// /*************************************************************************** // Aaru Data Preservation Suite // ---------------------------------------------------------------------------- // // Filename : Read.cs // Author(s) : Natalia Portillo // // Component : Disk image plugins. // // --[ Description ] ---------------------------------------------------------- // // Reads Sydex TeleDisk 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 . // // ---------------------------------------------------------------------------- // Copyright © 2011-2020 Natalia Portillo // ****************************************************************************/ using System; using System.IO; using System.Text; using Aaru.CommonTypes.Enums; using Aaru.CommonTypes.Exceptions; using Aaru.CommonTypes.Interfaces; using Aaru.Compression; using Aaru.Console; namespace Aaru.DiscImages { public sealed partial class TeleDisk { public bool Open(IFilter imageFilter) { _header = new TeleDiskHeader(); byte[] headerBytes = new byte[12]; _inStream = imageFilter.GetDataForkStream(); var stream = new MemoryStream(); _inStream.Seek(0, SeekOrigin.Begin); _inStream.Read(headerBytes, 0, 12); stream.Write(headerBytes, 0, 12); _header.Signature = BitConverter.ToUInt16(headerBytes, 0); if(_header.Signature != TD_MAGIC && _header.Signature != TD_ADV_COMP_MAGIC) return false; _header.Sequence = headerBytes[2]; _header.DiskSet = headerBytes[3]; _header.Version = headerBytes[4]; _header.DataRate = headerBytes[5]; _header.DriveType = headerBytes[6]; _header.Stepping = headerBytes[7]; _header.DosAllocation = headerBytes[8]; _header.Sides = headerBytes[9]; _header.Crc = BitConverter.ToUInt16(headerBytes, 10); _imageInfo.MediaTitle = Path.GetFileNameWithoutExtension(imageFilter.GetFilename()); _imageInfo.Version = $"{(_header.Version & 0xF0) >> 4}.{_header.Version & 0x0F}"; _imageInfo.Application = _imageInfo.Version; byte[] headerBytesForCrc = new byte[10]; Array.Copy(headerBytes, headerBytesForCrc, 10); ushort calculatedHeaderCrc = TeleDiskCrc(0x0000, headerBytesForCrc); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.signature = 0x{0:X4}", _header.Signature); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.sequence = 0x{0:X2}", _header.Sequence); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.diskSet = 0x{0:X2}", _header.DiskSet); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.version = 0x{0:X2}", _header.Version); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.dataRate = 0x{0:X2}", _header.DataRate); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.driveType = 0x{0:X2}", _header.DriveType); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.stepping = 0x{0:X2}", _header.Stepping); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.dosAllocation = 0x{0:X2}", _header.DosAllocation); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.sides = 0x{0:X2}", _header.Sides); AaruConsole.DebugWriteLine("TeleDisk plugin", "header.crc = 0x{0:X4}", _header.Crc); AaruConsole.DebugWriteLine("TeleDisk plugin", "calculated header crc = 0x{0:X4}", calculatedHeaderCrc); // We need more checks as the magic is too simply. // This may deny legal images // That would be much of a coincidence if(_header.Crc != calculatedHeaderCrc) { _aDiskCrcHasFailed = true; AaruConsole.DebugWriteLine("TeleDisk plugin", "Calculated CRC does not coincide with stored one."); } if(_header.Sequence != 0x00) return false; if(_header.DataRate != DATA_RATE_250KBPS && _header.DataRate != DATA_RATE_300KBPS && _header.DataRate != DATA_RATE_500KBPS) return false; if(_header.DriveType != DRIVE_TYPE_35_DD && _header.DriveType != DRIVE_TYPE_35_ED && _header.DriveType != DRIVE_TYPE_35_HD && _header.DriveType != DRIVE_TYPE_525_DD && _header.DriveType != DRIVE_TYPE_525_HD && _header.DriveType != DRIVE_TYPE_525_HD_DD_DISK && _header.DriveType != DRIVE_TYPE_8_INCH) return false; if(_header.Signature == TD_ADV_COMP_MAGIC) { int rd; _inStream.Seek(12, SeekOrigin.Begin); stream.Seek(12, SeekOrigin.Begin); var lzh = new TeleDiskLzh(_inStream); do if((rd = lzh.Decode(out byte[] obuf, BUFSZ)) > 0) stream.Write(obuf, 0, rd); while(rd == BUFSZ); } else { // Not using Stream.CopyTo() because it's failing with LZIP byte[] copybuf = new byte[_inStream.Length]; _inStream.Seek(0, SeekOrigin.Begin); _inStream.Read(copybuf, 0, copybuf.Length); stream.Seek(0, SeekOrigin.Begin); stream.Write(copybuf, 0, copybuf.Length); } stream.Seek(12, SeekOrigin.Begin); _imageInfo.CreationTime = DateTime.MinValue; if((_header.Stepping & COMMENT_BLOCK_PRESENT) == COMMENT_BLOCK_PRESENT) { _commentHeader = new TeleDiskCommentBlockHeader(); byte[] commentHeaderBytes = new byte[10]; stream.Read(commentHeaderBytes, 0, 10); _commentHeader.Crc = BitConverter.ToUInt16(commentHeaderBytes, 0); _commentHeader.Length = BitConverter.ToUInt16(commentHeaderBytes, 2); _commentHeader.Year = commentHeaderBytes[4]; _commentHeader.Month = commentHeaderBytes[5]; _commentHeader.Day = commentHeaderBytes[6]; _commentHeader.Hour = commentHeaderBytes[7]; _commentHeader.Minute = commentHeaderBytes[8]; _commentHeader.Second = commentHeaderBytes[9]; _commentBlock = new byte[_commentHeader.Length]; stream.Read(_commentBlock, 0, _commentHeader.Length); byte[] commentBlockForCrc = new byte[_commentHeader.Length + 8]; Array.Copy(commentHeaderBytes, 2, commentBlockForCrc, 0, 8); Array.Copy(_commentBlock, 0, commentBlockForCrc, 8, _commentHeader.Length); ushort cmtcrc = TeleDiskCrc(0, commentBlockForCrc); AaruConsole.DebugWriteLine("TeleDisk plugin", "Comment header"); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.crc = 0x{0:X4}", _commentHeader.Crc); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tCalculated CRC = 0x{0:X4}", cmtcrc); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.length = {0} bytes", _commentHeader.Length); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.year = {0}", _commentHeader.Year); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.month = {0}", _commentHeader.Month); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.day = {0}", _commentHeader.Day); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.hour = {0}", _commentHeader.Hour); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.minute = {0}", _commentHeader.Minute); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tcommentheader.second = {0}", _commentHeader.Second); _aDiskCrcHasFailed |= cmtcrc != _commentHeader.Crc; for(int i = 0; i < _commentBlock.Length; i++) // Replace NULLs, used by