// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// Filename       : VHDX.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Disk image plugins.
//
// --[ Description ] ----------------------------------------------------------
//
//     Manages Microsoft Hyper-V 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 © 2011-2018 Natalia Portillo
// ****************************************************************************/

using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using DiscImageChef.CommonTypes;
using DiscImageChef.Console;
using DiscImageChef.Filters;

namespace DiscImageChef.DiscImages
{
    public class Vhdx : ImagePlugin
    {
        #region Internal Structures
        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxIdentifier
        {
            /// <summary>
            /// Signature, <see cref="Vhdx.VHDX_SIGNATURE"/> 
            /// </summary>
            public ulong signature;
            /// <summary>
            /// UTF-16 string containing creator
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 512)] public byte[] creator;
        }

        struct VhdxHeader
        {
            /// <summary>
            /// Signature, <see cref="Vhdx.VHDX_HEADER_SIG"/> 
            /// </summary>
            public uint Signature;
            /// <summary>
            /// CRC-32C of whole 4096 bytes header with this field set to 0
            /// </summary>
            public uint Checksum;
            /// <summary>
            /// Sequence number
            /// </summary>
            public ulong Sequence;
            /// <summary>
            /// Unique identifier for file contents, must be changed on first write to metadata
            /// </summary>
            public Guid FileWriteGuid;
            /// <summary>
            /// Unique identifier for disk contents, must be changed on first write to metadata or data
            /// </summary>
            public Guid DataWriteGuid;
            /// <summary>
            /// Unique identifier for log entries
            /// </summary>
            public Guid LogGuid;
            /// <summary>
            /// Version of log format
            /// </summary>
            public ushort LogVersion;
            /// <summary>
            /// Version of VHDX format
            /// </summary>
            public ushort Version;
            /// <summary>
            /// Length in bytes of the log
            /// </summary>
            public uint LogLength;
            /// <summary>
            /// Offset from image start to the log
            /// </summary>
            public ulong LogOffset;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4016)] public byte[] Reserved;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxRegionTableHeader
        {
            /// <summary>
            /// Signature, <see cref="Vhdx.VHDX_REGION_SIG"/> 
            /// </summary>
            public uint signature;
            /// <summary>
            /// CRC-32C of whole 64Kb table with this field set to 0
            /// </summary>
            public uint checksum;
            /// <summary>
            /// How many entries follow this table
            /// </summary>
            public uint entries;
            /// <summary>
            /// Reserved
            /// </summary>
            public uint reserved;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxRegionTableEntry
        {
            /// <summary>
            /// Object identifier
            /// </summary>
            public Guid guid;
            /// <summary>
            /// Offset in image of the object
            /// </summary>
            public ulong offset;
            /// <summary>
            /// Length in bytes of the object
            /// </summary>
            public uint length;
            /// <summary>
            /// Flags
            /// </summary>
            public uint flags;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxMetadataTableHeader
        {
            /// <summary>
            /// Signature
            /// </summary>
            public ulong signature;
            /// <summary>
            /// Reserved
            /// </summary>
            public ushort reserved;
            /// <summary>
            /// How many entries are in the table
            /// </summary>
            public ushort entries;
            /// <summary>
            /// Reserved
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] public uint[] reserved2;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxMetadataTableEntry
        {
            /// <summary>
            /// Metadata ID
            /// </summary>
            public Guid itemId;
            /// <summary>
            /// Offset relative to start of metadata region
            /// </summary>
            public uint offset;
            /// <summary>
            /// Length in bytes
            /// </summary>
            public uint length;
            /// <summary>
            /// Flags
            /// </summary>
            public uint flags;
            /// <summary>
            /// Reserved
            /// </summary>
            public uint reserved;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxFileParameters
        {
            /// <summary>
            /// Block size in bytes
            /// </summary>
            public uint blockSize;
            /// <summary>
            /// Flags
            /// </summary>
            public uint flags;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxParentLocatorHeader
        {
            /// <summary>
            /// Type of parent virtual disk
            /// </summary>
            public Guid locatorType;
            public ushort reserved;
            /// <summary>
            /// How many KVPs are in this parent locator
            /// </summary>
            public ushort keyValueCount;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct VhdxParentLocatorEntry
        {
            /// <summary>
            /// Offset from metadata to key
            /// </summary>
            public uint keyOffset;
            /// <summary>
            /// Offset from metadata to value
            /// </summary>
            public uint valueOffset;
            /// <summary>
            /// Size of key
            /// </summary>
            public ushort keyLength;
            /// <summary>
            /// Size of value
            /// </summary>
            public ushort valueLength;
        }
        #endregion

