /// </summary>
        public readonly ushort blocks;
        /// <summary> Number of the first file's block. Value is changable</summary>
        public readonly ushort firstUsedBlock;
        /// <summary>Unknown</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)]
        public readonly byte[] unknown3;
    }

    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    readonly struct DirectoryEntry
    {
        /// <summary>File status</summary>
        public readonly byte status;
        /// <summary>Directory number (0 - root)</summary>
        public readonly byte directory;
        /// <summary>File name 14. symbols in ASCII KOI8</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
        public readonly byte[] filename;
        /// <summary>Block number</summary>
        public readonly ushort blockNo;
        /// <summary>Length in blocks</summary>
        public readonly ushort blocks;
        /// <summary>Address</summary>
        public readonly ushort address;
        /// <summary>Length</summary>
        public readonly ushort length;
    }

    enum FileStatus : byte
    {
        CommonFile  = 0,
        Protected   = 1,
        LogicalDisk = 2,
        BadFile     = 0x80,
        Deleted     = 0xFF
    }
}