// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : Read.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Disk image plugins.
//
// --[ Description ] ----------------------------------------------------------
//
//     Reads Connectix and Microsoft Virtual PC disk images.
//
// --[ 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 © 2011-2021 Natalia Portillo
// ****************************************************************************/

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using Aaru.Checksums;
using Aaru.CommonTypes;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Aaru.Console;
using Aaru.Helpers;

namespace Aaru.DiscImages
{
    public sealed partial class Vhd
    {
        /// <inheritdoc />
        public ErrorNumber Open(IFilter imageFilter)
        {
            Stream imageStream = imageFilter.GetDataForkStream();
            byte[] header      = new byte[512];
            byte[] footer;

            imageStream.Seek(0, SeekOrigin.Begin);
            imageStream.Read(header, 0, 512);

            if(imageStream.Length % 2 == 0)
            {
                footer = new byte[512];
                imageStream.Seek(-512, SeekOrigin.End);
                imageStream.Read(footer, 0, 512);
            }
            else
            {
                footer = new byte[511];
                imageStream.Seek(-511, SeekOrigin.End);
                imageStream.Read(footer, 0, 511);
            }

            uint  headerChecksum = BigEndianBitConverter.ToUInt32(header, 0x40);
            uint  footerChecksum = BigEndianBitConverter.ToUInt32(footer, 0x40);
            ulong headerCookie   = BigEndianBitConverter.ToUInt64(header, 0);
            ulong footerCookie   = BigEndianBitConverter.ToUInt64(footer, 0);

            header[0x40] = 0;
            header[0x41] = 0;
            header[0x42] = 0;
            header[0x43] = 0;
            footer[0x40] = 0;
            footer[0x41] = 0;
            footer[0x42] = 0;
            footer[0x43] = 0;

            uint headerCalculatedChecksum = VhdChecksum(header);
            uint footerCalculatedChecksum = VhdChecksum(footer);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "Header checksum = 0x{0:X8}, calculated = 0x{1:X8}",
                                       headerChecksum, headerCalculatedChecksum);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "Header checksum = 0x{0:X8}, calculated = 0x{1:X8}",
                                       footerChecksum, footerCalculatedChecksum);

            byte[] usableHeader;
            uint   usableChecksum;

            if(headerCookie   == IMAGE_COOKIE &&
               headerChecksum == headerCalculatedChecksum)
            {
                usableHeader   = header;
                usableChecksum = headerChecksum;
            }
            else if(footerCookie   == IMAGE_COOKIE &&
                    footerChecksum == footerCalculatedChecksum)
            {
                usableHeader   = footer;
                usableChecksum = footerChecksum;
            }
            else
            {
                AaruConsole.
                    ErrorWriteLine("(VirtualPC plugin): Both header and footer are corrupt, image cannot be opened.");

                return ErrorNumber.InvalidArgument;
            }

            _thisFooter = new HardDiskFooter
            {
                Cookie             = BigEndianBitConverter.ToUInt64(usableHeader, 0x00),
                Features           = BigEndianBitConverter.ToUInt32(usableHeader, 0x08),
                Version            = BigEndianBitConverter.ToUInt32(usableHeader, 0x0C),
                Offset             = BigEndianBitConverter.ToUInt64(usableHeader, 0x10),
                Timestamp          = BigEndianBitConverter.ToUInt32(usableHeader, 0x18),
                CreatorApplication = BigEndianBitConverter.ToUInt32(usableHeader, 0x1C),
                CreatorVersion     = BigEndianBitConverter.ToUInt32(usableHeader, 0x20),
                CreatorHostOs      = BigEndianBitConverter.ToUInt32(usableHeader, 0x24),
                OriginalSize       = BigEndianBitConverter.ToUInt64(usableHeader, 0x28),
                CurrentSize        = BigEndianBitConverter.ToUInt64(usableHeader, 0x30),
                DiskGeometry       = BigEndianBitConverter.ToUInt32(usableHeader, 0x38),
                DiskType           = BigEndianBitConverter.ToUInt32(usableHeader, 0x3C),
                Checksum           = usableChecksum,
                UniqueId           = BigEndianBitConverter.ToGuid(usableHeader, 0x44),
                SavedState         = usableHeader[0x54],
                Reserved           = new byte[usableHeader.Length - 0x55]
            };