        #region Internal Constants
        const ulong VHDX_SIGNATURE = 0x656C696678646876;
        const uint VHDX_HEADER_SIG = 0x64616568;
        const uint VHDX_REGION_SIG = 0x69676572;
        const ulong VHDX_METADATA_SIG = 0x617461646174656D;
        readonly Guid batGuid = new Guid("2DC27766-F623-4200-9D64-115E9BFD4A08");
        readonly Guid metadataGuid = new Guid("8B7CA206-4790-4B9A-B8FE-575F050F886E");
        readonly Guid fileParametersGuid = new Guid("CAA16737-FA36-4D43-B3B6-33F0AA44E76B");
        readonly Guid virtualDiskSizeGuid = new Guid("2FA54224-CD1B-4876-B211-5DBED83BF4B8");
        readonly Guid page83DataGuid = new Guid("BECA12AB-B2E6-4523-93EF-C309E000C746");
        readonly Guid logicalSectorSizeGuid = new Guid("8141BF1D-A96F-4709-BA47-F233A8FAAB5F");
        readonly Guid physicalSectorSizeGuid = new Guid("CDA348C7-445D-4471-9CC9-E9885251C556");
        readonly Guid parentLocatorGuid = new Guid("A8D35F2D-B30B-454D-ABF7-D3D84834AB0C");
        readonly Guid parentTypeVhdxGuid = new Guid("B04AEFB7-D19E-4A81-B789-25B8E9445913");

        const string PARENT_LINKAGE_KEY = "parent_linkage";
        const string PARENT_LINKAGE2_KEY = "parent_linkage2";
        const string RELATIVE_PATH_KEY = "relative_path";
        const string VOLUME_PATH_KEY = "volume_path";
        const string ABSOLUTE_WIN32_PATH_KEY = "absolute_win32_path";

        const uint REGION_FLAGS_REQUIRED = 0x01;

        const uint METADATA_FLAGS_USER = 0x01;
        const uint METADATA_FLAGS_VIRTUAL = 0x02;
        const uint METADATA_FLAGS_REQUIRED = 0x04;

        const uint FILE_FLAGS_LEAVE_ALLOCATED = 0x01;
        const uint FILE_FLAGS_HAS_PARENT = 0x02;

        /// <summary>Block has never been stored on this image, check parent</summary>
        const ulong PAYLOAD_BLOCK_NOT_PRESENT = 0x00;
        /// <summary>Block was stored on this image and is removed, return whatever data you wish</summary>
        const ulong PAYLOAD_BLOCK_UNDEFINED = 0x01;
        /// <summary>Block is filled with zeroes</summary>
        const ulong PAYLOAD_BLOCK_ZERO = 0x02;
        /// <summary>All sectors in this block were UNMAPed/TRIMed, return zeroes</summary>
        const ulong PAYLOAD_BLOCK_UNMAPPER = 0x03;
        /// <summary>Block is present on this image</summary>
        const ulong PAYLOAD_BLOCK_FULLY_PRESENT = 0x06;
        /// <summary>Block is present on image but there may be sectors present on parent image</summary>
        const ulong PAYLOAD_BLOCK_PARTIALLY_PRESENT = 0x07;

        const ulong SECTOR_BITMAP_NOT_PRESENT = 0x00;
        const ulong SECTOR_BITMAP_PRESENT = 0x06;

        const ulong BAT_FILE_OFFSET_MASK = 0xFFFFFFFFFFFC0000;
        const ulong BAT_FLAGS_MASK = 0x7;
        const ulong BAT_RESERVED_MASK = 0x3FFF8;
        #endregion

        #region Internal variables
        ulong virtualDiskSize;
        Guid page83Data;
        uint logicalSectorSize;
        uint physicalSectorSize;

        VhdxIdentifier vhdxId;
        VhdxHeader vHdr;
        VhdxRegionTableHeader vRegHdr;
        VhdxRegionTableEntry[] vRegs;
        VhdxMetadataTableHeader vMetHdr;
        VhdxMetadataTableEntry[] vMets;
        VhdxFileParameters vFileParms;
        VhdxParentLocatorHeader vParHdr;
        VhdxParentLocatorEntry[] vPars;

        long batOffset;
        long metadataOffset;

        long chunkRatio;
        ulong dataBlocks;

        ulong[] blockAllocationTable;
        ulong[] sectorBitmapPointers;
        byte[] sectorBitmap;
        ImagePlugin parentImage;
        bool hasParent;
        Stream imageStream;

        const int MAX_CACHE_SIZE = 16777216;
        int maxBlockCache;
        int maxSectorCache;