TeleDisk as newline markers, with UNIX newline marker if(_commentBlock[i] == 0x00) _commentBlock[i] = 0x0A; _imageInfo.Comments = Encoding.ASCII.GetString(_commentBlock); AaruConsole.DebugWriteLine("TeleDisk plugin", "Comment"); AaruConsole.DebugWriteLine("TeleDisk plugin", "{0}", _imageInfo.Comments); _imageInfo.CreationTime = new DateTime(_commentHeader.Year + 1900, _commentHeader.Month + 1, _commentHeader.Day, _commentHeader.Hour, _commentHeader.Minute, _commentHeader.Second, DateTimeKind.Unspecified); } if(_imageInfo.CreationTime == DateTime.MinValue) _imageInfo.CreationTime = imageFilter.GetCreationTime(); _imageInfo.LastModificationTime = imageFilter.GetLastWriteTime(); AaruConsole.DebugWriteLine("TeleDisk plugin", "Image created on {0}", _imageInfo.CreationTime); AaruConsole.DebugWriteLine("TeleDisk plugin", "Image modified on {0}", _imageInfo.LastModificationTime); AaruConsole.DebugWriteLine("TeleDisk plugin", "Parsing image"); _totalDiskSize = 0; _imageInfo.ImageSize = 0; int totalCylinders = -1; int totalHeads = -1; int maxSector = -1; int totalSectors = 0; long currentPos = stream.Position; _imageInfo.SectorSize = uint.MaxValue; _imageInfo.SectorsPerTrack = uint.MaxValue; // Count cylinders while(true) { var teleDiskTrack = new TeleDiskTrackHeader { Sectors = (byte)stream.ReadByte(), Cylinder = (byte)stream.ReadByte(), Head = (byte)stream.ReadByte(), Crc = (byte)stream.ReadByte() }; if(teleDiskTrack.Cylinder > totalCylinders) totalCylinders = teleDiskTrack.Cylinder; if(teleDiskTrack.Head > totalHeads) totalHeads = teleDiskTrack.Head; if(teleDiskTrack.Sectors == 0xFF) // End of disk image break; for(byte processedSectors = 0; processedSectors < teleDiskTrack.Sectors; processedSectors++) { var teleDiskSector = new TeleDiskSectorHeader(); var teleDiskData = new TeleDiskDataHeader(); byte[] dataSizeBytes = new byte[2]; teleDiskSector.Cylinder = (byte)stream.ReadByte(); teleDiskSector.Head = (byte)stream.ReadByte(); teleDiskSector.SectorNumber = (byte)stream.ReadByte(); teleDiskSector.SectorSize = (byte)stream.ReadByte(); teleDiskSector.Flags = (byte)stream.ReadByte(); teleDiskSector.Crc = (byte)stream.ReadByte(); if(teleDiskSector.SectorNumber > maxSector) maxSector = teleDiskSector.SectorNumber; if((teleDiskSector.Flags & FLAGS_SECTOR_DATALESS) != FLAGS_SECTOR_DATALESS && (teleDiskSector.Flags & FLAGS_SECTOR_SKIPPED) != FLAGS_SECTOR_SKIPPED) { stream.Read(dataSizeBytes, 0, 2); teleDiskData.DataSize = BitConverter.ToUInt16(dataSizeBytes, 0); teleDiskData.DataSize--; // Sydex decided to including dataEncoding byte as part of it teleDiskData.DataEncoding = (byte)stream.ReadByte(); byte[] data = new byte[teleDiskData.DataSize]; stream.Read(data, 0, teleDiskData.DataSize); } if(128 << teleDiskSector.SectorSize < _imageInfo.SectorSize) _imageInfo.SectorSize = (uint)(128 << teleDiskSector.SectorSize); totalSectors++; } } totalCylinders++; totalHeads++; if(totalCylinders <= 0 || totalHeads <= 0) throw new ImageNotSupportedException("No cylinders or heads found"); bool hasLeadOutOnHead0 = false; bool hasLeadOutOnHead1 = false; _imageInfo.Cylinders = (ushort)totalCylinders; _imageInfo.Heads = (byte)totalHeads; // Count sectors per track stream.Seek(currentPos, SeekOrigin.Begin); while(true) { var teleDiskTrack = new TeleDiskTrackHeader { Sectors = (byte)stream.ReadByte(), Cylinder = (byte)stream.ReadByte(), Head = (byte)stream.ReadByte(), Crc = (byte)stream.ReadByte() }; if(teleDiskTrack.Sectors == 0xFF) // End of disk image break; if(teleDiskTrack.Sectors < _imageInfo.SectorsPerTrack) if(teleDiskTrack.Cylinder + 1 == totalCylinders) { hasLeadOutOnHead0 |= teleDiskTrack.Head == 0; hasLeadOutOnHead1 |= teleDiskTrack.Head == 1; if(_imageInfo.Cylinders == totalCylinders) _imageInfo.Cylinders--; } else _imageInfo.SectorsPerTrack = teleDiskTrack.Sectors; for(byte processedSectors = 0; processedSectors < teleDiskTrack.Sectors; processedSectors++) { var teleDiskSector = new TeleDiskSectorHeader(); var teleDiskData = new TeleDiskDataHeader(); byte[] dataSizeBytes = new byte[2]; teleDiskSector.Cylinder = (byte)stream.ReadByte(); teleDiskSector.Head = (byte)stream.ReadByte(); teleDiskSector.SectorNumber = (byte)stream.ReadByte(); teleDiskSector.SectorSize = (byte)stream.ReadByte(); teleDiskSector.Flags = (byte)stream.ReadByte(); teleDiskSector.Crc = (byte)stream.ReadByte(); if((teleDiskSector.Flags & FLAGS_SECTOR_DATALESS) == FLAGS_SECTOR_DATALESS || (teleDiskSector.Flags & FLAGS_SECTOR_SKIPPED) == FLAGS_SECTOR_SKIPPED) continue; stream.Read(dataSizeBytes, 0, 2); teleDiskData.DataSize = BitConverter.ToUInt16(dataSizeBytes, 0); teleDiskData.DataSize--; // Sydex decided to including dataEncoding byte as part of it teleDiskData.DataEncoding = (byte)stream.ReadByte(); byte[] data = new byte[teleDiskData.DataSize]; stream.Read(data, 0, teleDiskData.DataSize); } } _sectorsData = new byte[totalCylinders][][][]; // Total sectors per track uint[][] spts = new uint[totalCylinders][]; AaruConsole.DebugWriteLine("TeleDisk plugin", "Found {0} cylinders and {1} heads with a maximum sector number of {2}", totalCylinders, totalHeads, maxSector); // Create heads for(int i = 0; i < totalCylinders; i++) { _sectorsData[i] = new byte[totalHeads][][]; spts[i] = new uint[totalHeads]; for(int j = 0; j < totalHeads; j++) _sectorsData[i][j] = new byte[maxSector + 1][]; } // Decode the image stream.Seek(currentPos, SeekOrigin.Begin); while(true) { var teleDiskTrack = new TeleDiskTrackHeader(); byte[] tdTrackForCrc = new byte[3]; teleDiskTrack.Sectors = (byte)stream.ReadByte(); teleDiskTrack.Cylinder = (byte)stream.ReadByte(); teleDiskTrack.Head = (byte)stream.ReadByte(); teleDiskTrack.Crc = (byte)stream.ReadByte(); tdTrackForCrc[0] = teleDiskTrack.Sectors; tdTrackForCrc[1] = teleDiskTrack.Cylinder; tdTrackForCrc[2] = teleDiskTrack.Head; byte tdTrackCalculatedCrc = (byte)(TeleDiskCrc(0, tdTrackForCrc) & 0xFF); AaruConsole.DebugWriteLine("TeleDisk plugin", "Track follows"); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tTrack cylinder: {0}\t", teleDiskTrack.Cylinder); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tTrack head: {0}\t", teleDiskTrack.Head); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tSectors in track: {0}\t", teleDiskTrack.Sectors); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tTrack header CRC: 0x{0:X2} (calculated 0x{1:X2})\t", teleDiskTrack.Crc, tdTrackCalculatedCrc); _aDiskCrcHasFailed |= tdTrackCalculatedCrc != teleDiskTrack.Crc; if(teleDiskTrack.Sectors == 0xFF) // End of