cramfs: Python parsing library

KS implementation details

License: MIT


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.


Runtime 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 kaitaistruct


Parse 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

Python source code to parse cramfs

# 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
from enum import Enum

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__))

class Cramfs(KaitaiStruct):
    def __init__(self, _io, _parent=None, _root=None):
        self._io = _io
        self._parent = _parent
        self._root = _root if _root else self

    def _read(self):
        self.super_block = Cramfs.SuperBlockStruct(self._io, self, self._root)

    class SuperBlockStruct(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self

        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._io.read_bytes(16)).decode(u"ASCII")
            self.root = Cramfs.Inode(self._io, self, self._root)

        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)

        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)

        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)

        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)

        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)

    class ChunkedDataInode(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self

        def _read(self):
            self.block_end_index = []
            for i in range(((self._parent.size + self._root.page_size) - 1) // self._root.page_size):

            self.raw_blocks = self._io.read_bytes_full()

    class Inode(KaitaiStruct):

        class FileType(Enum):
            fifo = 1
            chrdev = 2
            dir = 4
            blkdev = 6
            reg_file = 8
            symlink = 10
            socket = 12
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self

        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._io.read_bytes(self.namelen)).decode(u"utf-8")

        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)

        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()
            self._m_as_reg_file = Cramfs.ChunkedDataInode(io, self, self._root)
            return getattr(self, '_m_as_reg_file', None)

        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)

        def as_symlink(self):
            if hasattr(self, '_m_as_symlink'):
                return self._m_as_symlink

            io = self._root._io
            _pos = io.pos()
            self._m_as_symlink = Cramfs.ChunkedDataInode(io, self, self._root)
            return getattr(self, '_m_as_symlink', None)

        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)

        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)

        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)

        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)

        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)

        def as_dir(self):
            if hasattr(self, '_m_as_dir'):
                return self._m_as_dir

            io = self._root._io
            _pos = io.pos()
            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)
            return getattr(self, '_m_as_dir', None)

        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)

        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)

    class DirInode(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self

        def _read(self):
            if self._io.size() > 0:
                self.children = []
                i = 0
                while not self._io.is_eof():
                    self.children.append(Cramfs.Inode(self._io, self, self._root))
                    i += 1

    class Info(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self

        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 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)