Use the file position stored in the transaction_id whenever possible.
It is possible when _check_txn_pos() returns true; i.e. when the file
position does point to the transaction record header.

Remove ostloc and here arguments to _txn_undo_write(), as they can be
computed after the call.

Omit redundant tests in _txn_undo_write().  All the paths that lead
here verify that the file position is valid.

Remove some attribute lookup optimizations.

transactionalUndo() does argument checking and locking.  It calls
_transactional_undo(), which finds the right transaction record.  It calls
_txn_undo_write(), which writes the data records.

Add a summary comment above undoLog() that explains how the
transaction_id is created and used.

It makes more sense in this order, because the comments in undoLog()
help to explain what transactionalUndo() is doing.

appears to be broken.

undo to continue to work, and the IDs have to be base64 encoded to work on
HTML forms.  In future, non-transactional undo may be removed and the HTML
forms might be updated to perform the encoding of transaction IDs.

that environment, it is possible that all the data in the replicas
recoverable through the public api are identical, while the actual
on-disc representation differs.  This bug can be boiled down to doing
the following in "standard" ZODB:

    1. undoLog()
    2. pack()
    3. transactionalUndo()

Previously, undoLog() encoded the file position in the 'id' key of the
undo record, but of course the pack() breaks that file position.  We
fix this by encoding the oid of an object touched in the transaction
instead.  That way, transactionalUndo() can start at the current
revision of the object, and scan back until it can find a transaction
with a matching id to the one we're undoing.

This approach breaks when the transaction we're undoing doesn't touch
any objects, e.g. is an abortVersion() or commitVersion().  By edict,
that's a non-requirement for now.  We could fix that by doing a more
expensive binary search for the matching transaction.

WIBNI we had an index from tids to file positions? :)

really testing what we're interested in (they were testing the
equality of the exact layout of the undoInfo() -- not interesting).

suspicion that FileStorage (and an FS-backed ZEO) fails a
transactional undo after a pack, but Berkeley storage passes.

Two problems: A revid doesn't have the right type.  But even if we
decoded the revid using TimeStamp(revid).timeTime(), it would be the
wrong time.  We want to pack to the current time to delete older
revisions.

I believe the test case tried to keep one revision available so that
it could be packed.  The new test doesn't do that, so it will fail
even after we fix FileStorage.  I think the right answer is to call
time.time() after the second commit *and* make sure that there is at
least a one second delay between the two stores.

the underlying bug in transactionalUndo() on a standby storage.  If
our hypothesis is correct, the bug is in FileStorage, and is caused by
encoding the file position in the `id' field of the undoLog
information.  Note that Full just encodes the tid, but this is a
problem for FileStorage (we have a strategy for fixing this).

NOTE: checking this in on the trunk is mildly antisocial because it
introduces failures in the test suite.  I'm doing it this way because
1) it really isn't worth a branch, even a short lived one; 2) Jeremy
may have time to look at it before tomorrow; 3) I don't trust my
machine not to lock up and make this mod unavailable. :(

Either way, this /will/ get fixed by tomorrow.

The --nowrite option will disable writing.  (It's not possible to
enable writing and disable reading, so that's the only option.)

The problem was that the randomly generated test data was occasionally
invalid.  Fix is to hardcode a specific set of test data instead of
using random.

weightedIntersection|Union(). That's a contradiction to the
documentation and the implementation.

Also change to use time.localtime() instead of calling time.time()
first.  This is a Python 2.1-ism.

Per request by Andreas Jung.

don't pass, and have been prefixed by 'BUG'

Fix SF bug #516768 reported by Dave Wallace.

Replace use of PyMem_DEL() with PyObject_Del() on object dealloc
functions.  The use of PyMem_DEL() is incorrect for object
deallocation, because it only ever calls the low-level free().  If a
custom allocator like pymalloc is used, it needs to be called to free
the memory.

Fix SF bug #516768 reported by Dave Wallace.

Replace use of PyMem_DEL() with PyObject_Del() on object dealloc
functions.  The use of PyMem_DEL() is incorrect for object
deallocation, because it only ever calls the low-level free().  If a
custom allocator like pymalloc is used, it needs to be called to free
the memory.

Also replace bare malloc() and realloc() with PyMem_Malloc() and
PyMem_Realloc().  I think this isn't a strict bug fix, but a would be
nice.  It guarantees that BTrees objects get their memory from the
same allocator as the Python core.

   The previous, insane version was passing None or a thread id to "%.03f".

Add some whitespace around get_transaction() implementations.

The code was intended to be added to the Zope3 branch, not modified on
the trunk.

of the StandaloneZODB-1_0-branch into the trunk.  The
StandaloneZODB-1_0-branch is now dead!

trunk.  I'm *almost* done with the merge; the only file not yet merged
is FileStorage.py.

code that is needed for it yet.

Summary of changes:

- Add function gc_all_items() to call gc_item() on everything in
  dict.  This factors out common code in all the gc methods.

- Add check_size() function that factors out code to check cache size
  before starting a gc.

- Simplify argument processing in cc_invalidate(), avoiding a second
  call to PyArg_ParseTuple() when argument is a sequence instead of a
  dictionary.

- Chance code to reflect belief that NULL return from PyDict_GetItem()
  does not set exception, except in cases that don't apply for the
  pickle cache like comparing a string with high-order bit set to a
  Unicode object.

- Use if (!expr) instead of UNLESS().

- Remove all statements from conditionals.

- Reformat to 4 spaces and Python-style brace placement.

- Put whitespace around operators and after commas.