            Array.Copy(usableHeader, 0x55, _thisFooter.Reserved, 0, usableHeader.Length - 0x55);

            _thisDateTime = new DateTime(2000, 1, 1, 0, 0, 0, DateTimeKind.Utc);
            _thisDateTime = _thisDateTime.AddSeconds(_thisFooter.Timestamp);

            var sha1Ctx = new Sha1Context();
            sha1Ctx.Update(_thisFooter.Reserved);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.cookie = 0x{0:X8}", _thisFooter.Cookie);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.features = 0x{0:X8}", _thisFooter.Features);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.version = 0x{0:X8}", _thisFooter.Version);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.offset = {0}", _thisFooter.Offset);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.timestamp = 0x{0:X8} ({1})", _thisFooter.Timestamp,
                                       _thisDateTime);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.creatorApplication = 0x{0:X8} (\"{1}\")",
                                       _thisFooter.CreatorApplication,
                                       Encoding.ASCII.GetString(BigEndianBitConverter.GetBytes(_thisFooter.
                                                                    CreatorApplication)));

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.creatorVersion = 0x{0:X8}",
                                       _thisFooter.CreatorVersion);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.creatorHostOS = 0x{0:X8} (\"{1}\")",
                                       _thisFooter.CreatorHostOs,
                                       Encoding.ASCII.GetString(BigEndianBitConverter.
                                                                    GetBytes(_thisFooter.CreatorHostOs)));

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.originalSize = {0}", _thisFooter.OriginalSize);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.currentSize = {0}", _thisFooter.CurrentSize);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.diskGeometry = 0x{0:X8} (C/H/S: {1}/{2}/{3})",
                                       _thisFooter.DiskGeometry, (_thisFooter.DiskGeometry & 0xFFFF0000) >> 16,
                                       (_thisFooter.DiskGeometry & 0xFF00) >> 8, _thisFooter.DiskGeometry & 0xFF);

            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.diskType = 0x{0:X8}", _thisFooter.DiskType);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.checksum = 0x{0:X8}", _thisFooter.Checksum);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.uniqueId = {0}", _thisFooter.UniqueId);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.savedState = 0x{0:X2}", _thisFooter.SavedState);
            AaruConsole.DebugWriteLine("VirtualPC plugin", "footer.reserved's SHA1 = 0x{0}", sha1Ctx.End());

            if(_thisFooter.Version == VERSION1)
                _imageInfo.Version = "1.0";
            else
            {
                AaruConsole.
                    ErrorWriteLine($"(VirtualPC plugin): Unknown image type {_thisFooter.DiskType} found. Please submit a bug with an example image.");

                return ErrorNumber.InvalidArgument;
            }

            switch(_thisFooter.CreatorApplication)
            {
                case CREATOR_QEMU:
                {
                    _imageInfo.Application = "QEMU";

                    // QEMU always set same version
                    _imageInfo.ApplicationVersion = "Unknown";

                    break;
                }

                case CREATOR_VIRTUAL_BOX:
                {
                    _imageInfo.ApplicationVersion =
                        $"{(_thisFooter.CreatorVersion & 0xFFFF0000) >> 16}.{_thisFooter.CreatorVersion & 0x0000FFFF:D2}";

                    switch(_thisFooter.CreatorHostOs)
                    {
                        case CREATOR_MACINTOSH:
                        case CREATOR_MACINTOSH_OLD:
                            _imageInfo.Application = "VirtualBox for Mac";

                            break;
                        case CREATOR_WINDOWS:
                            // VirtualBox uses Windows creator for any other OS
                            _imageInfo.Application = "VirtualBox";

                            break;
                        default:
                            _imageInfo.Application =
                                $"VirtualBox for unknown OS \"{Encoding.ASCII.GetString(BigEndianBitConverter.GetBytes(_thisFooter.CreatorHostOs))}\"";

                            break;
                    }

                    break;
                }

                case CREATOR_VIRTUAL_SERVER:
                {
                    _imageInfo.Application = "Microsoft Virtual Server";

                    switch(_thisFooter.CreatorVersion)
                    {
                        case VERSION_VIRTUAL_SERVER2004:
                            _imageInfo.ApplicationVersion = "2004";

                            break;
                        default:
                            _imageInfo.ApplicationVersion = $"Unknown version 0x{_thisFooter.CreatorVersion:X8}";

