From 11a00be4ca31456cf654960f431e2dfd7f9b3cfb Mon Sep 17 00:00:00 2001
From: lifegpc <root@lifegpc.com>
Date: Tue, 14 Oct 2025 11:30:24 +0800
Subject: [PATCH] Add ZSTD support

---
 ArcFormats/ArcFormats.csproj  |  10 +++-
 ArcFormats/Circus/ImageCRX.cs |  13 ++++-
 ArcFormats/ZstdStream.cs      | 102 ++++++++++++++++++++++++++++++++++
 3 files changed, 123 insertions(+), 2 deletions(-)
 create mode 100644 ArcFormats/ZstdStream.cs

diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index 5094504e..7e7a5890 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -162,6 +162,7 @@
     <Compile Include="Unity\ScriptDSM.cs" />
     <Compile Include="Xuse\ArcNT.cs" />
     <Compile Include="Xuse\ArcWVB.cs" />
+    <Compile Include="ZstdStream.cs" />
     <Compile Include="Zyx\ImageXMG.cs" />
     <Compile Include="AudioAIFF.cs" />
     <Compile Include="Basil\ArcMIF.cs" />
@@ -1266,7 +1267,14 @@
     </EmbeddedResource>
     <EmbeddedResource Include="Strings\arcStrings.ru-RU.resx" />
   </ItemGroup>
-  <ItemGroup />
+  <ItemGroup>
+    <Content Include="x64\zstd.dll">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+    <Content Include="x86\zstd.dll">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>
     <PreBuildEvent>perl "$(SolutionDir)inc-revision.pl" "$(ProjectPath)" $(ConfigurationName)
diff --git a/ArcFormats/Circus/ImageCRX.cs b/ArcFormats/Circus/ImageCRX.cs
index b204f154..e0e2e10f 100644
--- a/ArcFormats/Circus/ImageCRX.cs
+++ b/ArcFormats/Circus/ImageCRX.cs
@@ -248,11 +248,22 @@ namespace GameRes.Formats.Circus
                 }
             }
 
+            private Stream GetDecompressStream() {
+                long pos = m_input.Position;
+                uint header = m_input.ReadUInt32();
+                m_input.Position = pos;
+                if (header == 0xFD2FB528) {
+                    var zstd = ZstdReader.Unpack(m_input.AsStream);
+                    return new MemoryStream(zstd);
+                } else
+                    return new ZLibStream(m_input.AsStream, CompressionMode.Decompress);
+            }
+
             private void UnpackV2 ()
             {
                 int pixel_size = m_bpp / 8;
                 int src_stride = m_width * pixel_size;
-                using (var zlib = new ZLibStream (m_input.AsStream, CompressionMode.Decompress, true))
+                using (var zlib = GetDecompressStream())
                 using (var src = new BinaryReader (zlib))
                 {
                     if (m_bpp >= 24)
diff --git a/ArcFormats/ZstdStream.cs b/ArcFormats/ZstdStream.cs
new file mode 100644
index 00000000..0c37afa4
--- /dev/null
+++ b/ArcFormats/ZstdStream.cs
@@ -0,0 +1,102 @@
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace GameRes.Compression
+{
+    public static class ZstdReader
+    {
+        private const int BUFFER_SIZE = 4096;
+
+        [DllImport("zstd.dll", CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr ZSTD_createDStream();
+
+        [DllImport("zstd.dll", CallingConvention = CallingConvention.Cdecl)]
+        private static extern int ZSTD_decompressStream(IntPtr zds, ref ZSTD_outBuffer output, ref ZSTD_inBuffer input);
+
+        [DllImport("zstd.dll", CallingConvention = CallingConvention.Cdecl)]
+        private static extern int ZSTD_freeDStream(IntPtr zds);
+
+        [StructLayout(LayoutKind.Sequential)]
+        private struct ZSTD_inBuffer
+        {
+            public IntPtr src;
+            public UIntPtr size;
+            public UIntPtr pos;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        private struct ZSTD_outBuffer
+        {
+            public IntPtr dst;
+            public UIntPtr size;
+            public UIntPtr pos;
+        }
+
+        public static byte[] Unpack(Stream compressedStream)
+        {
+            if (compressedStream == null) throw new ArgumentNullException(nameof(compressedStream));
+
+            IntPtr dctx = ZSTD_createDStream();
+            if (dctx == IntPtr.Zero)
+                throw new InvalidOperationException("Failed to create ZSTD_DStream.");
+
+            byte[] inBuf = new byte[BUFFER_SIZE];
+            byte[] outBuf = new byte[BUFFER_SIZE];
+            using (MemoryStream result = new MemoryStream())
+            {
+                try
+                {
+                    ZSTD_inBuffer input = new ZSTD_inBuffer();
+                    ZSTD_outBuffer output = new ZSTD_outBuffer();
+
+                    GCHandle inHandle = default, outHandle = default;
+                    try
+                    {
+                        inHandle = GCHandle.Alloc(inBuf, GCHandleType.Pinned);
+                        outHandle = GCHandle.Alloc(outBuf, GCHandleType.Pinned);
+
+                        int lastRet;
+                        while (true)
+                        {
+                            int bytesRead = compressedStream.Read(inBuf, 0, inBuf.Length);
+                            if (bytesRead == 0) break;
+
+                            input.src = inHandle.AddrOfPinnedObject();
+                            input.size = (UIntPtr)(uint)bytesRead;
+                            input.pos = UIntPtr.Zero;
+
+                            while (input.pos.ToUInt64() < input.size.ToUInt64())
+                            {
+                                output.dst = outHandle.AddrOfPinnedObject();
+                                output.size = (UIntPtr)(uint)outBuf.Length;
+                                output.pos = UIntPtr.Zero;
+
+                                lastRet = ZSTD_decompressStream(dctx, ref output, ref input);
+                                if (lastRet < 0)
+                                    throw new InvalidDataException($"ZSTD_decompressStream error: {lastRet}");
+
+                                if (output.pos.ToUInt64() > 0)
+                                    result.Write(outBuf, 0, (int)output.pos.ToUInt64());
+
+                                if (lastRet == 0) break;
+                            }
+                        }
+                    }
+                    finally
+                    {
+                        if (inHandle.IsAllocated) inHandle.Free();
+                        if (outHandle.IsAllocated) outHandle.Free();
+                    }
+
+                    return result.ToArray();
+                }
+                finally
+                {
+                    ZSTD_freeDStream(dctx);
+                }
+            }
+        }
+    }
+}