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import sys
from ctypes import Array, Structure, Union
_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 or union
if issubclass(typ, (Structure, Union)):
return typ
raise TypeError("This type does not support other endian: %s" % typ)
class _swapped_meta:
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)
class _swapped_struct_meta(_swapped_meta, type(Structure)): pass
class _swapped_union_meta(_swapped_meta, type(Union)): pass
################################################################
# Note: The Structure metaclass checks for the *presence* (not the
# value!) of a _swappedbytes_ 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_struct_meta):
"""Structure with big endian byte order"""
__slots__ = ()
_swappedbytes_ = None
LittleEndianUnion = Union
class BigEndianUnion(Union, metaclass=_swapped_union_meta):
"""Union with big endian byte order"""
__slots__ = ()
_swappedbytes_ = None
elif sys.byteorder == "big":
_OTHER_ENDIAN = "__ctype_le__"
BigEndianStructure = Structure
class LittleEndianStructure(Structure, metaclass=_swapped_struct_meta):
"""Structure with little endian byte order"""
__slots__ = ()
_swappedbytes_ = None
BigEndianUnion = Union
class LittleEndianUnion(Union, metaclass=_swapped_union_meta):
"""Union with little endian byte order"""
__slots__ = ()
_swappedbytes_ = None
else:
raise RuntimeError("Invalid byteorder")
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