This page hosts a formal specification of cramfs 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 = Cramfs.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = Cramfs(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.super_block # => get super block
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
# type: ignore
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import IntEnum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 11):
raise Exception("Incompatible Kaitai Struct Python API: 0.11 or later is required, but you have %s" % (kaitaistruct.__version__))
class Cramfs(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
super(Cramfs, self).__init__(_io)
self._parent = _parent
self._root = _root or self
self._read()
def _read(self):
self.super_block = Cramfs.SuperBlockStruct(self._io, self, self._root)
def _fetch_instances(self):
pass
self.super_block._fetch_instances()
class ChunkedDataInode(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
super(Cramfs.ChunkedDataInode, self).__init__(_io)
self._parent = _parent
self._root = _root
self._read()
def _read(self):
self.block_end_index = []
for i in range(((self._parent.size + self._root.page_size) - 1) // self._root.page_size):
self.block_end_index.append(self._io.read_u4le())
self.raw_blocks = self._io.read_bytes_full()
def _fetch_instances(self):
pass
for i in range(len(self.block_end_index)):
pass
class DirInode(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
super(Cramfs.DirInode, self).__init__(_io)
self._parent = _parent
self._root = _root
self._read()
def _read(self):
if self._io.size() > 0:
pass
self.children = []
i = 0
while not self._io.is_eof():
self.children.append(Cramfs.Inode(self._io, self, self._root))
i += 1
def _fetch_instances(self):
pass
if self._io.size() > 0:
pass
for i in range(len(self.children)):
pass
self.children[i]._fetch_instances()
class Info(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
super(Cramfs.Info, self).__init__(_io)
self._parent = _parent
self._root = _root
self._read()
def _read(self):
self.crc = self._io.read_u4le()
self.edition = self._io.read_u4le()
self.blocks = self._io.read_u4le()
self.files = self._io.read_u4le()
def _fetch_instances(self):
pass
class Inode(KaitaiStruct):
class FileType(IntEnum):
fifo = 1
chrdev = 2
dir = 4
blkdev = 6
reg_file = 8
symlink = 10
socket = 12
def __init__(self, _io, _parent=None, _root=None):
super(Cramfs.Inode, self).__init__(_io)
self._parent = _parent
self._root = _root
self._read()
def _read(self):
self.mode = self._io.read_u2le()
self.uid = self._io.read_u2le()
self.size_gid = self._io.read_u4le()
self.namelen_offset = self._io.read_u4le()
self.name = (self._io.read_bytes(self.namelen)).decode(u"UTF-8")
def _fetch_instances(self):
pass
_ = self.as_dir
if hasattr(self, '_m_as_dir'):
pass
self._m_as_dir._fetch_instances()
_ = self.as_reg_file
if hasattr(self, '_m_as_reg_file'):
pass
self._m_as_reg_file._fetch_instances()
_ = self.as_symlink
if hasattr(self, '_m_as_symlink'):
pass
self._m_as_symlink._fetch_instances()
@property
def as_dir(self):
if hasattr(self, '_m_as_dir'):
return self._m_as_dir
io = self._root._io
_pos = io.pos()
io.seek(self.offset)
self._raw__m_as_dir = io.read_bytes(self.size)
_io__raw__m_as_dir = KaitaiStream(BytesIO(self._raw__m_as_dir))
self._m_as_dir = Cramfs.DirInode(_io__raw__m_as_dir, self, self._root)
io.seek(_pos)
return getattr(self, '_m_as_dir', None)
@property
def as_reg_file(self):
if hasattr(self, '_m_as_reg_file'):
return self._m_as_reg_file
io = self._root._io
_pos = io.pos()
io.seek(self.offset)
self._m_as_reg_file = Cramfs.ChunkedDataInode(io, self, self._root)
io.seek(_pos)
return getattr(self, '_m_as_reg_file', None)
@property
def as_symlink(self):
if hasattr(self, '_m_as_symlink'):
return self._m_as_symlink
io = self._root._io
_pos = io.pos()
io.seek(self.offset)
