Add test dmg

Add read-only support for Dmg archives

src/SharpCompress/Archives/ArchiveFactory.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using SharpCompress.Archives.Dmg;
 using SharpCompress.Archives.GZip;
 using SharpCompress.Archives.Rar;
 using SharpCompress.Archives.SevenZip;
@@ -44,6 +45,12 @@ namespace SharpCompress.Archives
                 return GZipArchive.Open(stream, readerOptions);
             }
             stream.Seek(0, SeekOrigin.Begin);
+            if (DmgArchive.IsDmgFile(stream))
+            {
+                stream.Seek(0, SeekOrigin.Begin);
+                return DmgArchive.Open(stream, readerOptions);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
             if (RarArchive.IsRarFile(stream, readerOptions))
             {
                 stream.Seek(0, SeekOrigin.Begin);
@@ -55,7 +62,7 @@ namespace SharpCompress.Archives
                 stream.Seek(0, SeekOrigin.Begin);
                 return TarArchive.Open(stream, readerOptions);
             }
-            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip, LZip");
+            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip, LZip, Dmg");
         }
 
         public static IWritableArchive Create(ArchiveType type)
@@ -106,6 +113,12 @@ namespace SharpCompress.Archives
                 return GZipArchive.Open(fileInfo, options);
             }
             stream.Seek(0, SeekOrigin.Begin);
+            if (DmgArchive.IsDmgFile(stream))
+            {
+                stream.Seek(0, SeekOrigin.Begin);
+                return DmgArchive.Open(fileInfo, options);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
             if (RarArchive.IsRarFile(stream, options))
             {
                 return RarArchive.Open(fileInfo, options);
@@ -115,7 +128,7 @@ namespace SharpCompress.Archives
             {
                 return TarArchive.Open(fileInfo, options);
             }
-            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip");
+            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip, Dmg");
         }
 
         /// <summary>

src/SharpCompress/Archives/Dmg/DmgArchive.cs

@@ -0,0 +1,117 @@
+using SharpCompress.Common;
+using SharpCompress.Common.Dmg;
+using SharpCompress.Common.Dmg.Headers;
+using SharpCompress.Common.Dmg.HFS;
+using SharpCompress.Readers;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace SharpCompress.Archives.Dmg
+{
+    public class DmgArchive : AbstractArchive<DmgArchiveEntry, DmgVolume>
+    {
+        private readonly string _fileName;
+
+        internal DmgArchive(FileInfo fileInfo, ReaderOptions readerOptions)
+            : base(ArchiveType.Dmg, fileInfo, readerOptions)
+        {
+            _fileName = fileInfo.FullName;
+        }
+
+        internal DmgArchive(Stream stream, ReaderOptions readerOptions)
+            : base(ArchiveType.Dmg, stream.AsEnumerable(), readerOptions)
+        {
+            _fileName = string.Empty;
+        }
+
+        protected override IReader CreateReaderForSolidExtraction()
+            => new DmgReader(ReaderOptions, this, _fileName);
+
+        protected override IEnumerable<DmgArchiveEntry> LoadEntries(IEnumerable<DmgVolume> volumes)
+            => volumes.Single().LoadEntries();
+
+        protected override IEnumerable<DmgVolume> LoadVolumes(FileInfo file)
+            => new DmgVolume(this, file.OpenRead(), file.FullName, ReaderOptions).AsEnumerable();
+
+        protected override IEnumerable<DmgVolume> LoadVolumes(IEnumerable<Stream> streams)
+            => new DmgVolume(this, streams.Single(), string.Empty, ReaderOptions).AsEnumerable();
+
+        public static bool IsDmgFile(FileInfo fileInfo)
+        {
+            if (!fileInfo.Exists) return false;
+
+            using var stream = fileInfo.OpenRead();
+            return IsDmgFile(stream);
+        }
+
+        public static bool IsDmgFile(Stream stream)
+        {
+            long headerPos = stream.Length - DmgHeader.HeaderSize;
+            if (headerPos < 0) return false;
+            stream.Position = headerPos;
+
+            return DmgHeader.TryRead(stream, out _);
+        }
+
+        /// <summary>
+        /// Constructor expects a filepath to an existing file.
+        /// </summary>
+        /// <param name="filePath"></param>
+        /// <param name="readerOptions"></param>
+        public static DmgArchive Open(string filePath, ReaderOptions? readerOptions = null)
+        {
+            filePath.CheckNotNullOrEmpty(nameof(filePath));
+            return Open(new FileInfo(filePath), readerOptions ?? new ReaderOptions());
+        }
+
+        /// <summary>
+        /// Constructor with a FileInfo object to an existing file.
+        /// </summary>
+        /// <param name="fileInfo"></param>
+        /// <param name="readerOptions"></param>
+        public static DmgArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
+        {
+            fileInfo.CheckNotNull(nameof(fileInfo));
+            return new DmgArchive(fileInfo, readerOptions ?? new ReaderOptions());
+        }
+
+        /// <summary>
+        /// Takes a seekable Stream as a source
+        /// </summary>
+        /// <param name="stream"></param>
+        /// <param name="readerOptions"></param>
+        public static DmgArchive Open(Stream stream, ReaderOptions? readerOptions = null)
+        {
+            stream.CheckNotNull(nameof(stream));
+            return new DmgArchive(stream, readerOptions ?? new ReaderOptions());
+        }
+
+        private sealed class DmgReader : AbstractReader<DmgEntry, DmgVolume>
+        {
+            private readonly DmgArchive _archive;
+            private readonly string _fileName;
+            private readonly Stream? _partitionStream;
+
+            public override DmgVolume Volume { get; }
+
+            internal DmgReader(ReaderOptions readerOptions, DmgArchive archive, string fileName)
+                : base(readerOptions, ArchiveType.Dmg)
+            {
+                _archive = archive;
+                _fileName = fileName;
+                Volume = archive.Volumes.Single();
+
+                using var compressedStream = DmgUtil.LoadHFSPartitionStream(Volume.Stream, Volume.Header);
+                _partitionStream = compressedStream?.Decompress();
+            }
+
+            protected override IEnumerable<DmgEntry> GetEntries(Stream stream)
+            {
+                if (_partitionStream is null) return Array.Empty<DmgArchiveEntry>();
+                else return HFSUtil.LoadEntriesFromPartition(_partitionStream, _fileName, _archive);
+            }
+        }
+    }
+}

src/SharpCompress/Archives/Dmg/DmgArchiveEntry.cs

@@ -0,0 +1,32 @@
+using SharpCompress.Common.Dmg;
+using SharpCompress.Common.Dmg.HFS;
+using System;
+using System.IO;
+
+namespace SharpCompress.Archives.Dmg
+{
+    public sealed class DmgArchiveEntry : DmgEntry, IArchiveEntry
+    {
+        private readonly Stream? _stream;
+
+        public bool IsComplete { get; } = true;
+
+        public IArchive Archive { get; }
+
+        internal DmgArchiveEntry(Stream? stream, DmgArchive archive, HFSCatalogRecord record, string path, DmgFilePart part)
+            : base(record, path, stream?.Length ?? 0, part)
+        {
+            _stream = stream;
+            Archive = archive;
+        }
+
+        public Stream OpenEntryStream()
+        {
+            if (IsDirectory)
+                throw new NotSupportedException("Directories cannot be opened as stream");
+
+            _stream!.Position = 0;
+            return _stream;
+        }
+    }
+}

src/SharpCompress/Common/ArchiveException.cs

@@ -8,5 +8,10 @@ namespace SharpCompress.Common
             : base(message)
         {
         }
+
+        public ArchiveException(string message, Exception inner)
+            : base(message, inner)
+        {
+        }
     }
 }

src/SharpCompress/Common/ArchiveType.cs

@@ -6,6 +6,7 @@
         Zip,
         Tar,
         SevenZip,
-        GZip
+        GZip,
+        Dmg
     }
 }

src/SharpCompress/Common/Dmg/DmgBlockDataStream.cs

@@ -0,0 +1,323 @@
+using SharpCompress.Common.Dmg.Headers;
+using SharpCompress.Compressors;
+using SharpCompress.Compressors.ADC;
+using SharpCompress.Compressors.BZip2;
+using SharpCompress.Compressors.Deflate;
+using SharpCompress.IO;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace SharpCompress.Common.Dmg
+{
+    internal sealed class DmgBlockDataStream : Stream
+    {
+        private readonly Stream _baseStream;
+        private readonly DmgHeader _header;
+        private readonly BlkxTable _table;
+        private long _position;
+        private bool _isEnded;
+        private int _chunkIndex;
+        private Stream? _chunkStream;
+        private long _chunkPos;
+        
+        public override bool CanRead => true;
+        public override bool CanWrite => false;
+        public override bool CanSeek => true;
+        public override long Length { get; }
+
+        public override long Position
+        {
+            get => _position;
+            set
+            {
+                if ((value < 0) || (value > Length)) throw new ArgumentOutOfRangeException(nameof(value));
+
+                if (value == Length)
+                {
+                    // End of the stream
+
+                    _position = Length;
+                    _isEnded = true;
+                    _chunkIndex = -1;
+                    _chunkStream = null;
+                }
+                else if (value != _position)
+                {
+                    _position = value;
+
+                    // We can only seek over entire chunks at a time because some chunks may be compressed.
+                    // So we first find the chunk that we are now in, then we read to the exact position inside that chunk.
+
+                    for (int i = 0; i < _table.Chunks.Count; i++)
+                    {
+                        var chunk = _table.Chunks[i];
+                        if (IsChunkValid(chunk) && (chunk.UncompressedOffset <= (ulong)_position)
+                            && ((chunk.UncompressedOffset + chunk.UncompressedLength) > (ulong)_position))
+                        {
+                            if (i == _chunkIndex)
+                            {
+                                // We are still in the same chunk, so if the new position is
+                                // behind the previous one we can just read to the new position.
+
+                                long offset = (long)chunk.UncompressedOffset + _chunkPos;
+                                if (offset <= _position)
+                                {
+                                    long skip = _position - offset;
+                                    _chunkStream!.Skip(skip);
+                                    _chunkPos += skip;
+                                    break;
+                                }
+                            }
+
+                            _chunkIndex = i;
+                            _chunkStream = GetChunkStream();
+                            _chunkPos = 0;
+
+                            // If the chunk happens to not be compressed this read will still result in a fast seek
+                            if ((ulong)_position != chunk.UncompressedOffset)
+                            {
+                                long skip = _position - (long)chunk.UncompressedOffset;
+                                _chunkStream.Skip(skip);
+                                _chunkPos = skip;
+                            }
+
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        public DmgBlockDataStream(Stream baseStream, DmgHeader header, BlkxTable table)
+        {
+            if (!baseStream.CanRead) throw new ArgumentException("Requires a readable stream", nameof(baseStream));
+            if (!baseStream.CanSeek) throw new ArgumentException("Requires a seekable stream", nameof(baseStream));
+
+            _baseStream = baseStream;
+            _header = header;
+            _table = table;
+
+            Length = 0;
+            foreach (var chunk in table.Chunks)
+            {
+                if (IsChunkValid(chunk))
+                    Length += (long)chunk.UncompressedLength;
+            }
+
+            _position = 0;
+            _chunkIndex = -1;
+            _chunkIndex = GetNextChunk();
+            _isEnded = _chunkIndex < 0;
+            if (!_isEnded) _chunkStream = GetChunkStream();
+            _chunkPos = 0;
+        }
+
+        private static bool IsChunkValid(BlkxChunk chunk)
+        {
+            return chunk.Type switch
+            {
+                BlkxChunkType.Zero => true,
+                BlkxChunkType.Uncompressed => true,
+                BlkxChunkType.Ignore => true,
+                BlkxChunkType.AdcCompressed => true,
+                BlkxChunkType.ZlibCompressed => true,
+                BlkxChunkType.Bz2Compressed => true,
+                _ => false
+            };
+        }
+
+        private int GetNextChunk()
+        {
+            int index = _chunkIndex;
+            bool isValid = false;
+            while (!isValid)
+            {
+                index++;
+                if (index >= _table.Chunks.Count) return -1;
+
+                var chunk = _table.Chunks[index];
+                if (chunk.Type == BlkxChunkType.Last) return -1;
+
+                isValid = IsChunkValid(chunk);
+            }
+            return index;
+        }
+
+        private Stream GetChunkStream()
+        {
+            if (_chunkIndex < 0)
+                throw new InvalidOperationException("Invalid chunk index");
+
+            var chunk = _table.Chunks[_chunkIndex];
+
+            // For our purposes, ignore behaves the same as zero
+            if ((chunk.Type == BlkxChunkType.Zero) || (chunk.Type == BlkxChunkType.Ignore))
+                return new ConstantStream(0, (long)chunk.UncompressedLength);
+
+            // We first create a sub-stream on the region of the base stream where the
+            // (possibly compressed) data is physically located at.
+            var subStream = new SeekableSubStream(_baseStream,
+                (long)(_header.DataForkOffset + _table.DataOffset + chunk.CompressedOffset),
+                (long)chunk.CompressedLength);
+
+            // Then we nest that sub-stream into the apropriate compressed stream.
+            return chunk.Type switch
+            {
+                BlkxChunkType.Uncompressed => subStream,
+                BlkxChunkType.AdcCompressed => new ADCStream(subStream, CompressionMode.Decompress),
+                BlkxChunkType.ZlibCompressed => new ZlibStream(subStream, CompressionMode.Decompress),
+                BlkxChunkType.Bz2Compressed => new BZip2Stream(subStream, CompressionMode.Decompress, false),
+                _ => throw new InvalidOperationException("Invalid chunk type")
+            };
+        }
+
+        // Decompresses the entire stream in memory for faster extraction.
+        // This is about two orders of magnitude faster than decompressing
+        // on-the-fly while extracting, but also eats RAM for breakfest.
+        public Stream Decompress()
+        {
+            // We have to load all the chunks into separate memory streams first
+            // because otherwise the decompression threads would block each other
+            // and actually be slower than just a single decompression thread.
+
+            var rawStreams = new Stream?[_table.Chunks.Count];
+            for (int i = 0; i < rawStreams.Length; i++)
+            {
+                var chunk = _table.Chunks[i];
+                if (IsChunkValid(chunk))
+                {
+                    if ((chunk.Type == BlkxChunkType.Zero) || (chunk.Type == BlkxChunkType.Ignore))
+                    {
+                        rawStreams[i] = new ConstantStream(0, (long)chunk.UncompressedLength);
+                    }
+                    else
+                    {
+                        var subStream = new SeekableSubStream(_baseStream,
+                        (long)(_header.DataForkOffset + _table.DataOffset + chunk.CompressedOffset),
+                        (long)chunk.CompressedLength);
+
+                        var memStream = new MemoryStream();
+                        subStream.CopyTo(memStream);
+                        memStream.Position = 0;
+                        rawStreams[i] = memStream;
+                    }
+                }
+                else
+                {
+                    rawStreams[i] = null;
+                }
+            }
+
+            // Now we can decompress the chunks multithreaded
+
+            var streams = new Stream?[_table.Chunks.Count];
+            Parallel.For(0, streams.Length, i =>
+            {
+                var rawStream = rawStreams[i];
+                if (rawStream is not null)
+                {
+                    var chunk = _table.Chunks[i];
+                    if ((chunk.Type == BlkxChunkType.Zero)
+                     || (chunk.Type == BlkxChunkType.Ignore)
+                     || (chunk.Type == BlkxChunkType.Uncompressed))
+                    {
+                        streams[i] = rawStream;
+                    }
+                    else
+                    {
+                        Stream compStream = chunk.Type switch
+                        {
+                            BlkxChunkType.AdcCompressed => new ADCStream(rawStream, CompressionMode.Decompress),
+                            BlkxChunkType.ZlibCompressed => new ZlibStream(rawStream, CompressionMode.Decompress),
+                            BlkxChunkType.Bz2Compressed => new BZip2Stream(rawStream, CompressionMode.Decompress, false),
+                            _ => throw new InvalidOperationException("Invalid chunk type")
+                        };
+
+                        var memStream = new MemoryStream();
+                        compStream.CopyTo(memStream);
+                        compStream.Dispose();
+
+                        memStream.Position = 0;
+                        streams[i] = memStream;
+                    }
+
+                    rawStream.Dispose();
+                    rawStreams[i] = null;
+                }
+                else
+                {
+                    streams[i] = null;
+                }
+            });
+
+            return new CompositeStream((IEnumerable<Stream>)streams.Where(s => s is not null));
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            if (_isEnded) return 0;
+
+            int readCount = _chunkStream!.Read(buffer, offset, count);
+            _chunkPos += readCount;
+
+            while (readCount < count)
+            {
+                // Current chunk has ended, so we have to continue reading from the next chunk.
+
+                _chunkIndex = GetNextChunk();
+                if (_chunkIndex < 0)
+                {
+                    // We have reached the last chunk
+
+                    _isEnded = true;
+                    _chunkPos = 0;
+                    _position += readCount;
+                    return readCount;
+                }
+
+                _chunkStream = GetChunkStream();
+                int rc = _chunkStream.Read(buffer, offset + readCount, count - readCount);
+                _chunkPos = rc;
+                readCount += rc;
+            }
+
+            _position += readCount;
+            return readCount;
+        }
+
+        public override void Flush()
+        { }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            switch (origin)
+            {
+                case SeekOrigin.Begin:
+                    Position = offset;
+                    break;
+
+                case SeekOrigin.Current:
+                    Position += offset;
+                    break;
+
+                case SeekOrigin.End:
+                    Position = Length - offset;
+                    break;
+            }
+
+            return Position;
+        }
+
+        public override void SetLength(long value)
+            => throw new NotSupportedException();
+
+        public override void Write(byte[] buffer, int offset, int count)
+            => throw new NotSupportedException();
+
+        protected override void Dispose(bool disposing)
+        { }
+    }
+}

