file_sys: Cleanup to better match Switch file system constructs.

file_sys: Add factory class for RomFS file system.

src/core/file_sys/file_backend.h

@@ -1,66 +0,0 @@
-// Copyright 2014 Citra Emulator Project
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-#pragma once
-
-#include <cstddef>
-#include "common/common_types.h"
-#include "core/hle/result.h"
-
-////////////////////////////////////////////////////////////////////////////////////////////////////
-// FileSys namespace
-
-namespace FileSys {
-
-class FileBackend : NonCopyable {
-public:
-    FileBackend() {}
-    virtual ~FileBackend() {}
-
-    /**
-     * Read data from the file
-     * @param offset Offset in bytes to start reading data from
-     * @param length Length in bytes of data to read from file
-     * @param buffer Buffer to read data into
-     * @return Number of bytes read, or error code
-     */
-    virtual ResultVal<size_t> Read(u64 offset, size_t length, u8* buffer) const = 0;
-
-    /**
-     * Write data to the file
-     * @param offset Offset in bytes to start writing data to
-     * @param length Length in bytes of data to write to file
-     * @param flush The flush parameters (0 == do not flush)
-     * @param buffer Buffer to read data from
-     * @return Number of bytes written, or error code
-     */
-    virtual ResultVal<size_t> Write(u64 offset, size_t length, bool flush,
-                                    const u8* buffer) const = 0;
-
-    /**
-     * Get the size of the file in bytes
-     * @return Size of the file in bytes
-     */
-    virtual u64 GetSize() const = 0;
-
-    /**
-     * Set the size of the file in bytes
-     * @param size New size of the file
-     * @return true if successful
-     */
-    virtual bool SetSize(u64 size) const = 0;
-
-    /**
-     * Close the file
-     * @return true if the file closed correctly
-     */
-    virtual bool Close() const = 0;
-
-    /**
-     * Flushes the file
-     */
-    virtual void Flush() const = 0;
-};
-
-} // namespace FileSys