/*
 * Copyright 2020, Shubham Bhagat, shubhambhagat111@yahoo.com
 * All rights reserved. Distributed under the terms of the MIT License.
 */
#ifndef _EXTENT_H_
#define _EXTENT_H_


#include "Inode.h"
#include "system_dependencies.h"


#define DIR2_BLOCK_HEADER_MAGIC 0x58443242
	// for v4 system
#define XFS_DIR2_DATA_FD_COUNT 3
#define EXTENT_REC_SIZE		128
#define MASK(n) ((1UL << n) - 1)


// xfs_exntst_t
enum ExtentState {
	XFS_EXT_NORM,
	XFS_EXT_UNWRITTEN,
	XFS_EXT_INVALID
};


// xfs_dir2_data_free_t
struct FreeRegion {
				uint16			offset;
				uint16			length;
};


// xfs_dir2_data_hdr_t
struct ExtentDataHeader {
				uint32			magic;
				FreeRegion		bestfree[XFS_DIR2_DATA_FD_COUNT];
};


// xfs_dir2_data_entry_t
struct ExtentDataEntry {
				xfs_ino_t		inumber;
				uint8			namelen;
				uint8			name[];

// Followed by a file type (8bit) if applicable and a 16bit tag
// tag is the offset from start of the block
};


// xfs_dir2_data_unused_t
struct ExtentUnusedEntry {
				uint16			freetag;
					// takes the value 0xffff
				uint16			length;
					// freetag+length overrides the inumber of an entry
				uint16			tag;
};


// xfs_dir2_leaf_entry_t
struct ExtentLeafEntry {
				uint32			hashval;
				uint32			address;
					// offset into block after >> 3
};


// xfs_dir2_block_tail_t
struct ExtentBlockTail {
				uint32			count;
					// # of entries in leaf
				uint32			stale;
					// # of free leaf entries
};


struct ExtentMapEntry {
			xfs_fileoff_t		br_startoff;
				// logical file block offset
			xfs_fsblock_t		br_startblock;
				// absolute block number
			xfs_filblks_t		br_blockcount;
				// # of blocks
			uint8				br_state;
				// state of the extent
};


class Extent
{
public:
								Extent(Inode* inode);
								~Extent();
			status_t			Init();
			bool				BlockType();
			void				FillMapEntry(void* pointerToMap);
			ExtentDataHeader*	BlockHeader();
			ExtentBlockTail*	BlockTail(ExtentDataHeader* header);
			ExtentLeafEntry*	BlockFirstLeaf(ExtentBlockTail* tail);
			xfs_ino_t			GetIno();
			status_t			GetNext(char* name, size_t* length,
									xfs_ino_t* ino);
			status_t			Lookup(const char* name, size_t length,
									xfs_ino_t* id);
private:
			Inode*				fInode;
			ExtentMapEntry*		fMap;
			char*				fBlockBuffer;
				// This isn't inode data. It holds the directory block.
};


#endif