src/SharpCompress/Common/Dmg/DmgEntry.cs

@@ -0,0 +1,52 @@
+using SharpCompress.Common.Dmg.HFS;
+using System;
+using System.Collections.Generic;
+
+namespace SharpCompress.Common.Dmg
+{
+    public abstract class DmgEntry : Entry
+    {
+        public override string Key { get; }
+        public override bool IsDirectory { get; }
+        public override long Size { get; }
+        public override long CompressedSize { get; }
+        public override CompressionType CompressionType { get; }
+        public override DateTime? LastModifiedTime { get; }
+        public override DateTime? CreatedTime { get; }
+        public override DateTime? LastAccessedTime { get; }
+        public override DateTime? ArchivedTime { get; }
+        
+        public override long Crc { get; } = 0; // Not stored
+        public override string? LinkTarget { get; } = null;
+        public override bool IsEncrypted { get; } = false;
+        public override bool IsSplitAfter { get; } = false;
+
+        internal override IEnumerable<FilePart> Parts { get; }
+
+        internal DmgEntry(HFSCatalogRecord record, string path, long size, DmgFilePart part)
+        {
+            Key = path;
+            IsDirectory = record.Type == HFSCatalogRecordType.Folder;
+            Size = CompressedSize = size;              // There is no way to get the actual compressed size or the compression type of
+            CompressionType = CompressionType.Unknown; // a file in a DMG archive since the files are nested inside the HFS partition.
+            Parts = part.AsEnumerable();
+
+            if (IsDirectory)
+            {
+                var folder = (HFSCatalogFolder)record;
+                LastModifiedTime = (folder.AttributeModDate > folder.ContentModDate) ? folder.AttributeModDate : folder.ContentModDate;
+                CreatedTime = folder.CreateDate;
+                LastAccessedTime = folder.AccessDate;
+                ArchivedTime = folder.BackupDate;
+            }
+            else
+            {
+                var file = (HFSCatalogFile)record;
+                LastModifiedTime = (file.AttributeModDate > file.ContentModDate) ? file.AttributeModDate : file.ContentModDate;
+                CreatedTime = file.CreateDate;
+                LastAccessedTime = file.AccessDate;
+                ArchivedTime = file.BackupDate;
+            }
+        }
+    }
+}

src/SharpCompress/Common/Dmg/DmgFilePart.cs

@@ -0,0 +1,21 @@
+using System.IO;
+
+namespace SharpCompress.Common.Dmg
+{
+    internal sealed class DmgFilePart : FilePart
+    {
+        private readonly Stream _stream;
+
+        internal override string FilePartName { get; }
+
+        public DmgFilePart(Stream stream, string fileName)
+            : base(new ArchiveEncoding())
+        {
+            _stream = stream;
+            FilePartName = fileName;
+        }
+
+        internal override Stream GetCompressedStream() => _stream;
+        internal override Stream? GetRawStream() => null;
+    }
+}

src/SharpCompress/Common/Dmg/DmgUtil.cs

@@ -0,0 +1,183 @@
+using SharpCompress.Common.Dmg.Headers;
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Text;
+using System.Xml.Linq;
+
+namespace SharpCompress.Common.Dmg
+{
+    internal static class DmgUtil
+    {
+        private const string MalformedXmlMessage = "Malformed XML block";
+
+        private static T[] ParseArray<T>(in XElement parent, in Func<XElement, T> parseElement)
+        {
+            var list = new List<T>();
+
+            foreach (var node in parent.Elements())
+                list.Add(parseElement(node));
+
+            return list.ToArray();
+        }
+
+        private static Dictionary<string, T> ParseDict<T>(in XElement parent, in Func<XElement, T> parseValue)
+        {
+            var dict = new Dictionary<string, T>();
+
+            string? key = null;
+            foreach (var node in parent.Elements())
+            {
+                if (string.Equals(node.Name.LocalName, "key", StringComparison.Ordinal))
+                {
+                    key = node.Value;
+                }
+                else if (key is not null)
+                {
+                    var value = parseValue(node);
+                    dict.Add(key, value);
+                    key = null;
+                }
+            }
+
+            return dict;
+        }
+
+        private static Dictionary<string, Dictionary<string, Dictionary<string, string>[]>> ParsePList(in XDocument doc)
+        {
+            var dictNode = doc.Root?.Element("dict");
+            if (dictNode is null) throw new InvalidFormatException(MalformedXmlMessage);
+
+            static Dictionary<string, string> ParseObject(XElement parent)
+                => ParseDict(parent, node => node.Value);
+
+            static Dictionary<string, string>[] ParseObjectArray(XElement parent)
+                => ParseArray(parent, ParseObject);
+
+            static Dictionary<string, Dictionary<string, string>[]> ParseSubDict(XElement parent)
+                => ParseDict(parent, ParseObjectArray);
+
+            return ParseDict(dictNode, ParseSubDict);
+        }
+
+        private static BlkxData CreateDataFromDict(in Dictionary<string, string> dict)
+        {
+            static bool TryParseHex(string? s, out uint value)
+            {
+                value = 0;
+                if (string.IsNullOrEmpty(s)) return false;
+
+                if (s!.StartsWith("0x", StringComparison.OrdinalIgnoreCase))
+                    s = s.Substring(2);
+
+                return uint.TryParse(s, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out value);
+            }
+
+            if (!dict.TryGetValue("ID", out string? idStr) || !int.TryParse(idStr, out int id))
+                throw new InvalidFormatException(MalformedXmlMessage);
+            if (!dict.TryGetValue("Name", out string? name))
+                throw new InvalidFormatException(MalformedXmlMessage);
+            if (!dict.TryGetValue("Attributes", out string? attribStr) || !TryParseHex(attribStr, out uint attribs))
+                throw new InvalidFormatException(MalformedXmlMessage);
+            if (!dict.TryGetValue("Data", out string? base64Data) || string.IsNullOrEmpty(base64Data))
+                throw new InvalidFormatException(MalformedXmlMessage);
+
+            try
+            {
+                var data = Convert.FromBase64String(base64Data);
+                if (!BlkxTable.TryRead(data, out var table))
+                    throw new InvalidFormatException("Invalid BLKX table");
+
+                return new BlkxData(id, name, attribs, table!);
+            }
+            catch (FormatException ex)
+            {
+                throw new InvalidFormatException(MalformedXmlMessage, ex);
+            }
+        }
+
+        public static DmgBlockDataStream? LoadHFSPartitionStream(Stream baseStream, DmgHeader header)
+        {
+            if ((header.XMLOffset + header.XMLLength) >= (ulong)baseStream.Length)
+                throw new IncompleteArchiveException("XML block incomplete");
+            if ((header.DataForkOffset + header.DataForkLength) >= (ulong)baseStream.Length)
+                throw new IncompleteArchiveException("Data block incomplete");
+
+            baseStream.Position = (long)header.XMLOffset;
+            var xmlBuffer = new byte[header.XMLLength];
+            baseStream.Read(xmlBuffer, 0, (int)header.XMLLength);
+            var xml = Encoding.ASCII.GetString(xmlBuffer);
+
+            var doc = XDocument.Parse(xml);
+            var pList = ParsePList(doc);
+            if (!pList.TryGetValue("resource-fork", out var resDict) || !resDict.TryGetValue("blkx", out var blkxDicts))
+                throw new InvalidFormatException(MalformedXmlMessage);
+
+            var objs = new BlkxData[blkxDicts.Length];
+            for (int i = 0; i < objs.Length; i++)
+                objs[i] = CreateDataFromDict(blkxDicts[i]);
+
+            // Index 0 is the protective MBR partition
+            // Index 1 is the GPT header
+            // Index 2 is the GPT partition table
+
+            try
+            {
+                var headerData = objs[1];
+                using var headerStream = new DmgBlockDataStream(baseStream, header, headerData.Table);
+                if (!GptHeader.TryRead(headerStream, out var gptHeader))
+                    throw new InvalidFormatException("Invalid GPT header");
+
+                var tableData = objs[2];
+                using var tableStream = new DmgBlockDataStream(baseStream, header, tableData.Table);
+                var gptTable = new GptPartitionEntry[gptHeader!.EntriesCount];
+                for (int i = 0; i < gptHeader.EntriesCount; i++)
+                    gptTable[i] = GptPartitionEntry.Read(tableStream);
+
+                foreach (var entry in gptTable)
+                {
+                    if (entry.TypeGuid == PartitionFormat.AppleHFS)
+                    {
+                        BlkxData? partitionData = null;
+                        for (int i = 3; i < objs.Length; i++)
+                        {
+                            if (objs[i].Name.StartsWith(entry.Name, StringComparison.Ordinal))
+                            {
+                                partitionData = objs[i];
+                                break;
+                            }
+                        }
+
+                        if (partitionData is null)
+                            throw new InvalidFormatException($"Missing partition {entry.Name}");
+
+                        return new DmgBlockDataStream(baseStream, header, partitionData.Table);
+                    }
+                }
+
+                return null;
+            }
+            catch (EndOfStreamException ex)
+            {
+                throw new IncompleteArchiveException("Partition incomplete", ex);
+            }
+        }
+
+        private sealed class BlkxData
+        {
+            public int Id { get; }
+            public string Name { get; }
+            public uint Attributes { get; }
+            public BlkxTable Table { get; }
+
+            public BlkxData(int id, string name, uint attributes, BlkxTable table)
+            {
+                Id = id;
+                Name = name;
+                Attributes = attributes;
+                Table = table;
+            }
+        }
+    }
+}

src/SharpCompress/Common/Dmg/DmgVolume.cs

@@ -0,0 +1,38 @@
+using SharpCompress.Archives.Dmg;
+using SharpCompress.Common.Dmg.Headers;
+using SharpCompress.Common.Dmg.HFS;
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg
+{
+    public class DmgVolume : Volume
+    {
+        private readonly DmgArchive _archive;
+        private readonly string _fileName;
+
+        internal DmgHeader Header { get; }
+
+        public DmgVolume(DmgArchive archive, Stream stream, string fileName, Readers.ReaderOptions readerOptions)
+            : base(stream, readerOptions)
+        {
+            _archive = archive;
+            _fileName = fileName;
+
+            long pos = stream.Length - DmgHeader.HeaderSize;
+            if (pos < 0) throw new InvalidFormatException("Invalid DMG volume");
+            stream.Position = pos;
+
+            if (DmgHeader.TryRead(stream, out var header)) Header = header!;
+            else throw new InvalidFormatException("Invalid DMG volume");
+        }
+
+        internal IEnumerable<DmgArchiveEntry> LoadEntries()
+        {
+            var partitionStream = DmgUtil.LoadHFSPartitionStream(Stream, Header);
+            if (partitionStream is null) return Array.Empty<DmgArchiveEntry>();
+            else return HFSUtil.LoadEntriesFromPartition(partitionStream, _fileName, _archive);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSCatalogRecord.cs

