Aaru/DiscImageChef.Filesystems/CPM/Dir.cs

// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// Filename       : Dir.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : CP/M filesystem plugin.
//
// --[ Description ] ----------------------------------------------------------
//
//      Methods to show the CP/M filesystem directory.
//
// --[ 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;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;

namespace DiscImageChef.Filesystems.CPM
{
    partial class CPM : Filesystem
    {
        public override Errno ReadDir(string path, ref List<string> contents)
        {
            if(!mounted) return Errno.AccessDenied;

            if(!string.IsNullOrEmpty(path) && string.Compare(path, "/", StringComparison.OrdinalIgnoreCase) != 0)
                return Errno.NotSupported;

            contents = dirList;

            return Errno.NoError;
        }

        /// <summary>
        /// Checks that the given directory blocks follow the CP/M filesystem directory specification
        /// Corrupted directories will fail.
        /// FAT firectories will false positive if all files start with 0x05, and do not use full extentions, for example:
        /// "σAFILE.GZ" (using code page 437)
        /// </summary>
        /// <returns>False if the directory does not follow the directory specification</returns>
        /// <param name="directory">Directory blocks.</param>
        bool CheckDir(byte[] directory)
        {
            try
            {
                if(directory == null) return false;

                int fileCount = 0;

                for(int off = 0; off < directory.Length; off += 32)
                {
                    DirectoryEntry entry;
                    IntPtr dirPtr = Marshal.AllocHGlobal(32);
                    Marshal.Copy(directory, off, dirPtr, 32);
                    entry = (DirectoryEntry)Marshal.PtrToStructure(dirPtr, typeof(DirectoryEntry));
                    Marshal.FreeHGlobal(dirPtr);

                    if((entry.statusUser & 0x7F) < 0x20)
                    {
                        for(int f = 0; f < 8; f++) if(entry.filename[f] < 0x20 && entry.filename[f] != 0x00) return false;

                        for(int e = 0; e < 3; e++) if(entry.extension[e] < 0x20 && entry.extension[e] != 0x00) return false;

                        if(!ArrayHelpers.ArrayIsNullOrWhiteSpace(entry.filename)) fileCount++;
                    }
                    else if(entry.statusUser == 0x20)
                    {
                        for(int f = 0; f < 8; f++) if(entry.filename[f] < 0x20 && entry.filename[f] != 0x00) return false;

                        for(int e = 0; e < 3; e++) if(entry.extension[e] < 0x20 && entry.extension[e] != 0x00) return false;

                        label = Encoding.ASCII.GetString(directory, off + 1, 11).Trim();
                        labelCreationDate = new byte[4];
                        labelUpdateDate = new byte[4];
                        Array.Copy(directory, off + 24, labelCreationDate, 0, 4);
                        Array.Copy(directory, off + 28, labelUpdateDate, 0, 4);
                    }
                    else if(entry.statusUser == 0x21)
                        if(directory[off + 1] == 0x00) thirdPartyTimestamps = true;
                        else standardTimestamps |= directory[off + 21] == 0x00 && directory[off + 31] == 0x00;
                }

                return fileCount > 0;
            }
            catch { return false; }
        }
    }
}