Add SaveDataFileSystemCacheManager

src/LibHac/FsSystem/DirectorySaveDataFileSystem.cs

@@ -55,6 +55,11 @@ namespace LibHac.FsSystem
         private ISaveDataCommitTimeStampGetter _timeStampGetter;
         private RandomDataGenerator _randomGenerator;
 
+        // Additions to support caching
+        private ISaveDataExtraDataAccessorCacheObserver _cacheObserver;
+        private SaveDataSpaceId _spaceId;
+        private ulong _saveDataId;
+
         private class DirectorySaveDataFile : IFile
         {
             private IFile _baseFile;
@@ -171,6 +176,7 @@ namespace LibHac.FsSystem
 
         protected override void Dispose(bool disposing)
         {
+            _cacheObserver?.Unregister(_spaceId, _saveDataId);
             _baseFs?.Dispose();
             base.Dispose(disposing);
         }
@@ -797,7 +803,12 @@ namespace LibHac.FsSystem
         public void RegisterCacheObserver(ISaveDataExtraDataAccessorCacheObserver observer, SaveDataSpaceId spaceId,
             ulong saveDataId)
         {
-            throw new NotImplementedException();
+            _cacheObserver = observer;
+            _spaceId = spaceId;
+            _saveDataId = saveDataId;
         }
+
+        public SaveDataSpaceId GetSaveDataSpaceId() => _spaceId;
+        public ulong GetSaveDataId() => _saveDataId;
     }
 }

src/LibHac/FsSystem/ISaveDataFileSystemCacheManager.cs

@@ -1,14 +1,18 @@
 using System;
 using LibHac.Fs;
+using LibHac.Fs.Fsa;
 using LibHac.FsSystem.Save;
 
 namespace LibHac.FsSystem
 {
     public interface ISaveDataFileSystemCacheManager : IDisposable
     {
-        bool GetCache(out ReferenceCountedDisposable<SaveDataFileSystem> fileSystem, SaveDataSpaceId spaceId, ulong saveDataId);
+        bool GetCache(out ReferenceCountedDisposable<IFileSystem> fileSystem, SaveDataSpaceId spaceId, ulong saveDataId);
         void Register(ReferenceCountedDisposable<ApplicationTemporaryFileSystem> fileSystem);
         void Register(ReferenceCountedDisposable<SaveDataFileSystem> fileSystem);
         void Unregister(SaveDataSpaceId spaceId, ulong saveDataId);
+        
+        // LibHac addition
+        void Register(ReferenceCountedDisposable<DirectorySaveDataFileSystem> fileSystem);
     }
 }