disk image { AaruConsole.DebugWriteLine("TeleDisk plugin", "End of disk image arrived"); AaruConsole.DebugWriteLine("TeleDisk plugin", "Total of {0} data sectors, for {1} bytes", totalSectors, _totalDiskSize); break; } for(byte processedSectors = 0; processedSectors < teleDiskTrack.Sectors; processedSectors++) { var teleDiskSector = new TeleDiskSectorHeader(); var teleDiskData = new TeleDiskDataHeader(); byte[] dataSizeBytes = new byte[2]; byte[] decodedData; teleDiskSector.Cylinder = (byte)stream.ReadByte(); teleDiskSector.Head = (byte)stream.ReadByte(); teleDiskSector.SectorNumber = (byte)stream.ReadByte(); teleDiskSector.SectorSize = (byte)stream.ReadByte(); teleDiskSector.Flags = (byte)stream.ReadByte(); teleDiskSector.Crc = (byte)stream.ReadByte(); AaruConsole.DebugWriteLine("TeleDisk plugin", "\tSector follows"); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tAddressMark cylinder: {0}", teleDiskSector.Cylinder); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tAddressMark head: {0}", teleDiskSector.Head); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tAddressMark sector number: {0}", teleDiskSector.SectorNumber); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tSector size: {0}", teleDiskSector.SectorSize); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tSector flags: 0x{0:X2}", teleDiskSector.Flags); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tSector CRC (plus headers): 0x{0:X2}", teleDiskSector.Crc); uint lba = (uint)((teleDiskSector.Cylinder * _header.Sides * _imageInfo.SectorsPerTrack) + (teleDiskSector.Head * _imageInfo.SectorsPerTrack) + (teleDiskSector.SectorNumber - 1)); if((teleDiskSector.Flags & FLAGS_SECTOR_DATALESS) != FLAGS_SECTOR_DATALESS && (teleDiskSector.Flags & FLAGS_SECTOR_SKIPPED) != FLAGS_SECTOR_SKIPPED) { stream.Read(dataSizeBytes, 0, 2); teleDiskData.DataSize = BitConverter.ToUInt16(dataSizeBytes, 0); teleDiskData.DataSize--; // Sydex decided to including dataEncoding byte as part of it _imageInfo.ImageSize += teleDiskData.DataSize; teleDiskData.DataEncoding = (byte)stream.ReadByte(); byte[] data = new byte[teleDiskData.DataSize]; stream.Read(data, 0, teleDiskData.DataSize); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tData size (in-image): {0}", teleDiskData.DataSize); AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tData encoding: 0x{0:X2}", teleDiskData.DataEncoding); decodedData = DecodeTeleDiskData(teleDiskSector.SectorSize, teleDiskData.DataEncoding, data); byte tdSectorCalculatedCrc = (byte)(TeleDiskCrc(0, decodedData) & 0xFF); if(tdSectorCalculatedCrc != teleDiskSector.Crc) { AaruConsole.DebugWriteLine("TeleDisk plugin", "Sector {0}:{3}:{4} calculated CRC 0x{1:X2} differs from stored CRC 0x{2:X2}", teleDiskTrack.Cylinder, tdSectorCalculatedCrc, teleDiskSector.Crc, teleDiskTrack.Cylinder, teleDiskSector.SectorNumber); if((teleDiskSector.Flags & FLAGS_SECTOR_NO_ID) != FLAGS_SECTOR_NO_ID) _sectorsWhereCrcHasFailed.Add(lba); } } else decodedData = new byte[128 << teleDiskSector.SectorSize]; AaruConsole.DebugWriteLine("TeleDisk plugin", "\t\tLBA: {0}", lba); if((teleDiskSector.Flags & FLAGS_SECTOR_NO_ID) == FLAGS_SECTOR_NO_ID) continue; if(_sectorsData[teleDiskTrack.Cylinder][teleDiskTrack.Head][teleDiskSector.SectorNumber] != null) AaruConsole.DebugWriteLine("TeleDisk