Aaru/DiscImageChef.DiscImages/VHD/Read.cs

// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// 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 © 2011-2019 Natalia Portillo
// ****************************************************************************/

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using DiscImageChef.Checksums;
using DiscImageChef.CommonTypes;
using DiscImageChef.CommonTypes.Enums;
using DiscImageChef.CommonTypes.Exceptions;
using DiscImageChef.CommonTypes.Interfaces;
using DiscImageChef.Console;

namespace DiscImageChef.DiscImages
{
    public partial class Vhd
    {
        public bool 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);
            }

            BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;

            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);

            DicConsole.DebugWriteLine("VirtualPC plugin", "Header checksum = 0x{0:X8}, calculated = 0x{1:X8}",
                                      headerChecksum, headerCalculatedChecksum);
            DicConsole.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
                throw new
                    ImageNotSupportedException("(VirtualPC plugin): Both header and footer are corrupt, image cannot be opened.");

            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);

            Sha1Context sha1Ctx = new Sha1Context();
            sha1Ctx.Update(thisFooter.Reserved);

            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.cookie = 0x{0:X8}",   thisFooter.Cookie);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.features = 0x{0:X8}", thisFooter.Features);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.version = 0x{0:X8}",  thisFooter.Version);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.offset = {0}",        thisFooter.Offset);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.timestamp = 0x{0:X8} ({1})", thisFooter.Timestamp,
                                      thisDateTime);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.creatorApplication = 0x{0:X8} (\"{1}\")",
                                      thisFooter.CreatorApplication,
                                      Encoding.ASCII.GetString(BigEndianBitConverter.GetBytes(thisFooter
                                                                                                 .CreatorApplication)));
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.creatorVersion = 0x{0:X8}",
                                      thisFooter.CreatorVersion);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.creatorHostOS = 0x{0:X8} (\"{1}\")",
                                      thisFooter.CreatorHostOs,
                                      Encoding.ASCII.GetString(BigEndianBitConverter
                                                                  .GetBytes(thisFooter.CreatorHostOs)));
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.originalSize = {0}", thisFooter.OriginalSize);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.currentSize = {0}",  thisFooter.CurrentSize);
            DicConsole.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);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.diskType = 0x{0:X8}",     thisFooter.DiskType);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.checksum = 0x{0:X8}",     thisFooter.Checksum);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.uniqueId = {0}",          thisFooter.UniqueId);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.savedState = 0x{0:X2}",   thisFooter.SavedState);
            DicConsole.DebugWriteLine("VirtualPC plugin", "footer.reserved's SHA1 = 0x{0}", sha1Ctx.End());

            if(thisFooter.Version == VERSION1) imageInfo.Version = "1.0";
            else
                throw new
                    ImageNotSupportedException($"(VirtualPC plugin): Unknown image type {thisFooter.DiskType} found. Please submit a bug with an example image.");

            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;
                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.GetCreationTime();
            imageInfo.LastModificationTime = thisDateTime;
            imageInfo.MediaTitle           = Path.GetFileNameWithoutExtension(imageFilter.GetFilename());

            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);

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

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

                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);

                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.cookie = 0x{0:X8}", thisDynamic.Cookie);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.dataOffset = {0}",  thisDynamic.DataOffset);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.tableOffset = {0}", thisDynamic.TableOffset);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.headerVersion = 0x{0:X8}",
                                          thisDynamic.HeaderVersion);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.maxTableEntries = {0}",
                                          thisDynamic.MaxTableEntries);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.blockSize = {0}",     thisDynamic.BlockSize);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.checksum = 0x{0:X8}", thisDynamic.Checksum);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.parentID = {0}",      thisDynamic.ParentId);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.parentTimestamp = 0x{0:X8} ({1})",
                                          thisDynamic.ParentTimestamp, parentDateTime);
                DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.reserved = 0x{0:X8}", thisDynamic.Reserved);
                for(int i = 0; i < 8; i++)
                {
                    DicConsole.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)));
                    DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.locatorEntries[{0}].platformDataSpace = {1}",
                                              i, thisDynamic.LocatorEntries[i].PlatformDataSpace);
                    DicConsole.DebugWriteLine("VirtualPC plugin",
                                              "dynamic.locatorEntries[{0}].platformDataLength = {1}", i,
                                              thisDynamic.LocatorEntries[i].PlatformDataLength);
                    DicConsole.DebugWriteLine("VirtualPC plugin", "dynamic.locatorEntries[{0}].reserved = 0x{1:X8}", i,
                                              thisDynamic.LocatorEntries[i].Reserved);
                    DicConsole.DebugWriteLine("VirtualPC plugin",
                                              "dynamic.locatorEntries[{0}].platformDataOffset = {1}", i,
                                              thisDynamic.LocatorEntries[i].PlatformDataOffset);
                }