src/LibHac/FsSystem/SaveDataFileSystemCacheManager.cs

@@ -0,0 +1,159 @@
+using LibHac.Common;
+using LibHac.Diag;
+using LibHac.Fs;
+using LibHac.Fs.Fsa;
+using LibHac.FsSystem.Save;
+using LibHac.Os;
+
+namespace LibHac.FsSystem
+{
+    public class SaveDataFileSystemCacheManager : ISaveDataFileSystemCacheManager
+    {
+        private struct Cache
+        {
+            private ReferenceCountedDisposable<IFileSystem> _fileSystem;
+            private ulong _saveDataId;
+            private SaveDataSpaceId _spaceId;
+
+            public void Dispose()
+            {
+                _fileSystem?.Dispose();
+                _fileSystem = null;
+            }
+
+            public bool IsCached(SaveDataSpaceId spaceId, ulong saveDataId)
+            {
+                return _fileSystem is not null && _spaceId == spaceId && _saveDataId == saveDataId;
+            }
+
+            public ReferenceCountedDisposable<IFileSystem> Move()
+            {
+                return Shared.Move(ref _fileSystem);
+            }
+
+            // Note: Nintendo only supports caching SaveDataFileSystem. We support DirectorySaveDataFileSystem too,
+            // so instead of calling methods on SaveDataFileSystem to get the save data info,
+            // we pass them in as parameters.
+            // Todo: Create a new interface for those methods?
+            public void Register(ReferenceCountedDisposable<IFileSystem> fileSystem, SaveDataSpaceId spaceId,
+                ulong saveDataId)
+            {
+                _spaceId = spaceId;
+                _saveDataId = saveDataId;
+
+                _fileSystem?.Dispose();
+                _fileSystem = fileSystem;
+            }
+
+            public void Unregister()
+            {
+                _fileSystem?.Dispose();
+                _fileSystem = null;
+            }
+        }
+
+        private SdkRecursiveMutexType _mutex;
+        private Cache[] _cachedFileSystems;
+        private int _maxCachedFileSystemCount;
+        private int _nextCacheIndex;
+
+        public SaveDataFileSystemCacheManager()
+        {
+            _mutex.Initialize();
+        }
+
+        public void Dispose()
+        {
+            Cache[] caches = _cachedFileSystems;
+
+            for (int i = 0; i < caches.Length; i++)
+            {
+                caches[i].Dispose();
+            }
+        }
+
+        public Result Initialize(int maxCacheCount)
+        {
+            Assert.SdkRequiresGreaterEqual(maxCacheCount, 0);
+
+            using ScopedLock<SdkRecursiveMutexType> scopedLock = ScopedLock.Lock(ref _mutex);
+
+            Assert.SdkAssert(_cachedFileSystems is null);
+
+            _maxCachedFileSystemCount = maxCacheCount;
+            if (maxCacheCount <= 0)
+                return Result.Success;
+
+            // Note: The original checks for overflow here
+            _cachedFileSystems = new Cache[maxCacheCount];
+            return Result.Success;
+        }
+
+        public bool GetCache(out ReferenceCountedDisposable<IFileSystem> fileSystem, SaveDataSpaceId spaceId,
+            ulong saveDataId)
+        {
+            Assert.SdkRequiresGreaterEqual(_maxCachedFileSystemCount, 0);
+
+            using ScopedLock<SdkRecursiveMutexType> scopedLock = ScopedLock.Lock(ref _mutex);
+
+            for (int i = 0; i < _maxCachedFileSystemCount; i++)
+            {
+                if (_cachedFileSystems[i].IsCached(spaceId, saveDataId))
+                {
+                    fileSystem = _cachedFileSystems[i].Move();
+                    return true;
+                }
+            }
+
+            fileSystem = default;
+            return false;
+        }
+
+        public void Register(ReferenceCountedDisposable<ApplicationTemporaryFileSystem> fileSystem)
+        {
+            throw new System.NotImplementedException();
+        }
+
+        public void Register(ReferenceCountedDisposable<SaveDataFileSystem> fileSystem)
+        {
+            throw new System.NotImplementedException();
+        }
+
+        public void Register(ReferenceCountedDisposable<DirectorySaveDataFileSystem> fileSystem)
+        {
+            if (_maxCachedFileSystemCount <= 0)
+                return;
+
+            Assert.SdkRequiresGreaterEqual(_nextCacheIndex, 0);
+            Assert.SdkRequiresGreater(_maxCachedFileSystemCount, _nextCacheIndex);
+
+            if (fileSystem.Target.GetSaveDataSpaceId() == SaveDataSpaceId.SdSystem)
+                return;
+
+            Result rc = fileSystem.Target.Rollback();
+            if (rc.IsFailure()) return;
+
+            using ScopedLock<SdkRecursiveMutexType> scopedLock = ScopedLock.Lock(ref _mutex);
+
+            _cachedFileSystems[_nextCacheIndex].Register(fileSystem.AddReference<IFileSystem>(),
+                fileSystem.Target.GetSaveDataSpaceId(), fileSystem.Target.GetSaveDataId());
+
+            _nextCacheIndex = (_nextCacheIndex + 1) % _maxCachedFileSystemCount;
+        }
+
+        public void Unregister(SaveDataSpaceId spaceId, ulong saveDataId)
+        {
+            Assert.SdkRequiresGreaterEqual(_maxCachedFileSystemCount, 0);
+
+            using ScopedLock<SdkRecursiveMutexType> scopedLock = ScopedLock.Lock(ref _mutex);
+
+            for (int i = 0; i < _maxCachedFileSystemCount; i++)
+            {
+                if (_cachedFileSystems[i].IsCached(spaceId, saveDataId))
+                {
+                    _cachedFileSystems[i].Unregister();
+                }
+            }
+        }
+    }
+}