@@ -0,0 +1,336 @@
+using System;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSCatalogKey : HFSStructBase, IEquatable<HFSCatalogKey>, IComparable<HFSCatalogKey>, IComparable
+    {
+        private readonly StringComparer _comparer;
+
+        public uint ParentId { get; }
+
+        public string Name { get; }
+
+        private static StringComparer GetComparer(HFSKeyCompareType compareType, bool isHFSX)
+        {
+            if (isHFSX)
+            {
+                return compareType switch
+                {
+                    HFSKeyCompareType.CaseFolding => StringComparer.InvariantCultureIgnoreCase,
+                    HFSKeyCompareType.BinaryCompare => StringComparer.Ordinal,
+                    _ => StringComparer.InvariantCultureIgnoreCase
+                };
+            }
+            else
+            {
+                return StringComparer.InvariantCultureIgnoreCase;
+            }
+        }
+
+        public HFSCatalogKey(uint parentId, string name, HFSKeyCompareType compareType, bool isHFSX)
+        {
+            ParentId = parentId;
+            Name = name;
+            _comparer = GetComparer(compareType, isHFSX);
+        }
+
+        public HFSCatalogKey(byte[] key, HFSKeyCompareType compareType, bool isHFSX)
+        {
+            ReadOnlySpan<byte> data = key.AsSpan();
+            ParentId = ReadUInt32(ref data);
+            Name = ReadString(ref data, true);
+            _comparer = GetComparer(compareType, isHFSX);
+        }
+
+        public bool Equals(HFSCatalogKey? other)
+        {
+            if (other is null) return false;
+            else return (ParentId == other.ParentId) && _comparer.Equals(Name, other.Name);
+        }
+
+        public override bool Equals(object? obj)
+        {
+            if (obj is HFSCatalogKey other) return Equals(other);
+            else return false;
+        }
+
+        public int CompareTo(HFSCatalogKey? other)
+        {
+            if (other is null) return 1;
+
+            int result = ParentId.CompareTo(other.ParentId);
+            if (result == 0) result = _comparer.Compare(Name, other.Name);
+            return result;
+        }
+
+        public int CompareTo(object? obj)
+        {
+            if (obj is null) return 1;
+            else if (obj is HFSCatalogKey other) return CompareTo(other);
+            else throw new ArgumentException("Object is not of type CatalogKey", nameof(obj));
+        }
+
+        public override int GetHashCode()
+            => ParentId.GetHashCode() ^ _comparer.GetHashCode(Name);
+
+        public static bool operator ==(HFSCatalogKey? left, HFSCatalogKey? right)
+        {
+            if (left is null) return right is null;
+            else return left.Equals(right);
+        }
+
+        public static bool operator !=(HFSCatalogKey? left, HFSCatalogKey? right)
+        {
+            if (left is null) return right is not null;
+            else return !left.Equals(right);
+        }
+
+        public static bool operator <(HFSCatalogKey? left, HFSCatalogKey? right)
+        {
+            if (left is null) return right is not null;
+            else return left.CompareTo(right) < 0;
+        }
+
+        public static bool operator >(HFSCatalogKey? left, HFSCatalogKey? right)
+        {
+            if (left is null) return false;
+            else return left.CompareTo(right) > 0;
+        }
+
+        public static bool operator <=(HFSCatalogKey? left, HFSCatalogKey? right)
+        {
+            if (left is null) return true;
+            else return left.CompareTo(right) <= 0;
+        }
+
+        public static bool operator >=(HFSCatalogKey? left, HFSCatalogKey? right)
+        {
+            if (left is null) return right is null;
+            else return left.CompareTo(right) >= 0;
+        }
+    }
+
+    internal enum HFSCatalogRecordType : ushort
+    {
+        Folder = 0x0001,
+        File = 0x0002,
+        FolderThread = 0x0003,
+        FileThread = 0x0004
+    }
+
+    internal abstract class HFSCatalogRecord : HFSStructBase
+    {
+        public HFSCatalogRecordType Type { get; }
+
+        protected HFSCatalogRecord(HFSCatalogRecordType type)
+            => Type = type;
+
+        public static bool TryRead(ref ReadOnlySpan<byte> data, HFSKeyCompareType compareType, bool isHFSX, out HFSCatalogRecord? record)
+        {
+            record = null;
+
+            ushort rawType = ReadUInt16(ref data);
+            if (!Enum.IsDefined(typeof(HFSCatalogRecordType), rawType)) return false;
+
+            var type = (HFSCatalogRecordType)rawType;
+            switch (type)
+            {
+                case HFSCatalogRecordType.Folder:
+                    record = HFSCatalogFolder.Read(ref data);
+                    return true;
+
+                case HFSCatalogRecordType.File:
+                    record = HFSCatalogFile.Read(ref data);
+                    return true;
+
+                case HFSCatalogRecordType.FolderThread:
+                    record = HFSCatalogThread.Read(ref data, false, compareType, isHFSX);
+                    return true;
+
+                case HFSCatalogRecordType.FileThread:
+                    record = HFSCatalogThread.Read(ref data, true, compareType, isHFSX);
+                    return true;
+            }
+
+            return false;
+        }
+    }
+
+    internal sealed class HFSCatalogFolder : HFSCatalogRecord
+    {
+        public uint Valence { get; }
+        public uint FolderId { get; }
+        public DateTime CreateDate { get; }
+        public DateTime ContentModDate { get; }
+        public DateTime AttributeModDate { get; }
+        public DateTime AccessDate { get; }
+        public DateTime BackupDate { get; }
+        public HFSPermissions Permissions { get; }
+        public HFSFolderInfo Info { get; }
+        public uint TextEncoding { get; }
+
+        private HFSCatalogFolder(
+            uint valence,
+            uint folderId,
+            DateTime createDate,
+            DateTime contentModDate,
+            DateTime attributeModDate,
+            DateTime accessDate,
+            DateTime backupDate,
+            HFSPermissions permissions,
+            HFSFolderInfo info,
+            uint textEncoding)
+            : base(HFSCatalogRecordType.Folder)
+        {
+            Valence = valence;
+            FolderId = folderId;
+            CreateDate = createDate;
+            ContentModDate = contentModDate;
+            AttributeModDate = attributeModDate;
+            AccessDate = accessDate;
+            BackupDate = backupDate;
+            Permissions = permissions;
+            Info = info;
+            TextEncoding = textEncoding;
+        }
+
+        public static HFSCatalogFolder Read(ref ReadOnlySpan<byte> data)
+        {
+            _ = ReadUInt16(ref data); // reserved
+            uint valence = ReadUInt32(ref data);
+            uint folderId = ReadUInt32(ref data);
+            var createDate = ReadDate(ref data);
+            var contentModDate = ReadDate(ref data);
+            var attributeModDate = ReadDate(ref data);
+            var accessDate = ReadDate(ref data);
+            var backupDate = ReadDate(ref data);
+            var permissions = HFSPermissions.Read(ref data);
+            var info = HFSFolderInfo.Read(ref data);
+            uint textEncoding = ReadUInt32(ref data);
+            _ = ReadUInt32(ref data); // reserved
+
+            return new HFSCatalogFolder(
+                valence,
+                folderId,
+                createDate,
+                contentModDate,
+                attributeModDate,
+                accessDate,
+                backupDate,
+                permissions,
+                info,
+                textEncoding);
+        }
+    }
+
+    internal enum HFSFileFlags : ushort
+    {
+        LockedBit = 0x0000,
+        LockedMask = 0x0001,
+        ThreadExistsBit = 0x0001,
+        ThreadExistsMask = 0x0002
+    }
+
+    internal sealed class HFSCatalogFile : HFSCatalogRecord
+    {
+        public HFSFileFlags Flags { get; }
+        public uint FileId { get; }
+        public DateTime CreateDate { get; }
+        public DateTime ContentModDate { get; }
+        public DateTime AttributeModDate { get; }
+        public DateTime AccessDate { get; }
+        public DateTime BackupDate { get; }
+        public HFSPermissions Permissions { get; }
+        public HFSFileInfo Info { get; }
+        public uint TextEncoding { get; }
+
+        public HFSForkData DataFork { get; }
+        public HFSForkData ResourceFork { get; }
+
+        private HFSCatalogFile(
+            HFSFileFlags flags,
+            uint fileId,
+            DateTime createDate,
+            DateTime contentModDate,
+            DateTime attributeModDate,
+            DateTime accessDate,
+            DateTime backupDate,
+            HFSPermissions permissions,
+            HFSFileInfo info,
+            uint textEncoding,
+            HFSForkData dataFork,
+            HFSForkData resourceFork)
+            :base(HFSCatalogRecordType.File)
+        {
+            Flags = flags;
+            FileId = fileId;
+            CreateDate = createDate;
+            ContentModDate = contentModDate;
+            AttributeModDate = attributeModDate;
+            AccessDate = accessDate;
+            BackupDate = backupDate;
+            Permissions = permissions;
+            Info = info;
+            TextEncoding = textEncoding;
+            DataFork = dataFork;
+            ResourceFork = resourceFork;
+        }
+
+        public static HFSCatalogFile Read(ref ReadOnlySpan<byte> data)
+        {
+            var flags = (HFSFileFlags)ReadUInt16(ref data);
+            _ = ReadUInt32(ref data); // reserved
+            uint fileId = ReadUInt32(ref data);
+            var createDate = ReadDate(ref data);
+            var contentModDate = ReadDate(ref data);
+            var attributeModDate = ReadDate(ref data);
+            var accessDate = ReadDate(ref data);
+            var backupDate = ReadDate(ref data);
+            var permissions = HFSPermissions.Read(ref data);
+            var info = HFSFileInfo.Read(ref data);
+            uint textEncoding = ReadUInt32(ref data);
+            _ = ReadUInt32(ref data); // reserved
+
+            var dataFork = HFSForkData.Read(ref data);
+            var resourceFork = HFSForkData.Read(ref data);
+
+            return new HFSCatalogFile(
+                flags,
+                fileId,
+                createDate,
+                contentModDate,
+                attributeModDate,
+                accessDate,
+                backupDate,
+                permissions,
+                info,
+                textEncoding,
+                dataFork,
+                resourceFork);
+        }
+    }
+
+    internal sealed class HFSCatalogThread : HFSCatalogRecord
+    {
+        public uint ParentId { get; }
+        public string NodeName { get; }
+        public HFSCatalogKey CatalogKey { get; }
+
+        private HFSCatalogThread(uint parentId, string nodeName, bool isFile, HFSKeyCompareType compareType, bool isHFSX)
+            : base(isFile ? HFSCatalogRecordType.FileThread : HFSCatalogRecordType.FolderThread)
+        {
+            ParentId = parentId;
+            NodeName = nodeName;
+            CatalogKey = new HFSCatalogKey(ParentId, NodeName, compareType, isHFSX);
+        }
+
+        public static HFSCatalogThread Read(ref ReadOnlySpan<byte> data, bool isFile, HFSKeyCompareType compareType, bool isHFSX)
+        {
+            _ = ReadInt16(ref data); // reserved
+            uint parentId = ReadUInt32(ref data);
+            string nodeName = ReadString(ref data, true);
+
+            return new HFSCatalogThread(parentId, nodeName, isFile, compareType, isHFSX);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSExtentDescriptor.cs

@@ -0,0 +1,31 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSExtentDescriptor : HFSStructBase
+    {
+        public uint StartBlock { get; }
+        public uint BlockCount { get; }
+
+        private HFSExtentDescriptor(uint startBlock, uint blockCount)
+        {
+            StartBlock = startBlock;
+            BlockCount = blockCount;
+        }
+
+        public static HFSExtentDescriptor Read(Stream stream)
+        {
+            return new HFSExtentDescriptor(
+                ReadUInt32(stream),
+                ReadUInt32(stream));
+        }
+
+        public static HFSExtentDescriptor Read(ref ReadOnlySpan<byte> data)
+        {
+            return new HFSExtentDescriptor(
+                ReadUInt32(ref data),
+                ReadUInt32(ref data));
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSExtentRecord.cs

@@ -0,0 +1,115 @@
+using System;
+using System.Collections.Generic;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSExtentKey : HFSStructBase, IEquatable<HFSExtentKey>, IComparable<HFSExtentKey>, IComparable
+    {
+        public byte ForkType { get; }
+        public uint FileId { get; }
+        public uint StartBlock { get; }
+
+        public HFSExtentKey(byte forkType, uint fileId, uint startBlock)
+        {
+            ForkType = forkType;
+            FileId = fileId;
+            StartBlock = startBlock;
+        }
+
+        public HFSExtentKey(byte[] key)
+        {
+            ReadOnlySpan<byte> data = key.AsSpan();
+            ForkType = ReadUInt8(ref data);
+            _ = ReadUInt8(ref data); // padding
+            FileId = ReadUInt32(ref data);
+            StartBlock = ReadUInt32(ref data);
+        }
+
+        public bool Equals(HFSExtentKey? other)
+        {
+            if (other is null) return false;
+            else return (ForkType == other.ForkType) && (FileId == other.FileId) && (StartBlock == other.StartBlock);
+        }
+
+        public override bool Equals(object? obj)
+        {
+            if (obj is HFSExtentKey other) return Equals(other);
+            else return false;
+        }
+
+        public int CompareTo(HFSExtentKey? other)
+        {
+            if (other is null) return 1;
+
+            int result = FileId.CompareTo(other.FileId);
+            if (result == 0) result = ForkType.CompareTo(other.ForkType);
+            if (result == 0) result = StartBlock.CompareTo(other.StartBlock);
+            return result;
+        }
+
+        public int CompareTo(object? obj)
+        {
+            if (obj is null) return 1;
+            else if (obj is HFSExtentKey other) return CompareTo(other);
+            else throw new ArgumentException("Object is not of type ExtentKey", nameof(obj));
+        }
+
+        public override int GetHashCode()
+            => ForkType.GetHashCode() ^ FileId.GetHashCode() ^ StartBlock.GetHashCode();
+
+        public static bool operator ==(HFSExtentKey? left, HFSExtentKey? right)
+        {
+            if (left is null) return right is null;
+            else return left.Equals(right);
+        }
+
+        public static bool operator !=(HFSExtentKey? left, HFSExtentKey? right)
+        {
+            if (left is null) return right is not null;
+            else return !left.Equals(right);
+        }
+
+        public static bool operator <(HFSExtentKey? left, HFSExtentKey? right)
+        {
+            if (left is null) return right is not null;
+            else return left.CompareTo(right) < 0;
+        }
+
+        public static bool operator >(HFSExtentKey? left, HFSExtentKey? right)
+        {
+            if (left is null) return false;
+            else return left.CompareTo(right) > 0;
+        }
+
+        public static bool operator <=(HFSExtentKey? left, HFSExtentKey? right)
+        {
+            if (left is null) return true;
+            else return left.CompareTo(right) <= 0;
+        }
+
+        public static bool operator >=(HFSExtentKey? left, HFSExtentKey? right)
+        {
+            if (left is null) return right is null;
+            else return left.CompareTo(right) >= 0;
+        }
+    }
+
+    internal sealed class HFSExtentRecord : HFSStructBase
+    {
+        private const int ExtentCount = 8;
+
+        public IReadOnlyList<HFSExtentDescriptor> Extents { get; }
+
+        private HFSExtentRecord(IReadOnlyList<HFSExtentDescriptor> extents)
+            => Extents = extents;
+
+        public static HFSExtentRecord Read(ref ReadOnlySpan<byte> data)
+        {
+            var extents = new HFSExtentDescriptor[ExtentCount];
+            for (int i = 0; i < ExtentCount; i++)
+                extents[i] = HFSExtentDescriptor.Read(ref data);
+
+            return new HFSExtentRecord(extents);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSFinderInfo.cs