                            break;
                    }

                    break;
                }

                case CREATOR_VIRTUAL_PC:
                {
                    switch(_thisFooter.CreatorHostOs)
                    {
                        case CREATOR_MACINTOSH:
                        case CREATOR_MACINTOSH_OLD:
                            switch(_thisFooter.CreatorVersion)
                            {
                                case VERSION_VIRTUAL_PC_MAC:
                                    _imageInfo.Application        = "Connectix Virtual PC";
                                    _imageInfo.ApplicationVersion = "5, 6 or 7";

                                    break;
                                default:
                                    _imageInfo.ApplicationVersion =
                                        $"Unknown version 0x{_thisFooter.CreatorVersion:X8}";

                                    break;
                            }

                            break;
                        case CREATOR_WINDOWS:
                            switch(_thisFooter.CreatorVersion)
                            {
                                case VERSION_VIRTUAL_PC_MAC:
                                    _imageInfo.Application        = "Connectix Virtual PC";
                                    _imageInfo.ApplicationVersion = "5, 6 or 7";

                                    break;
                                case VERSION_VIRTUAL_PC2004:
                                    _imageInfo.Application        = "Microsoft Virtual PC";
                                    _imageInfo.ApplicationVersion = "2004";

                                    break;
                                case VERSION_VIRTUAL_PC2007:
                                    _imageInfo.Application        = "Microsoft Virtual PC";
                                    _imageInfo.ApplicationVersion = "2007";

                                    break;
                                default:
                                    _imageInfo.ApplicationVersion =
                                        $"Unknown version 0x{_thisFooter.CreatorVersion:X8}";

                                    break;
                            }

                            break;
                        default:
                            _imageInfo.Application =
                                $"Virtual PC for unknown OS \"{Encoding.ASCII.GetString(BigEndianBitConverter.GetBytes(_thisFooter.CreatorHostOs))}\"";

                            _imageInfo.ApplicationVersion = $"Unknown version 0x{_thisFooter.CreatorVersion:X8}";

                            break;
                    }

                    break;
                }

                case CREATOR_DISCIMAGECHEF:
                {
                    _imageInfo.Application = "DiscImageChef";

                    _imageInfo.ApplicationVersion =
                        $"{(_thisFooter.CreatorVersion & 0xFF000000) >> 24}.{(_thisFooter.CreatorVersion & 0xFF0000) >> 16}.{(_thisFooter.CreatorVersion & 0xFF00) >> 8}.{_thisFooter.CreatorVersion & 0xFF}";
                }

                    break;

                case CREATOR_AARU:
                {
                    _imageInfo.Application = "Aaru";

                    _imageInfo.ApplicationVersion =
                        $"{(_thisFooter.CreatorVersion & 0xFF000000) >> 24}.{(_thisFooter.CreatorVersion & 0xFF0000) >> 16}.{(_thisFooter.CreatorVersion & 0xFF00) >> 8}.{_thisFooter.CreatorVersion & 0xFF}";
                }

                    break;
                default:
                {
                    _imageInfo.Application =
                        $"Unknown application \"{Encoding.ASCII.GetString(BigEndianBitConverter.GetBytes(_thisFooter.CreatorHostOs))}\"";

                    _imageInfo.ApplicationVersion = $"Unknown version 0x{_thisFooter.CreatorVersion:X8}";

                    break;
                }
            }

            _thisFilter           = imageFilter;
            _imageInfo.ImageSize  = _thisFooter.CurrentSize;
            _imageInfo.Sectors    = _thisFooter.CurrentSize / 512;
            _imageInfo.SectorSize = 512;

            _imageInfo.CreationTime         = imageFilter.CreationTime;
            _imageInfo.LastModificationTime = _thisDateTime;
            _imageInfo.MediaTitle           = Path.GetFileNameWithoutExtension(imageFilter.Filename);

