Merge from 'tseaver-python_picklecache-2' branch:

```---------------------------------------------------------------------
r122975 | tseaver | 2011-09-27 13:31:54 -0400 (Tue, 27 Sep 2011) | 1 line

Move to match order defined in IPickleCache.
```

---------------------------------------------------------------------
r122974 | tseaver | 2011-09-27 13:31:06 -0400 (Tue, 27 Sep 2011) | 1 line

Tolerate being handed irrelevant arguments.
------------------------------------------------------------------------
r122973 | tseaver | 2011-09-27 13:31:05 -0400 (Tue, 27 Sep 2011) | 1 line

Enable 'Timestamp' fallback to 'timestamp' when extension unavailable.
------------------------------------------------------------------------
r122972 | tseaver | 2011-09-27 13:31:04 -0400 (Tue, 27 Sep 2011) | 3 lines

Don't raise KeyError for OID collision w/ same value object.

Also, implement stub of 'update_object_size_estimation'.
------------------------------------------------------------------------
r122971 | tseaver | 2011-09-27 13:31:03 -0400 (Tue, 27 Sep 2011) | 1 line

Document additional picklecache methods.

persistent/__init__.py

@@ -39,6 +39,13 @@ try:
 except ImportError:
     from picklecache import PickleCache
 
+try:
+    import TimeStamp
+except ImportError:
+    import timestamp as TimeStamp
+    import sys
+    sys.modules['persistent.TimeStamp'] = sys.modules['persistent.timestamp']
+
 if _HAVE_CPERSISTENCE:
     # Make an interface declaration for Persistent, if zope.interface
     # is available.  XXX that the pyPersistent version already does this?

persistent/interfaces.py

@@ -537,6 +537,16 @@ class IPickleCache(Interface):
             remove it from the ring.
         """
 
+    def debug_info():
+        """Return debugging data about objects in the cache.
+
+        o Return a sequence of tuples, (oid, refcount, typename, state).
+        """
+
+    def update_object_size_estimation(oid, new_size):
+        """Update the cache's size estimation for 'oid', if known to the cache.
+        """
+
     cache_size = Attribute(u'Target size of the cache')
     cache_drain_resistance = Attribute(u'Factor for draining cache below '
                                         u'target size')

persistent/picklecache.py

@@ -65,7 +65,8 @@ class PickleCache(object):
             raise ValueError('OID must be string: %s' % oid)
         # XXX
         if oid in self.persistent_classes or oid in self.data:
-            raise KeyError('Duplicate OID: %s' % oid)
+            if self.data[oid] is not value:
+                raise KeyError('Duplicate OID: %s' % oid)
         if type(value) is type:
             self.persistent_classes[oid] = value
         else:
@@ -226,6 +227,11 @@ class PickleCache(object):
                             ))
         return result
 
+    def update_object_size_estimation(self, oid, new_size):
+        """ See IPickleCache.
+        """
+        pass
+
     cache_size = property(lambda self: self.target_size)
     cache_drain_resistance = property(lambda self: self.drain_resistance)
     cache_non_ghost_count = property(lambda self: self.non_ghost_count)
@@ -254,4 +260,3 @@ class PickleCache(object):
                     break
         elif oid in self.persistent_classes:
             del self.persistent_classes[oid]
-

persistent/pyPersistence.py

@@ -80,7 +80,7 @@ class Persistent(object):
     __slots__ = ('__jar', '__oid', '__serial', '__flags', '__size')
     implements(IPersistent)
 
-    def __new__(cls):
+    def __new__(cls, *args, **kw):
         inst = super(Persistent, cls).__new__(cls)
         inst.__jar = None
         inst.__oid = None

persistent/tests/test_pypicklecache.py

@@ -92,6 +92,7 @@ class PickleCacheTests(unittest.TestCase):
         cache = self._makeOne()
         original = self._makePersist()
         cache['original'] = original
+        cache['original'] = original # doesn't raise
         duplicate = self._makePersist()
 
         try: