405 lines
14 KiB
C#
405 lines
14 KiB
C#
using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Threading;
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using System.Threading.Tasks;
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using Duplicati.Proprietary.DiskImage;
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using Duplicati.Proprietary.DiskImage.Disk;
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namespace Duplicati.Proprietary.DiskImage.Partition;
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/// <summary>
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/// Represents an MBR (Master Boot Record) partition table.
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/// MBR is the traditional partition table format used on BIOS-based systems.
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/// </summary>
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public class MBR : IPartitionTable
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{
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// Constants for MBR parsing
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private const int MbrSize = 512;
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private const int PartitionEntrySize = 16;
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private const int MaxPartitionEntries = 4;
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private const ushort MbrBootSignature = 0xAA55;
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// Internal state
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private bool m_parsed = false;
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private bool m_disposed = false;
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// MBR Header fields
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private ushort m_mbrBootSignature;
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private List<MBRPartitionEntry>? m_partitionEntries;
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// Additional tracking
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private IRawDisk? m_rawDisk;
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private byte[]? m_mbrBytes;
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private long m_bytesPerSector;
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// Partition storage
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private List<IPartition>? m_partitions;
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public MBR(IRawDisk? disk)
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{
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m_rawDisk = disk;
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}
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// IPartitionTable implementation
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public IRawDisk? RawDisk { get => m_rawDisk; }
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public PartitionTableType TableType => PartitionTableType.MBR;
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public async Task<bool> ParseAsync(IRawDisk disk, CancellationToken token)
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{
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m_bytesPerSector = disk.SectorSize;
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// Read the MBR (LBA 0)
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m_mbrBytes = new byte[MbrSize];
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using var bytestream = await disk.ReadBytesAsync(0, MbrSize, token).ConfigureAwait(false);
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await bytestream.ReadAtLeastAsync(m_mbrBytes, MbrSize, cancellationToken: token).ConfigureAwait(false);
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var result = await ParseMBRBytesAsync(m_mbrBytes, token).ConfigureAwait(false);
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return result;
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}
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public async Task<bool> ParseAsync(byte[] bytes, int sectorSize, CancellationToken token)
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{
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m_bytesPerSector = sectorSize;
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// Read MBR from the first sector
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m_mbrBytes = bytes[0..sectorSize];
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return await ParseMBRBytesAsync(m_mbrBytes, token).ConfigureAwait(false);
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}
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private async Task<bool> ParseMBRBytesAsync(byte[] bytes, CancellationToken token)
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{
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if (bytes.Length < MbrSize)
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throw new ArgumentException($"Byte array must be at least {MbrSize} bytes long.", nameof(bytes));
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// Read boot signature (2 bytes at offset 510)
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m_mbrBootSignature = BitConverter.ToUInt16(bytes, 510);
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// Verify boot signature
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if (m_mbrBootSignature != MbrBootSignature)
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return false;
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m_partitionEntries = [];
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// Parse partition entries (64 bytes starting at offset 446)
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for (int i = 0; i < MaxPartitionEntries; i++)
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{
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token.ThrowIfCancellationRequested();
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int offset = 446 + (i * PartitionEntrySize);
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var entry = ParsePartitionEntry(bytes, offset, i + 1);
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if (entry != null)
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{
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m_partitionEntries.Add(entry);
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// Add to partitions list for IPartitionTable implementation
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if (m_partitions == null)
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m_partitions = [];
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m_partitions.Add(new MBRPartition
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{
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PartitionNumber = i + 1,
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Type = entry.PartitionType,
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PartitionTable = this,
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StartOffset = entry.StartLBA * m_bytesPerSector,
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Size = entry.SizeInSectors * m_bytesPerSector,
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Name = $"Partition {i + 1}",
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FilesystemType = DetermineFilesystemType(entry),
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VolumeGuid = null,
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RawDisk = m_rawDisk,
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StartingLba = entry.StartLBA,
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EndingLba = entry.StartLBA + entry.SizeInSectors - 1
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});
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}
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}
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m_parsed = true;
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return true;
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}
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private MBRPartitionEntry? ParsePartitionEntry(byte[] bytes, int offset, int entryNumber)
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{
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// Read partition type byte
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byte partitionType = bytes[offset];
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// Skip empty entries
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if (partitionType == 0)
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return null;
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// Read CHS values (not commonly used, but we store them)
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byte startHead = bytes[offset + 1];
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byte startSector = bytes[offset + 2];
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ushort startCylinder = (ushort)(((bytes[offset + 3] & 0xC0) << 2) | bytes[offset + 2]);
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byte endHead = bytes[offset + 5];
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byte endSector = bytes[offset + 6];
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ushort endCylinder = (ushort)(((bytes[offset + 7] & 0xC0) << 2) | bytes[offset + 6]);
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// Read LBA values (more reliable than CHS)
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uint startLBA = BitConverter.ToUInt32(bytes, offset + 8);
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uint sizeInSectors = BitConverter.ToUInt32(bytes, offset + 12);
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// Skip entries with zero size
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if (sizeInSectors == 0)
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return null;
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return new MBRPartitionEntry
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{
