######################################################################
# This file should be kept compatible with Python 2.3, see PEP 291. #
######################################################################
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(_swapped_meta, self).__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):
"""Structure with big endian byte order"""
__metaclass__ = _swapped_meta
_swappedbytes_ = None

elif sys.byteorder == "big":
_OTHER_ENDIAN = "__ctype_le__"

BigEndianStructure = Structure
class LittleEndianStructure(Structure):
"""Structure with little endian byte order"""
__metaclass__ = _swapped_meta
_swappedbytes_ = None

else:
raise RuntimeError("Invalid byteorder")