[Zope3-checkins] CVS: Zope3/src/persistence - wref.py:1.2
Jim Fulton
jim at zope.com
Wed Jan 7 07:12:55 EST 2004
Update of /cvs-repository/Zope3/src/persistence
In directory cvs.zope.org:/tmp/cvs-serv11523/src/persistence
Modified Files:
wref.py
Log Message:
Added words to the weakref test.
Added basic PersistentWeakKeyDictionary objects.
=== Zope3/src/persistence/wref.py 1.1 => 1.2 ===
--- Zope3/src/persistence/wref.py:1.1 Tue Jan 6 14:50:38 2004
+++ Zope3/src/persistence/wref.py Wed Jan 7 07:12:53 2004
@@ -16,6 +16,8 @@
$Id$
"""
+from persistence import Persistent
+
WeakRefMarker = object()
class WeakRef(object):
@@ -26,7 +28,8 @@
specify an object to be called when the object is removed from the
database.
- Here's an example:
+ Here's an example. We'll start by creating a persistent object and
+ a refernce to it:
>>> import persistence.list
>>> import zodb.tests.util
@@ -35,6 +38,22 @@
>>> ref() is ob
True
+ The hash of the ref if the same as the hash of the refernced object:
+
+ >>> hash(ref) == hash(ob)
+ True
+
+ Two refs to the same object are equal:
+
+ >>> WeakRef(ob) == ref
+ True
+
+ >>> ob2 = persistence.list.PersistentList([1])
+ >>> WeakRef(ob2) == ref
+ False
+
+ Lets save the refernce and the refernced object in a database:
+
>>> db = zodb.tests.util.DB()
>>> conn1 = db.open()
@@ -42,22 +61,43 @@
>>> conn1.root()['ref'] = ref
>>> zodb.tests.util.commit()
+ If we oprn a new connection, sure enough, we can use the reference:
+
>>> conn2 = db.open()
- >>> conn1.root()['ref']() is conn1.root()['ob']
+ >>> conn2.root()['ref']() is conn2.root()['ob']
+ True
+ >>> hash(conn2.root()['ref']) == hash(conn2.root()['ob'])
True
- >>> del conn1.root()['ob']
+ But if we delete the referenced object and pack:
+
+ >>> del conn2.root()['ob']
>>> zodb.tests.util.commit()
>>> zodb.tests.util.pack(db)
+ And then look in a new connection:
+
>>> conn3 = db.open()
- >>> conn3.root()['ref']()
>>> conn3.root()['ob']
Traceback (most recent call last):
...
KeyError: 'ob'
+ Trying to dereference the refernce returns None:
+
+ >>> conn3.root()['ref']()
+
+ Trying to get a hash, raises a type error:
+
+ >>> hash(conn3.root()['ref'])
+ Traceback (most recent call last):
+ ...
+ TypeError: Weakly-referenced object has gone away
+
+ Always explicitly close databases: :)
+
>>> db.close()
+
"""
# We set _p_oid to a merker so that the serialization system can
@@ -78,4 +118,160 @@
except KeyError:
return None
return self._v_ob
+
+ def __hash__(self):
+ self = self()
+ if self is None:
+ raise TypeError('Weakly-referenced object has gone away')
+ return hash(self)
+
+ def __eq__(self, other):
+ self = self()
+ if self is None:
+ raise TypeError('Weakly-referenced object has gone away')
+ other = other()
+ if other is None:
+ raise TypeError('Weakly-referenced object has gone away')
+
+ return self == other
+
+class PersistentWeakKeyDictionary(Persistent):
+ """Persistent weak key dictionary
+
+ This is akin to WeakKeyDictionaries. Note, however, that removal
+ of items is extremely lazy. See below.
+
+ We'll start by creating a PersistentWeakKeyDictionary and adding
+ some persistent objects to it.