        Dictionary<ulong, byte[]> sectorCache;
        Dictionary<ulong, byte[]> blockCache;
        #endregion

        public Vhdx()
        {
            Name = "Microsoft VHDX";
            PluginUuid = new Guid("536B141B-D09C-4799-AB70-34631286EB9D");
            ImageInfo = new ImageInfo();
            ImageInfo.ReadableSectorTags = new List<SectorTagType>();
            ImageInfo.ReadableMediaTags = new List<MediaTagType>();
            ImageInfo.ImageHasPartitions = false;
            ImageInfo.ImageHasSessions = false;
            ImageInfo.ImageVersion = null;
            ImageInfo.ImageApplication = null;
            ImageInfo.ImageApplicationVersion = null;
            ImageInfo.ImageCreator = null;
            ImageInfo.ImageComments = null;
            ImageInfo.MediaManufacturer = null;
            ImageInfo.MediaModel = null;
            ImageInfo.MediaSerialNumber = null;
            ImageInfo.MediaBarcode = null;
            ImageInfo.MediaPartNumber = null;
            ImageInfo.MediaSequence = 0;
            ImageInfo.LastMediaSequence = 0;
            ImageInfo.DriveManufacturer = null;
            ImageInfo.DriveModel = null;
            ImageInfo.DriveSerialNumber = null;
            ImageInfo.DriveFirmwareRevision = null;
        }

        #region public methods
        public override bool IdentifyImage(Filter imageFilter)
        {
            Stream stream = imageFilter.GetDataForkStream();
            stream.Seek(0, SeekOrigin.Begin);

            if(stream.Length < 512) return false;

            byte[] vhdxIdB = new byte[Marshal.SizeOf(vhdxId)];
            stream.Read(vhdxIdB, 0, Marshal.SizeOf(vhdxId));
            vhdxId = new VhdxIdentifier();
            IntPtr idPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vhdxId));
            Marshal.Copy(vhdxIdB, 0, idPtr, Marshal.SizeOf(vhdxId));
            vhdxId = (VhdxIdentifier)Marshal.PtrToStructure(idPtr, typeof(VhdxIdentifier));
            Marshal.FreeHGlobal(idPtr);

            return vhdxId.signature == VHDX_SIGNATURE;
        }

        public override bool OpenImage(Filter imageFilter)
        {
            Stream stream = imageFilter.GetDataForkStream();
            stream.Seek(0, SeekOrigin.Begin);

            if(stream.Length < 512) return false;

            byte[] vhdxIdB = new byte[Marshal.SizeOf(vhdxId)];
            stream.Read(vhdxIdB, 0, Marshal.SizeOf(vhdxId));
            vhdxId = new VhdxIdentifier();
            IntPtr idPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vhdxId));
            Marshal.Copy(vhdxIdB, 0, idPtr, Marshal.SizeOf(vhdxId));
            vhdxId = (VhdxIdentifier)Marshal.PtrToStructure(idPtr, typeof(VhdxIdentifier));
            Marshal.FreeHGlobal(idPtr);

            if(vhdxId.signature != VHDX_SIGNATURE) return false;

            ImageInfo.ImageApplication = Encoding.Unicode.GetString(vhdxId.creator);

            stream.Seek(64 * 1024, SeekOrigin.Begin);
            byte[] vHdrB = new byte[Marshal.SizeOf(vHdr)];
            stream.Read(vHdrB, 0, Marshal.SizeOf(vHdr));
            vHdr = new VhdxHeader();
            IntPtr headerPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vHdr));
            Marshal.Copy(vHdrB, 0, headerPtr, Marshal.SizeOf(vHdr));
            vHdr = (VhdxHeader)Marshal.PtrToStructure(headerPtr, typeof(VhdxHeader));
            Marshal.FreeHGlobal(headerPtr);

            if(vHdr.Signature != VHDX_HEADER_SIG)
            {
                stream.Seek(128 * 1024, SeekOrigin.Begin);
                vHdrB = new byte[Marshal.SizeOf(vHdr)];
                stream.Read(vHdrB, 0, Marshal.SizeOf(vHdr));
                vHdr = new VhdxHeader();
                headerPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vHdr));
                Marshal.Copy(vHdrB, 0, headerPtr, Marshal.SizeOf(vHdr));
                vHdr = (VhdxHeader)Marshal.PtrToStructure(headerPtr, typeof(VhdxHeader));
                Marshal.FreeHGlobal(headerPtr);

                if(vHdr.Signature != VHDX_HEADER_SIG) throw new ImageNotSupportedException("VHDX header not found");
            }

            stream.Seek(192 * 1024, SeekOrigin.Begin);
            byte[] vRegTableB = new byte[Marshal.SizeOf(vRegHdr)];
            stream.Read(vRegTableB, 0, Marshal.SizeOf(vRegHdr));
            vRegHdr = new VhdxRegionTableHeader();
            IntPtr vRegTabPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vRegHdr));
            Marshal.Copy(vRegTableB, 0, vRegTabPtr, Marshal.SizeOf(vRegHdr));
            vRegHdr = (VhdxRegionTableHeader)Marshal.PtrToStructure(vRegTabPtr, typeof(VhdxRegionTableHeader));
            Marshal.FreeHGlobal(vRegTabPtr);

