Add support for ACE archives

src/SharpCompress/Common/Ace/AceCrc.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SharpCompress.Common.Ace
+{
+    public class AceCrc
+    {
+        // CRC-32 lookup table (standard polynomial 0xEDB88320, reflected)
+        private static readonly uint[] Crc32Table = GenerateTable();
+
+        private static uint[] GenerateTable()
+        {
+            var table = new uint[256];
+
+            for (int i = 0; i < 256; i++)
+            {
+                uint crc = (uint)i;
+
+                for (int j = 0; j < 8; j++)
+                {
+                    if ((crc & 1) != 0)
+                        crc = (crc >> 1) ^ 0xEDB88320u;
+                    else
+                        crc >>= 1;
+                }
+
+                table[i] = crc;
+            }
+
+            return table;
+        }
+
+        /// <summary>
+        /// Calculate ACE CRC-32 checksum.
+        /// ACE CRC-32 uses standard CRC-32 polynomial (0xEDB88320, reflected)
+        /// with init=0xFFFFFFFF but NO final XOR.
+        /// </summary>
+        public static uint AceCrc32(ReadOnlySpan<byte> data)
+        {
+            uint crc = 0xFFFFFFFFu;
+
+            foreach (byte b in data)
+            {
+                crc = (crc >> 8) ^ Crc32Table[(crc ^ b) & 0xFF];
+            }
+
+            return crc; // No final XOR for ACE
+        }
+
+        /// <summary>
+        /// ACE CRC-16 is the lower 16 bits of the ACE CRC-32.
+        /// </summary>
+        public static ushort AceCrc16(ReadOnlySpan<byte> data)
+        {
+            return (ushort)(AceCrc32(data) & 0xFFFF);
+        }
+    }
+}

src/SharpCompress/Common/Ace/AceEntry.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using SharpCompress.Common.Ace.Headers;
+
+namespace SharpCompress.Common.Ace
+{
+    public class AceEntry : Entry
+    {
+        private readonly AceFilePart _filePart;
+
+        internal AceEntry(AceFilePart filePart)
+        {
+            _filePart = filePart;
+        }
+
+        public override long Crc
+        {
+            get
+            {
+                if (_filePart == null)
+                {
+                    return 0;
+                }
+                return _filePart.Header.Crc32;
+            }
+        }
+
+        public override string? Key => _filePart?.Header.Filename;
+
+        public override string? LinkTarget => null;
+
+        public override long CompressedSize => _filePart?.Header.PackedSize ?? 0;
+
+        public override CompressionType CompressionType
+        {
+            get
+            {
+                if (_filePart.Header.CompressionType == Headers.CompressionType.Stored)
+                {
+                    return CompressionType.None;
+                }
+                return CompressionType.AceLZ77;
+            }
+        }
+
+        public override long Size => _filePart?.Header.OriginalSize ?? 0;
+
+        public override DateTime? LastModifiedTime => _filePart.Header.DateTime;
+
+        public override DateTime? CreatedTime => null;
+
+        public override DateTime? LastAccessedTime => null;
+
+        public override DateTime? ArchivedTime => null;
+
+        public override bool IsEncrypted => _filePart.Header.IsFileEncrypted;
+
+        public override bool IsDirectory => _filePart.Header.IsDirectory;
+
+        public override bool IsSplitAfter => false;
+
+        internal override IEnumerable<FilePart> Parts => _filePart.Empty();
+    }
+}

src/SharpCompress/Common/Ace/AceFilePart.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using SharpCompress.Common.Ace.Headers;
+using SharpCompress.IO;
+
+namespace SharpCompress.Common.Ace
+{
+    public class AceFilePart : FilePart
+    {
+        private readonly Stream _stream;
+        internal AceFileHeader Header { get; set; }
+
+        internal AceFilePart(AceFileHeader localAceHeader, Stream seekableStream)
+            : base(localAceHeader.ArchiveEncoding)
+        {
+            _stream = seekableStream;
+            Header = localAceHeader;
+        }
+
+        internal override string? FilePartName => Header.Filename;
+
+        internal override Stream GetCompressedStream()
+        {
+            if (_stream != null)
+            {
+                Stream compressedStream;
+                switch (Header.CompressionType)
+                {
+                    case Headers.CompressionType.Stored:
+                        compressedStream = new ReadOnlySubStream(
+                            _stream,
+                            Header.DataStartPosition,
+                            Header.PackedSize
+                        );
+                        break;
+                    default:
+                        throw new NotSupportedException(
+                            "CompressionMethod: " + Header.CompressionQuality
+                        );
+                }
+                return compressedStream;
+            }
+            return _stream.NotNull();
+        }
+
+        internal override Stream? GetRawStream() => _stream;
+    }
+}

src/SharpCompress/Common/Ace/AceVolume.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using SharpCompress.Common.Arj;
+using SharpCompress.Readers;
+
+namespace SharpCompress.Common.Ace
+{
+    public class AceVolume : Volume
+    {
+        public AceVolume(Stream stream, ReaderOptions readerOptions, int index = 0)
+            : base(stream, readerOptions, index) { }
+
+        public override bool IsFirstVolume
+        {
+            get { return true; }
+        }
+
+        /// <summary>
+        /// ArjArchive is part of a multi-part archive.
+        /// </summary>
+        public override bool IsMultiVolume
+        {
+            get { return false; }
+        }
+
+        internal IEnumerable<AceFilePart> GetVolumeFileParts()
+        {
+            return new List<AceFilePart>();
+        }
+    }
+}

