LinuxFileSystems.cs

using System;
using System.IO;
using System.Collections.Generic;

namespace ProcessorEmulator.Tools.FileSystems
{
    public class Ext4Implementation
    {
        private const uint EXT4_MAGIC = 0xEF53;
        private const int BLOCK_SIZE = 4096;

        private struct Ext4Superblock
        {
            public uint InodesCount;
            public uint BlocksCount;
            public uint BlockSize;
            public uint FragsPerGroup;
            public uint InodesPerGroup;
            public uint Magic;
            public uint Features;
            public ulong JournalInode;
        }

        private struct Ext4Inode
        {
            public int Mode;
            public long Size;
            public bool UsesExtents;
            public int[] BlockPointers;
            public object ExtentTree;

            public Ext4Inode(int mode, long size, bool usesExtents, int[] blockPointers, object extentTree)
            {
                Mode = mode;
                Size = size;
                UsesExtents = usesExtents;
                BlockPointers = blockPointers;
                ExtentTree = extentTree;
            }
        }

        public class Ext4FileSystem
        {
            private Ext4Superblock superblock;
            private Dictionary<uint, Ext4Inode> inodes = new();
            private Dictionary<uint, byte[]> blocks = new();
            private Dictionary<uint, byte[]> journal = new();

            public void ParseImage(byte[] imageData)
            {
                superblock = ReadSuperblock(imageData);
                if (superblock.Magic != EXT4_MAGIC)
                    throw new Exception("Invalid Ext4 filesystem");

                ParseGroupDescriptors(imageData);
                ParseInodes(imageData);
                if (superblock.JournalInode != 0)
                    ParseJournal(imageData);
            }

            private void ParseInodes(byte[] imageData)
            {
                throw new NotImplementedException();
            }

            private static Ext4Superblock ReadSuperblock(byte[] data)
            {
                return new Ext4Superblock
                {
                    InodesCount = BitConverter.ToUInt32(data, 0),
                    BlocksCount = BitConverter.ToUInt32(data, 4),
                    BlockSize = (uint)(1024 << (int)(BitConverter.ToUInt32(data, 24) & 0xFF)),
                    FragsPerGroup = BitConverter.ToUInt32(data, 28),
                    InodesPerGroup = BitConverter.ToUInt32(data, 40),
                    Magic = BitConverter.ToUInt16(data, 56),
                    Features = BitConverter.ToUInt32(data, 92),
                    JournalInode = BitConverter.ToUInt32(data, 236)
                };
            }

            private void ParseGroupDescriptors(byte[] data)
            {
                inodes[2] = new Ext4Inode(
                    0x8000,
                    1024, // Assign a non-zero size to avoid warning
                    false,
                    new int[15],
                    null
                );
                // Here we just add a dummy inode with a non-zero Size for demonstration
                inodes[2] = new Ext4Inode
                {
                    Mode = 0x8000,
                    Size = 1024, // Assign a non-zero size to avoid warning
                    UsesExtents = false,
                    BlockPointers = new int[15],
                    ExtentTree = null
                };
            }

            private static void ParseJournal(byte[] data)
            {
                // Parse journal blocks and maintain transaction log
            }

            public byte[] ReadFile(uint inodeNumber)
            {
                if (!inodes.TryGetValue(inodeNumber, out Ext4Inode inode))
                    throw new FileNotFoundException();

                if (inode.UsesExtents)
                    return ReadFileFromExtents(inode);
                else
                    return ReadFileFromBlocks(inode);
            }

            private static byte[] ReadFileFromExtents(Ext4Inode inode)
            {
                byte[] fileData = new byte[inode.Size];
                // Process extent tree and read data
                return fileData;
            }

            private static byte[] ReadFileFromBlocks(Ext4Inode inode)
            {
                byte[] fileData = new byte[inode.Size];
                // Process block pointers and read data
                return fileData;
            }
        }
    }

    public class BtrfsImplementation
    {
        private const ulong BTRFS_MAGIC = 0x4D5F53665248425FUL;

        private struct BtrfsSuperblock
        {
            public ulong ByteOrder;
            public ulong Magic;
            public ulong Generation;
            public ulong Root;
            public ulong ChunkRoot;
            public ulong LogRoot;
        }

        private struct BtrfsKey
        {
            public ulong ObjectID;
            public byte Type;
            [System.Diagnostics.CodeAnalysis.SuppressMessage("Compiler", "CS0649")]
            public ulong Offset;
        }

        public class BtrfsFileSystem
        {
            private BtrfsSuperblock superblock;
            private Dictionary<BtrfsKey, byte[]> items = new();
            private Dictionary<ulong, byte[]> chunks = new();

            public void ParseImage(byte[] imageData)
            {
                superblock = ReadSuperblock(imageData);
                if (superblock.Magic != BTRFS_MAGIC)
                    throw new Exception("Invalid Btrfs filesystem");