@@ -0,0 +1,145 @@
+using System;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal struct HFSPoint
+    {
+        public short V;
+        public short H;
+    }
+
+    internal struct HFSRect
+    {
+        public short Top;
+        public short Left;
+        public short Bottom;
+        public short Right;
+    }
+
+    [Flags]
+    internal enum HFSFinderFlags : ushort
+    {
+        None = 0x0000,
+
+        IsOnDesk = 0x0001,      /* Files and folders (System 6) */
+        Color = 0x000E,         /* Files and folders */
+        IsShared = 0x0040,      /* Files only (Applications only) If */
+                                /* clear, the application needs */
+                                /* to write to its resource fork, */
+                                /* and therefore cannot be shared */
+                                /* on a server */
+        HasNoINITs = 0x0080,    /* Files only (Extensions/Control */
+                                /* Panels only) */
+                                /* This file contains no INIT resource */
+        HasBeenInited = 0x0100, /* Files only.  Clear if the file */
+                                /* contains desktop database resources */
+                                /* ('BNDL', 'FREF', 'open', 'kind'...) */
+                                /* that have not been added yet.  Set */
+                                /* only by the Finder. */
+                                /* Reserved for folders */
+        HasCustomIcon = 0x0400, /* Files and folders */
+        IsStationery = 0x0800,  /* Files only */
+        NameLocked = 0x1000,    /* Files and folders */
+        HasBundle = 0x2000,     /* Files only */
+        IsInvisible = 0x4000,   /* Files and folders */
+        IsAlias = 0x8000        /* Files only */
+    }
+
+    [Flags]
+    internal enum HFSExtendedFinderFlags : ushort
+    {
+        None = 0x0000,
+
+        ExtendedFlagsAreInvalid = 0x8000, /* The other extended flags */
+                                          /* should be ignored */
+        HasCustomBadge = 0x0100,          /* The file or folder has a */
+                                          /* badge resource */
+        HasRoutingInfo = 0x0004           /* The file contains routing */
+                                          /* info resource */
+    }
+
+    internal sealed class HFSFileInfo : HFSStructBase
+    {
+        public string FileType { get; }             /* The type of the file */
+        public string FileCreator { get; }          /* The file's creator */
+        public HFSFinderFlags FinderFlags { get; }
+        public HFSPoint Location { get; }           /* File's location in the folder. */
+        public HFSExtendedFinderFlags ExtendedFinderFlags { get; }
+        public int PutAwayFolderId { get; }
+
+        private HFSFileInfo(
+            string fileType,
+            string fileCreator,
+            HFSFinderFlags finderFlags,
+            HFSPoint location,
+            HFSExtendedFinderFlags extendedFinderFlags,
+            int putAwayFolderId)
+        {
+            FileType = fileType;
+            FileCreator = fileCreator;
+            FinderFlags = finderFlags;
+            Location = location;
+            ExtendedFinderFlags = extendedFinderFlags;
+            PutAwayFolderId = putAwayFolderId;
+        }
+
+        public static HFSFileInfo Read(ref ReadOnlySpan<byte> data)
+        {
+            string fileType = ReadOSType(ref data);
+            string fileCreator = ReadOSType(ref data);
+            var finderFlags = (HFSFinderFlags)ReadUInt16(ref data);
+            var location = ReadPoint(ref data);
+            _ = ReadUInt16(ref data); // reserved
+            data = data.Slice(4 * sizeof(short)); // reserved
+            var extendedFinderFlags = (HFSExtendedFinderFlags)ReadUInt16(ref data);
+            _ = ReadInt16(ref data); // reserved
+            int putAwayFolderId = ReadInt32(ref data);
+
+            return new HFSFileInfo(fileType, fileCreator, finderFlags, location, extendedFinderFlags, putAwayFolderId);
+        }
+    }
+
+    internal sealed class HFSFolderInfo : HFSStructBase
+    {
+        public HFSRect WindowBounds { get; }    /* The position and dimension of the */
+                                                /* folder's window */
+        public HFSFinderFlags FinderFlags { get; }
+        public HFSPoint Location { get; }       /* Folder's location in the parent */
+                                                /* folder. If set to {0, 0}, the Finder */
+                                                /* will place the item automatically */
+        public HFSPoint ScrollPosition { get; } /* Scroll position (for icon views) */
+        public HFSExtendedFinderFlags ExtendedFinderFlags { get; }
+        public int PutAwayFolderId { get; }
+
+        private HFSFolderInfo(
+            HFSRect windowBounds,
+            HFSFinderFlags finderFlags,
+            HFSPoint location,
+            HFSPoint scrollPosition,
+            HFSExtendedFinderFlags extendedFinderFlags,
+            int putAwayFolderId)
+        {
+            WindowBounds = windowBounds;
+            FinderFlags = finderFlags;
+            Location = location;
+            ScrollPosition = scrollPosition;
+            ExtendedFinderFlags = extendedFinderFlags;
+            PutAwayFolderId = putAwayFolderId;
+        }
+
+        public static HFSFolderInfo Read(ref ReadOnlySpan<byte> data)
+        {
+            var windowBounds = ReadRect(ref data);
+            var finderFlags = (HFSFinderFlags)ReadUInt16(ref data);
+            var location = ReadPoint(ref data);
+            _ = ReadUInt16(ref data); // reserved
+            var scrollPosition = ReadPoint(ref data);
+            _ = ReadInt32(ref data); // reserved
+            var extendedFinderFlags = (HFSExtendedFinderFlags)ReadUInt16(ref data);
+            _ = ReadInt16(ref data); // reserved
+            int putAwayFolderId = ReadInt32(ref data);
+
+            return new HFSFolderInfo(windowBounds, finderFlags, location, scrollPosition, extendedFinderFlags, putAwayFolderId);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSForkData.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSForkData : HFSStructBase
+    {
+        private const int ExtentCount = 8;
+
+        public ulong LogicalSize { get; }
+        public uint ClumpSize { get; }
+        public uint TotalBlocks { get; }
+        public IReadOnlyList<HFSExtentDescriptor> Extents { get; }
+
+        private HFSForkData(ulong logicalSize, uint clumpSize, uint totalBlocks, IReadOnlyList<HFSExtentDescriptor> extents)
+        {
+            LogicalSize = logicalSize;
+            ClumpSize = clumpSize;
+            TotalBlocks = totalBlocks;
+            Extents = extents;
+        }
+
+        public static HFSForkData Read(Stream stream)
+        {
+            ulong logicalSize = ReadUInt64(stream);
+            uint clumpSize = ReadUInt32(stream);
+            uint totalBlocks = ReadUInt32(stream);
+
+            var extents = new HFSExtentDescriptor[ExtentCount];
+            for (int i = 0; i < ExtentCount; i++)
+                extents[i] = HFSExtentDescriptor.Read(stream);
+
+            return new HFSForkData(logicalSize, clumpSize, totalBlocks, extents);
+        }
+
+        public static HFSForkData Read(ref ReadOnlySpan<byte> data)
+        {
+            ulong logicalSize = ReadUInt64(ref data);
+            uint clumpSize = ReadUInt32(ref data);
+            uint totalBlocks = ReadUInt32(ref data);
+
+            var extents = new HFSExtentDescriptor[ExtentCount];
+            for (int i = 0; i < ExtentCount; i++)
+                extents[i] = HFSExtentDescriptor.Read(ref data);
+
+            return new HFSForkData(logicalSize, clumpSize, totalBlocks, extents);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSForkStream.cs

@@ -0,0 +1,196 @@
+using SharpCompress.IO;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSForkStream : Stream
+    {
+        private readonly Stream _baseStream;
+        private readonly HFSVolumeHeader _volumeHeader;
+        private readonly IReadOnlyList<HFSExtentDescriptor> _extents;
+        private long _position;
+        private bool _isEnded;
+        private int _extentIndex;
+        private Stream? _extentStream;
+
+        public override bool CanRead => true;
+        public override bool CanWrite => false;
+        public override bool CanSeek => true;
+        public override long Length { get; }
+
+        public override long Position
+        {
+            get => _position;
+            set
+            {
+                if ((value < 0) || (value > Length)) throw new ArgumentOutOfRangeException(nameof(value));
+
+                if (value == Length)
+                {
+                    // End of the stream
+
+                    _position = Length;
+                    _isEnded = true;
+                    _extentIndex = -1;
+                    _extentStream = null;
+                }
+                else if (value != _position)
+                {
+                    _position = value;
+
+                    // We first have to determine in which extent we are now, then we seek to the exact position in that extent.
+
+                    long offsetInExtent = _position;
+                    for (int i = 0; i < _extents.Count; i++)
+                    {
+                        var extent = _extents[i];
+                        long extentSize = extent.BlockCount * _volumeHeader.BlockSize;
+                        if (extentSize < offsetInExtent)
+                        {
+                            if (i == _extentIndex)
+                            {
+                                // We are in the same extent so just seek to the correct position
+                                _extentStream!.Position = offsetInExtent;
+                            }
+                            else
+                            {
+                                _extentIndex = i;
+                                _extentStream = GetExtentStream();
+                                _extentStream.Position = offsetInExtent;
+                            }
+
+                            break;
+                        }
+                        else
+                        {
+                            offsetInExtent -= extentSize;
+                        }
+                    }
+                }
+            }
+        }
+
+        public HFSForkStream(Stream baseStream, HFSVolumeHeader volumeHeader, HFSForkData forkData)
+        {
+            _baseStream = baseStream;
+            _volumeHeader = volumeHeader;
+            _extents = forkData.Extents;
+            Length = (long)forkData.LogicalSize;
+
+            _position = 0;
+            _extentIndex = -1;
+            _extentIndex = GetNextExtent();
+            _isEnded = _extentIndex < 0;
+            if (!_isEnded) _extentStream = GetExtentStream();
+        }
+
+        public HFSForkStream(
+            Stream baseStream, HFSVolumeHeader volumeHeader, HFSForkData forkData, uint fileId,
+            IReadOnlyDictionary<HFSExtentKey, HFSExtentRecord> extents)
+        {
+            _baseStream = baseStream;
+            _volumeHeader = volumeHeader;
+            Length = (long)forkData.LogicalSize;
+
+            uint blocks = (uint)forkData.Extents.Sum(e => e.BlockCount);
+            var totalExtents = new List<HFSExtentDescriptor>(forkData.Extents);
+            _extents = totalExtents;
+
+            var nextKey = new HFSExtentKey(0, fileId, blocks);
+            while (extents.TryGetValue(nextKey, out var record))
+            {
+                blocks += (uint)record.Extents.Sum(e => e.BlockCount);
+                totalExtents.AddRange(record.Extents);
+
+                nextKey = new HFSExtentKey(0, fileId, blocks);
+            }
+
+            _position = 0;
+            _extentIndex = -1;
+            _extentIndex = GetNextExtent();
+            _isEnded = _extentIndex < 0;
+            if (!_isEnded) _extentStream = GetExtentStream();
+        }
+
+        private int GetNextExtent()
+        {
+            int index = _extentIndex + 1;
+            if (index >= _extents.Count) return -1;
+
+            var extent = _extents[index];
+            if ((extent.StartBlock == 0) && (extent.BlockCount == 0)) return -1;
+            return index;
+        }
+
+        private Stream GetExtentStream()
+        {
+            if (_extentIndex < 0)
+                throw new InvalidOperationException("Invalid extent index");
+
+            var extent = _extents[_extentIndex];
+            return new HFSExtentStream(_baseStream, _volumeHeader, extent);
+        }
+
+        public override void Flush()
+        { }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            if (_isEnded) return 0;
+
+            count = (int)Math.Min(count, Length - Position);
+            int readCount = _extentStream!.Read(buffer, offset, count);
+            while (readCount < count)
+            {
+                _extentIndex = GetNextExtent();
+                if (_extentIndex < 0)
+                {
+                    _isEnded = true;
+                    return readCount;
+                }
+
+                _extentStream = GetExtentStream();
+                readCount += _extentStream.Read(buffer, offset + readCount, count - readCount);
+            }
+
+            _position += readCount;
+            return readCount;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            switch (origin)
+            {
+                case SeekOrigin.Begin:
+                    Position = offset;
+                    break;
+
+                case SeekOrigin.Current:
+                    Position += offset;
+                    break;
+
+                case SeekOrigin.End:
+                    Position = Length - offset;
+                    break;
+            }
+
+            return Position;
+        }
+
+        public override void SetLength(long value)
+            => throw new NotSupportedException();
+
+        public override void Write(byte[] buffer, int offset, int count)
+            => throw new NotSupportedException();
+
+        private sealed class HFSExtentStream : SeekableSubStream
+        {
+            public HFSExtentStream(Stream stream, HFSVolumeHeader volumeHeader, HFSExtentDescriptor extent)
+                : base(stream, (long)extent.StartBlock * volumeHeader.BlockSize, (long)extent.BlockCount * volumeHeader.BlockSize)
+            { }
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSKeyedRecord.cs

@@ -0,0 +1,91 @@
+using System;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal abstract class HFSKeyedRecord : HFSStructBase
+    {
+        private readonly HFSKeyCompareType _compareType;
+        private readonly bool _isHFSX;
+        private HFSCatalogKey? _catalogKey;
+        private HFSExtentKey? _extentKey;
+
+        public byte[] Key { get; }
+
+        public HFSCatalogKey GetCatalogKey() => _catalogKey ??= new HFSCatalogKey(Key, _compareType, _isHFSX);
+
+        public HFSExtentKey GetExtentKey() => _extentKey ??= new HFSExtentKey(Key);
+
+        protected HFSKeyedRecord(byte[] key, HFSKeyCompareType compareType, bool isHFSX)
+        {
+            Key = key;
+            _compareType = compareType;
+            _isHFSX = isHFSX;
+        }
+    }
+
+    internal sealed class HFSPointerRecord : HFSKeyedRecord
+    {
+        public uint NodeNumber { get; }
+
+        private HFSPointerRecord(byte[] key, uint nodeNumber, HFSKeyCompareType compareType, bool isHFSX)
+            : base(key, compareType, isHFSX)
+        {
+            NodeNumber = nodeNumber;
+        }
+
+        public static HFSPointerRecord Read(ref ReadOnlySpan<byte> data, HFSTreeHeaderRecord headerRecord, bool isHFSX)
+        {
+            bool isBigKey = headerRecord.Attributes.HasFlag(HFSTreeAttributes.BigKeys);
+            ushort keyLength = isBigKey ? ReadUInt16(ref data) : ReadUInt8(ref data);
+            if (!headerRecord.Attributes.HasFlag(HFSTreeAttributes.VariableIndexKeys)) keyLength = headerRecord.MaxKeyLength;
+            int keySize = (isBigKey ? 2 : 1) + keyLength;
+
+            var key = new byte[keyLength];
+            data.Slice(0, keyLength).CopyTo(key);
+            data = data.Slice(keyLength);
+
+            // data is always aligned to 2 bytes
+            if (keySize % 2 == 1) data = data.Slice(1);
+
+            uint nodeNumber = ReadUInt32(ref data);
+
+            return new HFSPointerRecord(key, nodeNumber, headerRecord.KeyCompareType, isHFSX);
+        }
+    }
+
+    internal sealed class HFSDataRecord : HFSKeyedRecord
+    {
+        public byte[] Data { get; }
+
+        private HFSDataRecord(byte[] key, byte[] data, HFSKeyCompareType compareType, bool isHFSX)
+            : base(key, compareType, isHFSX)
+        {
+            Data = data;
+        }
+
+        public static HFSDataRecord Read(ref ReadOnlySpan<byte> data, int size, HFSTreeHeaderRecord headerRecord, bool isHFSX)
+        {
+            bool isBigKey = headerRecord.Attributes.HasFlag(HFSTreeAttributes.BigKeys);
+            ushort keyLength = isBigKey ? ReadUInt16(ref data) : ReadUInt8(ref data);
+            int keySize = (isBigKey ? 2 : 1) + keyLength;
+            size -= keySize;
+
+            var key = new byte[keyLength];
+            data.Slice(0, keyLength).CopyTo(key);
+            data = data.Slice(keyLength);
+
+            // data is always aligned to 2 bytes
+            if (keySize % 2 == 1)
+            {
+                data = data.Slice(1);
+                size--;
+            }
+
+            var structData = new byte[size];
+            data.Slice(0, size).CopyTo(structData);
+            data = data.Slice(size);
+
+            return new HFSDataRecord(key, structData, headerRecord.KeyCompareType, isHFSX);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSPermissions.cs

