_endian.py (2000B)
- import sys
- from ctypes import *
- _array_type = type(Array)
- def _other_endian(typ):
- """Return the type with the 'other' byte order. Simple types like
- c_int and so on already have __ctype_be__ and __ctype_le__
- attributes which contain the types, for more complicated types
- arrays and structures are supported.
- """
- # check _OTHER_ENDIAN attribute (present if typ is primitive type)
- if hasattr(typ, _OTHER_ENDIAN):
- return getattr(typ, _OTHER_ENDIAN)
- # if typ is array
- if isinstance(typ, _array_type):
- return _other_endian(typ._type_) * typ._length_
- # if typ is structure
- if issubclass(typ, Structure):
- return typ
- raise TypeError("This type does not support other endian: %s" % typ)
- class _swapped_meta(type(Structure)):
- def __setattr__(self, attrname, value):
- if attrname == "_fields_":
- fields = []
- for desc in value:
- name = desc[0]
- typ = desc[1]
- rest = desc[2:]
- fields.append((name, _other_endian(typ)) + rest)
- value = fields
- super().__setattr__(attrname, value)
- ################################################################
- # Note: The Structure metaclass checks for the *presence* (not the
- # value!) of a _swapped_bytes_ attribute to determine the bit order in
- # structures containing bit fields.
- if sys.byteorder == "little":
- _OTHER_ENDIAN = "__ctype_be__"
- LittleEndianStructure = Structure
- class BigEndianStructure(Structure, metaclass=_swapped_meta):
- """Structure with big endian byte order"""
- __slots__ = ()
- _swappedbytes_ = None
- elif sys.byteorder == "big":
- _OTHER_ENDIAN = "__ctype_le__"
- BigEndianStructure = Structure
- class LittleEndianStructure(Structure, metaclass=_swapped_meta):
- """Structure with little endian byte order"""
- __slots__ = ()
- _swappedbytes_ = None
- else:
- raise RuntimeError("Invalid byteorder")