src/SharpCompress/Common/Ace/Headers/AceFileHeader.cs

@@ -0,0 +1,171 @@
+using System;
+using System.Buffers.Binary;
+using System.Collections.Generic;
+using System.IO;
+using System.Xml.Linq;
+using SharpCompress.Common.Arc;
+
+namespace SharpCompress.Common.Ace.Headers
+{
+    /// <summary>
+    /// ACE file entry header
+    /// </summary>
+    public sealed class AceFileHeader : AceHeader
+    {
+        public long DataStartPosition { get; private set; }
+        public long PackedSize { get; set; }
+        public long OriginalSize { get; set; }
+        public DateTime DateTime { get; set; }
+        public int Attributes { get; set; }
+        public uint Crc32 { get; set; }
+        public CompressionType CompressionType { get; set; }
+        public CompressionQuality CompressionQuality { get; set; }
+        public ushort Parameters { get; set; }
+        public string Filename { get; set; } = string.Empty;
+        public List<byte> Comment { get; set; } = new();
+
+        /// <summary>
+        /// File data offset in the archive
+        /// </summary>
+        public ulong DataOffset { get; set; }
+
+        public bool IsDirectory => (Attributes & 0x10) != 0;
+
+        public bool IsContinuedFromPrev =>
+            (HeaderFlags & SharpCompress.Common.Ace.Headers.HeaderFlags.CONTINUED_PREV) != 0;
+
+        public bool IsContinuedToNext =>
+            (HeaderFlags & SharpCompress.Common.Ace.Headers.HeaderFlags.CONTINUED_NEXT) != 0;
+
+        public int DictionarySize
+        {
+            get
+            {
+                int bits = Parameters & 0x0F;
+                return bits < 10 ? 1024 : 1 << bits;
+            }
+        }
+
+        public AceFileHeader(ArchiveEncoding archiveEncoding)
+            : base(archiveEncoding, AceHeaderType.FILE) { }
+
+        /// <summary>
+        /// Reads the next file entry header from the stream.
+        /// Returns null if no more entries or end of archive.
+        /// Supports both ACE 1.0 and ACE 2.0 formats.
+        /// </summary>
+        public override AceHeader? Read(Stream stream)
+        {
+            var headerData = ReadHeader(stream);
+            if (headerData.Length == 0)
+            {
+                return null;
+            }
+            int offset = 0;
+
+            // Header type (1 byte)
+            HeaderType = headerData[offset++];
+
+            // Skip recovery record headers (ACE 2.0 feature)
+            if (HeaderType == (byte)SharpCompress.Common.Ace.Headers.AceHeaderType.RECOVERY32)
+            {
+                // Skip to next header
+                return null;
+            }
+
+            if (HeaderType != (byte)SharpCompress.Common.Ace.Headers.AceHeaderType.FILE)
+            {
+                // Unknown header type - skip
+                return null;
+            }
+
+            // Header flags (2 bytes)
+            HeaderFlags = BitConverter.ToUInt16(headerData, offset);
+            offset += 2;
+
+            // Packed size (4 bytes)
+            PackedSize = BitConverter.ToUInt32(headerData, offset);
+            offset += 4;
+
+            // Original size (4 bytes)
+            OriginalSize = BitConverter.ToUInt32(headerData, offset);
+            offset += 4;
+
+            // File date/time in DOS format (4 bytes)
+            var dosDateTime = BitConverter.ToUInt32(headerData, offset);
+            DateTime = ConvertDosDateTime(dosDateTime);
+            offset += 4;
+
+            // File attributes (4 bytes)
+            Attributes = (int)BitConverter.ToUInt32(headerData, offset);
+            offset += 4;
+
+            // CRC32 (4 bytes)
+            Crc32 = BitConverter.ToUInt32(headerData, offset);
+            offset += 4;
+
+            // Compression type (1 byte)
+            byte compressionType = headerData[offset++];
+            CompressionType = GetCompressionType(compressionType);
+
+            // Compression quality/parameter (1 byte)
+            byte compressionQuality = headerData[offset++];
+            CompressionQuality = GetCompressionQuality(compressionQuality);
+
+            // Parameters (2 bytes)
+            Parameters = BitConverter.ToUInt16(headerData, offset);
+            offset += 2;
+
+            // Reserved (2 bytes) - skip
+            offset += 2;
+
+            // Filename length (2 bytes)
+            var filenameLength = BitConverter.ToUInt16(headerData, offset);
+            offset += 2;
+
+            // Filename
+            if (offset + filenameLength <= headerData.Length)
+            {
+                Filename = ArchiveEncoding.Decode(headerData, offset, filenameLength);
+                offset += filenameLength;
+            }
+
+            // Handle comment if present
+            if ((HeaderFlags & SharpCompress.Common.Ace.Headers.HeaderFlags.COMMENT) != 0)
+            {
+                // Comment length (2 bytes)
+                if (offset + 2 <= headerData.Length)
+                {
+                    ushort commentLength = BitConverter.ToUInt16(headerData, offset);
+                    offset += 2 + commentLength; // Skip comment
+                }
+            }
+
+            // Store the data start position
+            DataStartPosition = stream.Position;
+
+            return this;
+        }
+
+        public CompressionType GetCompressionType(byte value) =>
+            value switch
+            {
+                0 => CompressionType.Stored,
+                1 => CompressionType.Lz77,
+                2 => CompressionType.Blocked,
+                _ => CompressionType.Unknown,
+            };
+
+        public CompressionQuality GetCompressionQuality(byte value) =>
+            value switch
+            {
+                0 => CompressionQuality.None,
+                1 => CompressionQuality.Fastest,
+                2 => CompressionQuality.Fast,
+                3 => CompressionQuality.Normal,
+                4 => CompressionQuality.Good,
+                5 => CompressionQuality.Best,
+                _ => CompressionQuality.Unknown,
+            };
+    }
+}