Calculate/Patch crc32

Author: AXiX-official

README.md

@@ -18,7 +18,7 @@ Only support Unity 2017.x or later.
 - [x] Parsing and Reading
 - [x] Serialization
 - [ ] ~~Patching~~ (Will be re-introduced in a future version)
-- [ ] Calculate/Patch crc32
+- [x] Calculate/Patch crc32
 
 ### SerializedFile
 

UnityAsset.NET/Extensions/BundleFileExtensions.cs

@@ -1,5 +1,8 @@
 using UnityAsset.NET.Files;
+using UnityAsset.NET.Files.BundleFiles;
 using UnityAsset.NET.Files.SerializedFiles;
+using UnityAsset.NET.IO;
+using UnityAsset.NET.IO.Reader;
 
 namespace UnityAsset.NET.Extensions;
 
@@ -11,12 +14,35 @@ public static List<Asset> Assets(this BundleFile bf) =>
             .SelectMany(file => ((SerializedFile)file.File).Assets)
             .ToList();
 
-    /*public static void PatchCrc32(this BundleFile bf, uint newCrc32)
+    public static uint CalculateCrc32(this BundleFile bf)
     {
-        if (bf.Crc32 != newCrc32)
+        if (bf.Files.Any(file => file.File is not IReaderProvider))
+            throw new ArgumentException("The bundle file must contain at least one IReaderProvider.");
+
+        var buffer = new byte[8092];
+        uint crc = 0;
+        foreach (var file in bf.Files)
         {
-            var patchBytes = CRC32.rCRC(newCrc32, bf.Crc32);
-            bf.Files.Add(new FileWrapper(new DataBuffer(patchBytes), new FileEntry(0, 4, 0, "crc32-patch-data")));
+            var rp = (IReaderProvider)file.File;
+            var reader = rp.CreateReader();
+            while (reader.Remaining > 0)
+            {
+                var bytesRead = reader.Read(buffer, 0, 8092);
+                crc = CRC32.CalculateCRC32(buffer.AsSpan(0, bytesRead), crc);
+            }
         }
-    }*/
+
+        return crc;
+    }
+    
+    public static void PatchCrc32(this BundleFile bf, uint newCrc32)
+    {
+        var oldCrc = bf.CalculateCrc32();
+        if (newCrc32 == oldCrc)
+            return;
+        var patch = CRC32.rCRC(oldCrc, newCrc32);
+        var offset = bf.Files[^1].Info.Offset + bf.Files[^1].Info.Size;
+        var entry = new FileEntry(offset, (ulong)patch.Length, 0, "crc32Patch");
+        bf.Files.Add(new (new MemoryReaderProvider(patch), entry));
+    }
 }

UnityAsset.NET/Files/BundleFiles/BundleFile.cs

@@ -33,8 +33,6 @@ public class BundleFile : IFile
     /// Optional key for UnityCN encryption
     /// </summary>
     public readonly string? UnityCnKey;
-
-    public uint? Crc32;
 
     public IVirtualFileInfo? SourceVirtualFile { get; private set; }
 

UnityAsset.NET/IO/Reader/MemoryReader.cs

@@ -130,4 +130,20 @@ public string ReadNullTerminatedString()
 
     // TEMPORARY: make it writable 
     public Span<byte> AsWritableSpan => _data.Span;
+}
+
+public class MemoryReaderProvider : IReaderProvider
+{
+    private readonly Memory<byte> _data;
+    public MemoryReaderProvider(byte[] data)
+    {
+        _data = new Memory<byte>(data);
+    }
+    
+    public MemoryReaderProvider(Memory<byte> data)
+    {
+        _data = data;
+    }
+    
+    public IReader CreateReader(Endianness endian = Endianness.BigEndian) => new MemoryReader(_data, 0, endian);
 }