cramfs: Python parsing library

KS implementation details

License: MIT

References

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.

Usage

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

Code

Parse a local file and get structure in memory:

data = Cramfs.from_file("path/to/local/file.cramfs")

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

cramfs.py

# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

from pkg_resources import parse_version
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum


if parse_version(kaitaistruct.__version__) < parse_version('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
        self._read()

    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
            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)

        @property
        def flag_fsid_v2(self):
            if hasattr(self, '_m_flag_fsid_v2'):
                return self._m_flag_fsid_v2 if hasattr(self, '_m_flag_fsid_v2') else None

            self._m_flag_fsid_v2 = ((self.flags >> 0) & 1)
            return self._m_flag_fsid_v2 if hasattr(self, '_m_flag_fsid_v2') else None

        @property
        def flag_holes(self):
            if hasattr(self, '_m_flag_holes'):
                return self._m_flag_holes if hasattr(self, '_m_flag_holes') else None

            self._m_flag_holes = ((self.flags >> 8) & 1)
            return self._m_flag_holes if hasattr(self, '_m_flag_holes') else None

        @property
        def flag_wrong_signature(self):
            if hasattr(self, '_m_flag_wrong_signature'):
                return self._m_flag_wrong_signature if hasattr(self, '_m_flag_wrong_signature') else None

            self._m_flag_wrong_signature = ((self.flags >> 9) & 1)
            return self._m_flag_wrong_signature if hasattr(self, '_m_flag_wrong_signature') else None

        @property
        def flag_sorted_dirs(self):
            if hasattr(self, '_m_flag_sorted_dirs'):
                return self._m_flag_sorted_dirs if hasattr(self, '_m_flag_sorted_dirs') else None

            self._m_flag_sorted_dirs = ((self.flags >> 1) & 1)
            return self._m_flag_sorted_dirs if hasattr(self, '_m_flag_sorted_dirs') else None

        @property
        def flag_shifted_root_offset(self):
            if hasattr(self, '_m_flag_shifted_root_offset'):
                return self._m_flag_shifted_root_offset if hasattr(self, '_m_flag_shifted_root_offset') else None

            self._m_flag_shifted_root_offset = ((self.flags >> 10) & 1)
            return self._m_flag_shifted_root_offset if hasattr(self, '_m_flag_shifted_root_offset') else 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
            self._read()

        def _read(self):
            self.block_end_index = [None] * (((self._parent.size + self._root.page_size) - 1) // self._root.page_size)
            for i in range(((self._parent.size + self._root.page_size) - 1) // self._root.page_size):
                self.block_end_index[i] = self._io.read_u4le()

            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
            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")

        @property
        def attr(self):
            if hasattr(self, '_m_attr'):
                return self._m_attr if hasattr(self, '_m_attr') else None

            self._m_attr = ((self.mode >> 9) & 7)
            return self._m_attr if hasattr(self, '_m_attr') else None

        @property
        def as_reg_file(self):
            if hasattr(self, '_m_as_reg_file'):
                return self._m_as_reg_file if hasattr(self, '_m_as_reg_file') else None

            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 self._m_as_reg_file if hasattr(self, '_m_as_reg_file') else None

        @property
        def perm_u(self):
            if hasattr(self, '_m_perm_u'):
                return self._m_perm_u if hasattr(self, '_m_perm_u') else None

            self._m_perm_u = ((self.mode >> 6) & 7)
            return self._m_perm_u if hasattr(self, '_m_perm_u') else None

        @property
        def as_symlink(self):
            if hasattr(self, '_m_as_symlink'):
                return self._m_as_symlink if hasattr(self, '_m_as_symlink') else None

            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 self._m_as_symlink if hasattr(self, '_m_as_symlink') else None

        @property
        def perm_o(self):
            if hasattr(self, '_m_perm_o'):
                return self._m_perm_o if hasattr(self, '_m_perm_o') else None

            self._m_perm_o = (self.mode & 7)
            return self._m_perm_o if hasattr(self, '_m_perm_o') else None

        @property
        def size(self):
            if hasattr(self, '_m_size'):
                return self._m_size if hasattr(self, '_m_size') else None

            self._m_size = (self.size_gid & 16777215)
            return self._m_size if hasattr(self, '_m_size') else None

        @property
        def gid(self):
            if hasattr(self, '_m_gid'):
                return self._m_gid if hasattr(self, '_m_gid') else None

            self._m_gid = (self.size_gid >> 24)
            return self._m_gid if hasattr(self, '_m_gid') else None

        @property
        def perm_g(self):
            if hasattr(self, '_m_perm_g'):
                return self._m_perm_g if hasattr(self, '_m_perm_g') else None

            self._m_perm_g = ((self.mode >> 3) & 7)
            return self._m_perm_g if hasattr(self, '_m_perm_g') else None

        @property
        def namelen(self):
            if hasattr(self, '_m_namelen'):
                return self._m_namelen if hasattr(self, '_m_namelen') else None

            self._m_namelen = ((self.namelen_offset & 63) << 2)
            return self._m_namelen if hasattr(self, '_m_namelen') else None

        @property
        def as_dir(self):
            if hasattr(self, '_m_as_dir'):
                return self._m_as_dir if hasattr(self, '_m_as_dir') else None

            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 self._m_as_dir if hasattr(self, '_m_as_dir') else None

        @property
        def type(self):
            if hasattr(self, '_m_type'):
                return self._m_type if hasattr(self, '_m_type') else None

            self._m_type = KaitaiStream.resolve_enum(Cramfs.Inode.FileType, ((self.mode >> 12) & 15))
            return self._m_type if hasattr(self, '_m_type') else None

        @property
        def offset(self):
            if hasattr(self, '_m_offset'):
                return self._m_offset if hasattr(self, '_m_offset') else None

            self._m_offset = (((self.namelen_offset >> 6) & 67108863) << 2)
            return self._m_offset if hasattr(self, '_m_offset') else 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
            self._read()

        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
            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()


    @property
    def page_size(self):
        if hasattr(self, '_m_page_size'):
            return self._m_page_size if hasattr(self, '_m_page_size') else None

        self._m_page_size = 4096
        return self._m_page_size if hasattr(self, '_m_page_size') else None