@@ -0,0 +1,35 @@
+using System;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSPermissions : HFSStructBase
+    {
+        public uint OwnerID { get; }
+        public uint GroupID { get; }
+        public byte AdminFlags { get; }
+        public byte OwnerFlags { get; }
+        public ushort FileMode { get; }
+        public uint Special { get; }
+
+        private HFSPermissions(uint ownerID, uint groupID, byte adminFlags, byte ownerFlags, ushort fileMode, uint special)
+        {
+            OwnerID = ownerID;
+            GroupID = groupID;
+            AdminFlags = adminFlags;
+            OwnerFlags = ownerFlags;
+            FileMode = fileMode;
+            Special = special;
+        }
+
+        public static HFSPermissions Read(ref ReadOnlySpan<byte> data)
+        {
+            return new HFSPermissions(
+                ReadUInt32(ref data),
+                ReadUInt32(ref data),
+                ReadUInt8(ref data),
+                ReadUInt8(ref data),
+                ReadUInt16(ref data),
+                ReadUInt32(ref data));
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSStructBase.cs

@@ -0,0 +1,187 @@
+using System;
+using System.Buffers.Binary;
+using System.IO;
+using System.Text;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal abstract class HFSStructBase
+    {
+        private const int StringSize = 510;
+        private const int OSTypeSize = 4;
+        private static readonly DateTime Epoch = new DateTime(1904, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+        private static readonly byte[] _buffer = new byte[StringSize];
+
+        protected static byte ReadUInt8(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(byte)) != sizeof(byte))
+                throw new EndOfStreamException();
+
+            return _buffer[0];
+        }
+
+        protected static ushort ReadUInt16(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(ushort)) != sizeof(ushort))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadUInt16BigEndian(_buffer);
+        }
+
+        protected static short ReadInt16(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(short)) != sizeof(short))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadInt16BigEndian(_buffer);
+        }
+
+        protected static uint ReadUInt32(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(uint)) != sizeof(uint))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadUInt32BigEndian(_buffer);
+        }
+
+        protected static int ReadInt32(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(int)) != sizeof(int))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadInt32BigEndian(_buffer);
+        }
+
+        protected static ulong ReadUInt64(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(ulong)) != sizeof(ulong))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadUInt64BigEndian(_buffer);
+        }
+
+        protected static long ReadInt64(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(long)) != sizeof(long))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadInt64BigEndian(_buffer);
+        }
+
+        protected static string ReadString(Stream stream)
+        {
+            ushort length = ReadUInt16(stream);
+            if (stream.Read(_buffer, 0, StringSize) != StringSize)
+                throw new EndOfStreamException();
+            return Encoding.Unicode.GetString(_buffer, 0, Math.Min(length * 2, StringSize));
+        }
+
+        protected static DateTime ReadDate(Stream stream)
+        {
+            uint seconds = ReadUInt32(stream);
+            var span = TimeSpan.FromSeconds(seconds);
+            return Epoch + span;
+        }
+
+        protected static byte ReadUInt8(ref ReadOnlySpan<byte> data)
+        {
+            byte val = data[0];
+            data = data.Slice(sizeof(byte));
+            return val;
+        }
+
+        protected static ushort ReadUInt16(ref ReadOnlySpan<byte> data)
+        {
+            ushort val = BinaryPrimitives.ReadUInt16BigEndian(data);
+            data = data.Slice(sizeof(ushort));
+            return val;
+        }
+
+        protected static short ReadInt16(ref ReadOnlySpan<byte> data)
+        {
+            short val = BinaryPrimitives.ReadInt16BigEndian(data);
+            data = data.Slice(sizeof(short));
+            return val;
+        }
+
+        protected static uint ReadUInt32(ref ReadOnlySpan<byte> data)
+        {
+            uint val = BinaryPrimitives.ReadUInt32BigEndian(data);
+            data = data.Slice(sizeof(uint));
+            return val;
+        }
+
+        protected static int ReadInt32(ref ReadOnlySpan<byte> data)
+        {
+            int val = BinaryPrimitives.ReadInt32BigEndian(data);
+            data = data.Slice(sizeof(int));
+            return val;
+        }
+
+        protected static ulong ReadUInt64(ref ReadOnlySpan<byte> data)
+        {
+            ulong val = BinaryPrimitives.ReadUInt64BigEndian(data);
+            data = data.Slice(sizeof(ulong));
+            return val;
+        }
+
+        protected static long ReadInt64(ref ReadOnlySpan<byte> data)
+        {
+            long val = BinaryPrimitives.ReadInt64BigEndian(data);
+            data = data.Slice(sizeof(long));
+            return val;
+        }
+
+        protected static string ReadString(ref ReadOnlySpan<byte> data, bool truncate)
+        {
+            int length = ReadUInt16(ref data);
+            if (truncate)
+            {
+                length = Math.Min(length * 2, StringSize);
+                data.Slice(0, length).CopyTo(_buffer);
+                data = data.Slice(length);
+                return Encoding.BigEndianUnicode.GetString(_buffer, 0, length);
+            }
+            else
+            {
+                data.Slice(0, StringSize).CopyTo(_buffer);
+                data = data.Slice(StringSize);
+                return Encoding.BigEndianUnicode.GetString(_buffer, 0, Math.Min(length * 2, StringSize));
+            }
+        }
+
+        protected static DateTime ReadDate(ref ReadOnlySpan<byte> data)
+        {
+            uint seconds = ReadUInt32(ref data);
+            var span = TimeSpan.FromSeconds(seconds);
+            return Epoch + span;
+        }
+
+        protected static string ReadOSType(ref ReadOnlySpan<byte> data)
+        {
+            data.Slice(0, OSTypeSize).CopyTo(_buffer);
+            data = data.Slice(OSTypeSize);
+            return Encoding.ASCII.GetString(_buffer, 0, OSTypeSize).NullTerminate();
+        }
+
+        protected static HFSPoint ReadPoint(ref ReadOnlySpan<byte> data)
+        {
+            return new HFSPoint()
+            {
+                V = ReadInt16(ref data),
+                H = ReadInt16(ref data)
+            };
+        }
+
+        protected static HFSRect ReadRect(ref ReadOnlySpan<byte> data)
+        {
+            return new HFSRect()
+            {
+                Top = ReadInt16(ref data),
+                Left = ReadInt16(ref data),
+                Bottom = ReadInt16(ref data),
+                Right = ReadInt16(ref data)
+            };
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSTreeHeaderRecord.cs

@@ -0,0 +1,108 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal enum HFSTreeType : byte
+    {
+        HFS = 0,         // control file
+        User = 128,      // user btree type starts from 128
+        Reserved = 255
+    }
+
+    internal enum HFSKeyCompareType : byte
+    {
+        CaseFolding = 0xCF,	  // case-insensitive
+        BinaryCompare = 0xBC  // case-sensitive
+    }
+
+    [Flags]
+    internal enum HFSTreeAttributes : uint
+    {
+        None = 0x00000000,
+        BadClose = 0x00000001,
+        BigKeys = 0x00000002,
+        VariableIndexKeys = 0x00000004
+    }
+
+    internal sealed class HFSTreeHeaderRecord : HFSStructBase
+    {
+        public ushort TreeDepth;
+        public uint RootNode;
+        public uint LeafRecords;
+        public uint FirstLeafNode;
+        public uint LastLeafNode;
+        public ushort NodeSize;
+        public ushort MaxKeyLength;
+        public uint TotalNodes;
+        public uint FreeNodes;
+        public uint ClumpSize;
+        public HFSTreeType TreeType;
+        public HFSKeyCompareType KeyCompareType;
+        public HFSTreeAttributes Attributes;
+
+        private HFSTreeHeaderRecord(
+            ushort treeDepth,
+            uint rootNode,
+            uint leafRecords,
+            uint firstLeafNode,
+            uint lastLeafNode,
+            ushort nodeSize,
+            ushort maxKeyLength,
+            uint totalNodes,
+            uint freeNodes,
+            uint clumpSize,
+            HFSTreeType treeType,
+            HFSKeyCompareType keyCompareType,
+            HFSTreeAttributes attributes)
+        {
+            TreeDepth = treeDepth;
+            RootNode = rootNode;
+            LeafRecords = leafRecords;
+            FirstLeafNode = firstLeafNode;
+            LastLeafNode = lastLeafNode;
+            NodeSize = nodeSize;
+            MaxKeyLength = maxKeyLength;
+            TotalNodes = totalNodes;
+            FreeNodes = freeNodes;
+            ClumpSize = clumpSize;
+            TreeType = treeType;
+            KeyCompareType = keyCompareType;
+            Attributes = attributes;
+        }
+
+        public static HFSTreeHeaderRecord Read(Stream stream)
+        {
+            ushort treeDepth = ReadUInt16(stream);
+            uint rootNode = ReadUInt32(stream);
+            uint leafRecords = ReadUInt32(stream);
+            uint firstLeafNode = ReadUInt32(stream);
+            uint lastLeafNode = ReadUInt32(stream);
+            ushort nodeSize = ReadUInt16(stream);
+            ushort maxKeyLength = ReadUInt16(stream);
+            uint totalNodes = ReadUInt32(stream);
+            uint freeNodes = ReadUInt32(stream);
+            _ = ReadUInt16(stream); // reserved
+            uint clumpSize = ReadUInt32(stream);
+            var treeType = (HFSTreeType)ReadUInt8(stream);
+            var keyCompareType = (HFSKeyCompareType)ReadUInt8(stream);
+            var attributes = (HFSTreeAttributes)ReadUInt32(stream);
+            for (int i = 0; i < 16; i++) _ = ReadUInt32(stream); // reserved
+
+            return new HFSTreeHeaderRecord(
+                treeDepth,
+                rootNode,
+                leafRecords,
+                firstLeafNode,
+                lastLeafNode,
+                nodeSize,
+                maxKeyLength,
+                totalNodes,
+                freeNodes,
+                clumpSize,
+                treeType,
+                keyCompareType,
+                attributes);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSTreeNode.cs

@@ -0,0 +1,167 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal abstract class HFSTreeNode : HFSStructBase
+    {
+        private static byte[]? _buffer = null;
+
+        public HFSTreeNodeDescriptor Descriptor { get; }
+
+        protected HFSTreeNode(HFSTreeNodeDescriptor descriptor)
+            => Descriptor = descriptor;
+
+        public static bool TryRead(Stream stream, HFSTreeHeaderRecord headerRecord, bool isHFSX, out HFSTreeNode? node)
+        {
+            node = null;
+
+            if (!HFSTreeNodeDescriptor.TryRead(stream, out var descriptor)) return false;
+
+            int size = (int)headerRecord.NodeSize - HFSTreeNodeDescriptor.Size;
+            if ((_buffer is null) || (_buffer.Length < size))
+                _buffer = new byte[size * 2];
+
+            if (stream.Read(_buffer, 0, size) != size)
+                throw new EndOfStreamException();
+            ReadOnlySpan<byte> data = _buffer.AsSpan(0, size);
+
+            switch (descriptor!.Kind)
+            {
+                case HFSTreeNodeKind.Leaf:
+                    node = HFSLeafTreeNode.Read(descriptor, data, headerRecord, isHFSX);
+                    return true;
+
+                case HFSTreeNodeKind.Index:
+                    node = HFSIndexTreeNode.Read(descriptor, data, headerRecord, isHFSX);
+                    return true;
+
+                case HFSTreeNodeKind.Map:
+                    node = HFSMapTreeNode.Read(descriptor, data);
+                    return true;
+            }
+
+            return false;
+        }
+    }
+
+    internal sealed class HFSHeaderTreeNode : HFSTreeNode
+    {
+        private const int UserDataSize = 128;
+
+        public HFSTreeHeaderRecord HeaderRecord { get; }
+
+        public IReadOnlyList<byte> UserData { get; }
+
+        public IReadOnlyList<byte> Map { get; }
+
+        private HFSHeaderTreeNode(
+            HFSTreeNodeDescriptor descriptor,
+            HFSTreeHeaderRecord headerRecord,
+            IReadOnlyList<byte> userData,
+            IReadOnlyList<byte> map)
+            : base(descriptor)
+        {
+            HeaderRecord = headerRecord;
+            UserData = userData;
+            Map = map;
+        }
+
+        public static HFSHeaderTreeNode Read(HFSTreeNodeDescriptor descriptor, Stream stream)
+        {
+            if (descriptor.Kind != HFSTreeNodeKind.Header)
+                throw new ArgumentException("Descriptor does not define a header node");
+
+            var headerRecord = HFSTreeHeaderRecord.Read(stream);
+            var userData = new byte[UserDataSize];
+            if (stream.Read(userData, 0, UserDataSize) != UserDataSize)
+                throw new EndOfStreamException();
+
+            int mapSize = (int)(headerRecord.NodeSize - 256);
+            var map = new byte[mapSize];
+            if (stream.Read(map, 0, mapSize) != mapSize)
+                throw new EndOfStreamException();
+
+            // offset values (not required for header node)
+            _ = ReadUInt16(stream);
+            _ = ReadUInt16(stream);
+            _ = ReadUInt16(stream);
+            _ = ReadUInt16(stream);
+
+            return new HFSHeaderTreeNode(descriptor, headerRecord, userData, map);
+        }
+    }
+
+    internal sealed class HFSMapTreeNode : HFSTreeNode
+    {
+        public IReadOnlyList<byte> Map { get; }
+
+        private HFSMapTreeNode(HFSTreeNodeDescriptor descriptor, IReadOnlyList<byte> map)
+            : base(descriptor)
+        {
+            Map = map;
+        }
+
+        public static HFSMapTreeNode Read(HFSTreeNodeDescriptor descriptor, ReadOnlySpan<byte> data)
+        {
+            int mapSize = data.Length - 6;
+            var map = new byte[mapSize];
+            data.Slice(0, mapSize).CopyTo(map);
+
+            return new HFSMapTreeNode(descriptor, map);
+        }
+    }
+
+    internal sealed class HFSIndexTreeNode : HFSTreeNode
+    {
+        public IReadOnlyList<HFSPointerRecord> Records { get; }
+
+        private HFSIndexTreeNode(HFSTreeNodeDescriptor descriptor, IReadOnlyList<HFSPointerRecord> records)
+            : base(descriptor)
+        {
+            Records = records;
+        }
+
+        public static HFSIndexTreeNode Read(HFSTreeNodeDescriptor descriptor, ReadOnlySpan<byte> data, HFSTreeHeaderRecord headerRecord, bool isHFSX)
+        {
+            int recordCount = descriptor.NumRecords;
+            var records = new HFSPointerRecord[recordCount];
+            for (int i = 0; i < recordCount; i++)
+                records[i] = HFSPointerRecord.Read(ref data, headerRecord, isHFSX);
+            return new HFSIndexTreeNode(descriptor, records);
+        }
+    }
+
+    internal sealed class HFSLeafTreeNode : HFSTreeNode
+    {
+        public IReadOnlyList<HFSDataRecord> Records { get; }
+
+        private HFSLeafTreeNode(HFSTreeNodeDescriptor descriptor, IReadOnlyList<HFSDataRecord> records)
+            : base(descriptor)
+        {
+            Records = records;
+        }
+
+        public static HFSLeafTreeNode Read(HFSTreeNodeDescriptor descriptor, ReadOnlySpan<byte> data, HFSTreeHeaderRecord headerRecord, bool isHFSX)
+        {
+            int recordCount = descriptor.NumRecords;
+            var recordOffsets = new int[recordCount + 1];
+            for (int i = 0; i < recordOffsets.Length; i++)
+            {
+                var offsetData = data.Slice(data.Length - (2 * i) - 2);
+                ushort offset = ReadUInt16(ref offsetData);
+                recordOffsets[i] = offset;
+            }
+
+            var records = new HFSDataRecord[recordCount];
+            for (int i = 0; i < recordCount; i++)
+            {
+                int size = recordOffsets[i + 1] - recordOffsets[i];
+                records[i] = HFSDataRecord.Read(ref data, size, headerRecord, isHFSX);
+            }
+
+            return new HFSLeafTreeNode(descriptor, records);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSTreeNodeDescriptor.cs

