Merge pull request #726 from Erior/feature/7ZipDelta

Add support for 7ZipDelta decompress

src/SharpCompress/Compressors/Filters/DeltaFilter.cs

@@ -0,0 +1,42 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.Compressors.Filters
+{
+    internal class DeltaFilter : Filter
+    {
+        private const int DISTANCE_MIN = 1;
+        private const int DISTANCE_MAX = 256;
+        private const int DISTANCE_MASK = DISTANCE_MAX - 1;
+
+        private int _distance;
+        private byte[] _history;
+        private int _position;
+
+        public DeltaFilter(bool isEncoder, Stream baseStream, byte[] info)
+            : base(isEncoder, baseStream, 1)
+        {
+            _distance = info[0];
+            _history = new byte[DISTANCE_MAX];
+            _position = 0;
+
+            if (_distance < DISTANCE_MIN)
+            {
+                throw new NotSupportedException();
+            }
+        }
+
+        protected override int Transform(byte[] buffer, int offset, int count)
+        {
+            int end = offset + count;
+
+            for( int i = offset; i < end; i++ )
+            {
+                buffer[i] += _history[(_distance + _position--) & DISTANCE_MASK];
+                _history[_position & DISTANCE_MASK] = buffer[i];
+            }
+
+            return count;
+        }
+    }
+}

src/SharpCompress/Compressors/LZMA/Registry.cs

@@ -13,6 +13,7 @@ namespace SharpCompress.Compressors.LZMA;
 internal static class DecoderRegistry
 {
     private const uint K_COPY = 0x0;
+    private const uint K_DELTA = 0x3;
     private const uint K_LZMA2 = 0x21;
     private const uint K_LZMA = 0x030101;
     private const uint K_PPMD = 0x030401;
@@ -37,6 +38,8 @@ long limit
                     throw new NotSupportedException();
                 }
                 return inStreams.Single();
+            case K_DELTA:
+                return new DeltaFilter(false, inStreams.Single(), info);
             case K_LZMA:
             case K_LZMA2:
                 return new LzmaStream(info, inStreams.Single(), -1, limit);

tests/SharpCompress.Test/SevenZip/SevenZipArchiveTests.cs

@@ -109,4 +109,8 @@ public class SevenZipArchiveTests : ArchiveTests
     //"7Zip.BZip2.split.005",
     //"7Zip.BZip2.split.006",
     //"7Zip.BZip2.split.007"
+
+    [Fact]
+    public void SevenZipArchive_delta_FileRead() =>
+        ArchiveFileRead("7Zip.delta.7z");
 }