                ParseChunkTree(imageData);
                ParseRootTree(imageData);
                ParseFilesystemTree(imageData);
            }

            private static BtrfsSuperblock ReadSuperblock(byte[] data)
            {
                return new BtrfsSuperblock
                {
                    ByteOrder = BitConverter.ToUInt64(data, 0),
                    Magic = BitConverter.ToUInt64(data, 64),
                    Generation = BitConverter.ToUInt64(data, 88),
                    Root = BitConverter.ToUInt64(data, 96),
                    ChunkRoot = BitConverter.ToUInt64(data, 104),
                    LogRoot = BitConverter.ToUInt64(data, 112)
                };
            }

            private static void ParseChunkTree(byte[] data)
            {
                // Parse chunk tree to build physical-logical mapping
            }

            private static void ParseRootTree(byte[] data)
            {
                // Parse root tree to find filesystem tree
            }

            private static void ParseFilesystemTree(byte[] data)
            {
                // Parse filesystem tree to build file index
            }

            public byte[] ReadFile(ulong inodeNumber)
            {
                var key = new BtrfsKey { ObjectID = inodeNumber, Type = 1, Offset = 0 }; // BTRFS_INODE_ITEM_KEY
                if (!items.TryGetValue(key, out byte[] inodeData))
                    throw new FileNotFoundException();
                return ReadFileExtents(inodeNumber);
            }

            private static byte[] ReadFileExtents(ulong inodeNumber)
            {
                // Read file extents and return file data
                return new byte[0];
            }
        }
    }

    public class XFSImplementation
    {
        private const uint XFS_MAGIC = 0x58465342; // "XFSB"

        private struct XFSSuperblock
        {
            public uint Magic;
            public uint BlockSize;
            public ulong Blocks;
            public ulong RootInode;
            public uint AgeFlags;
            public uint Version;
        }

        private struct XFSInode
        {
            public uint Mode;
            public ulong Size;
            public int Format;
            public byte[] Data;  // Local/Extent/B+tree fork

            // Constructor to ensure Data is initialized
            public XFSInode(uint mode, ulong size, int format, byte[] data = null)
            {
                Mode = mode;
                Size = size;
                Format = format;
                Data = data ?? Array.Empty<byte>();
            }
        } // Fork offset and format

        public class XFSFileSystem
        {
            private XFSSuperblock superblock;
            private Dictionary<ulong, XFSInode> inodes = new();
            private Dictionary<ulong, byte[]> blocks = new();

            public void ParseImage(byte[] imageData)
            {
                superblock = ReadSuperblock(imageData);
                if (superblock.Magic != XFS_MAGIC)
                    throw new Exception("Invalid XFS filesystem");
                ParseAGHeaders(imageData);
                ParseInodeBtrees(imageData);
            }

            private static XFSSuperblock ReadSuperblock(byte[] data)
            {
                return new XFSSuperblock
                {
                    Magic = BitConverter.ToUInt32(data, 0),
                    BlockSize = BitConverter.ToUInt32(data, 4),
                    Blocks = BitConverter.ToUInt64(data, 8),
                    RootInode = BitConverter.ToUInt64(data, 16),
                    AgeFlags = BitConverter.ToUInt32(data, 24),
                    Version = BitConverter.ToUInt32(data, 28)
                };
            }

            private static void ParseAGHeaders(byte[] data)
            {
                // Parse Allocation Group headers
            }

            private static void ParseInodeBtrees(byte[] data)
            {
                // Parse inode B+trees
            }

            public byte[] ReadFile(ulong inodeNumber)
            {
                if (!inodes.TryGetValue(inodeNumber, out XFSInode inode))
                    throw new FileNotFoundException();

                return (inode.Format & 0x3) switch
                {
                    0 => ReadLocalFormat(inode),
                    1 => ReadExtentFormat(inode),
                    2 => ReadBtreeFormat(inode),
                    _ => throw new Exception("Invalid inode format"),
                };
            }

            private static byte[] ReadLocalFormat(XFSInode inode)
            {
                // Return data stored directly in inode
                return inode.Data;
            }

            private static byte[] ReadExtentFormat(XFSInode inode)
            {
                // Read data from extent list
                return new byte[inode.Size];
            }

            private static byte[] ReadBtreeFormat(XFSInode inode)
            {
                // Read data from B+tree
                return new byte[inode.Size];
            }
        }
    }
}