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

                if(thisDynamic.HeaderVersion != VERSION1)
                    throw new
                        ImageNotSupportedException($"(VirtualPC plugin): Unknown image type {thisFooter.DiskType} found. Please submit a bug with an example image.");

                DateTime startTime = DateTime.UtcNow;

                blockAllocationTable = new uint[thisDynamic.MaxTableEntries];

                // Safe and slow code. It takes 76,572 ms to fill a 30720 entries BAT
                /*
                byte[] bat = new byte[thisDynamic.maxTableEntries * 4];
                imageStream.Seek((long)thisDynamic.tableOffset, SeekOrigin.Begin);
                imageStream.Read(bat, 0, (int)(thisDynamic.maxTableEntries * 4));
                for (int i = 0; i < thisDynamic.maxTableEntries; i++)
                    blockAllocationTable[i] = BigEndianBitConverter.ToUInt32(bat, 4 * i);

                DateTime endTime = DateTime.UtcNow;
                DicConsole.DebugWriteLine("VirtualPC plugin", "Filling the BAT took {0} seconds", (endTime-startTime).TotalSeconds);
                */

                // How many sectors uses the BAT
                uint batSectorCount = (uint)Math.Ceiling((double)thisDynamic.MaxTableEntries * 4 / 512);

                byte[] batSectorBytes = new byte[512];

                // Unsafe and fast code. It takes 4 ms to fill a 30720 entries BAT
                for(int i = 0; i < batSectorCount; i++)
                {
                    imageStream.Seek((long)thisDynamic.TableOffset + i * 512, SeekOrigin.Begin);
                    imageStream.Read(batSectorBytes, 0, 512);
                    // This does the big-endian trick but reverses the order of elements also
                    Array.Reverse(batSectorBytes);
                    GCHandle handle = GCHandle.Alloc(batSectorBytes, GCHandleType.Pinned);
                    BatSector batSector =
                        (BatSector)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(BatSector));
                    handle.Free();
                    // This restores the order of elements
                    Array.Reverse(batSector.blockPointer);
                    if(blockAllocationTable.Length >= i * 512 / 4 + 512 / 4)
                        Array.Copy(batSector.blockPointer, 0, blockAllocationTable, i * 512 / 4, 512 / 4);
                    else
                        Array.Copy(batSector.blockPointer, 0, blockAllocationTable, i * 512 / 4,
                                   blockAllocationTable.Length - i * 512              / 4);
                }

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

                // Too noisy
                /*
                    for (int i = 0; i < thisDynamic.maxTableEntries; i++)
                        DicConsole.DebugWriteLine("VirtualPC plugin", "blockAllocationTable[{0}] = {1}", i, blockAllocationTable[i]);
                */

                // Get the roundest number of sectors needed to store the block bitmap
                bitmapSize = (uint)Math.Ceiling((double)thisDynamic.BlockSize / 512
                                                                                // 1 bit per sector on the bitmap
                                                                              / 8
                                                                                // and aligned to 512 byte boundary
                                                                              / 512);
                DicConsole.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 true;
                }
                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:
                                    DicConsole.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:
                                    DicConsole.DebugWriteLine("VirtualPC plugin",
                                                              "dynamic.locatorEntries[{0}] = \"{1}\"", i,
                                                              Encoding.BigEndianUnicode
                                                                      .GetString(locatorEntriesData[i]));
                                    break;
                                case PLATFORM_CODE_MACINTOSH_URI:
                                    DicConsole.DebugWriteLine("VirtualPC plugin",
                                                              "dynamic.locatorEntries[{0}] = \"{1}\"", i,
                                                              Encoding.UTF8.GetString(locatorEntriesData[i]));
                                    break;
                                default:
                                    DicConsole.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
                                {
                                    DicConsole.DebugWriteLine("VirtualPC plugin",
                                                              "Unsupported protocol classified found in URI parent path: \"{0}\"",
                                                              parentPath);
                                    parentPath = null;
                                }

