A simple wrapper which allows to read a UTF-16 encoded string that starts with a byte order mark (BOM). The BOM indicates the endianness of the UTF-16 encoding, which can be either big-endian (BE) or little-endian (LE).
Use:
value to get the string value with BOM stripped, regardless of endianness.is_be and is_le to check the endianness indicated by the BOM.bom to check the raw byte order mark.This page hosts a formal specification of UTF-16 string with BOM using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All Python code generated by Kaitai Struct depends on the Kaitai Struct runtime library for Python. You must add this dependency to your project before you can parse or serialize any data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = Utf16WithBom.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = Utf16WithBom(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.bom # => The byte order mark (BOM) is a special marker at the beginning of the
string that indicates the endianness of the UTF-16 encoding. The
character U+FEFF is used as the BOM, and its byte representation differs
based on endianness:
* For big-endian (BE) UTF-16, it's `[0xFE, 0xFF]`
* For little-endian (LE) UTF-16, it's `[0xFF, 0xFE]`
This implementation checks for the presence of a valid BOM and strips it
from the resulting string value.
data.is_be # => True if the byte order mark indicates big-endian UTF-16 encoding.
# 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
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 Utf16WithBom(KaitaiStruct):
"""A simple wrapper which allows to read a UTF-16 encoded string that starts
with a byte order mark (BOM). The BOM indicates the endianness of the UTF-16
encoding, which can be either big-endian (BE) or little-endian (LE).
Use:
* `value` to get the string value with BOM stripped, regardless of endianness.
* `is_be` and `is_le` to check the endianness indicated by the BOM.
* `bom` to check the raw byte order mark.
.. seealso::
- https://en.wikipedia.org/wiki/Byte_order_mark
"""
def __init__(self, _io, _parent=None, _root=None):
super(Utf16WithBom, self).__init__(_io)
self._parent = _parent
self._root = _root or self
self._read()
def _read(self):
self.bom = self._io.read_bytes(2)
if not ((self.bom == b"\xFE\xFF") or (self.bom == b"\xFF\xFE")) :
raise kaitaistruct.ValidationNotAnyOfError(self.bom, self._io, u"/seq/0")
if self.is_be:
pass
self.str_be = (self._io.read_bytes_full()).decode(u"UTF-16BE")
if self.is_le:
pass
self.str_le = (self._io.read_bytes_full()).decode(u"UTF-16LE")
def _fetch_instances(self):
pass
if self.is_be:
pass
if self.is_le:
pass
@property
def is_be(self):
"""True if the byte order mark indicates big-endian UTF-16 encoding."""
if hasattr(self, '_m_is_be'):
return self._m_is_be
self._m_is_be = self.bom == b"\xFE\xFF"
return getattr(self, '_m_is_be', None)
@property
def is_le(self):
"""True if the byte order mark indicates little-endian UTF-16 encoding."""
if hasattr(self, '_m_is_le'):
return self._m_is_le
self._m_is_le = self.bom == b"\xFF\xFE"
return getattr(self, '_m_is_le', None)
@property
def value(self):
"""The string value with BOM stripped, regardless of endianness."""
if hasattr(self, '_m_value'):
return self._m_value
self._m_value = (self.str_be if self.is_be else self.str_le)
return getattr(self, '_m_value', None)