plugin", (teleDiskSector.Flags & FLAGS_SECTOR_DUPLICATE) == FLAGS_SECTOR_DUPLICATE ? "\t\tSector {0} on cylinder {1} head {2} is duplicate, and marked so" : "\t\tSector {0} on cylinder {1} head {2} is duplicate, but is not marked so", teleDiskSector.SectorNumber, teleDiskSector.Cylinder, teleDiskSector.Head); else { _sectorsData[teleDiskTrack.Cylinder][teleDiskTrack.Head][teleDiskSector.SectorNumber] = decodedData; _totalDiskSize += (uint)decodedData.Length; } } } var leadOutMs = new MemoryStream(); if(hasLeadOutOnHead0) for(int i = 0; i < _sectorsData[totalCylinders - 1][0].Length; i++) if(_sectorsData[totalCylinders - 1][0][i] != null) leadOutMs.Write(_sectorsData[totalCylinders - 1][0][i], 0, _sectorsData[totalCylinders - 1][0][i].Length); if(hasLeadOutOnHead1) for(int i = 0; i < _sectorsData[totalCylinders - 1][1].Length; i++) if(_sectorsData[totalCylinders - 1][1][i] != null) leadOutMs.Write(_sectorsData[totalCylinders - 1][1][i], 0, _sectorsData[totalCylinders - 1][1][i].Length); if(leadOutMs.Length != 0) { _leadOut = leadOutMs.ToArray(); _imageInfo.ReadableMediaTags.Add(MediaTagType.Floppy_LeadOut); } _imageInfo.Sectors = _imageInfo.Cylinders * _imageInfo.Heads * _imageInfo.SectorsPerTrack; _imageInfo.MediaType = DecodeTeleDiskDiskType(); _imageInfo.XmlMediaType = XmlMediaType.BlockMedia; AaruConsole.VerboseWriteLine("TeleDisk image contains a disk of type {0}", _imageInfo.MediaType); if(!string.IsNullOrEmpty(_imageInfo.Comments)) AaruConsole.VerboseWriteLine("TeleDisk comments: {0}", _imageInfo.Comments); _inStream.Dispose(); stream.Dispose(); return true; } public byte[] ReadSector(ulong sectorAddress) { (ushort cylinder, byte head, byte sector) = LbaToChs(sectorAddress); if(cylinder >= _sectorsData.Length) throw new ArgumentOutOfRangeException(nameof(sectorAddress), "Sector address not found"); if(head >= _sectorsData[cylinder].Length) throw new ArgumentOutOfRangeException(nameof(sectorAddress), "Sector address not found"); if(sector > _sectorsData[cylinder][head].Length) throw new ArgumentOutOfRangeException(nameof(sectorAddress), "Sector address not found"); return _sectorsData[cylinder][head][sector]; } public byte[] ReadSectors(ulong sectorAddress, uint length) { if(sectorAddress > _imageInfo.Sectors - 1) throw new ArgumentOutOfRangeException(nameof(sectorAddress), "Sector address not found"); if(sectorAddress + length > _imageInfo.Sectors) throw new ArgumentOutOfRangeException(nameof(length), "Requested more sectors than available"); var buffer = new MemoryStream(); for(uint i = 0; i < length; i++) { byte[] sector = ReadSector(sectorAddress + i) ?? new byte[_imageInfo.SectorSize]; buffer.Write(sector, 0, sector.Length); } return buffer.ToArray(); } public byte[] ReadSectorLong(ulong sectorAddress) => ReadSectors(sectorAddress, 1); public byte[] ReadSectorsLong(ulong sectorAddress, uint length) => ReadSectors(sectorAddress, length); public byte[] ReadDiskTag(MediaTagType tag) { if(tag != MediaTagType.Floppy_LeadOut) throw new FeatureUnsupportedImageException("Feature not supported by image format"); if(_leadOut != null) return _leadOut; throw new FeatureNotPresentImageException("Lead-out not present in disk image"); } } }