            _imageInfo.Cylinders       = (_thisFooter.DiskGeometry & 0xFFFF0000) >> 16;
            _imageInfo.Heads           = (_thisFooter.DiskGeometry & 0xFF00)     >> 8;
            _imageInfo.SectorsPerTrack = _thisFooter.DiskGeometry & 0xFF;

            if(_thisFooter.DiskType == TYPE_DYNAMIC ||
               _thisFooter.DiskType == TYPE_DIFFERENCING)
            {
                imageStream.Seek((long)_thisFooter.Offset, SeekOrigin.Begin);
                byte[] dynamicBytes = new byte[1024];
                imageStream.Read(dynamicBytes, 0, 1024);

                uint dynamicChecksum = BigEndianBitConverter.ToUInt32(dynamicBytes, 0x24);

                dynamicBytes[0x24] = 0;
                dynamicBytes[0x25] = 0;
                dynamicBytes[0x26] = 0;
                dynamicBytes[0x27] = 0;

                uint dynamicChecksumCalculated = VhdChecksum(dynamicBytes);

                AaruConsole.DebugWriteLine("VirtualPC plugin",
                                           "Dynamic header checksum = 0x{0:X8}, calculated = 0x{1:X8}", dynamicChecksum,
                                           dynamicChecksumCalculated);

                if(dynamicChecksum != dynamicChecksumCalculated)
                {
                    AaruConsole.
                        ErrorWriteLine("(VirtualPC plugin): Both header and footer are corrupt, image cannot be opened.");

                    return ErrorNumber.InvalidArgument;
                }

                _thisDynamic = new DynamicDiskHeader
                {
                    LocatorEntries = new ParentLocatorEntry[8],
                    Reserved2      = new byte[256]
                };

                for(int i = 0; i < 8; i++)
                    _thisDynamic.LocatorEntries[i] = new ParentLocatorEntry();

                _thisDynamic.Cookie          = BigEndianBitConverter.ToUInt64(dynamicBytes, 0x00);
                _thisDynamic.DataOffset      = BigEndianBitConverter.ToUInt64(dynamicBytes, 0x08);
                _thisDynamic.TableOffset     = BigEndianBitConverter.ToUInt64(dynamicBytes, 0x10);
                _thisDynamic.HeaderVersion   = BigEndianBitConverter.ToUInt32(dynamicBytes, 0x18);
                _thisDynamic.MaxTableEntries = BigEndianBitConverter.ToUInt32(dynamicBytes, 0x1C);
                _thisDynamic.BlockSize       = BigEndianBitConverter.ToUInt32(dynamicBytes, 0x20);
                _thisDynamic.Checksum        = dynamicChecksum;
                _thisDynamic.ParentId        = BigEndianBitConverter.ToGuid(dynamicBytes, 0x28);
                _thisDynamic.ParentTimestamp = BigEndianBitConverter.ToUInt32(dynamicBytes, 0x38);
                _thisDynamic.Reserved        = BigEndianBitConverter.ToUInt32(dynamicBytes, 0x3C);
                _thisDynamic.ParentName      = Encoding.BigEndianUnicode.GetString(dynamicBytes, 0x40, 512);

                for(int i = 0; i < 8; i++)
                {
                    _thisDynamic.LocatorEntries[i].PlatformCode =
                        BigEndianBitConverter.ToUInt32(dynamicBytes, 0x240 + 0x00 + (24 * i));

                    _thisDynamic.LocatorEntries[i].PlatformDataSpace =
                        BigEndianBitConverter.ToUInt32(dynamicBytes, 0x240 + 0x04 + (24 * i));

                    _thisDynamic.LocatorEntries[i].PlatformDataLength =
                        BigEndianBitConverter.ToUInt32(dynamicBytes, 0x240 + 0x08 + (24 * i));

                    _thisDynamic.LocatorEntries[i].Reserved =
                        BigEndianBitConverter.ToUInt32(dynamicBytes, 0x240 + 0x0C + (24 * i));

                    _thisDynamic.LocatorEntries[i].PlatformDataOffset =
                        BigEndianBitConverter.ToUInt64(dynamicBytes, 0x240 + 0x10 + (24 * i));
                }

                Array.Copy(dynamicBytes, 0x300, _thisDynamic.Reserved2, 0, 256);