self._m_as_symlink = Cramfs.ChunkedDataInode(io, self, self._root)
io.seek(_pos)
return getattr(self, '_m_as_symlink', None)
@property
def attr(self):
if hasattr(self, '_m_attr'):
return self._m_attr
self._m_attr = self.mode >> 9 & 7
return getattr(self, '_m_attr', None)
@property
def gid(self):
if hasattr(self, '_m_gid'):
return self._m_gid
self._m_gid = self.size_gid >> 24
return getattr(self, '_m_gid', None)
@property
def namelen(self):
if hasattr(self, '_m_namelen'):
return self._m_namelen
self._m_namelen = (self.namelen_offset & 63) << 2
return getattr(self, '_m_namelen', None)
@property
def offset(self):
if hasattr(self, '_m_offset'):
return self._m_offset
self._m_offset = (self.namelen_offset >> 6 & 67108863) << 2
return getattr(self, '_m_offset', None)
@property
def perm_g(self):
if hasattr(self, '_m_perm_g'):
return self._m_perm_g
self._m_perm_g = self.mode >> 3 & 7
return getattr(self, '_m_perm_g', None)
@property
def perm_o(self):
if hasattr(self, '_m_perm_o'):
return self._m_perm_o
self._m_perm_o = self.mode & 7
return getattr(self, '_m_perm_o', None)
@property
def perm_u(self):
if hasattr(self, '_m_perm_u'):
return self._m_perm_u
self._m_perm_u = self.mode >> 6 & 7
return getattr(self, '_m_perm_u', None)
@property
def size(self):
if hasattr(self, '_m_size'):
return self._m_size
self._m_size = self.size_gid & 16777215
return getattr(self, '_m_size', None)
@property
def type(self):
if hasattr(self, '_m_type'):
return self._m_type
self._m_type = KaitaiStream.resolve_enum(Cramfs.Inode.FileType, self.mode >> 12 & 15)
return getattr(self, '_m_type', None)
class SuperBlockStruct(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
super(Cramfs.SuperBlockStruct, self).__init__(_io)
self._parent = _parent
self._root = _root
self._read()
def _read(self):
self.magic = self._io.read_bytes(4)
if not self.magic == b"\x45\x3D\xCD\x28":
raise kaitaistruct.ValidationNotEqualError(b"\x45\x3D\xCD\x28", self.magic, self._io, u"/types/super_block_struct/seq/0")
self.size = self._io.read_u4le()
self.flags = self._io.read_u4le()
self.future = self._io.read_u4le()
self.signature = self._io.read_bytes(16)
if not self.signature == b"\x43\x6F\x6D\x70\x72\x65\x73\x73\x65\x64\x20\x52\x4F\x4D\x46\x53":
raise kaitaistruct.ValidationNotEqualError(b"\x43\x6F\x6D\x70\x72\x65\x73\x73\x65\x64\x20\x52\x4F\x4D\x46\x53", self.signature, self._io, u"/types/super_block_struct/seq/4")
self.fsid = Cramfs.Info(self._io, self, self._root)
self.name = (self._io.read_bytes(16)).decode(u"ASCII")
self.root = Cramfs.Inode(self._io, self, self._root)
def _fetch_instances(self):
pass
self.fsid._fetch_instances()
self.root._fetch_instances()
@property
def flag_fsid_v2(self):
if hasattr(self, '_m_flag_fsid_v2'):
return self._m_flag_fsid_v2
self._m_flag_fsid_v2 = self.flags >> 0 & 1
return getattr(self, '_m_flag_fsid_v2', None)
@property
def flag_holes(self):
if hasattr(self, '_m_flag_holes'):
return self._m_flag_holes
self._m_flag_holes = self.flags >> 8 & 1
return getattr(self, '_m_flag_holes', None)
@property
def flag_shifted_root_offset(self):
if hasattr(self, '_m_flag_shifted_root_offset'):
return self._m_flag_shifted_root_offset
self._m_flag_shifted_root_offset = self.flags >> 10 & 1
return getattr(self, '_m_flag_shifted_root_offset', None)
@property
def flag_sorted_dirs(self):
if hasattr(self, '_m_flag_sorted_dirs'):
return self._m_flag_sorted_dirs
self._m_flag_sorted_dirs = self.flags >> 1 & 1
return getattr(self, '_m_flag_sorted_dirs', None)
@property
def flag_wrong_signature(self):
if hasattr(self, '_m_flag_wrong_signature'):
return self._m_flag_wrong_signature
self._m_flag_wrong_signature = self.flags >> 9 & 1
return getattr(self, '_m_flag_wrong_signature', None)
@property
def page_size(self):
if hasattr(self, '_m_page_size'):
return self._m_page_size
self._m_page_size = 4096
return getattr(self, '_m_page_size', None)