@@ -0,0 +1,55 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal enum HFSTreeNodeKind : sbyte
+    {
+        Leaf = -1,
+        Index = 0,
+        Header = 1,
+        Map = 2
+    }
+
+    internal sealed class HFSTreeNodeDescriptor : HFSStructBase
+    {
+        public const int Size = 14;
+
+        public uint FLink { get; }
+        public uint BLink { get; }
+        public HFSTreeNodeKind Kind { get; }
+        public byte Height { get; }
+        public ushort NumRecords { get; }
+
+        private HFSTreeNodeDescriptor(uint fLink, uint bLink, HFSTreeNodeKind kind, byte height, ushort numRecords)
+        {
+            FLink = fLink;
+            BLink = bLink;
+            Kind = kind;
+            Height = height;
+            NumRecords = numRecords;
+        }
+
+        public static bool TryRead(Stream stream, out HFSTreeNodeDescriptor? descriptor)
+        {
+            descriptor = null;
+
+            uint fLink = ReadUInt32(stream);
+            uint bLink = ReadUInt32(stream);
+
+            sbyte rawKind = (sbyte)ReadUInt8(stream);
+            if (!Enum.IsDefined(typeof(HFSTreeNodeKind), rawKind)) return false;
+            var kind = (HFSTreeNodeKind)rawKind;
+
+            byte height = ReadUInt8(stream);
+            if (((kind == HFSTreeNodeKind.Header) || (kind == HFSTreeNodeKind.Map)) && (height != 0)) return false;
+            if ((kind == HFSTreeNodeKind.Leaf) && (height != 1)) return false;
+
+            ushort numRecords = ReadUInt16(stream);
+            _ = ReadUInt16(stream); // reserved
+
+            descriptor = new HFSTreeNodeDescriptor(fLink, bLink, kind, height, numRecords);
+            return true;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSUtil.cs

@@ -0,0 +1,206 @@
+using SharpCompress.Archives.Dmg;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal static class HFSUtil
+    {
+        private const string CorruptHFSMessage = "Corrupt HFS volume";
+
+        private static (HFSHeaderTreeNode, IReadOnlyList<HFSTreeNode>) ReadTree(Stream stream, bool isHFSX)
+        {
+            if (!HFSTreeNodeDescriptor.TryRead(stream, out var headerDesc))
+                throw new InvalidFormatException(CorruptHFSMessage);
+            var header = HFSHeaderTreeNode.Read(headerDesc!, stream);
+
+            var nodes = new HFSTreeNode[header.HeaderRecord.TotalNodes];
+            nodes[0] = header;
+
+            for (int i = 1; i < nodes.Length; i++)
+            {
+                if (!HFSTreeNode.TryRead(stream, header.HeaderRecord, isHFSX, out var node))
+                    throw new InvalidFormatException(CorruptHFSMessage);
+
+                nodes[i] = node!;
+            }
+
+            return (header, nodes);
+        }
+
+        private static void EnumerateExtentsTree(
+            IReadOnlyList<HFSTreeNode> extentsTree,
+            IDictionary<HFSExtentKey, HFSExtentRecord> records,
+            int parentIndex)
+        {
+            var parent = extentsTree[parentIndex];
+            if (parent is HFSLeafTreeNode leafNode)
+            {
+                foreach (var record in leafNode.Records)
+                {
+                    ReadOnlySpan<byte> data = record.Data.AsSpan();
+                    var recordData = HFSExtentRecord.Read(ref data);
+                    var key = record.GetExtentKey();
+                    records.Add(key, recordData);
+                }
+            }
+            else if (parent is HFSIndexTreeNode indexNode)
+            {
+                foreach (var record in indexNode.Records)
+                    EnumerateExtentsTree(extentsTree, records, (int)record.NodeNumber);
+            }
+            else
+            {
+                throw new InvalidFormatException(CorruptHFSMessage);
+            }
+        }
+
+        private static IReadOnlyDictionary<HFSExtentKey, HFSExtentRecord> LoadExtents(IReadOnlyList<HFSTreeNode> extentsTree, int rootIndex)
+        {
+            var records = new Dictionary<HFSExtentKey, HFSExtentRecord>();
+            if (rootIndex == 0) return records;
+
+            EnumerateExtentsTree(extentsTree, records, rootIndex);
+            return records;
+        }
+
+        private static void EnumerateCatalogTree(
+            HFSHeaderTreeNode catalogHeader,
+            IReadOnlyList<HFSTreeNode> catalogTree,
+            IDictionary<HFSCatalogKey, HFSCatalogRecord> records,
+            IDictionary<uint, HFSCatalogThread> threads,
+            int parentIndex,
+            bool isHFSX)
+        {
+            var parent = catalogTree[parentIndex];
+            if (parent is HFSLeafTreeNode leafNode)
+            {
+                foreach (var record in leafNode.Records)
+                {
+                    ReadOnlySpan<byte> data = record.Data.AsSpan();
+                    if (HFSCatalogRecord.TryRead(ref data, catalogHeader.HeaderRecord.KeyCompareType, isHFSX, out var recordData))
+                    {
+                        var key = record.GetCatalogKey();
+                        if ((recordData!.Type == HFSCatalogRecordType.FileThread) || (recordData!.Type == HFSCatalogRecordType.FolderThread))
+                        {
+                            threads.Add(key.ParentId, (HFSCatalogThread)recordData);
+                        }
+                        else
+                        {
+                            records.Add(key, recordData);
+                        }
+                    }
+                    else
+                    {
+                        throw new InvalidFormatException(CorruptHFSMessage);
+                    }
+                }
+            }
+            else if (parent is HFSIndexTreeNode indexNode)
+            {
+                foreach (var record in indexNode.Records)
+                    EnumerateCatalogTree(catalogHeader, catalogTree, records, threads, (int)record.NodeNumber, isHFSX);
+            }
+            else
+            {
+                throw new InvalidFormatException(CorruptHFSMessage);
+            }
+        }
+
+        private static (HFSCatalogKey, HFSCatalogRecord) GetRecord(uint id, IDictionary<HFSCatalogKey, HFSCatalogRecord> records, IDictionary<uint, HFSCatalogThread> threads)
+        {
+            if (threads.TryGetValue(id, out var thread))
+            {
+                if (records.TryGetValue(thread.CatalogKey, out var record))
+                    return (thread.CatalogKey, record!);
+            }
+
+            throw new InvalidFormatException(CorruptHFSMessage);
+        }
+
+        private static string SanitizePath(string path)
+        {
+            var sb = new StringBuilder(path.Length);
+            foreach (char c in path)
+            {
+                if (!char.IsControl(c))
+                    sb.Append(c);
+            }
+            return sb.ToString();
+        }
+
+        private static string GetPath(HFSCatalogKey key, IDictionary<HFSCatalogKey, HFSCatalogRecord> records, IDictionary<uint, HFSCatalogThread> threads)
+        {
+            if (key.ParentId == 1)
+            {
+                return key.Name;
+            }
+            else
+            {
+                var (parentKey, _) = GetRecord(key.ParentId, records, threads);
+                var path = Path.Combine(GetPath(parentKey, records, threads), key.Name);
+                return SanitizePath(path);
+            }
+        }
+
+        private static IEnumerable<DmgArchiveEntry> LoadEntriesFromCatalogTree(
+            Stream partitionStream,
+            DmgFilePart filePart,
+            HFSVolumeHeader volumeHeader,
+            HFSHeaderTreeNode catalogHeader,
+            IReadOnlyList<HFSTreeNode> catalogTree,
+            IReadOnlyDictionary<HFSExtentKey, HFSExtentRecord> extents,
+            DmgArchive archive,
+            int rootIndex)
+        {
+            if (rootIndex == 0) return Array.Empty<DmgArchiveEntry>();
+
+            var records = new Dictionary<HFSCatalogKey, HFSCatalogRecord>();
+            var threads = new Dictionary<uint, HFSCatalogThread>();
+            EnumerateCatalogTree(catalogHeader, catalogTree, records, threads, rootIndex, volumeHeader.IsHFSX);
+
+            var entries = new List<DmgArchiveEntry>();
+            foreach (var kvp in records)
+            {
+                var key = kvp.Key;
+                var record = kvp.Value;
+
+                string path = GetPath(key, records, threads);
+                var stream = (record is HFSCatalogFile file) ? new HFSForkStream(partitionStream, volumeHeader, file.DataFork, file.FileId, extents) : null;
+                var entry = new DmgArchiveEntry(stream, archive, record, path, filePart);
+                entries.Add(entry);
+            }
+
+            return entries;
+        }
+
+        public static IEnumerable<DmgArchiveEntry> LoadEntriesFromPartition(Stream partitionStream, string fileName, DmgArchive archive)
+        {
+            if (!HFSVolumeHeader.TryRead(partitionStream, out var volumeHeader))
+                throw new InvalidFormatException(CorruptHFSMessage);
+            var filePart = new DmgFilePart(partitionStream, fileName);
+
+            var extentsFile = volumeHeader!.ExtentsFile;
+            var extentsStream = new HFSForkStream(partitionStream, volumeHeader, extentsFile);
+            var (extentsHeader, extentsTree) = ReadTree(extentsStream, volumeHeader.IsHFSX);
+
+            var extents = LoadExtents(extentsTree, (int)extentsHeader.HeaderRecord.RootNode);
+
+            var catalogFile = volumeHeader!.CatalogFile;
+            var catalogStream = new HFSForkStream(partitionStream, volumeHeader, catalogFile);
+            var (catalogHeader, catalogTree) = ReadTree(catalogStream, volumeHeader.IsHFSX);
+
+            return LoadEntriesFromCatalogTree(
+                partitionStream,
+                filePart,
+                volumeHeader,
+                catalogHeader,
+                catalogTree,
+                extents,
+                archive,
+                (int)catalogHeader.HeaderRecord.RootNode);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/HFS/HFSVolumeHeader.cs

@@ -0,0 +1,179 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.HFS
+{
+    internal sealed class HFSVolumeHeader : HFSStructBase
+    {
+        private const ushort SignaturePlus = 0x482B;
+        private const ushort SignatureX = 0x4858;
+        private const int FinderInfoCount = 8;
+
+        public bool IsHFSX { get; }
+        public ushort Version { get; }
+        public uint Attributes { get; }
+        public uint LastMountedVersion { get; }
+        public uint JournalInfoBlock { get; }
+
+        public DateTime CreateDate { get; }
+        public DateTime ModifyDate { get; }
+        public DateTime BackupDate { get; }
+        public DateTime CheckedDate { get; }
+
+        public uint FileCount { get; }
+        public uint FolderCount { get; }
+
+        public uint BlockSize { get; }
+        public uint TotalBlocks { get; }
+        public uint FreeBlocks { get; }
+
+        public uint NextAllocation { get; }
+        public uint RsrcClumpSize { get; }
+        public uint DataClumpSize { get; }
+        public uint NextCatalogID { get; }
+
+        public uint WriteCount { get; }
+        public ulong EncodingsBitmap { get; }
+
+        public IReadOnlyList<uint> FinderInfo { get; }
+
+        public HFSForkData AllocationFile { get; }
+        public HFSForkData ExtentsFile { get; }
+        public HFSForkData CatalogFile { get; }
+        public HFSForkData AttributesFile { get; }
+        public HFSForkData StartupFile { get; }
+
+        public HFSVolumeHeader(
+            bool isHFSX,
+            ushort version,
+            uint attributes,
+            uint lastMountedVersion,
+            uint journalInfoBlock,
+            DateTime createDate,
+            DateTime modifyDate,
+            DateTime backupDate,
+            DateTime checkedDate,
+            uint fileCount,
+            uint folderCount,
+            uint blockSize,
+            uint totalBlocks,
+            uint freeBlocks,
+            uint nextAllocation,
+            uint rsrcClumpSize,
+            uint dataClumpSize,
+            uint nextCatalogID,
+            uint writeCount,
+            ulong encodingsBitmap,
+            IReadOnlyList<uint> finderInfo,
+            HFSForkData allocationFile,
+            HFSForkData extentsFile,
+            HFSForkData catalogFile,
+            HFSForkData attributesFile,
+            HFSForkData startupFile)
+        {
+            IsHFSX = isHFSX;
+            Version = version;
+            Attributes = attributes;
+            LastMountedVersion = lastMountedVersion;
+            JournalInfoBlock = journalInfoBlock;
+            CreateDate = createDate;
+            ModifyDate = modifyDate;
+            BackupDate = backupDate;
+            CheckedDate = checkedDate;
+            FileCount = fileCount;
+            FolderCount = folderCount;
+            BlockSize = blockSize;
+            TotalBlocks = totalBlocks;
+            FreeBlocks = freeBlocks;
+            NextAllocation = nextAllocation;
+            RsrcClumpSize = rsrcClumpSize;
+            DataClumpSize = dataClumpSize;
+            NextCatalogID = nextCatalogID;
+            WriteCount = writeCount;
+            EncodingsBitmap = encodingsBitmap;
+            FinderInfo = finderInfo;
+            AllocationFile = allocationFile;
+            ExtentsFile = extentsFile;
+            CatalogFile = catalogFile;
+            AttributesFile = attributesFile;
+            StartupFile = startupFile;
+        }
+
+        private static IReadOnlyList<uint> ReadFinderInfo(Stream stream)
+        {
+            var finderInfo = new uint[FinderInfoCount];
+            for (int i = 0; i < FinderInfoCount; i++)
+                finderInfo[i] = ReadUInt32(stream);
+            return finderInfo;
+        }
+
+        public static bool TryRead(Stream stream, out HFSVolumeHeader? header)
+        {
+            header = null;
+            stream.Skip(1024); // reserved bytes
+
+            bool isHFSX;
+            ushort sig = ReadUInt16(stream);
+            if (sig == SignaturePlus) isHFSX = false;
+            else if (sig == SignatureX) isHFSX = true;
+            else return false;
+
+            ushort version = ReadUInt16(stream);
+            uint attributes = ReadUInt32(stream);
+            uint lastMountedVersion = ReadUInt32(stream);
+            uint journalInfoBlock = ReadUInt32(stream);
+            DateTime createDate = ReadDate(stream);
+            DateTime modifyDate = ReadDate(stream);
+            DateTime backupDate = ReadDate(stream);
+            DateTime checkedDate = ReadDate(stream);
+            uint fileCount = ReadUInt32(stream);
+            uint folderCount = ReadUInt32(stream);
+            uint blockSize = ReadUInt32(stream);
+            uint totalBlocks = ReadUInt32(stream);
+            uint freeBlocks = ReadUInt32(stream);
+            uint nextAllocation = ReadUInt32(stream);
+            uint rsrcClumpSize = ReadUInt32(stream);
+            uint dataClumpSize = ReadUInt32(stream);
+            uint nextCatalogID = ReadUInt32(stream);
+            uint writeCount = ReadUInt32(stream);
+            ulong encodingsBitmap = ReadUInt64(stream);
+            IReadOnlyList<uint> finderInfo = ReadFinderInfo(stream);
+            HFSForkData allocationFile = HFSForkData.Read(stream);
+            HFSForkData extentsFile = HFSForkData.Read(stream);
+            HFSForkData catalogFile = HFSForkData.Read(stream);
+            HFSForkData attributesFile = HFSForkData.Read(stream);
+            HFSForkData startupFile = HFSForkData.Read(stream);
+
+            header = new HFSVolumeHeader(
+                isHFSX,
+                version,
+                attributes,
+                lastMountedVersion,
+                journalInfoBlock,
+                createDate,
+                modifyDate,
+                backupDate,
+                checkedDate,
+                fileCount,
+                folderCount,
+                blockSize,
+                totalBlocks,
+                freeBlocks,
+                nextAllocation,
+                rsrcClumpSize,
+                dataClumpSize,
+                nextCatalogID,
+                writeCount,
+                encodingsBitmap,
+                finderInfo,
+                allocationFile,
+                extentsFile,
+                catalogFile,
+                attributesFile,
+                startupFile);
+
+            return true;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/BlkxChunk.cs

