Format mostly used by Google Chrome and various Android apps to store resources such as translated strings, help messages and images.
This page hosts a formal specification of Chrome PAK serialization format 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 = ChromePak.from_file("path/to/local/file.pak")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = ChromePak(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.version # => only versions 4 and 5 are supported
# 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 ChromePak(KaitaiStruct):
"""Format mostly used by Google Chrome and various Android apps to store
resources such as translated strings, help messages and images.
.. seealso::
Source - https://web.archive.org/web/20220126211447/https://dev.chromium.org/developers/design-documents/linuxresourcesandlocalizedstrings
.. seealso::
Source - https://chromium.googlesource.com/chromium/src/tools/grit/+/3c36f27/grit/format/data_pack.py
.. seealso::
Source - https://chromium.googlesource.com/chromium/src/tools/grit/+/8a23eae/grit/format/data_pack.py
"""
class Encodings(Enum):
binary = 0
utf8 = 1
utf16 = 2
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.version = self._io.read_u4le()
if not ((self.version == 4) or (self.version == 5)) :
raise kaitaistruct.ValidationNotAnyOfError(self.version, self._io, u"/seq/0")
if self.version == 4:
self.num_resources_v4 = self._io.read_u4le()
self.encoding = KaitaiStream.resolve_enum(ChromePak.Encodings, self._io.read_u1())
if self.version == 5:
self.v5_part = ChromePak.HeaderV5Part(self._io, self, self._root)
self.resources = []
for i in range((self.num_resources + 1)):
self.resources.append(ChromePak.Resource(i, i < self.num_resources, self._io, self, self._root))
self.aliases = []
for i in range(self.num_aliases):
self.aliases.append(ChromePak.Alias(self._io, self, self._root))
class HeaderV5Part(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.encoding_padding = self._io.read_bytes(3)
self.num_resources = self._io.read_u2le()
self.num_aliases = self._io.read_u2le()
class Resource(KaitaiStruct):
def __init__(self, idx, has_body, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self.idx = idx
self.has_body = has_body
self._read()
def _read(self):
self.id = self._io.read_u2le()
self.ofs_body = self._io.read_u4le()
@property
def len_body(self):
"""MUST NOT be accessed until the next `resource` is parsed."""
if hasattr(self, '_m_len_body'):
return self._m_len_body
if self.has_body:
self._m_len_body = (self._parent.resources[(self.idx + 1)].ofs_body - self.ofs_body)
return getattr(self, '_m_len_body', None)
@property
def body(self):
"""MUST NOT be accessed until the next `resource` is parsed."""
if hasattr(self, '_m_body'):
return self._m_body
if self.has_body:
_pos = self._io.pos()
self._io.seek(self.ofs_body)
self._m_body = self._io.read_bytes(self.len_body)
self._io.seek(_pos)
return getattr(self, '_m_body', None)
class Alias(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.id = self._io.read_u2le()
self.resource_idx = self._io.read_u2le()
if not self.resource_idx <= (self._parent.num_resources - 1):
raise kaitaistruct.ValidationGreaterThanError((self._parent.num_resources - 1), self.resource_idx, self._io, u"/types/alias/seq/1")
@property
def resource(self):
if hasattr(self, '_m_resource'):
return self._m_resource
self._m_resource = self._parent.resources[self.resource_idx]
return getattr(self, '_m_resource', None)
@property
def num_resources(self):
if hasattr(self, '_m_num_resources'):
return self._m_num_resources
self._m_num_resources = (self.v5_part.num_resources if self.version == 5 else self.num_resources_v4)
return getattr(self, '_m_num_resources', None)
@property
def num_aliases(self):
if hasattr(self, '_m_num_aliases'):
return self._m_num_aliases
self._m_num_aliases = (self.v5_part.num_aliases if self.version == 5 else 0)
return getattr(self, '_m_num_aliases', None)