Implemented file name shortening

src/Core/SecureFolderFS.Core.Dokany/AppModels/DokanyOptions.cs

@@ -1,8 +1,8 @@
-using SecureFolderFS.Core.FileSystem.AppModels;
+using System;
+using System.Collections.Generic;
+using SecureFolderFS.Core.FileSystem.AppModels;
 using SecureFolderFS.Shared.Extensions;
 using SecureFolderFS.Storage.VirtualFileSystem;
-using System;
-using System.Collections.Generic;
 
 namespace SecureFolderFS.Core.Dokany.AppModels
 {
@@ -36,6 +36,7 @@ public static DokanyOptions ToOptions(IDictionary<string, object> options)
                 IsCachingFileNames = (bool?)options.Get(nameof(IsCachingFileNames)) ?? true,
                 IsCachingDirectoryIds = (bool?)options.Get(nameof(IsCachingDirectoryIds)) ?? true,
                 RecycleBinSize = (long?)options.Get(nameof(RecycleBinSize)) ?? 0L,
+                ShorteningThreshold = (int?)options.Get(nameof(ShorteningThreshold)) ?? 0,
 
                 // Dokany specific
                 MountPoint = (string?)options.Get(nameof(MountPoint))

src/Core/SecureFolderFS.Core.Dokany/Callbacks/OnDeviceDokany.cs

@@ -90,6 +90,9 @@ public override NtStatus CreateFile(string fileName, FileAccess access, FileShar
                             {
                             }
 
+                            // Materialize sidecar for the new directory name if shortened
+                            ciphertextPath = GetCiphertextPathForUse(fileName) ?? ciphertextPath;
+
                             // Create directory
                             _ = Directory.CreateDirectory(ciphertextPath);
 
@@ -172,6 +175,10 @@ public override NtStatus CreateFile(string fileName, FileAccess access, FileShar
                     if (specifics.Options.IsReadOnly && mode.IsWriteFlag())
                         throw FileSystemExceptions.FileSystemReadOnly;
 
+                    // Materialize sidecar for the new file name if shortened
+                    if (mode is FileMode.CreateNew or FileMode.Create or FileMode.OpenOrCreate)
+                        ciphertextPath = GetCiphertextPathForUse(fileName) ?? ciphertextPath;
+
                     var openAccess = readAccess ? System.IO.FileAccess.Read : System.IO.FileAccess.ReadWrite;
                     if (mode == FileMode.CreateNew && readAccess)
                         openAccess = System.IO.FileAccess.ReadWrite;
@@ -252,6 +259,11 @@ public override void Cleanup(string fileName, IDokanFileInfo info)
                     {
                         NativeRecycleBinHelpers.DeleteOrRecycle(ciphertextPath, specifics, StorableType.File);
                     }
+
+                    // Clean up sidecar after successful delete/recycle
+                    NativePathHelpers.DeleteSidecarFile(
+                        Path.GetFileName(ciphertextPath),
+                        Path.GetDirectoryName(ciphertextPath) ?? string.Empty);
                 }
                 catch (UnauthorizedAccessException)
                 {
@@ -537,7 +549,7 @@ public override NtStatus DeleteDirectory(string fileName, IDokanFileInfo info)
         public override NtStatus MoveFile(string oldName, string newName, bool replace, IDokanFileInfo info)
         {
             var oldCiphertextPath = GetCiphertextPath(oldName);
-            var newCiphertextPath = GetCiphertextPath(newName);
+            var newCiphertextPath = GetCiphertextPathForUse(newName);
             var fileNameCombined = $"{oldName} -> {newName}";
 
             if (oldCiphertextPath is null || newCiphertextPath is null)
@@ -564,6 +576,11 @@ public override NtStatus MoveFile(string oldName, string newName, bool replace,
                         File.Move(oldCiphertextPath, newCiphertextPath);
                     }
 
+                    // Clean up old sidecar after successful move
+                    NativePathHelpers.DeleteSidecarFile(
+                        Path.GetFileName(oldCiphertextPath),
+                        Path.GetDirectoryName(oldCiphertextPath) ?? string.Empty);
+
                     return Trace(DokanResult.Success, fileNameCombined, info);
                 }
                 else if (replace)
@@ -579,6 +596,11 @@ public override NtStatus MoveFile(string oldName, string newName, bool replace,
                     File.Delete(newCiphertextPath);
                     File.Move(oldCiphertextPath, newCiphertextPath);
 