@@ -0,0 +1,49 @@
+using System;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal enum BlkxChunkType : uint
+    {
+        Zero = 0x00000000u,
+        Uncompressed = 0x00000001u,
+        Ignore = 0x00000002u,
+        AdcCompressed = 0x80000004u,
+        ZlibCompressed = 0x80000005u,
+        Bz2Compressed = 0x80000006u,
+        Comment = 0x7FFFFFFEu,
+        Last = 0xFFFFFFFFu,
+    }
+
+    internal sealed class BlkxChunk : DmgStructBase
+    {
+        private const int SectorSize = 512;
+
+        public BlkxChunkType Type { get; }      // Compression type used or chunk type
+        public uint Comment { get; }            // "+beg" or "+end", if EntryType is comment (0x7FFFFFFE). Else reserved.
+        public ulong UncompressedOffset { get; }      // Start sector of this chunk
+        public ulong UncompressedLength { get; }       // Number of sectors in this chunk
+        public ulong CompressedOffset { get; }  // Start of chunk in data fork
+        public ulong CompressedLength { get; }  // Count of bytes of chunk, in data fork
+
+        private BlkxChunk(BlkxChunkType type, uint comment, ulong sectorNumber, ulong sectorCount, ulong compressedOffset, ulong compressedLength)
+        {
+            Type = type;
+            Comment = comment;
+            UncompressedOffset = sectorNumber * SectorSize;
+            UncompressedLength = sectorCount * SectorSize;
+            CompressedOffset = compressedOffset;
+            CompressedLength = compressedLength;
+        }
+
+        public static bool TryRead(ref ReadOnlySpan<byte> data, out BlkxChunk? chunk)
+        {
+            chunk = null;
+
+            var type = (BlkxChunkType)ReadUInt32(ref data);
+            if (!Enum.IsDefined(typeof(BlkxChunkType), type)) return false;
+
+            chunk = new BlkxChunk(type, ReadUInt32(ref data), ReadUInt64(ref data), ReadUInt64(ref data), ReadUInt64(ref data), ReadUInt64(ref data));
+            return true;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/BlkxTable.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Collections.Generic;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal sealed class BlkxTable : DmgStructBase
+    {
+        private const uint Signature = 0x6d697368u;
+
+        public uint Version { get; }             // Current version is 1
+        public ulong SectorNumber { get; }       // Starting disk sector in this blkx descriptor
+        public ulong SectorCount { get; }        // Number of disk sectors in this blkx descriptor
+
+        public ulong DataOffset { get; }
+        public uint BuffersNeeded { get; }
+        public uint BlockDescriptors { get; }    // Number of descriptors
+
+        public UdifChecksum Checksum { get; }
+
+        public IReadOnlyList<BlkxChunk> Chunks { get; }
+
+        private BlkxTable(
+            uint version,
+            ulong sectorNumber,
+            ulong sectorCount,
+            ulong dataOffset,
+            uint buffersNeeded,
+            uint blockDescriptors,
+            UdifChecksum checksum,
+            IReadOnlyList<BlkxChunk> chunks)
+        {
+            Version = version;
+            SectorNumber = sectorNumber;
+            SectorCount = sectorCount;
+            DataOffset = dataOffset;
+            BuffersNeeded = buffersNeeded;
+            BlockDescriptors = blockDescriptors;
+            Checksum = checksum;
+            Chunks = chunks;
+        }
+
+        public static bool TryRead(in byte[] buffer, out BlkxTable? header)
+        {
+            header = null;
+
+            ReadOnlySpan<byte> data = buffer.AsSpan();
+
+            uint sig = ReadUInt32(ref data);
+            if (sig != Signature) return false;
+
+            uint version = ReadUInt32(ref data);
+            ulong sectorNumber = ReadUInt64(ref data);
+            ulong sectorCount = ReadUInt64(ref data);
+
+            ulong dataOffset = ReadUInt64(ref data);
+            uint buffersNeeded = ReadUInt32(ref data);
+            uint blockDescriptors = ReadUInt32(ref data);
+
+            data = data.Slice(6 * sizeof(uint)); // reserved
+
+            var checksum = UdifChecksum.Read(ref data);
+
+            uint chunkCount = ReadUInt32(ref data);
+            var chunks = new BlkxChunk[chunkCount];
+            for (int i = 0; i < chunkCount; i++)
+            {
+                if (!BlkxChunk.TryRead(ref data, out var chunk)) return false;
+                chunks[i] = chunk!;
+            }
+
+            header = new BlkxTable(version, sectorNumber, sectorCount, dataOffset, buffersNeeded, blockDescriptors, checksum, chunks);
+            return true;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/DmgHeader.cs

@@ -0,0 +1,138 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal sealed class DmgHeader : DmgStructBase
+    {
+        public const int HeaderSize = 512;
+        private const uint Signature = 0x6B6F6C79u;
+        private const int UuidSize = 16; // 128 bit
+
+        public uint Version { get; }                     // Current version is 4
+        public uint Flags { get; }                       // Flags
+        public ulong RunningDataForkOffset { get; }      //
+        public ulong DataForkOffset { get; }             // Data fork offset (usually 0, beginning of file)
+        public ulong DataForkLength { get; }             // Size of data fork (usually up to the XMLOffset, below)
+        public ulong RsrcForkOffset { get; }             // Resource fork offset, if any
+        public ulong RsrcForkLength { get; }             // Resource fork length, if any
+        public uint SegmentNumber { get; }               // Usually 1, may be 0
+        public uint SegmentCount { get; }                // Usually 1, may be 0
+        public IReadOnlyList<byte> SegmentID { get; }    // 128-bit GUID identifier of segment (if SegmentNumber !=0)
+
+        public UdifChecksum DataChecksum { get; }
+
+        public ulong XMLOffset { get; }                  // Offset of property list in DMG, from beginning
+        public ulong XMLLength { get; }                  // Length of property list
+
+        public UdifChecksum Checksum { get; }
+        
+        public uint ImageVariant { get; }                // Commonly 1
+        public ulong SectorCount { get; }                // Size of DMG when expanded, in sectors
+
+        private DmgHeader(
+            uint version,
+            uint flags,
+            ulong runningDataForkOffset,
+            ulong dataForkOffset,
+            ulong dataForkLength,
+            ulong rsrcForkOffset,
+            ulong rsrcForkLength,
+            uint segmentNumber,
+            uint segmentCount,
+            IReadOnlyList<byte> segmentID,
+            UdifChecksum dataChecksum,
+            ulong xMLOffset,
+            ulong xMLLength,
+            UdifChecksum checksum,
+            uint imageVariant,
+            ulong sectorCount)
+        {
+            Version = version;
+            Flags = flags;
+            RunningDataForkOffset = runningDataForkOffset;
+            DataForkOffset = dataForkOffset;
+            DataForkLength = dataForkLength;
+            RsrcForkOffset = rsrcForkOffset;
+            RsrcForkLength = rsrcForkLength;
+            SegmentNumber = segmentNumber;
+            SegmentCount = segmentCount;
+            SegmentID = segmentID;
+            DataChecksum = dataChecksum;
+            XMLOffset = xMLOffset;
+            XMLLength = xMLLength;
+            Checksum = checksum;
+            ImageVariant = imageVariant;
+            SectorCount = sectorCount;
+        }
+
+        private static void ReadUuid(ref ReadOnlySpan<byte> data, byte[] buffer)
+        {
+            data.Slice(0, UuidSize).CopyTo(buffer);
+            data = data.Slice(UuidSize);
+        }
+
+        internal static bool TryRead(Stream input, out DmgHeader? header)
+        {
+            header = null;
+
+            var buffer = new byte[HeaderSize];
+            int count = input.Read(buffer, 0, HeaderSize);
+            if (count != HeaderSize) return false;
+            ReadOnlySpan<byte> data = buffer.AsSpan();
+
+            uint sig = ReadUInt32(ref data);
+            if (sig != Signature) return false;
+
+            uint version = ReadUInt32(ref data);
+
+            uint size = ReadUInt32(ref data);
+            if (size != (uint)HeaderSize) return false;
+
+            uint flags = ReadUInt32(ref data);
+            ulong runningDataForkOffset = ReadUInt64(ref data);
+            ulong dataForkOffset = ReadUInt64(ref data);
+            ulong dataForkLength = ReadUInt64(ref data);
+            ulong rsrcForkOffset = ReadUInt64(ref data);
+            ulong rsrcForkLength = ReadUInt64(ref data);
+            uint segmentNumber = ReadUInt32(ref data);
+            uint segmentCount = ReadUInt32(ref data);
+
+            var segmentID = new byte[UuidSize];
+            ReadUuid(ref data, segmentID);
+
+            var dataChecksum = UdifChecksum.Read(ref data);
+
+            ulong xmlOffset = ReadUInt64(ref data);
+            ulong xmlLength = ReadUInt64(ref data);
+
+            data = data.Slice(120); // Reserved bytes
+
+            var checksum = UdifChecksum.Read(ref data);
+
+            uint imageVariant = ReadUInt32(ref data);
+            ulong sectorCount = ReadUInt64(ref data);
+
+            header = new DmgHeader(
+                version,
+                flags,
+                runningDataForkOffset,
+                dataForkOffset,
+                dataForkLength,
+                rsrcForkOffset,
+                rsrcForkLength,
+                segmentNumber,
+                segmentCount,
+                segmentID,
+                dataChecksum,
+                xmlOffset,
+                xmlLength,
+                checksum,
+                imageVariant,
+                sectorCount);
+
+            return true;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/DmgStructBase.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Buffers.Binary;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal abstract class DmgStructBase
+    {
+        protected static uint ReadUInt32(ref ReadOnlySpan<byte> data)
+        {
+            uint val = BinaryPrimitives.ReadUInt32BigEndian(data);
+            data = data.Slice(sizeof(uint));
+            return val;
+        }
+
+        protected static ulong ReadUInt64(ref ReadOnlySpan<byte> data)
+        {
+            ulong val = BinaryPrimitives.ReadUInt64BigEndian(data);
+            data = data.Slice(sizeof(ulong));
+            return val;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/GptHeader.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Buffers.Binary;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal sealed class GptHeader : GptStructBase
+    {
+        private const int HeaderSize = 92;
+        private static readonly ulong Signature = BinaryPrimitives.ReadUInt64LittleEndian(new byte[] { 69, 70, 73, 32, 80, 65, 82, 84 });
+
+        public uint Revision { get; }
+        public uint Crc32Header { get; }
+        public ulong CurrentLba { get; }
+        public ulong BackupLba { get; }
+        public ulong FirstUsableLba { get; }
+        public ulong LastUsableLba { get; }
+        public Guid DiskGuid { get; }
+        public ulong EntriesStart { get; }
+        public uint EntriesCount { get; }
+        public uint EntriesSize { get; }
+        public uint Crc32Array { get; }
+
+        private GptHeader(
+            uint revision,
+            uint crc32Header,
+            ulong currentLba,
+            ulong backupLba,
+            ulong firstUsableLba,
+            ulong lastUsableLba,
+            Guid diskGuid,
+            ulong entriesStart,
+            uint entriesCount,
+            uint entriesSize,
+            uint crc32Array)
+        {
+            Revision = revision;
+            Crc32Header = crc32Header;
+            CurrentLba = currentLba;
+            BackupLba = backupLba;
+            FirstUsableLba = firstUsableLba;
+            LastUsableLba = lastUsableLba;
+            DiskGuid = diskGuid;
+            EntriesStart = entriesStart;
+            EntriesCount = entriesCount;
+            EntriesSize = entriesSize;
+            Crc32Array = crc32Array;
+        }
+
+        public static bool TryRead(Stream stream, out GptHeader? header)
+        {
+            header = null;
+
+            ulong sig = ReadUInt64(stream);
+            if (sig != Signature) return false;
+
+            uint revision = ReadUInt32(stream);
+
+            uint headerSize = ReadUInt32(stream);
+            if (headerSize != HeaderSize) return false;
+
+            uint crc32Header = ReadUInt32(stream);
+            _ = ReadUInt32(stream); // reserved
+            ulong currentLba = ReadUInt64(stream);
+            ulong backupLba = ReadUInt64(stream);
+            ulong firstUsableLba = ReadUInt64(stream);
+            ulong lastUsableLba = ReadUInt64(stream);
+            Guid diskGuid = ReadGuid(stream);
+            ulong entriesStart = ReadUInt64(stream);
+            uint entriesCount = ReadUInt32(stream);
+            uint entriesSize = ReadUInt32(stream);
+            uint crc32Array = ReadUInt32(stream);
+
+            header = new GptHeader(
+                revision,
+                crc32Header,
+                currentLba,
+                backupLba,
+                firstUsableLba,
+                lastUsableLba,
+                diskGuid,
+                entriesStart,
+                entriesCount,
+                entriesSize,
+                crc32Array);
+
+            return true;
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/GptPartitionEntry.cs

