[Zope3-dev] Heads up: zope.app.intid and zope.app.keyreference are now op

[Benji York]

Jim Fulton wrote:
> Right, but to manage the integer ids, we need to be able to turn objects
> into keys, since many objects are not valid keys.  The key reference
> framework provides a way to generate keys from objects.  The key reference
> adapter for persistent objects has the extremely inconvenient property
> that you can't compute a key reference for a persistent object until
> it has been added to a database.  Key references based on guids wouldn't
> have this negative property.

Oh, now I see where GUIDs came in.  I would instead propose to make 
key references not dependent on OIDs.  I would just define a 
light-weight way of generating lots of guaranteed-unique IDs. 
Something like this, perhaps (this particular implementation requires 
Python 2.4):

NUM_ID_BITS = 64
BIGGEST_ID = (2 << (NUM_ID_BITS + 1) - 1)
NUM_TIME_BITS = 48
BIGGEST_TIME = (2 << (NUM_TIME_BITS + 1) - 1)

def getTime():
     result = int(time.time()*1000)
     assert result <= BIGGEST_TIME
     return result

def ids():
     last_time = None
     while True:
         current_time = getTime()
         if current_time != last_time:
             counter = 0
         else:
             counter += 1

         result = current_time << (NUM_ID_BITS-NUM_TIME_BITS) | counter
         assert result <= BIGGEST_ID
         yield result
         last_time = current_time

getId = ids().next

This give you as many unique IDs you could need, but the resulting ID 
would have to be stored on the object, just like the GUID would.
-- 
Benji York
Sr. Software Engineer
Zope Corporation