+
+ >>> d = PersistentWeakKeyDictionary()
+ >>> import zodb.tests.util
+ >>> p1 = zodb.tests.util.P('p1')
+ >>> p2 = zodb.tests.util.P('p2')
+ >>> p3 = zodb.tests.util.P('p3')
+ >>> d[p1] = 1
+ >>> d[p2] = 2
+ >>> d[p3] = 3
+
+ We'll create an extra persustent object that's not in the dict:
+
+ >>> p4 = zodb.tests.util.P('p4')
+
+ Now we'll excercise iteration and item access:
+
+ >>> l = [(str(k), d[k], d.get(k)) for k in d]
+ >>> l.sort()
+ >>> l
+ [('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
+
+ And the containment operator:
+
+ >>> [p in d for p in [p1, p2, p3, p4]]
+ [True, True, True, False]
+
+ We can add the dict and the refernced objects to a database:
+
+ >>> db = zodb.tests.util.DB()
+
+ >>> conn1 = db.open()
+ >>> conn1.root()['p1'] = p1
+ >>> conn1.root()['d'] = d
+ >>> conn1.root()['p2'] = p2
+ >>> conn1.root()['p3'] = p3
+ >>> zodb.tests.util.commit()
+
+ And things still work, as before:
+
+ >>> l = [(str(k), d[k], d.get(k)) for k in d]
+ >>> l.sort()
+ >>> l
+ [('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
+ >>> [p in d for p in [p1, p2, p3, p4]]
+ [True, True, True, False]
+
+ Likewise, we can read the objects from another connection and
+ things still work.
+
+ >>> conn2 = db.open()
+ >>> d = conn2.root()['d']
+ >>> p1 = conn2.root()['p1']
+ >>> p2 = conn2.root()['p2']
+ >>> p3 = conn2.root()['p3']
+ >>> l = [(str(k), d[k], d.get(k)) for k in d]
+ >>> l.sort()
+ >>> l
+ [('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
+ >>> [p in d for p in [p1, p2, p3, p4]]
+ [True, True, True, False]
+
+ Now, we'll delete one of the objects from the database, but *not*
+ from the dictionary:
+
+ >>> del conn2.root()['p2']
+ >>> zodb.tests.util.commit()
+
+ And pack the database, so that the no-longer referenced p2 is
+ actuallt removed from the database.
+
+ >>> zodb.tests.util.pack(db)
+
+ Now if we access the dictionary in a new connection, it no longer
+ has p2:
+
+ >>> conn3 = db.open()
+ >>> d = conn3.root()['d']
+ >>> l = [(str(k), d[k], d.get(k)) for k in d]
+ >>> l.sort()
+ >>> l
+ [('P(p1)', 1, 1), ('P(p3)', 3, 3)]
+
+ It's worth nothing that that the versions of the dictionary in
+ conn1 and conn2 still have p2, because p2 is still in the caches
+ for those connections.
+
+ Always explicitly close databases: :)
+
+ >>> db.close()
+
+ """
+ # XXX it is expensive trying to load dead objects from the database.
+ # It would be helpful if the data manager/connection cached these.
+
+
+ def __init__(self):
+ self.data = {}
+
+ def __getstate__(self):
+ state = Persistent.__getstate__(self)
+ state['data'] = state['data'].items()
+ return state
+
+ def __setstate__(self, state):
+ state['data'] = dict([
+ (k, v) for (k, v) in state['data']
+ if k() is not None
+ ])
+ Persistent.__setstate__(self, state)
+
+ def __setitem__(self, key, value):
+ self.data[WeakRef(key)] = value
+
+ def __getitem__(self, key):
+ return self.data[WeakRef(key)]
+
+ def __delitem__(self, key):
+ del self.data[WeakRef(key)]
+
+ def get(self, key):
+ return self.data.get(WeakRef(key))
+
+ def __contains__(self, key):
+ return WeakRef(key) in self.data
+
+ def __iter__(self):
+ for k in self.data:
+ yield k()
+
+ # XXX Someone else can fill out the rest of the methods, with tests. :)
+
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