@@ -0,0 +1,36 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal sealed class GptPartitionEntry : GptStructBase
+    {
+        public Guid TypeGuid { get; }
+        public Guid Guid { get; }
+        public ulong FirstLba { get; }
+        public ulong LastLba { get; }
+        public ulong Attributes { get; }
+        public string Name { get; }
+
+        private GptPartitionEntry(Guid typeGuid, Guid guid, ulong firstLba, ulong lastLba, ulong attributes, string name)
+        {
+            TypeGuid = typeGuid;
+            Guid = guid;
+            FirstLba = firstLba;
+            LastLba = lastLba;
+            Attributes = attributes;
+            Name = name;
+        }
+
+        public static GptPartitionEntry Read(Stream stream)
+        {
+            return new GptPartitionEntry(
+                ReadGuid(stream),
+                ReadGuid(stream),
+                ReadUInt64(stream),
+                ReadUInt64(stream),
+                ReadUInt64(stream),
+                ReadString(stream, 72));
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/GptStructBase.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Buffers.Binary;
+using System.IO;
+using System.Text;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal abstract class GptStructBase
+    {
+        private static readonly byte[] _buffer = new byte[8];
+
+        protected static ushort ReadUInt16(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(ushort)) != sizeof(ushort))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadUInt16LittleEndian(_buffer);
+        }
+
+        protected static uint ReadUInt32(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(uint)) != sizeof(uint))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadUInt32LittleEndian(_buffer);
+        }
+
+        protected static ulong ReadUInt64(Stream stream)
+        {
+            if (stream.Read(_buffer, 0, sizeof(ulong)) != sizeof(ulong))
+                throw new EndOfStreamException();
+
+            return BinaryPrimitives.ReadUInt64LittleEndian(_buffer);
+        }
+
+        protected static Guid ReadGuid(Stream stream)
+        {
+            int a = (int)ReadUInt32(stream);
+            short b = (short)ReadUInt16(stream);
+            short c = (short)ReadUInt16(stream);
+
+            if (stream.Read(_buffer, 0, 8) != 8)
+                throw new EndOfStreamException();
+
+            return new Guid(a, b, c, _buffer);
+        }
+
+        protected static string ReadString(Stream stream, int byteSize)
+        {
+            var buffer = new byte[byteSize];
+            if (stream.Read(buffer, 0, byteSize) != byteSize)
+                throw new EndOfStreamException();
+            return Encoding.Unicode.GetString(buffer).NullTerminate();
+        }
+    }
+}

src/SharpCompress/Common/Dmg/Headers/UdifChecksum.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+
+namespace SharpCompress.Common.Dmg.Headers
+{
+    internal sealed class UdifChecksum : DmgStructBase
+    {
+        private const int MaxSize = 32; // * 4 to get byte size
+
+        public uint Type { get; }
+        public uint Size { get; } // in bits
+        public IReadOnlyList<uint> Bits { get; }
+
+        private UdifChecksum(uint type, uint size, IReadOnlyList<uint> bits)
+        {
+            Type = type;
+            Size = size;
+            Bits = bits;
+        }
+
+        public static UdifChecksum Read(ref ReadOnlySpan<byte> data)
+        {
+            uint type = ReadUInt32(ref data);
+            uint size = ReadUInt32(ref data);
+
+            var bits = new uint[MaxSize];
+            for (int i = 0; i < MaxSize; i++)
+                bits[i] = ReadUInt32(ref data);
+
+            return new UdifChecksum(type, size, bits);
+        }
+    }
+}

src/SharpCompress/Common/Dmg/PartitionFormat.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace SharpCompress.Common.Dmg
+{
+    internal static class PartitionFormat
+    {
+        public static readonly Guid AppleHFS         = new Guid("48465300-0000-11AA-AA11-00306543ECAC");
+        public static readonly Guid AppleUFS         = new Guid("55465300-0000-11AA-AA11-00306543ECAC");
+        public static readonly Guid AppleBoot        = new Guid("426F6F74-0000-11AA-AA11-00306543ECAC");
+        public static readonly Guid AppleRaid        = new Guid("52414944-0000-11AA-AA11-00306543ECAC");
+        public static readonly Guid AppleRaidOffline = new Guid("52414944-5F4F-11AA-AA11-00306543ECAC");
+        public static readonly Guid AppleLabel       = new Guid("4C616265-6C00-11AA-AA11-00306543ECAC");
+    }
+}

src/SharpCompress/Common/IncompleteArchiveException.cs

@@ -1,4 +1,6 @@
-namespace SharpCompress.Common
+using System;
+
+namespace SharpCompress.Common
 {
     public class IncompleteArchiveException : ArchiveException
     {
@@ -6,5 +8,10 @@
             : base(message)
         {
         }
+
+        public IncompleteArchiveException(string message, Exception inner)
+            : base(message, inner)
+        {
+        }
     }
 }

src/SharpCompress/IO/CompositeStream.cs

@@ -0,0 +1,172 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace SharpCompress.IO
+{
+    internal class CompositeStream : Stream
+    {
+        private readonly IReadOnlyList<Stream> _streams;
+        private long _pos;
+        private int _streamIndex;
+        private long _streamPos;
+
+        public override bool CanRead { get; }
+        public override bool CanWrite { get; }
+        public override bool CanSeek { get; }
+        public override long Length { get; }
+
+        public override long Position
+        {
+            get => _pos;
+            set
+            {
+                if (!CanSeek) throw new NotSupportedException();
+                if ((value < 0) || (value > Length)) throw new ArgumentOutOfRangeException(nameof(value));
+
+                _pos = value;
+
+                _streamIndex = -1;
+                long offset = _pos;
+                for (int i = 0; i < _streams.Count; i++)
+                {
+                    var stream = _streams[i];
+                    if (offset < stream.Length)
+                    {
+                        _streamIndex = i;
+                        _streamPos = offset;
+                        break;
+                    }
+                    else
+                    {
+                        offset -= stream.Length;
+                    }
+                }
+            }
+        }
+
+        public CompositeStream(IReadOnlyList<Stream> streams)
+        {
+            CanRead = true;
+            CanWrite = false;
+            CanSeek = true;
+            Length = 0;
+            _pos = 0;
+            _streamIndex = 0;
+            _streamPos = 0;
+
+            _streams = streams;
+            foreach (var stream in _streams)
+            {
+                if (!stream.CanRead) throw new ArgumentException("All streams must be readable");
+                if (!stream.CanSeek) CanSeek = false;
+                Length += stream.Length;
+            }
+        }
+
+        public CompositeStream(IEnumerable<Stream> streams)
+            : this((IReadOnlyList<Stream>)streams.ToArray())
+        { }
+
+        public CompositeStream(params Stream[] streams)
+            : this((IReadOnlyList<Stream>)streams)
+        { }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            Stream? GetCurrent()
+            {
+                if ((_streamIndex < 0) || (_streamIndex >= _streams.Count)) return null;
+                else return _streams[_streamIndex];
+            }
+
+            if (CanSeek)
+            {
+                var stream = GetCurrent();
+                if (stream is null) return 0;
+
+                stream.Position = _streamPos;
+                int readCount = stream.Read(buffer, offset, count);
+                _pos += readCount;
+                _streamPos += readCount;
+
+                while (readCount < count)
+                {
+                    _streamIndex++;
+                    stream = GetCurrent();
+                    if (stream is null) return readCount;
+
+                    stream.Position = _streamPos = 0;
+                    int rc = stream.Read(buffer, offset + readCount, count - readCount);
+                    readCount += rc;
+                    _pos += rc;
+                    _streamPos += rc;
+                }
+
+                return readCount;
+            }
+            else
+            {
+                var stream = GetCurrent();
+                if (stream is null) return 0;
+
+                int readCount = stream.Read(buffer, offset, count);
+                _pos += readCount;
+
+                while (readCount < count)
+                {
+                    _streamIndex++;
+                    stream = GetCurrent();
+                    if (stream is null) return readCount;
+
+                    int rc = stream.Read(buffer, offset + readCount, count - readCount);
+                    readCount += rc;
+                    _pos += rc;
+                }
+
+                return readCount;
+            }
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            if (CanSeek)
+            {
+                long ClampPos(long value) => Math.Min(Math.Max(value, 0), Length);
+
+                switch (origin)
+                {
+                    case SeekOrigin.Begin:
+                        Position = ClampPos(offset);
+                        break;
+
+                    case SeekOrigin.Current:
+                        Position = ClampPos(Position + offset);
+                        break;
+
+                    case SeekOrigin.End:
+                        Position = ClampPos(Length - offset);
+                        break;
+                }
+            }
+            
+            return Position;
+        }
+
+        public override void Flush()
+        { }
+
+        public override void Write(byte[] buffer, int offset, int count)
+            => throw new NotSupportedException();
+
+        public override void SetLength(long value)
+            => throw new NotSupportedException();
+
+        protected override void Dispose(bool disposing)
+        {
+            foreach (var stream in _streams)
+                stream.Dispose();
+        }
+    }
+}

src/SharpCompress/IO/ConstantStream.cs

@@ -0,0 +1,81 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.IO
+{
+    internal class ConstantStream : Stream
+    {
+        private long _length;
+        private long _pos;
+
+        public byte Value { get; set; }
+
+        public override bool CanRead => true;
+        public override bool CanWrite => false;
+        public override bool CanSeek => true;
+        public override long Length => _length;
+
+        public override long Position
+        {
+            get => _pos;
+            set
+            {
+                if ((value < 0) || (value > Length)) throw new ArgumentOutOfRangeException(nameof(value));
+                _pos = value;
+            }
+        }
+
+        public ConstantStream(byte value, long length)
+        {
+            Value = value;
+            _length = length;
+            _pos = 0;
+        }
+
+        private long ClampPos(long value) => Math.Min(Math.Max(value, 0), Length);
+
+        public override void Flush()
+        { }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            count = (int)Math.Min(count, Length - Position);
+            for (int i = 0; i < count; i++)
+                buffer[i + offset] = Value;
+            Position += count;
+            return count;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            switch (origin)
+            {
+                case SeekOrigin.Begin:
+                    Position = ClampPos(offset);
+                    break;
+
+                case SeekOrigin.Current:
+                    Position = ClampPos(Position + offset);
+                    break;
+
+                case SeekOrigin.End:
+                    Position = ClampPos(Length - offset);
+                    break;
+            }
+
+            return Position;
+        }
+
+        public override void SetLength(long value)
+        {
+            _length = value;
+            Position = ClampPos(Position);
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+            => throw new NotSupportedException();
+
+        protected override void Dispose(bool disposing)
+        { }
+    }
+}

src/SharpCompress/IO/SeekableSubStream.cs

@@ -0,0 +1,79 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.IO
+{
+    internal class SeekableSubStream : NonDisposingStream
+    {
+        private readonly long _origin;
+        private long _pos;
+
+        public override bool CanRead => true;
+        public override bool CanWrite => false;
+        public override bool CanSeek => true;
+        public override long Length { get; }
+
+        public override long Position
+        {
+            get => _pos;
+            set
+            {
+                if ((value < 0) || (value > Length)) throw new ArgumentOutOfRangeException(nameof(value));
+                _pos = value;
+            }
+        }
+
+        public SeekableSubStream(Stream stream, long origin, long length)
+            : base(stream, false)
+        {
+            if (!stream.CanRead) throw new ArgumentException("Requires a readable stream", nameof(stream));
+            if (!stream.CanSeek) throw new ArgumentException("Requires a seekable stream", nameof(stream));
+
+            _origin = origin;
+            Length = length;
+            _pos = 0;
+        }
+
+        public override void Flush()
+        { }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            count = (int)Math.Min(count, Length - Position);
+
+            Stream.Position = Position + _origin;
+            count = Stream.Read(buffer, offset, count);
+
+            Position += count;
+            return count;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            long ClampPos(long value) => Math.Min(Math.Max(value, 0), Length);
+
+            switch (origin)
+            {
+                case SeekOrigin.Begin:
+                    Position = ClampPos(offset);
+                    break;
+
+                case SeekOrigin.Current:
+                    Position = ClampPos(Position + offset);
+                    break;
+
+                case SeekOrigin.End:
+                    Position = ClampPos(Length - offset);
+                    break;
+            }
+
+            return Position;
+        }
+
+        public override void SetLength(long value)
+            => throw new NotSupportedException();
+
+        public override void Write(byte[] buffer, int offset, int count)
+            => throw new NotSupportedException();
+    }
+}

src/SharpCompress/Utility.cs

@@ -315,5 +315,12 @@ namespace SharpCompress
         {
             return source.Replace('\0', ' ').Trim();
         }
+
+        public static string NullTerminate(this string source)
+        {
+            int index = source.IndexOf('\0');
+            if (index < 0) return source;
+            return source.Substring(0, index);
+        }
     }
 }

tests/SharpCompress.Test/Dmg/DmgArchiveTests.cs

@@ -0,0 +1,57 @@
+using Xunit;
+
+namespace SharpCompress.Test.Dmg
+{
+    public class DmgArchiveTests : ArchiveTests
+    {
+        // ToDo: create the required test archives
+
+        [Fact]
+        public void DmgArchive_StreamRead()
+        {
+            ArchiveStreamRead("Dmg.dmg");
+        }
+
+        [Fact]
+        public void DmgArchive_PathRead()
+        {
+            ArchiveFileRead("Dmg.dmg");
+        }
+
+        [Fact]
+        public void DmgArchive_ADC_StreamRead()
+        {
+            ArchiveStreamRead("Dmg.dmg");
+        }
+
+        //[Fact]
+        //public void DmgArchive_ADC_PathRead()
+        //{
+        //    ArchiveFileRead("Dmg_ADC.dmg");
+        //}
+
+        //[Fact]
+        //public void DmgArchive_Zlib_StreamRead()
+        //{
+        //    ArchiveStreamRead("Dmg_zLib.dmg");
+        //}
+
+        //[Fact]
+        //public void DmgArchive_Zlib_PathRead()
+        //{
+        //    ArchiveFileRead("Dmg_zLib.dmg");
+        //}
+
+        //[Fact]
+        //public void DmgArchive_Bz2_StreamRead()
+        //{
+        //    ArchiveStreamRead("Dmg_bz2.dmg");
+        //}
+
+        //[Fact]
+        //public void DmgArchive_Bz2_PathRead()
+        //{
+        //    ArchiveFileRead("Dmg_bz2.dmg");
+        //}
+    }
+}