                _parentDateTime = new DateTime(2000, 1, 1, 0, 0, 0, DateTimeKind.Utc);
                _parentDateTime = _parentDateTime.AddSeconds(_thisDynamic.ParentTimestamp);

                sha1Ctx = new Sha1Context();
                sha1Ctx.Update(_thisDynamic.Reserved2);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.cookie = 0x{0:X8}", _thisDynamic.Cookie);
                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.dataOffset = {0}", _thisDynamic.DataOffset);
                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.tableOffset = {0}", _thisDynamic.TableOffset);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.headerVersion = 0x{0:X8}",
                                           _thisDynamic.HeaderVersion);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.maxTableEntries = {0}",
                                           _thisDynamic.MaxTableEntries);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.blockSize = {0}", _thisDynamic.BlockSize);
                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.checksum = 0x{0:X8}", _thisDynamic.Checksum);
                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.parentID = {0}", _thisDynamic.ParentId);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.parentTimestamp = 0x{0:X8} ({1})",
                                           _thisDynamic.ParentTimestamp, _parentDateTime);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.reserved = 0x{0:X8}", _thisDynamic.Reserved);

                for(int i = 0; i < 8; i++)
                {
                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                               "dynamic.locatorEntries[{0}].platformCode = 0x{1:X8} (\"{2}\")", i,
                                               _thisDynamic.LocatorEntries[i].PlatformCode,
                                               Encoding.ASCII.GetString(BigEndianBitConverter.GetBytes(_thisDynamic.
                                                                            LocatorEntries[i].PlatformCode)));

                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                               "dynamic.locatorEntries[{0}].platformDataSpace = {1}", i,
                                               _thisDynamic.LocatorEntries[i].PlatformDataSpace);

                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                               "dynamic.locatorEntries[{0}].platformDataLength = {1}", i,
                                               _thisDynamic.LocatorEntries[i].PlatformDataLength);

                    AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.locatorEntries[{0}].reserved = 0x{1:X8}", i,
                                               _thisDynamic.LocatorEntries[i].Reserved);

                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                               "dynamic.locatorEntries[{0}].platformDataOffset = {1}", i,
                                               _thisDynamic.LocatorEntries[i].PlatformDataOffset);
                }

                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.parentName = \"{0}\"", _thisDynamic.ParentName);
                AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.reserved2's SHA1 = 0x{0}", sha1Ctx.End());

                if(_thisDynamic.HeaderVersion != VERSION1)
                {
                    AaruConsole.
                        ErrorWriteLine($"(VirtualPC plugin): Unknown image type {_thisFooter.DiskType} found. Please submit a bug with an example image.");

                    return ErrorNumber.InvalidArgument;
                }

                DateTime startTime = DateTime.UtcNow;

                _blockAllocationTable = new uint[_thisDynamic.MaxTableEntries];

                byte[] bat = new byte[_thisDynamic.MaxTableEntries * 4];
                imageStream.Seek((long)_thisDynamic.TableOffset, SeekOrigin.Begin);
                imageStream.Read(bat, 0, bat.Length);

                ReadOnlySpan<byte> span = bat;

                _blockAllocationTable = MemoryMarshal.Cast<byte, uint>(span).
                                                      Slice(0, (int)_thisDynamic.MaxTableEntries).ToArray();

                for(int i = 0; i < _blockAllocationTable.Length; i++)
                    _blockAllocationTable[i] = Swapping.Swap(_blockAllocationTable[i]);

                DateTime endTime = DateTime.UtcNow;

                AaruConsole.DebugWriteLine("VirtualPC plugin", "Filling the BAT took {0} seconds",
                                           (endTime - startTime).TotalSeconds);

                _bitmapSize = (uint)Math.Ceiling((double)_thisDynamic.BlockSize / 512

                                                 // 1 bit per sector on the bitmap
                                               / 8

                                                 // and aligned to 512 byte boundary
                                               / 512);

                AaruConsole.DebugWriteLine("VirtualPC plugin", "Bitmap is {0} sectors", _bitmapSize);
            }

            _imageInfo.XmlMediaType = XmlMediaType.BlockMedia;

            switch(_thisFooter.DiskType)
            {
                case TYPE_FIXED:
                case TYPE_DYNAMIC:
                {
                    // Nothing to do here, really.
                    return ErrorNumber.NoError;
                }

                case TYPE_DIFFERENCING:
                {
                    _locatorEntriesData = new byte[8][];

                    for(int i = 0; i < 8; i++)
                        if(_thisDynamic.LocatorEntries[i].PlatformCode != 0x00000000)
                        {
                            _locatorEntriesData[i] = new byte[_thisDynamic.LocatorEntries[i].PlatformDataLength];
                            imageStream.Seek((long)_thisDynamic.LocatorEntries[i].PlatformDataOffset, SeekOrigin.Begin);

