library should load mac and windows file together

in one operation system

Author: Folleach

GeometryDashAPI.sln.DotSettings

@@ -1,2 +1,3 @@
 <wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
-	<s:Boolean x:Key="/Default/UserDictionary/Words/=LEVELCONTENT/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=LEVELCONTENT/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=xored/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

GeometryDashAPI/Data/DatFileFormat.cs

@@ -0,0 +1,7 @@
+namespace GeometryDashAPI.Data;
+
+public enum DatFileFormat
+{
+    Windows,
+    Mac
+}

GeometryDashAPI/Data/GameData.cs

@@ -10,6 +10,10 @@ namespace GeometryDashAPI.Data
 {
     public class GameData
     {
+        // This is xored gzip magick bytes: 'C?'
+        // see more https://en.wikipedia.org/wiki/Gzip
+        private static readonly byte[] XorDatFileMagickBytes = [ 0x43, 0x3f ];
+
         public Plist DataPlist { get; set; }
 
         private readonly GameDataType? type;
@@ -34,36 +38,41 @@ public virtual async Task LoadAsync(string fileName)
             using var file = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read, 4096, useAsync: true);
 #endif
             var data = new byte[file.Length];
-            await file.ReadAsync(data, 0, data.Length);
+            _ = await file.ReadAsync(data, 0, data.Length);
 
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+            if (data.AsSpan().Slice(0, XorDatFileMagickBytes.Length).IndexOf(XorDatFileMagickBytes) != 0)
             {
-                string decryptedData = Crypt.LoadSaveAsMacOS(data);
+                // mac files
+                var decryptedData = Crypt.LoadSaveAsMacOS(data);
                 DataPlist = new Plist(Encoding.ASCII.GetBytes(decryptedData));
+                return;
             }
-            else
-            {
-                var xor = Crypt.XOR(data, 0xB);
-                var index = xor.AsSpan().IndexOf((byte)0);
-                var gZipDecompress =
-                    Crypt.GZipDecompress(
-                        GameConvert.FromBase64(Encoding.ASCII.GetString(xor, 0, index >= 0 ? index : xor.Length)));
-                DataPlist = new Plist(Encoding.ASCII.GetBytes(gZipDecompress));
-            }
+
+            // windows files
+            var xor = Crypt.XOR(data, 0xB);
+            var index = xor.AsSpan().IndexOf((byte)0);
+            var gZipDecompress =
+                Crypt.GZipDecompress(
+                    GameConvert.FromBase64(Encoding.ASCII.GetString(xor, 0, index >= 0 ? index : xor.Length)));
+            DataPlist = new Plist(Encoding.ASCII.GetBytes(gZipDecompress));
         }
-    
+
         /// <summary>
         /// Saves class data to a file as a game save<br/><br/>
         /// Before saving, make sure that you have closed the game. Otherwise, after closing, the game will overwrite the file<br/>
         /// </summary>
         /// <param name="fullName">File to write the data.<br />
         /// use <b>null</b> value for default resolving
         /// </param>
-        public void Save(string? fullName = null)
+        /// <param name="format">
+        /// Specify if you want to save the file in a format specific to another operating system.<br />
+        /// Leave <b>null</b> to save the file for the current operating system
+        /// </param>
+        public void Save(string? fullName = null, DatFileFormat? format = null)
         {
             using var memory = new MemoryStream();
             DataPlist.SaveToStream(memory);
-            File.WriteAllBytes(fullName ?? ResolveFileName(type), GetFileContent(memory));
+            File.WriteAllBytes(fullName ?? ResolveFileName(type), GetFileContent(memory, format ?? ResolveFileFormat()));
         }
 
         /// <summary>
@@ -73,15 +82,19 @@ public void Save(string? fullName = null)
         /// <param name="fileName">File to write the data.<br />
         /// use <b>null</b> value for default resolving
         /// </param>
-        public async Task SaveAsync(string? fileName = null)
+        /// <param name="format">
+        /// Specify if you want to save the file in a format specific to another operating system.<br />
+        /// Leave <b>null</b> to save the file for the current operating system
+        /// </param>
+        public async Task SaveAsync(string? fileName = null, DatFileFormat? format = null)
         {
             using var memory = new MemoryStream();
             await DataPlist.SaveToStreamAsync(memory);
 #if NETSTANDARD2_1
-            await File.WriteAllBytesAsync(fileName ?? ResolveFileName(type), GetFileContent(memory));
+            await File.WriteAllBytesAsync(fileName ?? ResolveFileName(type), GetFileContent(memory, format ?? ResolveFileFormat()));
 #else
             using var file = new FileStream(fileName ?? ResolveFileName(type), FileMode.Create, FileAccess.ReadWrite, FileShare.Read, 4096, useAsync: true);
-            var data = GetFileContent(memory);
+            var data = GetFileContent(memory, format ?? ResolveFileFormat());
             await file.WriteAsync(data, 0, data.Length);
 #endif
         }
@@ -93,21 +106,39 @@ public static string ResolveFileName(GameDataType? type)
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                 return $@"{Environment.GetEnvironmentVariable("LocalAppData")}\GeometryDash\CC{type}.dat";
             if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
-                return $@"/Users/{Environment.GetEnvironmentVariable("USER")}/Library/Application Support/GeometryDash/CC{type}.dat";
+                return $"/Users/{Environment.GetEnvironmentVariable("USER")}/Library/Application Support/GeometryDash/CC{type}.dat";
             throw new InvalidOperationException($"can't resolve the directory with the saves on your operating system: '{RuntimeInformation.OSDescription}'. Use certain file name");
         }
 
-        private static byte[] GetFileContent(MemoryStream memory)
+        public static DatFileFormat ResolveFileFormat()
         {
             if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
-            {
-                var encrypted = Crypt.SavingSaveAsMacOS(memory.ToArray());
-                return encrypted;
-            }
+                return DatFileFormat.Mac;
+            return DatFileFormat.Windows;
+        }
+
+        private static byte[] GetFileContent(MemoryStream memory, DatFileFormat format)
+        {
+            if (format == DatFileFormat.Mac)
+                return Crypt.SavingSaveAsMacOS(memory.ToArray());
 
             var base64 = GameConvert.ToBase64(Crypt.GZipCompress(memory.ToArray()));
             return Crypt.XOR(Encoding.ASCII.GetBytes(base64), 0xB);
+        }
 
+        private static bool StartsWith(Stream stream, ReadOnlySpan<byte> prefix)
+        {
+            if (!stream.CanSeek)
+                throw new ArgumentException($"{nameof(stream)} is not seekable. This can lead to bugs.");
+            if (stream.Length < prefix.Length)
+                return false;
+            var position = stream.Position;
+            var buffer = new byte[prefix.Length];
+            var read = 0;
+            while (read != buffer.Length)
+                read += stream.Read(buffer, read, buffer.Length - read);
+            stream.Seek(position, SeekOrigin.Begin);
+            return buffer.AsSpan().IndexOf(prefix) == 0;
         }
     }
 }