            if(vRegHdr.signature != VHDX_REGION_SIG)
            {
                stream.Seek(256 * 1024, SeekOrigin.Begin);
                vRegTableB = new byte[Marshal.SizeOf(vRegHdr)];
                stream.Read(vRegTableB, 0, Marshal.SizeOf(vRegHdr));
                vRegHdr = new VhdxRegionTableHeader();
                vRegTabPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vRegHdr));
                Marshal.Copy(vRegTableB, 0, vRegTabPtr, Marshal.SizeOf(vRegHdr));
                vRegHdr = (VhdxRegionTableHeader)Marshal.PtrToStructure(vRegTabPtr, typeof(VhdxRegionTableHeader));
                Marshal.FreeHGlobal(vRegTabPtr);

                if(vRegHdr.signature != VHDX_REGION_SIG)
                    throw new ImageNotSupportedException("VHDX region table not found");
            }

            vRegs = new VhdxRegionTableEntry[vRegHdr.entries];
            for(int i = 0; i < vRegs.Length; i++)
            {
                byte[] vRegB = new byte[Marshal.SizeOf(vRegs[i])];
                stream.Read(vRegB, 0, Marshal.SizeOf(vRegs[i]));
                vRegs[i] = new VhdxRegionTableEntry();
                IntPtr vRegPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vRegs[i]));
                Marshal.Copy(vRegB, 0, vRegPtr, Marshal.SizeOf(vRegs[i]));
                vRegs[i] = (VhdxRegionTableEntry)Marshal.PtrToStructure(vRegPtr, typeof(VhdxRegionTableEntry));
                Marshal.FreeHGlobal(vRegPtr);

                if(vRegs[i].guid == batGuid) batOffset = (long)vRegs[i].offset;
                else if(vRegs[i].guid == metadataGuid) metadataOffset = (long)vRegs[i].offset;
                else if((vRegs[i].flags & REGION_FLAGS_REQUIRED) == REGION_FLAGS_REQUIRED)
                    throw new
                        ImageNotSupportedException(string.Format("Found unsupported and required region Guid {0}, not proceeding with image.",
                                                                 vRegs[i].guid));
            }

            if(batOffset == 0) throw new Exception("BAT not found, cannot continue.");

            if(metadataOffset == 0) throw new Exception("Metadata not found, cannot continue.");

            uint fileParamsOff = 0, vdSizeOff = 0, p83Off = 0, logOff = 0, physOff = 0, parentOff = 0;

            stream.Seek(metadataOffset, SeekOrigin.Begin);
            byte[] metTableB = new byte[Marshal.SizeOf(vMetHdr)];
            stream.Read(metTableB, 0, Marshal.SizeOf(vMetHdr));
            vMetHdr = new VhdxMetadataTableHeader();
            IntPtr metTablePtr = Marshal.AllocHGlobal(Marshal.SizeOf(vMetHdr));
            Marshal.Copy(metTableB, 0, metTablePtr, Marshal.SizeOf(vMetHdr));
            vMetHdr = (VhdxMetadataTableHeader)Marshal.PtrToStructure(metTablePtr, typeof(VhdxMetadataTableHeader));
            Marshal.FreeHGlobal(metTablePtr);

            vMets = new VhdxMetadataTableEntry[vMetHdr.entries];
            for(int i = 0; i < vMets.Length; i++)
            {
                byte[] vMetB = new byte[Marshal.SizeOf(vMets[i])];
                stream.Read(vMetB, 0, Marshal.SizeOf(vMets[i]));
                vMets[i] = new VhdxMetadataTableEntry();
                IntPtr vMetPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vMets[i]));
                Marshal.Copy(vMetB, 0, vMetPtr, Marshal.SizeOf(vMets[i]));
                vMets[i] = (VhdxMetadataTableEntry)Marshal.PtrToStructure(vMetPtr, typeof(VhdxMetadataTableEntry));
                Marshal.FreeHGlobal(vMetPtr);

                if(vMets[i].itemId == fileParametersGuid) fileParamsOff = vMets[i].offset;
                else if(vMets[i].itemId == virtualDiskSizeGuid) vdSizeOff = vMets[i].offset;
                else if(vMets[i].itemId == page83DataGuid) p83Off = vMets[i].offset;
                else if(vMets[i].itemId == logicalSectorSizeGuid) logOff = vMets[i].offset;
                else if(vMets[i].itemId == physicalSectorSizeGuid) physOff = vMets[i].offset;
                else if(vMets[i].itemId == parentLocatorGuid) parentOff = vMets[i].offset;
                else if((vMets[i].flags & METADATA_FLAGS_REQUIRED) == METADATA_FLAGS_REQUIRED)
                    throw new
                        ImageNotSupportedException(string.Format("Found unsupported and required metadata Guid {0}, not proceeding with image.",
                                                                 vMets[i].itemId));
            }