+                    // Clean up old sidecar after successful move
+                    NativePathHelpers.DeleteSidecarFile(
+                        Path.GetFileName(oldCiphertextPath),
+                        Path.GetDirectoryName(oldCiphertextPath) ?? string.Empty);
+
                     return Trace(DokanResult.Success, fileNameCombined, info);
                 }
                 else
@@ -824,5 +846,10 @@ public override NtStatus FindStreams(string fileName, out IList<FileInformation>
         {
             return NativePathHelpers.GetCiphertextPath(plaintextName, specifics);
         }
+
+        private string? GetCiphertextPathForUse(string plaintextName)
+        {
+            return NativePathHelpers.GetCiphertextPathForUse(plaintextName, specifics);
+        }
     }
 }

src/Core/SecureFolderFS.Core.FUSE/AppModels/FuseOptions.cs

@@ -61,6 +61,7 @@ public static FuseOptions ToOptions(IDictionary<string, object> options)
                 IsCachingFileNames = (bool?)options.Get(nameof(IsCachingFileNames)) ?? true,
                 IsCachingDirectoryIds = (bool?)options.Get(nameof(IsCachingDirectoryIds)) ?? true,
                 RecycleBinSize = (long?)options.Get(nameof(RecycleBinSize)) ?? 0L,
+                ShorteningThreshold = (int?)options.Get(nameof(ShorteningThreshold)) ?? 0,
 
                 // FUSE specific
                 MountPoint = (string?)options.Get(nameof(MountPoint)),

src/Core/SecureFolderFS.Core.FUSE/Callbacks/OnDeviceFuse.cs

@@ -1,11 +1,14 @@
+using System.Runtime.CompilerServices;
+using System.Text;
+using OwlCore.Storage;
 using SecureFolderFS.Core.FileSystem;
+using SecureFolderFS.Core.FileSystem.Helpers;
 using SecureFolderFS.Core.FileSystem.Helpers.Paths;
+using SecureFolderFS.Core.FileSystem.Helpers.Paths.Abstract;
 using SecureFolderFS.Core.FileSystem.Helpers.Paths.Native;
+using SecureFolderFS.Core.FileSystem.Helpers.RecycleBin.Native;
 using SecureFolderFS.Core.FUSE.OpenHandles;
 using SecureFolderFS.Core.FUSE.UnsafeNative;
-using System.Runtime.CompilerServices;
-using System.Text;
-using SecureFolderFS.Core.FileSystem.Helpers.Paths.Abstract;
 using Tmds.Fuse;
 using Tmds.Linux;
 using static SecureFolderFS.Core.FUSE.UnsafeNative.UnsafeNativeApis;
@@ -65,7 +68,7 @@ public override unsafe int Create(ReadOnlySpan<byte> path, mode_t mode, ref Fuse
             if (FuseOptions!.IsReadOnly)
                 return -EROFS;
 
-            var ciphertextPath = GetCiphertextPath(path);
+            var ciphertextPath = GetCiphertextPathForUse(path);
             if (ciphertextPath is null)
                 return -ENOENT;
 
@@ -259,7 +262,7 @@ public override unsafe int MkDir(ReadOnlySpan<byte> path, mode_t mode)
             if (FuseOptions!.IsReadOnly)
                 return -EROFS;
 
-            var ciphertextPath = GetCiphertextPath(path);
+            var ciphertextPath = GetCiphertextPathForUse(path);
             if (ciphertextPath is null)
                 return -ENOENT;
 
@@ -410,7 +413,7 @@ public override unsafe int Rename(ReadOnlySpan<byte> path, ReadOnlySpan<byte> ne
                 return -EROFS;
 
             var ciphertextPath = GetCiphertextPath(path);
-            var newCiphertextPath = GetCiphertextPath(newPath);
+            var newCiphertextPath = GetCiphertextPathForUse(newPath);
             if (ciphertextPath is null || newCiphertextPath is null)
                 return -ENOENT;
 
@@ -421,10 +424,15 @@ public override unsafe int Rename(ReadOnlySpan<byte> path, ReadOnlySpan<byte> ne
                     return -errno;
             }
 
+            // Clean up old sidecar after successful rename
+            NativePathHelpers.DeleteSidecarFile(
+                Path.GetFileName(ciphertextPath),
+                Path.GetDirectoryName(ciphertextPath) ?? string.Empty);
+
             return 0;
         }
 
