Kernel: Split the FATFileSystem.{cpp,h} files into smaller components

Kernel/FileSystem/FATFS/FileSystem.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2022, Undefine <undefine@undefine.pl>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/OwnPtr.h>
+#include <AK/RefPtr.h>
+#include <AK/Types.h>
+#include <Kernel/FileSystem/BlockBasedFileSystem.h>
+#include <Kernel/FileSystem/FATFS/Definitions.h>
+#include <Kernel/FileSystem/Inode.h>
+#include <Kernel/Forward.h>
+#include <Kernel/KBuffer.h>
+
+namespace Kernel {
+
+class FATFS final : public BlockBasedFileSystem {
+    friend FATInode;
+
+public:
+    static ErrorOr<NonnullLockRefPtr<FileSystem>> try_create(OpenFileDescription&);
+
+    virtual ~FATFS() override = default;
+    virtual StringView class_name() const override { return "FATFS"sv; }
+    virtual Inode& root_inode() override;
+
+private:
+    virtual ErrorOr<void> initialize_while_locked() override;
+    virtual bool is_initialized_while_locked() override;
+    // FIXME: This is not a proper way to clear last mount of a FAT filesystem,
+    // but for now we simply have no other way to properly do it.
+    virtual ErrorOr<void> prepare_to_clear_last_mount() override { return {}; }
+
+    FATFS(OpenFileDescription&);
+
+    static constexpr u8 signature_1 = 0x28;
+    static constexpr u8 signature_2 = 0x29;
+
+    static constexpr u32 first_data_cluster = 2;
+
+    FAT32BootRecord const* boot_record() const { return reinterpret_cast<FAT32BootRecord const*>(m_boot_record->data()); };
+
+    BlockBasedFileSystem::BlockIndex first_block_of_cluster(u32 cluster) const;
+
+    OwnPtr<KBuffer> m_boot_record;
+    LockRefPtr<FATInode> m_root_inode;
+    u32 m_first_data_sector;
+};
+
+}