            byte[] tmp;

            if(fileParamsOff != 0)
            {
                stream.Seek(fileParamsOff + metadataOffset, SeekOrigin.Begin);
                tmp = new byte[8];
                stream.Read(tmp, 0, 8);
                vFileParms = new VhdxFileParameters();
                vFileParms.blockSize = BitConverter.ToUInt32(tmp, 0);
                vFileParms.flags = BitConverter.ToUInt32(tmp, 4);
            }
            else throw new Exception("File parameters not found.");

            if(vdSizeOff != 0)
            {
                stream.Seek(vdSizeOff + metadataOffset, SeekOrigin.Begin);
                tmp = new byte[8];
                stream.Read(tmp, 0, 8);
                virtualDiskSize = BitConverter.ToUInt64(tmp, 0);
            }
            else throw new Exception("Virtual disk size not found.");

            if(p83Off != 0)
            {
                stream.Seek(p83Off + metadataOffset, SeekOrigin.Begin);
                tmp = new byte[16];
                stream.Read(tmp, 0, 16);
                page83Data = new Guid(tmp);
            }

            if(logOff != 0)
            {
                stream.Seek(logOff + metadataOffset, SeekOrigin.Begin);
                tmp = new byte[4];
                stream.Read(tmp, 0, 4);
                logicalSectorSize = BitConverter.ToUInt32(tmp, 0);
            }
            else throw new Exception("Logical sector size not found.");

            if(physOff != 0)
            {
                stream.Seek(physOff + metadataOffset, SeekOrigin.Begin);
                tmp = new byte[4];
                stream.Read(tmp, 0, 4);
                physicalSectorSize = BitConverter.ToUInt32(tmp, 0);
            }
            else throw new Exception("Physical sector size not found.");

            if(parentOff != 0 && (vFileParms.flags & FILE_FLAGS_HAS_PARENT) == FILE_FLAGS_HAS_PARENT)
            {
                stream.Seek(parentOff + metadataOffset, SeekOrigin.Begin);
                byte[] vParHdrB = new byte[Marshal.SizeOf(vMetHdr)];
                stream.Read(vParHdrB, 0, Marshal.SizeOf(vMetHdr));
                vParHdr = new VhdxParentLocatorHeader();
                IntPtr vParHdrPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vMetHdr));
                Marshal.Copy(vParHdrB, 0, vParHdrPtr, Marshal.SizeOf(vMetHdr));
                vParHdr = (VhdxParentLocatorHeader)Marshal.PtrToStructure(vParHdrPtr, typeof(VhdxParentLocatorHeader));
                Marshal.FreeHGlobal(vParHdrPtr);

                if(vParHdr.locatorType != parentTypeVhdxGuid)
                    throw new
                        ImageNotSupportedException(string.Format("Found unsupported and required parent locator type {0}, not proceeding with image.",
                                                                 vParHdr.locatorType));

                vPars = new VhdxParentLocatorEntry[vParHdr.keyValueCount];
                for(int i = 0; i < vPars.Length; i++)
                {
                    byte[] vParB = new byte[Marshal.SizeOf(vPars[i])];
                    stream.Read(vParB, 0, Marshal.SizeOf(vPars[i]));
                    vPars[i] = new VhdxParentLocatorEntry();
                    IntPtr vParPtr = Marshal.AllocHGlobal(Marshal.SizeOf(vPars[i]));
                    Marshal.Copy(vParB, 0, vParPtr, Marshal.SizeOf(vPars[i]));
                    vPars[i] = (VhdxParentLocatorEntry)Marshal.PtrToStructure(vParPtr, typeof(VhdxParentLocatorEntry));
                    Marshal.FreeHGlobal(vParPtr);
                }
            }
            else if((vFileParms.flags & FILE_FLAGS_HAS_PARENT) == FILE_FLAGS_HAS_PARENT)
                throw new Exception("Parent locator not found.");

            if((vFileParms.flags & FILE_FLAGS_HAS_PARENT) == FILE_FLAGS_HAS_PARENT &&
               vParHdr.locatorType == parentTypeVhdxGuid)
            {
                parentImage = new Vhdx();
                bool parentWorks = false;
                Filter parentFilter;

                foreach(VhdxParentLocatorEntry parentEntry in vPars)
                {
                    stream.Seek(parentEntry.keyOffset + metadataOffset, SeekOrigin.Begin);
                    byte[] tmpKey = new byte[parentEntry.keyLength];
                    stream.Read(tmpKey, 0, tmpKey.Length);
                    string entryType = Encoding.Unicode.GetString(tmpKey);

                    if(string.Compare(entryType, RELATIVE_PATH_KEY, StringComparison.OrdinalIgnoreCase) == 0)
                    {
                        stream.Seek(parentEntry.valueOffset + metadataOffset, SeekOrigin.Begin);
                        byte[] tmpVal = new byte[parentEntry.valueLength];
                        stream.Read(tmpVal, 0, tmpVal.Length);
                        string entryValue = Encoding.Unicode.GetString(tmpVal);

