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#
# This is a copy on write dictionary and set which abuses classes to try and be nice and fast.
#
# Copyright (C) 2006 Tim Ansell
#
# Please Note:
# Be careful when using mutable types (ie Dict and Lists) - operations involving these are SLOW.
# Assign a file to __warn__ to get warnings about slow operations.
#
import copy
ImmutableTypes = (
bool,
complex,
float,
int,
tuple,
frozenset,
str
)
MUTABLE = "__mutable__"
class COWMeta(type):
pass
class COWDictMeta(COWMeta):
__warn__ = False
__hasmutable__ = False
__marker__ = tuple()
def __str__(cls):
# FIXME: I have magic numbers!
return "<COWDict Level: %i Current Keys: %i>" % (cls.__count__, len(cls.__dict__) - 3)
__repr__ = __str__
def cow(cls):
class C(cls):
__count__ = cls.__count__ + 1
return C
copy = cow
__call__ = cow
def __setitem__(cls, key, value):
if value is not None and not isinstance(value, ImmutableTypes):
if not isinstance(value, COWMeta):
cls.__hasmutable__ = True
key += MUTABLE
setattr(cls, key, value)
def __getmutable__(cls, key, readonly=False):
nkey = key + MUTABLE
try:
return cls.__dict__[nkey]
except KeyError:
pass
value = getattr(cls, nkey)
if readonly:
return value
if not cls.__warn__ is False and not isinstance(value, COWMeta):
print("Warning: Doing a copy because %s is a mutable type." % key, file=cls.__warn__)
try:
value = value.copy()
except AttributeError as e:
value = copy.copy(value)
setattr(cls, nkey, value)
return value
__getmarker__ = []
def __getreadonly__(cls, key, default=__getmarker__):
"""
Get a value (even if mutable) which you promise not to change.
"""
return cls.__getitem__(key, default, True)
def __getitem__(cls, key, default=__getmarker__, readonly=False):
try:
try:
value = getattr(cls, key)
except AttributeError:
value = cls.__getmutable__(key, readonly)
# This is for values which have been deleted
if value is cls.__marker__:
raise AttributeError("key %s does not exist." % key)
return value
except AttributeError as e:
if not default is cls.__getmarker__:
return default
raise KeyError(str(e))
def __delitem__(cls, key):
cls.__setitem__(key, cls.__marker__)
def __revertitem__(cls, key):
if key not in cls.__dict__:
key += MUTABLE
delattr(cls, key)
def __contains__(cls, key):
return cls.has_key(key)
def has_key(cls, key):
value = cls.__getreadonly__(key, cls.__marker__)
if value is cls.__marker__:
return False
return True
def iter(cls, type, readonly=False):
for key in dir(cls):
if key.startswith("__"):
continue
if key.endswith(MUTABLE):
key = key[:-len(MUTABLE)]
if type == "keys":
yield key
try:
if readonly:
value = cls.__getreadonly__(key)
else:
value = cls[key]
except KeyError:
continue
if type == "values":
yield value
if type == "items":
yield (key, value)
return
def iterkeys(cls):
return cls.iter("keys")
def itervalues(cls, readonly=False):
if not cls.__warn__ is False and cls.__hasmutable__ and readonly is False:
print("Warning: If you aren't going to change any of the values call with True.", file=cls.__warn__)
return cls.iter("values", readonly)
def iteritems(cls, readonly=False):
if not cls.__warn__ is False and cls.__hasmutable__ and readonly is False:
print("Warning: If you aren't going to change any of the values call with True.", file=cls.__warn__)
return cls.iter("items", readonly)
class COWSetMeta(COWDictMeta):
def __str__(cls):
# FIXME: I have magic numbers!
return "<COWSet Level: %i Current Keys: %i>" % (cls.__count__, len(cls.__dict__) - 3)
__repr__ = __str__
def cow(cls):
class C(cls):
__count__ = cls.__count__ + 1
return C
def add(cls, value):
COWDictMeta.__setitem__(cls, repr(hash(value)), value)
def remove(cls, value):
COWDictMeta.__delitem__(cls, repr(hash(value)))
def __in__(cls, value):
return repr(hash(value)) in COWDictMeta
def iterkeys(cls):
raise TypeError("sets don't have keys")
def iteritems(cls):
raise TypeError("sets don't have 'items'")
# These are the actual classes you use!
class COWDictBase(metaclass=COWDictMeta):
__count__ = 0
class COWSetBase(metaclass=COWSetMeta):
__count__ = 0
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