This page hosts a formal specification of vfat using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = Vfat.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = Vfat(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.boot_sector # => get boot sector
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
import dos_datetime
class Vfat(KaitaiStruct):
"""
.. seealso::
Source - https://download.microsoft.com/download/0/8/4/084c452b-b772-4fe5-89bb-a0cbf082286a/fatgen103.doc
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.boot_sector = Vfat.BootSector(self._io, self, self._root)
class ExtBiosParamBlockFat32(KaitaiStruct):
"""Extended BIOS Parameter Block for FAT32."""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.ls_per_fat = self._io.read_u4le()
self.has_active_fat = self._io.read_bits_int_le(1) != 0
self.reserved1 = self._io.read_bits_int_le(3)
self.active_fat_id = self._io.read_bits_int_le(4)
self._io.align_to_byte()
self.reserved2 = self._io.read_bytes(1)
if not self.reserved2 == b"\x00":
raise kaitaistruct.ValidationNotEqualError(b"\x00", self.reserved2, self._io, u"/types/ext_bios_param_block_fat32/seq/4")
self.fat_version = self._io.read_u2le()
self.root_dir_start_clus = self._io.read_u4le()
self.ls_fs_info = self._io.read_u2le()
self.boot_sectors_copy_start_ls = self._io.read_u2le()
self.reserved3 = self._io.read_bytes(12)
self.phys_drive_num = self._io.read_u1()
self.reserved4 = self._io.read_u1()
self.ext_boot_sign = self._io.read_u1()
self.volume_id = self._io.read_bytes(4)
self.partition_volume_label = (KaitaiStream.bytes_strip_right(self._io.read_bytes(11), 32)).decode(u"ASCII")
self.fs_type_str = (KaitaiStream.bytes_strip_right(self._io.read_bytes(8), 32)).decode(u"ASCII")
class BootSector(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.jmp_instruction = self._io.read_bytes(3)
self.oem_name = (KaitaiStream.bytes_strip_right(self._io.read_bytes(8), 32)).decode(u"ASCII")
self.bpb = Vfat.BiosParamBlock(self._io, self, self._root)
if not (self.is_fat32):
self.ebpb_fat16 = Vfat.ExtBiosParamBlockFat16(self._io, self, self._root)
if self.is_fat32:
self.ebpb_fat32 = Vfat.ExtBiosParamBlockFat32(self._io, self, self._root)
@property
def pos_fats(self):
"""Offset of FATs in bytes from start of filesystem."""
if hasattr(self, '_m_pos_fats'):
return self._m_pos_fats
self._m_pos_fats = (self.bpb.bytes_per_ls * self.bpb.num_reserved_ls)
return getattr(self, '_m_pos_fats', None)
@property
def ls_per_fat(self):
if hasattr(self, '_m_ls_per_fat'):
return self._m_ls_per_fat
self._m_ls_per_fat = (self.ebpb_fat32.ls_per_fat if self.is_fat32 else self.bpb.ls_per_fat)
return getattr(self, '_m_ls_per_fat', None)
@property
def ls_per_root_dir(self):
"""Size of root directory in logical sectors.
.. seealso::
FAT: General Overview of On-Disk Format, section "FAT Data Structure"
"""
if hasattr(self, '_m_ls_per_root_dir'):
return self._m_ls_per_root_dir
self._m_ls_per_root_dir = (((self.bpb.max_root_dir_rec * 32) + self.bpb.bytes_per_ls) - 1) // self.bpb.bytes_per_ls
return getattr(self, '_m_ls_per_root_dir', None)
@property
def is_fat32(self):
"""Determines if filesystem is FAT32 (true) or FAT12/16 (false)
by analyzing some preliminary conditions in BPB. Used to
determine whether we should parse post-BPB data as
`ext_bios_param_block_fat16` or `ext_bios_param_block_fat32`.