                        try
                        {
                            parentFilter =
                                new FiltersList().GetFilter(Path.Combine(imageFilter.GetParentFolder(), entryValue));
                            if(parentFilter != null && parentImage.OpenImage(parentFilter))
                            {
                                parentWorks = true;
                                break;
                            }
                        }
                        catch { parentWorks = false; }

                        string relEntry = Path.Combine(Path.GetDirectoryName(imageFilter.GetPath()), entryValue);

                        try
                        {
                            parentFilter =
                                new FiltersList().GetFilter(Path.Combine(imageFilter.GetParentFolder(), relEntry));
                            if(parentFilter != null && parentImage.OpenImage(parentFilter))
                            {
                                parentWorks = true;
                                break;
                            }
                        }
                        catch { continue; }
                    }
                    else if(string.Compare(entryType, VOLUME_PATH_KEY, StringComparison.OrdinalIgnoreCase) == 0 ||
                            string.Compare(entryType, ABSOLUTE_WIN32_PATH_KEY, StringComparison.OrdinalIgnoreCase) == 0)
                    {
                        stream.Seek(parentEntry.valueOffset + metadataOffset, SeekOrigin.Begin);
                        byte[] tmpVal = new byte[parentEntry.valueLength];
                        stream.Read(tmpVal, 0, tmpVal.Length);
                        string entryValue = Encoding.Unicode.GetString(tmpVal);

                        try
                        {
                            parentFilter =
                                new FiltersList().GetFilter(Path.Combine(imageFilter.GetParentFolder(), entryValue));
                            if(parentFilter != null && parentImage.OpenImage(parentFilter))
                            {
                                parentWorks = true;
                                break;
                            }
                        }
                        catch { continue; }
                    }
                }

                if(!parentWorks) throw new Exception("Image is differential but parent cannot be opened.");

                hasParent = true;
            }

            chunkRatio = (long)((Math.Pow(2, 23) * logicalSectorSize) / vFileParms.blockSize);
            dataBlocks = virtualDiskSize / vFileParms.blockSize;
            if((virtualDiskSize % vFileParms.blockSize) > 0) dataBlocks++;

            long batEntries;
            if(hasParent)
            {
                long sectorBitmapBlocks = (long)dataBlocks / chunkRatio;
                if((dataBlocks % (ulong)chunkRatio) > 0) sectorBitmapBlocks++;
                sectorBitmapPointers = new ulong[sectorBitmapBlocks];

                batEntries = sectorBitmapBlocks * (chunkRatio - 1);
            }
            else batEntries = (long)(dataBlocks + ((dataBlocks - 1) / (ulong)chunkRatio));

            DicConsole.DebugWriteLine("VHDX plugin", "Reading BAT");

            long readChunks = 0;
            blockAllocationTable = new ulong[dataBlocks];
            byte[] batB = new byte[batEntries * 8];
            stream.Seek(batOffset, SeekOrigin.Begin);
            stream.Read(batB, 0, batB.Length);

            ulong skipSize = 0;
            for(ulong i = 0; i < dataBlocks; i++)
            {
                if(readChunks == chunkRatio)
                {
                    if(hasParent)
                        sectorBitmapPointers[skipSize / 8] = BitConverter.ToUInt64(batB, (int)(i * 8 + skipSize));

                    readChunks = 0;
                    skipSize += 8;
                }
                else
                {
                    blockAllocationTable[i] = BitConverter.ToUInt64(batB, (int)(i * 8 + skipSize));
                    readChunks++;
                }
            }

            if(hasParent)
            {
                DicConsole.DebugWriteLine("VHDX plugin", "Reading Sector Bitmap");

                MemoryStream sectorBmpMs = new MemoryStream();
                foreach(ulong pt in sectorBitmapPointers)
                {
                    if((pt & BAT_FLAGS_MASK) == SECTOR_BITMAP_NOT_PRESENT)
                    {
                        sectorBmpMs.Write(new byte[1048576], 0, 1048576);
                    }
                    else if((pt & BAT_FLAGS_MASK) == SECTOR_BITMAP_PRESENT)
                    {
                        stream.Seek((long)((pt & BAT_FILE_OFFSET_MASK) * 1048576), SeekOrigin.Begin);
                        byte[] bmp = new byte[1048576];
                        stream.Read(bmp, 0, bmp.Length);
                        sectorBmpMs.Write(bmp, 0, bmp.Length);
                    }
                    else if((pt & BAT_FLAGS_MASK) != 0)
                        throw new
                            ImageNotSupportedException(string
                                                           .Format("Unsupported sector bitmap block flags (0x{0:X16}) found, not proceeding.",
                                                                   pt & BAT_FLAGS_MASK));
                }

