ext2.h

/* ext2.h - Read-only ext2 filesystem driver for Pactor64 */

#ifndef _EXT2_H

#define _EXT2_H

#include "pactor64.h"

/* ext2 magic number */

#define EXT2_SUPER_MAGIC 0xEF53

/* ext2 superblock (at byte offset 1024 from start of partition) */

typedef struct {

    uint32_t s_inodes_count;

    uint32_t s_blocks_count;

    uint32_t s_r_blocks_count;

    uint32_t s_free_blocks_count;

    uint32_t s_free_inodes_count;

    uint32_t s_first_data_block;

    uint32_t s_log_block_size;

    uint32_t s_log_frag_size;

    uint32_t s_blocks_per_group;

    uint32_t s_frags_per_group;

    uint32_t s_inodes_per_group;

    uint32_t s_mtime;

    uint32_t s_wtime;

    uint16_t s_mnt_count;

    uint16_t s_max_mnt_count;

    uint16_t s_magic;

    uint16_t s_state;

    uint16_t s_errors;

    uint16_t s_minor_rev_level;

    uint32_t s_lastcheck;

    uint32_t s_checkinterval;

    uint32_t s_creator_os;

    uint32_t s_rev_level;

    uint16_t s_def_resuid;

    uint16_t s_def_resgid;

    /* Extended fields (rev >= 1) */

    uint32_t s_first_ino;

    uint16_t s_inode_size;

    uint16_t s_block_group_nr;

    uint32_t s_feature_compat;

    uint32_t s_feature_incompat;

    uint32_t s_feature_ro_compat;

    uint8_t  s_uuid[16];

    char     s_volume_name[16];

    char     s_last_mounted[64];

    uint32_t s_algo_usage_bitmap;

} __attribute__((packed)) ext2_superblock_t;

/* Block group descriptor */

typedef struct {

    uint32_t bg_block_bitmap;

    uint32_t bg_inode_bitmap;

    uint32_t bg_inode_table;

    uint16_t bg_free_blocks_count;

    uint16_t bg_free_inodes_count;

    uint16_t bg_used_dirs_count;

    uint16_t bg_pad;

    uint8_t  bg_reserved[12];

} __attribute__((packed)) ext2_bgd_t;

/* Inode */

typedef struct {

    uint16_t i_mode;

    uint16_t i_uid;

    uint32_t i_size;

    uint32_t i_atime;

    uint32_t i_ctime;

    uint32_t i_mtime;

    uint32_t i_dtime;

    uint16_t i_gid;

    uint16_t i_links_count;

    uint32_t i_blocks;

    uint32_t i_flags;

    uint32_t i_osd1;

    uint32_t i_block[15]; /* 0-11 direct, 12 indirect, 13 double, 14 triple */

    uint32_t i_generation;

    uint32_t i_file_acl;

    uint32_t i_dir_acl;

    uint32_t i_faddr;

    uint8_t  i_osd2[12];

} __attribute__((packed)) ext2_inode_t;

/* Directory entry */

typedef struct {

    uint32_t inode;

    uint16_t rec_len;

    uint8_t  name_len;

    uint8_t  file_type;

    char     name[];

} __attribute__((packed)) ext2_dirent_t;

/* Directory entry file types */

#define EXT2_FT_UNKNOWN  0

#define EXT2_FT_REG_FILE 1

#define EXT2_FT_DIR      2

#define EXT2_FT_CHRDEV   3

#define EXT2_FT_BLKDEV   4

#define EXT2_FT_FIFO     5

#define EXT2_FT_SOCK     6

#define EXT2_FT_SYMLINK  7

/* Inode mode bits */

#define EXT2_S_IFREG  0x8000

#define EXT2_S_IFDIR  0x4000

#define EXT2_S_IFLNK  0xA000

/* Root inode */

#define EXT2_ROOT_INO 2

/* Maximum path component length */

#define EXT2_NAME_LEN 255

/* Block device read function type */

typedef int (*block_read_fn)(uint64_t lba, uint32_t count, void *buf);

/* ext2 filesystem context */

typedef struct {

    block_read_fn   read_block;

    ext2_superblock_t sb;

    ext2_bgd_t     *bgdt;       /* Block group descriptor table */

    uint32_t        block_size;

    uint32_t        inodes_per_group;

    uint32_t        inode_size;

    uint32_t        groups_count;

} ext2_fs_t;

/* File handle */

typedef struct {

    ext2_fs_t      *fs;

    ext2_inode_t    inode;

    uint32_t        inode_num;

    uint32_t        size;

    uint32_t        position;

} ext2_file_t;

/* Directory entry callback */

typedef void (*ext2_dirent_cb)(const char *name, uint8_t name_len,

                               uint32_t inode, uint8_t file_type, void *ctx);

/* Initialize ext2 filesystem from block device */

int ext2_init(ext2_fs_t *fs, block_read_fn read_fn);

/* Open a file by path (returns 0 on success) */

int ext2_open(ext2_fs_t *fs, const char *path, ext2_file_t *file);

/* Read from an open file */

int ext2_read(ext2_file_t *file, void *buf, uint32_t size);

/* Close an open file */

void ext2_close(ext2_file_t *file);

/* Read directory entries (callback-based) */

int ext2_readdir(ext2_fs_t *fs, uint32_t dir_inode, ext2_dirent_cb cb, void *ctx);

/* Read a raw inode by number */

int ext2_read_inode(ext2_fs_t *fs, uint32_t inode_num, ext2_inode_t *inode);

/* Mount ext2 from ATA disk at given partition LBA offset */

int ext2_mount(ext2_fs_t *fs, uint32_t part_lba);

#endif /* _EXT2_H */