Workaround the inability to access FAT attributes in Linux

src/LibHac/Fs/ConcatenationDirectory.cs

@@ -1,5 +1,9 @@
 using System.Collections.Generic;
 
+#if NETCOREAPP
+using System.Runtime.InteropServices;
+#endif
+
 namespace LibHac.Fs
 {
     public class ConcatenationDirectory : IDirectory
@@ -23,7 +27,7 @@ namespace LibHac.Fs
         {
             foreach (DirectoryEntry entry in ParentDirectory.Read())
             {
-                bool isSplit = ConcatenationFileSystem.HasConcatenationFileAttribute(entry.Attributes);
+                bool isSplit = IsConcatenationFile(entry);
 
                 if (!CanReturnEntry(entry, isSplit)) continue;
 
@@ -44,7 +48,7 @@ namespace LibHac.Fs
 
             foreach (DirectoryEntry entry in ParentDirectory.Read())
             {
-                bool isSplit = ConcatenationFileSystem.HasConcatenationFileAttribute(entry.Attributes);
+                bool isSplit = IsConcatenationFile(entry);
 
                 if (CanReturnEntry(entry, isSplit)) count++;
             }
@@ -57,5 +61,21 @@ namespace LibHac.Fs
             return Mode.HasFlag(OpenDirectoryMode.Files) && (entry.Type == DirectoryEntryType.File || isSplit) ||
                    Mode.HasFlag(OpenDirectoryMode.Directories) && entry.Type == DirectoryEntryType.Directory && !isSplit;
         }
+
+        private bool IsConcatenationFile(DirectoryEntry entry)
+        {
+#if NETCOREAPP
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                return ConcatenationFileSystem.HasConcatenationFileAttribute(entry.Attributes);
+            }
+            else
+            {
+                return ParentFileSystem.IsConcatenationFile(entry.FullPath);
+            }
+#else
+            return ConcatenationFileSystem.HasConcatenationFileAttribute(entry.Attributes);
+#endif
+        }
     }
 }

src/LibHac/Fs/ConcatenationFileSystem.cs

@@ -1,6 +1,10 @@
 using System;
 using System.Collections.Generic;
 
+#if NETCOREAPP
+using System.Runtime.InteropServices;
+#endif
+
 namespace LibHac.Fs
 {
     public class ConcatenationFileSystem : IFileSystem
@@ -17,11 +21,39 @@ namespace LibHac.Fs
             SubFileSize = subFileSize;
         }
 
+        // .NET Core on platforms other than Windows doesn't support getting the
+        // archive flag in FAT file systems. Try to work around that for now for reading, 
+        // but writing still won't work properly on those platforms
         internal bool IsConcatenationFile(string path)
         {
+#if NETCOREAPP
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                return HasConcatenationFileAttribute(BaseFileSystem.GetFileAttributes(path));
+            }
+            else
+            {
+                return IsConcatenationFileHeuristic(path);
+            }
+#else
             return HasConcatenationFileAttribute(BaseFileSystem.GetFileAttributes(path));
+#endif
         }
 
+#if NETCOREAPP
+        private bool IsConcatenationFileHeuristic(string path)
+        {
+            if (BaseFileSystem.GetEntryType(path) != DirectoryEntryType.Directory) return false;
+
+            if (BaseFileSystem.GetEntryType(PathTools.Combine(path, "00")) != DirectoryEntryType.File) return false;
+
+            if (BaseFileSystem.OpenDirectory(path, OpenDirectoryMode.Directories).GetEntryCount() > 0) return false;
+
+            // Should be enough checks to avoid most false positives. Maybe
+            return true;
+        }
+#endif
+
         internal static bool HasConcatenationFileAttribute(NxFileAttributes attributes)
         {
             return (attributes & NxFileAttributes.Directory) != 0 && (attributes & NxFileAttributes.Archive) != 0;