                sectorBitmap = sectorBmpMs.ToArray();
                sectorBmpMs.Close();
            }

            maxBlockCache = (int)(MAX_CACHE_SIZE / vFileParms.blockSize);
            maxSectorCache = (int)(MAX_CACHE_SIZE / logicalSectorSize);

            imageStream = stream;

            sectorCache = new Dictionary<ulong, byte[]>();
            blockCache = new Dictionary<ulong, byte[]>();

            ImageInfo.ImageCreationTime = imageFilter.GetCreationTime();
            ImageInfo.ImageLastModificationTime = imageFilter.GetLastWriteTime();
            ImageInfo.ImageName = Path.GetFileNameWithoutExtension(imageFilter.GetFilename());
            ImageInfo.SectorSize = logicalSectorSize;
            ImageInfo.XmlMediaType = XmlMediaType.BlockMedia;
            ImageInfo.MediaType = MediaType.GENERIC_HDD;
            ImageInfo.ImageSize = virtualDiskSize;
            ImageInfo.Sectors = ImageInfo.ImageSize / ImageInfo.SectorSize;
            ImageInfo.DriveSerialNumber = page83Data.ToString();

            // TODO: Separate image application from version, need several samples.

            ImageInfo.Cylinders = (uint)((ImageInfo.Sectors / 16) / 63);
            ImageInfo.Heads = 16;
            ImageInfo.SectorsPerTrack = 63;

            return true;
        }

        bool CheckBitmap(ulong sectorAddress)
        {
            long index = (long)(sectorAddress / 8);
            int shift = (int)(sectorAddress % 8);
            byte val = (byte)(1 << shift);

            if(index > sectorBitmap.LongLength) return false;

            return ((sectorBitmap[index] & val) == val);
        }

        public override bool ImageHasPartitions()
        {
            return false;
        }

        public override ulong GetImageSize()
        {
            return ImageInfo.ImageSize;
        }

        public override ulong GetSectors()
        {
            return ImageInfo.Sectors;
        }

        public override uint GetSectorSize()
        {
            return ImageInfo.SectorSize;
        }

        public override string GetImageFormat()
        {
            return "VHDX";
        }

        public override string GetImageVersion()
        {
            return ImageInfo.ImageVersion;
        }

        public override string GetImageApplication()
        {
            return ImageInfo.ImageApplication;
        }

        public override string GetImageApplicationVersion()
        {
            return ImageInfo.ImageApplicationVersion;
        }

        public override string GetImageCreator()
        {
            return ImageInfo.ImageCreator;
        }

        public override DateTime GetImageCreationTime()
        {
            return ImageInfo.ImageCreationTime;
        }

        public override DateTime GetImageLastModificationTime()
        {
            return ImageInfo.ImageLastModificationTime;
        }

        public override string GetImageName()
        {
            return ImageInfo.ImageName;
        }

        public override MediaType GetMediaType()
        {
            return MediaType.GENERIC_HDD;
        }

        public override byte[] ReadSector(ulong sectorAddress)
        {
            if(sectorAddress > ImageInfo.Sectors - 1)
                throw new ArgumentOutOfRangeException(nameof(sectorAddress),
                                                      string.Format("Sector address {0} not found", sectorAddress));

            byte[] sector;

            if(sectorCache.TryGetValue(sectorAddress, out sector)) return sector;

            ulong index = (sectorAddress * logicalSectorSize) / vFileParms.blockSize;
            ulong secOff = (sectorAddress * logicalSectorSize) % vFileParms.blockSize;

            ulong blkPtr = blockAllocationTable[index];
            ulong blkFlags = blkPtr & BAT_FLAGS_MASK;

            if((blkPtr & BAT_RESERVED_MASK) != 0)
                throw new ImageNotSupportedException(string.Format("Unknown flags (0x{0:X16}) set in block pointer",
                                                                   blkPtr & BAT_RESERVED_MASK));

            if((blkFlags & BAT_FLAGS_MASK) == PAYLOAD_BLOCK_NOT_PRESENT)
                return hasParent ? parentImage.ReadSector(sectorAddress) : new byte[logicalSectorSize];

            if((blkFlags & BAT_FLAGS_MASK) == PAYLOAD_BLOCK_UNDEFINED || (blkFlags & BAT_FLAGS_MASK) == PAYLOAD_BLOCK_ZERO ||
               (blkFlags & BAT_FLAGS_MASK) == PAYLOAD_BLOCK_UNMAPPER) return new byte[logicalSectorSize];