                            imageStream.Read(_locatorEntriesData[i], 0,
                                             (int)_thisDynamic.LocatorEntries[i].PlatformDataLength);

                            switch(_thisDynamic.LocatorEntries[i].PlatformCode)
                            {
                                case PLATFORM_CODE_WINDOWS_ABSOLUTE:
                                case PLATFORM_CODE_WINDOWS_RELATIVE:
                                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                                               "dynamic.locatorEntries[{0}] = \"{1}\"", i,
                                                               Encoding.ASCII.GetString(_locatorEntriesData[i]));

                                    break;
                                case PLATFORM_CODE_WINDOWS_ABSOLUTE_U:
                                case PLATFORM_CODE_WINDOWS_RELATIVE_U:
                                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                                               "dynamic.locatorEntries[{0}] = \"{1}\"", i,
                                                               Encoding.BigEndianUnicode.
                                                                        GetString(_locatorEntriesData[i]));

                                    break;
                                case PLATFORM_CODE_MACINTOSH_URI:
                                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                                               "dynamic.locatorEntries[{0}] = \"{1}\"", i,
                                                               Encoding.UTF8.GetString(_locatorEntriesData[i]));

                                    break;
                                default:
                                    AaruConsole.DebugWriteLine("VirtualPC plugin", "dynamic.locatorEntries[{0}] =", i);
                                    PrintHex.PrintHexArray(_locatorEntriesData[i], 64);

                                    break;
                            }
                        }

                    int    currentLocator = 0;
                    bool   locatorFound   = false;
                    string parentPath     = null;

                    while(!locatorFound &&
                          currentLocator < 8)
                    {
                        switch(_thisDynamic.LocatorEntries[currentLocator].PlatformCode)
                        {
                            case PLATFORM_CODE_WINDOWS_ABSOLUTE:
                            case PLATFORM_CODE_WINDOWS_RELATIVE:
                                parentPath = Encoding.ASCII.GetString(_locatorEntriesData[currentLocator]);

                                break;
                            case PLATFORM_CODE_WINDOWS_ABSOLUTE_U:
                            case PLATFORM_CODE_WINDOWS_RELATIVE_U:
                                parentPath = Encoding.BigEndianUnicode.GetString(_locatorEntriesData[currentLocator]);

                                break;
                            case PLATFORM_CODE_MACINTOSH_URI:
                                parentPath =
                                    Uri.UnescapeDataString(Encoding.UTF8.
                                                                    GetString(_locatorEntriesData[currentLocator]));

                                if(parentPath.StartsWith("file://localhost", StringComparison.InvariantCulture))
                                    parentPath = parentPath.Remove(0, 16);
                                else
                                {
                                    AaruConsole.DebugWriteLine("VirtualPC plugin",
                                                               "Unsupported protocol classified found in URI parent path: \"{0}\"",
                                                               parentPath);

                                    parentPath = null;
                                }

                                break;
                        }

                        if(parentPath != null)
                        {
                            AaruConsole.DebugWriteLine("VirtualPC plugin", "Possible parent path: \"{0}\"", parentPath);

                            IFilter parentFilter =
                                new FiltersList().GetFilter(Path.Combine(imageFilter.ParentFolder, parentPath));

                            if(parentFilter != null)
                                locatorFound = true;

                            if(!locatorFound)
                                parentPath = null;
                        }

                        currentLocator++;
                    }

                    if(!locatorFound)
                    {
                        AaruConsole.
                            ErrorWriteLine("(VirtualPC plugin): Cannot find parent file for differencing disk image");

                        return ErrorNumber.NoSuchFile;
                    }

                    {
                        _parentImage = new Vhd();

                        IFilter parentFilter =
                            new FiltersList().GetFilter(Path.Combine(imageFilter.ParentFolder, parentPath));

                        if(parentFilter == null)
                        {
                            AaruConsole.ErrorWriteLine("(VirtualPC plugin): Cannot find parent image filter");

                            return ErrorNumber.NoSuchFile;
                        }
                        /*                            PluginBase plugins = new PluginBase();
                                                    plugins.RegisterAllPlugins();
                                                    if (!plugins.ImagePluginsList.TryGetValue(Name.ToLower(), out parentImage))
                                                    {
                                                        AaruConsole.ErrorWriteLine("(VirtualPC plugin): Unable to open myself");
                                                        return ErrorNumber.InvalidArgument;
                                                    }*/