"""
if hasattr(self, '_m_is_fat32'):
return self._m_is_fat32
self._m_is_fat32 = self.bpb.max_root_dir_rec == 0
return getattr(self, '_m_is_fat32', None)
@property
def size_fat(self):
"""Size of one FAT in bytes."""
if hasattr(self, '_m_size_fat'):
return self._m_size_fat
self._m_size_fat = (self.bpb.bytes_per_ls * self.ls_per_fat)
return getattr(self, '_m_size_fat', None)
@property
def pos_root_dir(self):
"""Offset of root directory in bytes from start of filesystem."""
if hasattr(self, '_m_pos_root_dir'):
return self._m_pos_root_dir
self._m_pos_root_dir = (self.bpb.bytes_per_ls * (self.bpb.num_reserved_ls + (self.ls_per_fat * self.bpb.num_fats)))
return getattr(self, '_m_pos_root_dir', None)
@property
def size_root_dir(self):
"""Size of root directory in bytes."""
if hasattr(self, '_m_size_root_dir'):
return self._m_size_root_dir
self._m_size_root_dir = (self.ls_per_root_dir * self.bpb.bytes_per_ls)
return getattr(self, '_m_size_root_dir', None)
class BiosParamBlock(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.bytes_per_ls = self._io.read_u2le()
self.ls_per_clus = self._io.read_u1()
self.num_reserved_ls = self._io.read_u2le()
self.num_fats = self._io.read_u1()
self.max_root_dir_rec = self._io.read_u2le()
self.total_ls_2 = self._io.read_u2le()
self.media_code = self._io.read_u1()
self.ls_per_fat = self._io.read_u2le()
self.ps_per_track = self._io.read_u2le()
self.num_heads = self._io.read_u2le()
self.num_hidden_sectors = self._io.read_u4le()
self.total_ls_4 = self._io.read_u4le()
class RootDirectoryRec(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.file_name = self._io.read_bytes(11)
self._raw_attrs = self._io.read_bytes(1)
_io__raw_attrs = KaitaiStream(BytesIO(self._raw_attrs))
self.attrs = Vfat.RootDirectoryRec.AttrFlags(_io__raw_attrs, self, self._root)
self.reserved = self._io.read_bytes(10)
self._raw_last_write_time = self._io.read_bytes(4)
_io__raw_last_write_time = KaitaiStream(BytesIO(self._raw_last_write_time))
self.last_write_time = dos_datetime.DosDatetime(_io__raw_last_write_time)
self.start_clus = self._io.read_u2le()
self.file_size = self._io.read_u4le()
class AttrFlags(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.read_only = self._io.read_bits_int_le(1) != 0
self.hidden = self._io.read_bits_int_le(1) != 0
self.system = self._io.read_bits_int_le(1) != 0
self.volume_id = self._io.read_bits_int_le(1) != 0
self.is_directory = self._io.read_bits_int_le(1) != 0
self.archive = self._io.read_bits_int_le(1) != 0
self.reserved = self._io.read_bits_int_le(2)
@property
def long_name(self):
if hasattr(self, '_m_long_name'):
return self._m_long_name
self._m_long_name = ((self.read_only) and (self.hidden) and (self.system) and (self.volume_id))
return getattr(self, '_m_long_name', None)
class RootDirectory(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.records = []
for i in range(self._root.boot_sector.bpb.max_root_dir_rec):
self.records.append(Vfat.RootDirectoryRec(self._io, self, self._root))
class ExtBiosParamBlockFat16(KaitaiStruct):
"""Extended BIOS Parameter Block (DOS 4.0+, OS/2 1.0+). Used only
for FAT12 and FAT16.
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.phys_drive_num = self._io.read_u1()
self.reserved1 = self._io.read_u1()
self.ext_boot_sign = self._io.read_u1()
self.volume_id = self._io.read_bytes(4)
self.partition_volume_label = (KaitaiStream.bytes_strip_right(self._io.read_bytes(11), 32)).decode(u"ASCII")
self.fs_type_str = (KaitaiStream.bytes_strip_right(self._io.read_bytes(8), 32)).decode(u"ASCII")
@property
def fats(self):
if hasattr(self, '_m_fats'):
return self._m_fats
_pos = self._io.pos()
self._io.seek(self.boot_sector.pos_fats)
self._m_fats = []
for i in range(self.boot_sector.bpb.num_fats):
self._m_fats.append(self._io.read_bytes(self.boot_sector.size_fat))
self._io.seek(_pos)
return getattr(self, '_m_fats', None)
@property
def root_dir(self):
if hasattr(self, '_m_root_dir'):
return self._m_root_dir
_pos = self._io.pos()
self._io.seek(self.boot_sector.pos_root_dir)
self._raw__m_root_dir = self._io.read_bytes(self.boot_sector.size_root_dir)
_io__raw__m_root_dir = KaitaiStream(BytesIO(self._raw__m_root_dir))
self._m_root_dir = Vfat.RootDirectory(_io__raw__m_root_dir, self, self._root)
self._io.seek(_pos)
return getattr(self, '_m_root_dir', None)