                                break;
                        }

                        if(parentPath != null)
                        {
                            DicConsole.DebugWriteLine("VirtualPC plugin", "Possible parent path: \"{0}\"", parentPath);
                            IFilter parentFilter =
                                new FiltersList().GetFilter(Path.Combine(imageFilter.GetParentFolder(), parentPath));

                            if(parentFilter != null) locatorFound = true;

                            if(!locatorFound) parentPath = null;
                        }

                        currentLocator++;
                    }

                    if(!locatorFound)
                        throw new
                            FileNotFoundException("(VirtualPC plugin): Cannot find parent file for differencing disk image");

                    {
                        parentImage = new Vhd();
                        IFilter parentFilter =
                            new FiltersList().GetFilter(Path.Combine(imageFilter.GetParentFolder(), parentPath));

                        if(parentFilter == null)
                            throw new ImageNotSupportedException("(VirtualPC plugin): Cannot find parent image filter");
                        /*                            PluginBase plugins = new PluginBase();
                                                    plugins.RegisterAllPlugins();
                                                    if (!plugins.ImagePluginsList.TryGetValue(Name.ToLower(), out parentImage))
                                                        throw new SystemException("(VirtualPC plugin): Unable to open myself");*/

                        if(!parentImage.Identify(parentFilter))
                            throw new
                                ImageNotSupportedException("(VirtualPC plugin): Parent image is not a Virtual PC disk image");

                        if(!parentImage.Open(parentFilter))
                            throw new ImageNotSupportedException("(VirtualPC plugin): Cannot open parent disk image");

                        // 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)
                            throw new
                                ImageNotSupportedException("(VirtualPC plugin): Parent image is of different size");
                    }

                    return true;
                }
                case TYPE_DEPRECATED1:
                case TYPE_DEPRECATED2:
                case TYPE_DEPRECATED3:
                {
                    throw new
                        ImageNotSupportedException("(VirtualPC plugin): Deprecated image type found. Please submit a bug with an example image.");
                }
                default:
                {
                    throw new
                        ImageNotSupportedException($"(VirtualPC plugin): Unknown image type {thisFooter.DiskType} found. Please submit a bug with an example image.");
                }
            }
        }

        public byte[] ReadSector(ulong sectorAddress)
        {
            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) return new byte[512];

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

                    // Offset of block in file
                    uint blockOffset = blockAllocationTable[blockNumber] * 512;

                    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;

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

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

                    byte[] data         = new byte[512];
                    uint   sectorOffset = blockAllocationTable[blockNumber] + bitmapSize + sectorInBlock;
                    thisStream = thisFilter.GetDataForkStream();

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

                    return data;

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

                    // Read sector from parent image
                }
                default: return ReadSectors(sectorAddress, 1);
            }
        }

        public byte[] ReadSectors(ulong sectorAddress, uint length)
        {
            switch(thisFooter.DiskType)
            {
                case TYPE_FIXED:
                {
                    byte[] data       = new byte[512 * length];
                    Stream thisStream = thisFilter.GetDataForkStream();

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

                    return data;
                }
                // 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)
                    {
                        suffix            = ReadSectors(sectorAddress + remainingInBlock, length - remainingInBlock);
                        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) return prefix;

                    byte[] data = new byte[512 * length];
                    Array.Copy(prefix, 0, data, 0,             prefix.Length);
                    Array.Copy(suffix, 0, data, prefix.Length, suffix.Length);
                    return data;
                }
                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
                    byte[] fullData = new byte[512 * length];
                    for(ulong i = 0; i < length; i++)
                    {
                        byte[] oneSector = ReadSector(sectorAddress + i);
                        Array.Copy(oneSector, 0, fullData, (int)(i * 512), 512);
                    }

                    return fullData;
                }
                case TYPE_DEPRECATED1:
                case TYPE_DEPRECATED2:
                case TYPE_DEPRECATED3:
                {
                    throw new
                        ImageNotSupportedException("(VirtualPC plugin): Deprecated image type found. Please submit a bug with an example image.");
                }
                default:
                {
                    throw new
                        ImageNotSupportedException($"(VirtualPC plugin): Unknown image type {thisFooter.DiskType} found. Please submit a bug with an example image.");
                }
            }
        }
    }
}