                        if(!_parentImage.Identify(parentFilter))
                        {
                            AaruConsole.
                                ErrorWriteLine("(VirtualPC plugin): Parent image is not a Virtual PC disk image");

                            return ErrorNumber.InvalidArgument;
                        }

                        ErrorNumber parentError = _parentImage.Open(parentFilter);

                        if(parentError != ErrorNumber.NoError)
                        {
                            AaruConsole.
                                ErrorWriteLine($"(VirtualPC plugin): Error {parentError} opening parent disk image");

                            return parentError;
                        }

                        // While specification says that parent and child disk images should contain UUID relationship
                        // in reality it seems that old differencing disk images stored a parent UUID that, nonetheless
                        // the parent never stored itself. So the only real way to know that images are related is
                        // because the parent IS found and SAME SIZE. Ugly...
                        // More funny even, tested parent images show an empty host OS, and child images a correct one.
                        if(_parentImage.Info.Sectors == _imageInfo.Sectors)
                            return ErrorNumber.NoError;

                        AaruConsole.ErrorWriteLine("(VirtualPC plugin): Parent image is of different size");

                        return ErrorNumber.InvalidArgument;
                    }

                    return ErrorNumber.NoError;
                }

                case TYPE_DEPRECATED1:
                case TYPE_DEPRECATED2:
                case TYPE_DEPRECATED3:
                    AaruConsole.
                        ErrorWriteLine("(VirtualPC plugin): Deprecated image type found. Please submit a bug with an example image.");

                    return ErrorNumber.NotImplemented;

                default:
                    AaruConsole.
                        ErrorWriteLine($"(VirtualPC plugin): Unknown image type {_thisFooter.DiskType} found. Please submit a bug with an example image.");

                    return ErrorNumber.InvalidArgument;
            }
        }

        /// <inheritdoc />
        public ErrorNumber ReadSector(ulong sectorAddress, out byte[] buffer)
        {
            switch(_thisFooter.DiskType)
            {
                case TYPE_DIFFERENCING:
                {
                    // Block number for BAT searching
                    uint blockNumber = (uint)Math.Floor(sectorAddress / (_thisDynamic.BlockSize / 512.0));

                    // Sector number inside of block
                    uint sectorInBlock = (uint)(sectorAddress % (_thisDynamic.BlockSize / 512));

                    if(_blockAllocationTable[blockNumber] == 0xFFFFFFFF)
                    {
                        buffer = new byte[512];

                        return ErrorNumber.NoError;
                    }

                    byte[] bitmap = new byte[_bitmapSize * 512];

                    // Offset of block in file
                    long blockOffset = _blockAllocationTable[blockNumber] * 512L;

                    int bitmapByte = (int)Math.Floor((double)sectorInBlock / 8);
                    int bitmapBit  = (int)(sectorInBlock % 8);

                    Stream thisStream = _thisFilter.GetDataForkStream();

                    thisStream.Seek(blockOffset, SeekOrigin.Begin);
                    thisStream.Read(bitmap, 0, (int)_bitmapSize * 512);

                    byte mask  = (byte)(1 << (7 - bitmapBit));
                    bool dirty = (bitmap[bitmapByte] & mask) == mask;

                    /*
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "bitmapSize = {0}", bitmapSize);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "blockNumber = {0}", blockNumber);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "sectorInBlock = {0}", sectorInBlock);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "blockOffset = {0}", blockOffset);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "bitmapByte = {0}", bitmapByte);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "bitmapBit = {0}", bitmapBit);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "mask = 0x{0:X2}", mask);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "dirty = 0x{0}", dirty);
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "bitmap = ");
                    PrintHex.PrintHexArray(bitmap, 64);
                    */

                    // Sector has been written, read from child image
                    if(!dirty)
                        return _parentImage.ReadSector(sectorAddress, out buffer);
                    /* Too noisy
                        AaruConsole.DebugWriteLine("VirtualPC plugin", "Sector {0} is dirty", sectorAddress);
                        */

                    buffer = new byte[512];
                    uint sectorOffset = _blockAllocationTable[blockNumber] + _bitmapSize + sectorInBlock;
                    thisStream = _thisFilter.GetDataForkStream();

                    thisStream.Seek(sectorOffset * 512, SeekOrigin.Begin);
                    thisStream.Read(buffer, 0, 512);

                    return ErrorNumber.NoError;