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EntryNumber = entryNumber,
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PartitionType = DeterminePartitionType(partitionType),
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PartitionTypeByte = partitionType,
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StartLBA = startLBA,
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SizeInSectors = sizeInSectors,
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StartHead = startHead,
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StartSector = startSector,
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StartCylinder = startCylinder,
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EndHead = endHead,
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EndSector = endSector,
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EndCylinder = endCylinder
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};
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}
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private static PartitionType DeterminePartitionType(byte typeByte)
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{
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// MBR partition type byte mappings
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return typeByte switch
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{
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0x01 => PartitionType.Primary, // FAT12
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0x04 => PartitionType.Primary, // FAT16 (less than 32MB)
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0x06 => PartitionType.Primary, // FAT16
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0x07 => PartitionType.Primary, // NTFS or IFS
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0x0B => PartitionType.Primary, // FAT32 (CHS)
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0x0C => PartitionType.Primary, // FAT32 (LBA)
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0x0E => PartitionType.Primary, // FAT16 (LBA)
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0x0F => PartitionType.Extended, // Extended (LBA)
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0x11 => PartitionType.Primary, // Hidden FAT12 (CHS)
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0x14 => PartitionType.Primary, // Hidden FAT16 (CHS, less than 32MB)
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0x16 => PartitionType.Primary, // Hidden FAT16
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0x17 => PartitionType.Primary, // Hidden NTFS
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0x1B => PartitionType.Primary, // Hidden FAT32 (CHS)
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0x1C => PartitionType.Primary, // Hidden FAT32 (LBA)
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0x1E => PartitionType.Primary, // Hidden FAT16 (LBA)
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0x5 => PartitionType.Extended, // Extended (CHS)
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0x85 => PartitionType.Logical, // Linux extended
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0x8E => PartitionType.Primary, // Linux LVM
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0xEE => PartitionType.Protective, // GPT protective
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0xEF => PartitionType.EFI, // EFI System Partition
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0xFD => PartitionType.Primary, // Linux RAID
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_ => PartitionType.Unknown
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};
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}
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private static FileSystemType DetermineFilesystemType(MBRPartitionEntry entry)
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{
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// Determine filesystem type based on partition type byte
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return entry.PartitionTypeByte switch
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{
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0x01 or 0x11 or 0x81 => FileSystemType.FAT12,
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0x04 or 0x06 or 0x0E or 0x14 or 0x16 or 0x1E => FileSystemType.FAT16,
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0x0B or 0x0C or 0x1B or 0x1C => FileSystemType.FAT32,
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0x07 or 0x17 => FileSystemType.NTFS,
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0xEF => FileSystemType.Unknown, // EFI System Partition, actual FS unknown
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_ => FileSystemType.Unknown
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};
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}
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// MBR-specific properties
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public ushort MbrBootSignatureValue => m_parsed ? m_mbrBootSignature : throw new InvalidOperationException("MBR not parsed.");
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public int NumPartitionEntries => m_parsed ? (m_partitionEntries?.Count ?? 0) : throw new InvalidOperationException("MBR not parsed.");
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// IPartitionTable methods
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public async IAsyncEnumerable<IPartition> EnumeratePartitions([System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
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{
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if (!m_parsed)
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throw new InvalidOperationException("MBR not parsed.");
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if (m_partitions != null)
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{
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foreach (var partition in m_partitions)
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{
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cancellationToken.ThrowIfCancellationRequested();
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yield return partition;
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}
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}
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}
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public async Task<IPartition?> GetPartitionAsync(int partitionNumber, CancellationToken cancellationToken)
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{
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if (!m_parsed)
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throw new InvalidOperationException("MBR not parsed.");
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if (m_partitions == null)
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return null;
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if (partitionNumber >= 1 && partitionNumber <= m_partitions.Count)
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return m_partitions[partitionNumber - 1];
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return null;
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}
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public Task<Stream> GetProtectiveMbrAsync(CancellationToken cancellationToken)
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{
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// MBR doesn't have a protective MBR - it IS the MBR
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throw new NotSupportedException("MBR partition tables do not have a protective MBR. Use GetPartitionAsync instead.");
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}
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public Task<Stream> GetPartitionTableDataAsync(CancellationToken cancellationToken)
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{
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if (!m_parsed || m_mbrBytes == null)
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throw new InvalidOperationException("MBR not parsed.");
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// Return the MBR sector (512 bytes)
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return Task.FromResult<Stream>(new MemoryStream(m_mbrBytes, writable: false));
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}
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public void Dispose()
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{
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Dispose(true);
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GC.SuppressFinalize(this);
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}
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protected virtual void Dispose(bool disposing)
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{
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if (!m_disposed)
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{
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if (disposing)
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{
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m_mbrBytes = null;
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if (m_partitions != null)
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{
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foreach (var partition in m_partitions)
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partition.Dispose();
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m_partitions = null;
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}
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}
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m_disposed = true;
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}
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}
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/// <summary>
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/// Represents an MBR partition entry.
