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from .key import Key
class Store:
"""
A key-value store that uses ``asdf._block.key.Key``
to allow use of keys that:
- are not hashable (so any object can be used)
- when the key is garbage collected, the value
will be unretrievable
"""
def __init__(self):
# store contains 2 layers of lookup: id(obj), Key
self._by_id = {}
def lookup_by_object(self, obj, default=None):
if isinstance(obj, Key):
# if obj is a Key, look up the object
obj_id = id(obj._ref())
# and use the Key
obj_key = obj
else:
obj_id = id(obj)
obj_key = None
# if id is unknown, return default
if obj_id not in self._by_id:
return default
# first, lookup by id: O(1)
by_key = self._by_id[obj_id]
# if we have a key
if obj_key:
# use the key to get an existing value
# or default if this Key is unknown
return by_key.get(obj_key, default)
# we have seen this id(obj) before
# look for a matching key: O(N)
for key, value in by_key.items():
if key._matches_object(obj):
return value
# no match, return default
return default
def assign_object(self, obj, value):
if isinstance(obj, Key):
if not obj._is_valid():
msg = "Invalid key used for assign_object"
raise ValueError(msg)
obj_id = id(obj._ref())
obj_key = obj
else:
obj_id = id(obj)
obj_key = None
# if the id is unknown, just set it
if obj_id not in self._by_id:
if obj_key is None:
obj_key = Key(obj)
self._by_id[obj_id] = {obj_key: value}
return
# if id is known
by_key = self._by_id[obj_id]
# look for a matching matching key
if obj_key is None:
for key in by_key:
if key._matches_object(obj):
by_key[key] = value
return
# we didn't find a matching key, so make one
obj_key = Key(obj)
# if no match was found, add using the key
self._by_id[obj_id][obj_key] = value
def keys_for_value(self, value):
for oid, by_key in self._by_id.items():
for key, stored_value in by_key.items():
if stored_value == value and key._is_valid():
yield key
def _cleanup(self, object_id=None):
if object_id is None:
for oid in set(self._by_id):
self._cleanup(oid)
return
by_key = self._by_id[object_id]
keys_to_remove = [k for k in by_key if not k._is_valid()]
for key in keys_to_remove:
del by_key[key]
if not len(by_key):
del self._by_id[object_id]
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