Virtual Filesystem (#597)

* Add VfsFile and VfsDirectory classes

* Finish abstract Vfs classes

* Implement RealVfsFile (computer fs backend)

* Finish RealVfsFile and RealVfsDirectory

* Finished OffsetVfsFile

* More changes

* Fix import paths

* Major refactor

* Remove double const

* Use experimental/filesystem or filesystem depending on compiler

* Port partition_filesystem

* More changes

* More Overhaul

* FSP_SRV fixes

* Fixes and testing

* Try to get filesystem to compile

* Filesystem on linux

* Remove std::filesystem and document/test

* Compile fixes

* Missing include

* Bug fixes

* Fixes

* Rename v_file and v_dir

* clang-format fix

* Rename NGLOG_* to LOG_*

* Most review changes

* Fix TODO

* Guess 'main' to be Directory by filename

src/core/hle/service/filesystem/filesystem.h

@@ -6,6 +6,8 @@
 
 #include <memory>
 #include "common/common_types.h"
+#include "core/file_sys/filesystem.h"
+#include "core/file_sys/vfs.h"
 #include "core/hle/result.h"
 
 namespace FileSys {
@@ -29,12 +31,136 @@ enum class Type {
     SDMC = 3,
 };
 
+// A class that wraps a VfsDirectory with methods that return ResultVal and ResultCode instead of
+// pointers and booleans. This makes using a VfsDirectory with switch services much easier and
+// avoids repetitive code.
+class VfsDirectoryServiceWrapper {
+public:
+    explicit VfsDirectoryServiceWrapper(FileSys::VirtualDir backing);
+
+    /**
+     * Get a descriptive name for the archive (e.g. "RomFS", "SaveData", etc.)
+     */
+    std::string GetName() const;
+
+    /**
+     * Create a file specified by its path
+     * @param path Path relative to the Archive
+     * @param size The size of the new file, filled with zeroes
+     * @return Result of the operation
+     */
+    ResultCode CreateFile(const std::string& path, u64 size) const;
+
+    /**
+     * Delete a file specified by its path
+     * @param path Path relative to the archive
+     * @return Result of the operation
+     */
+    ResultCode DeleteFile(const std::string& path) const;
+
+    /**
+     * Create a directory specified by its path
+     * @param path Path relative to the archive
+     * @return Result of the operation
+     */
+    ResultCode CreateDirectory(const std::string& path) const;
+
+    /**
+     * Delete a directory specified by its path
+     * @param path Path relative to the archive
+     * @return Result of the operation
+     */
+    ResultCode DeleteDirectory(const std::string& path) const;
+
+    /**
+     * Delete a directory specified by its path and anything under it
+     * @param path Path relative to the archive
+     * @return Result of the operation
+     */
+    ResultCode DeleteDirectoryRecursively(const std::string& path) const;
+
+    /**
+     * Rename a File specified by its path
+     * @param src_path Source path relative to the archive
+     * @param dest_path Destination path relative to the archive
+     * @return Result of the operation
+     */
+    ResultCode RenameFile(const std::string& src_path, const std::string& dest_path) const;
+
+    /**
+     * Rename a Directory specified by its path
+     * @param src_path Source path relative to the archive
+     * @param dest_path Destination path relative to the archive
+     * @return Result of the operation
+     */
+    ResultCode RenameDirectory(const std::string& src_path, const std::string& dest_path) const;
+
+    /**
+     * Open a file specified by its path, using the specified mode
+     * @param path Path relative to the archive
+     * @param mode Mode to open the file with
+     * @return Opened file, or error code
+     */
+    ResultVal<FileSys::VirtualFile> OpenFile(const std::string& path, FileSys::Mode mode) const;
+
+    /**
+     * Open a directory specified by its path
+     * @param path Path relative to the archive
+     * @return Opened directory, or error code
+     */
+    ResultVal<FileSys::VirtualDir> OpenDirectory(const std::string& path);
+
+    /**
+     * Get the free space
+     * @return The number of free bytes in the archive
+     */
+    u64 GetFreeSpaceSize() const;
+
+    /**
+     * Get the type of the specified path
+     * @return The type of the specified path or error code
+     */
+    ResultVal<FileSys::EntryType> GetEntryType(const std::string& path) const;
+
+private:
+    FileSys::VirtualDir backing;
+};
+
+// A class that deferres the creation of a filesystem until a later time.
+// This is useful if construction depends on a variable not known when the filesystem is registered.
+// Construct this with a filesystem (VirtualDir) to avoid the deferrence feature or override the
+//     CreateFilesystem method which will be called on first use.
+struct DeferredFilesystem {
+    DeferredFilesystem() = default;
+
+    explicit DeferredFilesystem(FileSys::VirtualDir vfs_directory) : fs(std::move(vfs_directory)) {}
+
+    FileSys::VirtualDir Get() {
+        if (fs == nullptr)
+            fs = CreateFilesystem();
+
+        return fs;
+    }
+
+    virtual ~DeferredFilesystem() = default;
+
+protected:
+    virtual FileSys::VirtualDir CreateFilesystem() {
+        return fs;
+    }
+
+private:
+    FileSys::VirtualDir fs;
+};
+
 /**
  * Registers a FileSystem, instances of which can later be opened using its IdCode.
  * @param factory FileSystem backend interface to use
  * @param type Type used to access this type of FileSystem
  */
-ResultCode RegisterFileSystem(std::unique_ptr<FileSys::FileSystemFactory>&& factory, Type type);
+ResultCode RegisterFileSystem(std::unique_ptr<DeferredFilesystem>&& fs, Type type);
+
+ResultCode RegisterRomFS(FileSys::VirtualFile fs);
 
 /**
  * Opens a file system
@@ -42,8 +168,9 @@ ResultCode RegisterFileSystem(std::unique_ptr<FileSys::FileSystemFactory>&& fact
  * @param path Path to the file system, used with Binary paths
  * @return FileSys::FileSystemBackend interface to the file system
  */
-ResultVal<std::unique_ptr<FileSys::FileSystemBackend>> OpenFileSystem(Type type,
-                                                                      FileSys::Path& path);
+ResultVal<FileSys::VirtualDir> OpenFileSystem(Type type);
+
+ResultVal<FileSys::VirtualFile> OpenRomFS();
 
 /**
  * Formats a file system