LZ4 Decode

Author: AXiX-official

UnityAsset.NET/Compression.cs UnityAsset.NET/Compression/Compression.csUnityAsset.NET/Compression.cs renamed to UnityAsset.NET/Compression/Compression.cs

@@ -12,7 +12,7 @@ public static void DecompressToStream(ReadOnlySpan<byte> compressedData, Stream
         {
             case "lz4":
                 byte[] decompressedData = new byte[decompressedSize];
-                LZ4Codec.Decode(compressedData, new Span<byte>(decompressedData));
+                LZ4.Decode(compressedData, new Span<byte>(decompressedData));
                 decompressedStream.Write(decompressedData, 0, decompressedData.Length);
                 break;
             case "lzma":

UnityAsset.NET/Compression/LZ4.cs

@@ -0,0 +1,53 @@
+namespace UnityAsset.NET;
+
+public static class LZ4
+{
+    public static unsafe int Decode(ReadOnlySpan<byte> source, Span<byte> target)
+    {
+        int length1 = source.Length;
+        if (length1 <= 0)
+            return 0;
+        fixed (byte* sourcePtr = &source.GetPinnableReference())
+        fixed (byte* targetPtr = &target.GetPinnableReference())
+        {
+            byte* s = sourcePtr;
+            byte* t = targetPtr;
+            byte* sourceEnd = sourcePtr + source.Length;
+            while (s < sourceEnd)
+            {
+                byte token = *s++;
+                int literalLength = token >> 4;
+                int matchLength = token & 0xF;
+                if (literalLength == 0xF)
+                {
+                    byte b;
+                    do
+                    {
+                        b = *s++;
+                        literalLength += b;
+                    } while (b == 0xFF && s < sourceEnd);
+                }
+                Buffer.MemoryCopy(s, t, literalLength, literalLength);
+                s += literalLength;
+                t += literalLength;
+
+                if (s >= sourceEnd) break;
+
+                int offset = *s++ | (*s++ << 8);
+                if (matchLength == 0xF)
+                {
+                    byte b;
+                    do
+                    {
+                        b = *s++;
+                        matchLength += b;
+                    } while (b == 0xFF && s < sourceEnd);
+                }
+                matchLength += 4;
+                Buffer.MemoryCopy(t - offset, t, matchLength, matchLength);
+                t += matchLength;
+            }
+            return (int)(t - targetPtr);
+        }
+    }
+}