Linux下FAT文件系统

#define SECTOR_SIZE 512 /* sector size (bytes) */

#define SECTOR_BITS 9 /* log2(SECTOR_SIZE) */

#define MSDOS_DPB (MSDOS_DPS) /* dir entries per block */

#define MSDOS_DPB_BITS 4 /* log2(MSDOS_DPB) */

#define MSDOS_DPS (SECTOR_SIZE / sizeof(struct msdos_dir_entry))

#define MSDOS_DPS_BITS 4 /* log2(MSDOS_DPS) */

#define CF_LE_W(v) le16_to_cpu(v)

#define CF_LE_L(v) le32_to_cpu(v)

#define CT_LE_W(v) cpu_to_le16(v)

#define CT_LE_L(v) cpu_to_le32(v)

#define MSDOS_ROOT_INO 1 /* == MINIX_ROOT_INO */

#define MSDOS_DIR_BITS 5 /* log2(sizeof(struct msdos_dir_entry)) */

/* directory limit */

#define FAT_MAX_DIR_ENTRIES (65536)

#define FAT_MAX_DIR_SIZE (FAT_MAX_DIR_ENTRIES << MSDOS_DIR_BITS)

#define ATTR_NONE 0 /* no attribute bits */

#define ATTR_RO 1 /* read-only */

#define ATTR_HIDDEN 2 /* hidden */

#define ATTR_SYS 4 /* system */

#define ATTR_VOLUME 8 /* volume label */

#define ATTR_DIR 16 /* directory */

#define ATTR_ARCH 32 /* archived */

/* attribute bits that are copied "as is" */

#define ATTR_UNUSED (ATTR_VOLUME | ATTR_ARCH | ATTR_SYS | ATTR_HIDDEN)

/* bits that are used by the Windows 95/Windows NT extended FAT */

#define ATTR_EXT (ATTR_RO | ATTR_HIDDEN | ATTR_SYS | ATTR_VOLUME)

#define CASE_LOWER_BASE 8 /* base is lower case */

#define CASE_LOWER_EXT 16 /* extension is lower case */

#define DELETED_FLAG 0xe5 /* marks file as deleted when in name[0] */

#define IS_FREE(n) (!*(n) || *(n) == DELETED_FLAG)

#define MSDOS_NAME 11 /* maximum name length */

#define MSDOS_LONGNAME 256 /* maximum name length */

#define MSDOS_SLOTS 21 /* max # of slots for short and long names */

#define MSDOS_DOT ". " /* ".", padded to MSDOS_NAME chars */

#define MSDOS_DOTDOT ".. " /* "..", padded to MSDOS_NAME chars */

#define FAT_FIRST_ENT(s, x) ((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 :

MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x))

/* start of data cluster's entry (number of reserved clusters) */

#define FAT_START_ENT 2

/* maximum number of clusters */

#define MAX_FAT12 0xFF4

#define MAX_FAT16 0xFFF4

#define MAX_FAT32 0x0FFFFFF6

#define MAX_FAT(s) (MSDOS_SB(s)->fat_bits == 32 ? MAX_FAT32 :

MSDOS_SB(s)->fat_bits == 16 ? MAX_FAT16 : MAX_FAT12)

/* bad cluster mark */

#define BAD_FAT12 0xFF7

#define BAD_FAT16 0xFFF7

#define BAD_FAT32 0x0FFFFFF7

/* standard EOF */

#define EOF_FAT12 0xFFF

#define EOF_FAT16 0xFFFF

#define EOF_FAT32 0x0FFFFFFF

#define FAT_ENT_FREE (0)

#define FAT_ENT_BAD (BAD_FAT32)

#define FAT_ENT_EOF (EOF_FAT32)

#define FAT_FSINFO_SIG1 0x41615252

#define FAT_FSINFO_SIG2 0x61417272

#define IS_FSINFO(x) (le32_to_cpu((x)->signature1) == FAT_FSINFO_SIG1

&& le32_to_cpu((x)->signature2) == FAT_FSINFO_SIG2)

struct __fat_dirent {

long d_ino;

__kernel_off_t d_off;

unsigned short d_reclen;

char d_name[256]; /* We must not include limits.h! */

};

/* ioctl commands */

#define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct __fat_dirent[2])

#define VFAT_IOCTL_READDIR_SHORT _IOR('r', 2, struct __fat_dirent[2])

/* has used 0x72 ('r') in collision, so skip a few */

#define FAT_IOCTL_GET_ATTRIBUTES _IOR('r', 0x10, __u32)

#define FAT_IOCTL_SET_ATTRIBUTES _IOW('r', 0x11, __u32)

struct fat_boot_sector {

__u8 ignored[3]; /* Boot strap short or near jump */

__u8 system_id[8]; /* Name - can be used to special case partition manager volumes */

__u8 sector_size[2]; /* bytes per logical sector */

__u8 sec_per_clus; /* sectors/cluster */

__le16 reserved; /* reserved sectors */

__u8 fats; /* number of FATs */

__u8 dir_entries[2]; /* root directory entries */

__u8 sectors[2]; /* number of sectors */

__u8 media; /* media code */

__le16 fat_length; /* sectors/FAT */

__le16 secs_track; /* sectors per track */

__le16 heads; /* number of heads */

__le32 hidden; /* hidden sectors (unused) */

__le32 total_sect; /* number of sectors (if sectors == 0) */

/* The following fields are only used by FAT32 */

__le32 fat32_length; /* sectors/FAT */

__le16 flags; /* bit 8: fat mirroring, low 4: active fat */

__u8 version[2]; /* major, minor filesystem version */

__le32 root_cluster; /* first cluster in root directory */

__le16 info_sector; /* filesystem info sector */

__le16 backup_boot; /* backup boot sector */

__le16 reserved2[6]; /* Unused */

};

struct fat_boot_fsinfo {

__le32 signature1; /* 0x41615252L */

__le32 reserved1[120]; /* Nothing as far as I can tell */

__le32 signature2; /* 0x61417272L */

__le32 free_clusters; /* Free cluster count. -1 if unknown */

__le32 next_cluster; /* Most recently allocated cluster */

__le32 reserved2[4];

};

struct msdos_dir_entry {

__u8 name[MSDOS_NAME];/* name and extension */

__u8 attr; /* attribute bits */

__u8 lcase; /* Case for base and extension */

__u8 ctime_cs; /* Creation time, centiseconds (0-199) */

__le16 ctime; /* Creation time */

__le16 cdate; /* Creation date */

__le16 adate; /* Last access date */

__le16 starthi; /* High 16 bits of cluster in FAT32 */

__le16 time,date,start;/* time, date and first cluster */

__le32 size; /* file size (in bytes) */

};

/* Up to 13 characters of the name */

struct msdos_dir_slot {

__u8 id; /* sequence number for slot */

__u8 name0_4[10]; /* first 5 characters in name */

__u8 attr; /* attribute byte */

__u8 reserved; /* always 0 */

__u8 alias_checksum; /* checksum for 8.3 alias */

__u8 name5_10[12]; /* 6 more characters in name */

__le16 start; /* starting cluster number, 0 in long slots */

__u8 name11_12[4]; /* last 2 characters in name */

};

#ifdef __KERNEL__

/* media of boot sector */

static inline int fat_valid_media(u8 media)

{

return 0xf8 <= media || media == 0xf0;

}

#endif /* !__KERNEL__ */