            bool partialBlock;
            partialBlock = !((blkFlags & BAT_FLAGS_MASK) == PAYLOAD_BLOCK_FULLY_PRESENT);
            partialBlock = (blkFlags & BAT_FLAGS_MASK) == PAYLOAD_BLOCK_PARTIALLY_PRESENT;

            if(partialBlock && hasParent && !CheckBitmap(sectorAddress)) return parentImage.ReadSector(sectorAddress);

            byte[] block;

            if(!blockCache.TryGetValue(blkPtr & BAT_FILE_OFFSET_MASK, out block))
            {
                block = new byte[vFileParms.blockSize];
                imageStream.Seek((long)((blkPtr & BAT_FILE_OFFSET_MASK)), SeekOrigin.Begin);
                imageStream.Read(block, 0, block.Length);

                if(blockCache.Count >= maxBlockCache) blockCache.Clear();

                blockCache.Add(blkPtr & BAT_FILE_OFFSET_MASK, block);
            }

            sector = new byte[logicalSectorSize];
            Array.Copy(block, (int)secOff, sector, 0, sector.Length);

            if(sectorCache.Count >= maxSectorCache) sectorCache.Clear();

            sectorCache.Add(sectorAddress, sector);

            return sector;
        }

        public override byte[] ReadSectors(ulong sectorAddress, uint length)
        {
            if(sectorAddress > ImageInfo.Sectors - 1)
                throw new ArgumentOutOfRangeException(nameof(sectorAddress),
                                                      string.Format("Sector address {0} not found", sectorAddress));

            if(sectorAddress + length > ImageInfo.Sectors)
                throw new ArgumentOutOfRangeException(nameof(length),
                                                      string.Format("Requested more sectors ({0}) than available ({1})",
                                                                    sectorAddress + length, ImageInfo.Sectors));

            MemoryStream ms = new MemoryStream();

            for(uint i = 0; i < length; i++)
            {
                byte[] sector = ReadSector(sectorAddress + i);
                ms.Write(sector, 0, sector.Length);
            }

            return ms.ToArray();
        }
        #endregion

        #region private methods
        static uint VhdxChecksum(byte[] data)
        {
            uint checksum = 0;
            foreach(byte b in data) checksum += b;

            return ~checksum;
        }
        #endregion

        #region Unsupported features
        public override string GetImageComments()
        {
            return null;
        }

        public override byte[] ReadDiskTag(MediaTagType tag)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorTag(ulong sectorAddress, SectorTagType tag)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSector(ulong sectorAddress, uint track)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorTag(ulong sectorAddress, uint track, SectorTagType tag)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorsTag(ulong sectorAddress, uint length, SectorTagType tag)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectors(ulong sectorAddress, uint length, uint track)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorsTag(ulong sectorAddress, uint length, uint track, SectorTagType tag)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorLong(ulong sectorAddress)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorLong(ulong sectorAddress, uint track)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorsLong(ulong sectorAddress, uint length)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override byte[] ReadSectorsLong(ulong sectorAddress, uint length, uint track)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override string GetMediaManufacturer()
        {
            return null;
        }

        public override string GetMediaModel()
        {
            return null;
        }

        public override string GetMediaSerialNumber()
        {
            return null;
        }

        public override string GetMediaBarcode()
        {
            return null;
        }

        public override string GetMediaPartNumber()
        {
            return null;
        }

        public override int GetMediaSequence()
        {
            return 0;
        }

        public override int GetLastDiskSequence()
        {
            return 0;
        }

        public override string GetDriveManufacturer()
        {
            return null;
        }

        public override string GetDriveModel()
        {
            return null;
        }

        public override string GetDriveSerialNumber()
        {
            return null;
        }

        public override List<Partition> GetPartitions()
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override List<Track> GetTracks()
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override List<Track> GetSessionTracks(Session session)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override List<Track> GetSessionTracks(ushort session)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override List<Session> GetSessions()
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override bool? VerifySector(ulong sectorAddress)
        {
            return null;
        }

        public override bool? VerifySector(ulong sectorAddress, uint track)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override bool? VerifySectors(ulong sectorAddress, uint length, out List<ulong> failingLbas,
                                            out List<ulong> unknownLbas)
        {
            failingLbas = new List<ulong>();
            unknownLbas = new List<ulong>();
            for(ulong i = 0; i < ImageInfo.Sectors; i++) unknownLbas.Add(i);

            return null;
        }

        public override bool? VerifySectors(ulong sectorAddress, uint length, uint track, out List<ulong> failingLbas,
                                            out List<ulong> unknownLbas)
        {
            throw new FeatureUnsupportedImageException("Feature not supported by image format");
        }

        public override bool? VerifyMediaImage()
        {
            return null;
        }
        #endregion
    }
}