                    /* Too noisy
                    AaruConsole.DebugWriteLine("VirtualPC plugin", "Sector {0} is clean", sectorAddress);
                    */

                    // Read sector from parent image
                }

                default: return ReadSectors(sectorAddress, 1, out buffer);
            }
        }

        /// <inheritdoc />
        public ErrorNumber ReadSectors(ulong sectorAddress, uint length, out byte[] buffer)
        {
            buffer = null;

            switch(_thisFooter.DiskType)
            {
                case TYPE_FIXED:
                {
                    buffer = new byte[512 * length];
                    Stream thisStream = _thisFilter.GetDataForkStream();

                    thisStream.Seek((long)(sectorAddress * 512), SeekOrigin.Begin);
                    thisStream.Read(buffer, 0, (int)(512 * length));

                    return ErrorNumber.NoError;
                }

                // Contrary to Microsoft's specifications that tell us to check the bitmap
                // and in case of unused sector just return zeros, as blocks are allocated
                // as a whole, this would waste time and miss cache, so we read any sector
                // as long as it is in the block.
                case TYPE_DYNAMIC:
                {
                    // Block number for BAT searching
                    uint blockNumber = (uint)Math.Floor(sectorAddress / (_thisDynamic.BlockSize / 512.0));

                    // Sector number inside of block
                    uint sectorInBlock = (uint)(sectorAddress % (_thisDynamic.BlockSize / 512));

                    // How many sectors before reaching end of block
                    uint remainingInBlock = (_thisDynamic.BlockSize / 512) - sectorInBlock;

                    // Data that needs to be read from another block
                    byte[] suffix = null;

                    // How many sectors to read from this block
                    uint sectorsToReadHere;

                    // Asked to read more sectors than are remaining in block
                    if(length > remainingInBlock)
                    {
                        ErrorNumber errno = ReadSectors(sectorAddress + remainingInBlock, length - remainingInBlock,
                                                        out suffix);

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

                        sectorsToReadHere = remainingInBlock;
                    }
                    else
                        sectorsToReadHere = length;

                    // Offset of sector in file
                    uint sectorOffset = _blockAllocationTable[blockNumber] + _bitmapSize + sectorInBlock;

                    // Data that can be read in this block
                    byte[] prefix = new byte[sectorsToReadHere * 512];

                    // 0xFFFFFFFF means unallocated
                    if(_blockAllocationTable[blockNumber] != 0xFFFFFFFF)
                    {
                        Stream thisStream = _thisFilter.GetDataForkStream();
                        thisStream.Seek(sectorOffset * 512, SeekOrigin.Begin);
                        thisStream.Read(prefix, 0, (int)(512 * sectorsToReadHere));
                    }

                    // If it is unallocated, just fill with zeroes
                    else
                        Array.Clear(prefix, 0, prefix.Length);

                    // If we needed to read from another block, join all the data
                    if(suffix == null)
                    {
                        buffer = prefix;

                        return ErrorNumber.NoError;
                    }

                    buffer = new byte[512 * length];
                    Array.Copy(prefix, 0, buffer, 0, prefix.Length);
                    Array.Copy(suffix, 0, buffer, prefix.Length, suffix.Length);

                    return ErrorNumber.NoError;
                }

                case TYPE_DIFFERENCING:
                {
                    // As on differencing images, each independent sector can be read from child or parent
                    // image, we must read sector one by one
                    buffer = new byte[512 * length];

                    for(ulong i = 0; i < length; i++)
                    {
                        ErrorNumber errno = ReadSector(sectorAddress + i, out byte[] oneSector);

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

                        Array.Copy(oneSector, 0, buffer, (int)(i * 512), 512);
                    }

                    return ErrorNumber.NoError;
                }

                case TYPE_DEPRECATED1:
                case TYPE_DEPRECATED2:
                case TYPE_DEPRECATED3:
                    AaruConsole.
                        ErrorWriteLine("(VirtualPC plugin): Deprecated image type found. Please submit a bug with an example image.");

                    return ErrorNumber.NotImplemented;

                default:
                    AaruConsole.
                        ErrorWriteLine($"(VirtualPC plugin): Unknown image type {_thisFooter.DiskType} found. Please submit a bug with an example image.");

                    return ErrorNumber.InvalidArgument;
            }
        }
    }
}