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/// </summary>
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private class MBRPartitionEntry
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{
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public int EntryNumber { get; init; }
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public PartitionType PartitionType { get; init; }
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public byte PartitionTypeByte { get; init; }
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public uint StartLBA { get; init; }
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public uint SizeInSectors { get; init; }
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public byte StartHead { get; init; }
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public byte StartSector { get; init; }
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public ushort StartCylinder { get; init; }
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public byte EndHead { get; init; }
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public byte EndSector { get; init; }
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public ushort EndCylinder { get; init; }
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}
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/// <summary>
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/// Represents an MBR partition.
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/// </summary>
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private class MBRPartition : IPartition
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{
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public int PartitionNumber { get; init; }
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public PartitionType Type { get; init; }
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public required IPartitionTable PartitionTable { get; init; }
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public long StartOffset { get; init; }
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public long Size { get; init; }
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public string? Name { get; init; }
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public FileSystemType FilesystemType { get; init; }
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public Guid? VolumeGuid { get; init; }
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public required IRawDisk? RawDisk { get; init; }
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public long StartingLba { get; init; }
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public long EndingLba { get; init; }
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public long Attributes { get; init; }
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public Task<Stream> OpenReadAsync(CancellationToken cancellationToken)
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{
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if (RawDisk == null)
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throw new InvalidOperationException("RawDisk not available.");
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return RawDisk.ReadBytesAsync(StartOffset, (int)Math.Min(Size, int.MaxValue), cancellationToken);
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}
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public Task<Stream> OpenWriteAsync(CancellationToken cancellationToken)
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{
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if (RawDisk == null)
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throw new InvalidOperationException("RawDisk not available.");
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// Return a stream that wraps the raw disk write capability
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return Task.FromResult<Stream>(new PartitionWriteStream(RawDisk, StartOffset, Size));
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}
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public void Dispose()
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{
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// No unmanaged resources to dispose
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}
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}
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/// <summary>
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/// A stream that writes data to a partition on the raw disk.
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/// </summary>
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private class PartitionWriteStream : Stream
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{
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private readonly IRawDisk _disk;
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private readonly long _startOffset;
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private readonly long _maxSize;
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private readonly MemoryStream _buffer;
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private bool _disposed = false;
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public PartitionWriteStream(IRawDisk disk, long startOffset, long maxSize)
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{
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_disk = disk;
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_startOffset = startOffset;
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_maxSize = maxSize;
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_buffer = new MemoryStream();
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}
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public override bool CanRead => false;
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public override bool CanSeek => true;
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public override bool CanWrite => true;
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public override long Length => _buffer.Length;
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public override long Position
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{
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get => _buffer.Position;
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set => _buffer.Position = value;
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}
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public override void Flush() => _buffer.Flush();
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public override int Read(byte[] buffer, int offset, int count) => throw new NotSupportedException();
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public override long Seek(long offset, SeekOrigin origin) => _buffer.Seek(offset, origin);
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public override void SetLength(long value)
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{
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if (value > _maxSize)
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throw new IOException($"Cannot write beyond partition size of {_maxSize} bytes.");
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_buffer.SetLength(value);
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}
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public override void Write(byte[] buffer, int offset, int count)
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{
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if (_buffer.Position + count > _maxSize)
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throw new IOException($"Cannot write beyond partition size of {_maxSize} bytes.");
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_buffer.Write(buffer, offset, count);
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}
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protected override void Dispose(bool disposing)
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{
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if (!_disposed)
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{
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if (disposing)
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{
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// Write all buffered data to disk
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_buffer.Position = 0;
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var data = _buffer.ToArray();
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if (data.Length > 0)
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{
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_disk.WriteBytesAsync(_startOffset, data, CancellationToken.None).GetAwaiter().GetResult();
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}
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_buffer.Dispose();
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}
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_disposed = true;
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}
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base.Dispose(disposing);
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}
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}
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}
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