-        public override unsafe int RmDir(ReadOnlySpan<byte> path)
+        public override int RmDir(ReadOnlySpan<byte> path)
         {
             if (FuseOptions!.IsReadOnly)
                 return -EROFS;
@@ -437,17 +445,38 @@ public override unsafe int RmDir(ReadOnlySpan<byte> path)
                 return -ENOTEMPTY;
 
             var directoryIdPath = Path.Combine(ciphertextPath, FileSystem.Constants.Names.DIRECTORY_ID_FILENAME);
-
-            // Remove DirectoryID
-            File.Delete(directoryIdPath);
             specifics.DirectoryIdCache.CacheRemove(directoryIdPath);
 
-            fixed (byte *ciphertextPathPtr = Encoding.UTF8.GetBytes(ciphertextPath))
+            try
             {
-                if (rmdir(ciphertextPathPtr) == -1)
-                    return -errno;
+                NativeRecycleBinHelpers.DeleteOrRecycle(ciphertextPath, specifics, StorableType.Folder);
+            }
+            catch (FileNotFoundException)
+            {
+                return -ENOENT;
+            }
+            catch (DirectoryNotFoundException)
+            {
+                return -ENOENT;
+            }
+            catch (UnauthorizedAccessException)
+            {
+                return -EACCES;
+            }
+            catch (IOException ioEx) when (ErrorHandlingHelpers.IsDiskFullException(ioEx))
+            {
+                return -ENOSPC;
+            }
+            catch
+            {
+                return -EIO;
             }
 
+            // Clean up sidecar after successful delete/recycle
+            NativePathHelpers.DeleteSidecarFile(
+                Path.GetFileName(ciphertextPath),
+                Path.GetDirectoryName(ciphertextPath) ?? string.Empty);
+
             return 0;
         }
 
@@ -529,7 +558,7 @@ public override int Truncate(ReadOnlySpan<byte> path, ulong length, FuseFileInfo
         /// <remarks>
         /// This method is also responsible for file deletion.
         /// </remarks>
-        public override unsafe int Unlink(ReadOnlySpan<byte> path)
+        public override int Unlink(ReadOnlySpan<byte> path)
         {
             if (FuseOptions!.IsReadOnly)
                 return -EROFS;
@@ -541,11 +570,35 @@ public override unsafe int Unlink(ReadOnlySpan<byte> path)
             if (Directory.Exists(ciphertextPath))
                 return -EISDIR;
 
-            fixed (byte *ciphertextPathPtr = Encoding.UTF8.GetBytes(ciphertextPath))
+            try
             {
-                if (unlink(ciphertextPathPtr) == -1)
-                    return -errno;
+                NativeRecycleBinHelpers.DeleteOrRecycle(ciphertextPath, specifics, StorableType.File);
+            }
+            catch (FileNotFoundException)
+            {
+                return -ENOENT;
+            }
+            catch (DirectoryNotFoundException)
+            {
+                return -ENOENT;
+            }
+            catch (UnauthorizedAccessException)
+            {
+                return -EACCES;
+            }
+            catch (IOException ioEx) when (ErrorHandlingHelpers.IsDiskFullException(ioEx))
+            {
+                return -ENOSPC;
             }
+            catch
+            {
+                return -EIO;
+            }
+
+            // Clean up sidecar after successful delete/recycle
+            NativePathHelpers.DeleteSidecarFile(
+                Path.GetFileName(ciphertextPath),
+                Path.GetDirectoryName(ciphertextPath) ?? string.Empty);
 
             return 0;
         }
@@ -569,7 +622,7 @@ public override unsafe int UpdateTimestamps(ReadOnlySpan<byte> path, ref timespe
                         return -errno;
 
                     var result = futimens(*(int*)fd, times);
-                    UnsafeNativeApis.CloseDir(fd);
+                    CloseDir(fd);
 
                     if (result == -1)
                         return -errno;
@@ -614,12 +667,21 @@ public override int Write(ReadOnlySpan<byte> path, ulong offset, ReadOnlySpan<by
             return buffer.Length;
         }
 
