"""Abstract base class for implementing xml enum types."""
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import struct
from itertools import izip
from pyffi.object_models.xml.basic import BasicBase
from pyffi.object_models.editable import EditableComboBox
class _MetaEnumBase(type):
"""This metaclass checks for the presence of _enumkeys, _enumvalues,
and _numbytes attributes. It also adds enum class attributes.
Used as metaclass of EnumBase."""
def __init__(cls, name, bases, dct):
super(_MetaEnumBase, cls).__init__(name, bases, dct)
# consistency checks
if not '_enumkeys' in dct:
raise TypeError('%s: missing _enumkeys attribute'%cls)
if not '_enumvalues' in dct:
raise TypeError('%s: missing _enumvalues attribute'%cls)
if not '_numbytes' in dct:
raise TypeError('%s: missing _numbytes attribute'%cls)
# check storage type
if cls._numbytes == 1:
cls._struct = '<B'
elif cls._numbytes == 2:
cls._struct = '<H'
elif cls._numbytes == 4:
cls._struct = '<I'
else:
raise RuntimeError("unsupported enum numbytes")
# template type?
cls._is_template = False
# does the type contain a Ref or a Ptr?
cls._has_links = False
# does the type contain a Ref?
cls._has_refs = False
# does the type contain a string?
cls._has_strings = False
# for other read/write checking
cls._min = 0
cls._max = (1 << (cls._numbytes * 8)) - 1
# set enum values as class attributes
for item, value in izip(cls._enumkeys, cls._enumvalues):
setattr(cls, item, value)
class EnumBase(BasicBase, EditableComboBox):
__metaclass__ = _MetaEnumBase
_enumkeys = []
_enumvalues = []
_numbytes = 1 # default width of an enum
#
# BasicBase methods
#
def __init__(self, **kwargs):
super(EnumBase, self).__init__(**kwargs)
self._value = 0
def get_value(self):
"""Return stored value."""
return self._value
def set_value(self, value):
"""Set value to C{value}."""
try:
val = int(value)
except ValueError:
try:
val = int(value, 16) # for '0x...' strings
except ValueError:
if value in self._enumkeys:
val = getattr(self, value)
else:
raise ValueError(
"cannot convert value '%s' to integer"%value)
if not val in self._enumvalues:
raise ValueError('invalid enum value (%i)' % val)
self._value = val
def read(self, stream, **kwargs):
"""Read value from stream."""
self._value = struct.unpack(self._struct, stream.read(self._numbytes))[0]
def write(self, stream, **kwargs):
"""Write value to stream."""
stream.write(struct.pack(self._struct, self._value))
def __str__(self):
try:
return self._enumkeys[self._enumvalues.index(self.get_value())]
except ValueError:
# not in _enumvalues list
return "<INVALID (%i)>" % self.get_value()
def get_size(self, **kwargs):
"""Return size of this type."""
return self._numbytes
def get_hash(self, **kwargs):
"""Return a hash value for this value."""
return self.get_value()
#
# EditableComboBox methods
#
def get_editor_keys(self):
"""List or tuple of strings, each string describing an item."""
return self._enumkeys
def set_editor_value(self, index):
"""Set value from item index."""
self.set_value(self._enumvalues[index])
def get_editor_value(self):
"""Get the item index from the enum value."""
return self._enumvalues.index(self._value)
def get_detail_display(self):
"""Return object that can be used to display the instance."""
try:
return self._enumkeys[self._enumvalues.index(self._value)]
except ValueError:
# value self._value is not in the self._enumvalues list
return "<INVALID (0x%08X)>" % self._value
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