-        protected override unsafe string? GetCiphertextPath(ReadOnlySpan<byte> plaintextName)
+        protected override unsafe string? GetCiphertextPath(ReadOnlySpan<byte> nativePlaintextName)
+        {
+            fixed (byte *plaintextNamePtr = nativePlaintextName)
+            {
+                var directoryId = new byte[FileSystem.Constants.DIRECTORY_ID_SIZE];
+                return NativePathHelpers.GetCiphertextPath(Encoding.UTF8.GetString(plaintextNamePtr, nativePlaintextName.Length), specifics, directoryId);
+            }
+        }
+
+        private unsafe string? GetCiphertextPathForUse(ReadOnlySpan<byte> nativePlaintextName)
         {
-            fixed (byte *plaintextNamePtr = plaintextName)
+            fixed (byte *plaintextNamePtr = nativePlaintextName)
             {
                 var directoryId = new byte[FileSystem.Constants.DIRECTORY_ID_SIZE];
-                return NativePathHelpers.GetCiphertextPath(Encoding.UTF8.GetString(plaintextNamePtr, plaintextName.Length), specifics, directoryId);
+                return NativePathHelpers.GetCiphertextPathForUse(Encoding.UTF8.GetString(plaintextNamePtr, nativePlaintextName.Length), specifics, directoryId);
             }
         }
     }

src/Core/SecureFolderFS.Core.FileSystem/Constants.cs

@@ -18,6 +18,8 @@ public static class FileSystem
         public static class Names
         {
             public const string ENCRYPTED_FILE_EXTENSION = ".sffs";
+            public const string SHORTENED_FILE_EXTENSION = ".sffsn";
+            public const string SIDECAR_FILE_EXTENSION = ".sffsi";
             public const string DIRECTORY_ID_FILENAME = "dirid.iv";
             public const string RECYCLE_BIN_NAME = "recycle_bin";
             public const string RECYCLE_BIN_CONFIGURATION_FILENAME = "recycle_bin.cfg";

src/Core/SecureFolderFS.Core.FileSystem/Exceptions/OrphanSidecarException.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace SecureFolderFS.Core.FileSystem.Exceptions
+{
+    /// <summary>
+    /// Exception thrown when a sidecar file (.sffsi) exists without a matching shortened file (.sffsn).
+    /// </summary>
+    public sealed class OrphanSidecarException : Exception
+    {
+        public OrphanSidecarException(string sidecarName)
+            : base($"Orphan sidecar file has no matching shortened file: {sidecarName}")
+        {
+        }
+    }
+}

src/Core/SecureFolderFS.Core.FileSystem/Helpers/Health/HealthHelpers.Directory.cs

@@ -3,7 +3,6 @@
 using System.Threading;
 using System.Threading.Tasks;
 using OwlCore.Storage;
-using SecureFolderFS.Core.Cryptography;
 using SecureFolderFS.Core.FileSystem.Helpers.Paths;
 using SecureFolderFS.Core.FileSystem.Helpers.Paths.Abstract;
 using SecureFolderFS.Shared.ComponentModel;
@@ -15,10 +14,10 @@ namespace SecureFolderFS.Core.FileSystem.Helpers.Health
 {
     public static partial class HealthHelpers
     {
-        public static async Task<IResult> RepairDirectoryAsync(IFolder affected, Security security, CancellationToken cancellationToken)
+        public static async Task<IResult> RepairDirectoryAsync(IFolder affected, FileSystemSpecifics specifics, CancellationToken cancellationToken)
         {
             // Return success if no encryption is used
-            if (security.NameCrypt is null)
+            if (specifics.Security.NameCrypt is null)
                 return Result.Success;
 
             if (affected is not IRenamableFolder renamableFolder)
@@ -39,9 +38,15 @@ public static async Task<IResult> RepairDirectoryAsync(IFolder affected, Securit
                     if (PathHelpers.IsCoreName(item.Name))
                         continue;
 
-                    // Encrypt a new name and rename
-                    var encryptedName = AbstractPathHelpers.EncryptNewName(item.Name, directoryId, security);
+                    // Remember old name for sidecar cleanup
+                    var oldName = item.Name;
+
+                    // Encrypt a new name (writes sidecar if shortening applies) and rename
+                    var encryptedName = await AbstractPathHelpers.EncryptNewNameForUseAsync(item.Name, directoryId, affected, specifics, cancellationToken);
                     _ = await renamableFolder.RenameAsync(item, encryptedName, cancellationToken);
+
+                    // Clean up old sidecar if the previous name was shortened
+                    await AbstractPathHelpers.DeleteSidecarFileAsync(oldName, renamableFolder, cancellationToken);
                 }
 
                 return Result.Success;