[Zope-Checkins] CVS: Packages/ZODB - BaseStorage.py:1.34.4.4 DemoStorage.py:1.18.10.2

[Tim Peters]

Update of /cvs-repository/Packages/ZODB
In directory cvs.zope.org:/tmp/cvs-serv20696/ZODB

Modified Files:
      Tag: Zope-2_7-branch
	BaseStorage.py DemoStorage.py 
Log Message:
DemoStorage:  Added implementations for registerDB() and new_oid().  As
Tres discovered the hard way, wrapping a ZEO client storage as a
DemoStorage base storage yields insane behavior otherwise.

BaseStorage.new_oid():  Rewrite to eliminate recursion, and hence also the
need for the undocumented and irregular `last=` argument.

Other:  removed the `last=` argument to new_oid() every place that felt
compelled to spread that insanity ;-).  Seriously, it served no purpose
at all elsewhere, and looks like people just cut 'n pasted in fear.


=== Packages/ZODB/BaseStorage.py 1.34.4.3 => 1.34.4.4 ===
--- Packages/ZODB/BaseStorage.py:1.34.4.3	Mon Feb 28 16:20:41 2005
+++ Packages/ZODB/BaseStorage.py	Fri Apr 22 15:36:07 2005
@@ -17,6 +17,7 @@
 """
 import cPickle
 import time
+from struct import pack as _structpack, unpack as _structunpack
 
 import ThreadLock
 import zLOG
@@ -48,10 +49,15 @@
         t=time.time()
         t=self._ts=apply(TimeStamp,(time.gmtime(t)[:5]+(t%60,)))
         self._serial=`t`
+
+        # ._oid is the highest oid in use (0 is always in use -- it's
+        # a reserved oid for the root object).  Our new_oid() method
+        # increments it by 1, and returns the result.  It's really a
+        # 64-bit integer stored as an 8-byte big-endian string.
         if base is None:
-            self._oid='\0\0\0\0\0\0\0\0'
+            self._oid = '\0\0\0\0\0\0\0\0'
         else:
-            self._oid=base._oid
+            self._oid = base._oid
 
     def abortVersion(self, src, transaction):
         if transaction is not self._transaction:
@@ -87,24 +93,22 @@
     def modifiedInVersion(self, oid):
         return ''
 
-    def new_oid(self, last=None):
-        # 'last' is only for internal use, not part of the public API
+    def new_oid(self):
         if self._is_read_only:
             raise POSException.ReadOnlyError()
-        if last is None:
-            self._lock_acquire()
-            try:
-                last=self._oid
-                d=ord(last[-1])
-                if d < 255: last=last[:-1]+chr(d+1)
-                else:       last=self.new_oid(last[:-1])
-                self._oid=last
-                return last
-            finally: self._lock_release()
-        else:
-            d=ord(last[-1])
-            if d < 255: return last[:-1]+chr(d+1)+'\0'*(8-len(last))
-            else:       return self.new_oid(last[:-1])
+        self._lock_acquire()
+        try:
+            last = self._oid
+            d = ord(last[-1])
+            if d < 255:  # fast path for the usual case
+                last = last[:-1] + chr(d+1)
+            else:        # there's a carry out of the last byte
+                last_as_long, = _structunpack(">Q", last)
+                last = _structpack(">Q", last_as_long + 1)
+            self._oid = last
+            return last
+        finally:
+            self._lock_release()
 
     # Update the maximum oid in use, under protection of a lock.  The
     # maximum-in-use attribute is changed only if possible_new_max_oid is


=== Packages/ZODB/DemoStorage.py 1.18.10.1 => 1.18.10.2 ===
--- Packages/ZODB/DemoStorage.py:1.18.10.1	Mon Jul 21 12:37:18 2003
+++ Packages/ZODB/DemoStorage.py	Fri Apr 22 15:36:07 2005
@@ -20,7 +20,7 @@
 
   - Provide a volatile storage that is useful for giving demonstrations.
 
-The demo strorage can have a "base" storage that is used in a
+The demo storage can have a "base" storage that is used in a
 read-only fashion. The base storage must not not to contain version
 data.
 
@@ -82,15 +82,16 @@
 __version__='$Revision$'[11:-2]
 
 import base64, time, string
-from ZODB import POSException, BaseStorage, utils
+from ZODB import POSException, utils
+from ZODB.BaseStorage import BaseStorage
 from TimeStamp import TimeStamp
 from cPickle import loads
 from BTrees import OOBTree
 
-class DemoStorage(BaseStorage.BaseStorage):
+class DemoStorage(BaseStorage):
 
     def __init__(self, name='Demo Storage', base=None, quota=None):
-        BaseStorage.BaseStorage.__init__(self, name, base)
+        BaseStorage.__init__(self, name, base)
 
         # We use a BTree because the items are sorted!
         self._data=OOBTree.OOBTree()
@@ -104,6 +105,23 @@
             raise POSException.StorageError, (
                 "Demo base storage has version data")
 
+    # While we officially don't support wrapping a non-read-only base
+    # storage, it has proved useful for test suites to wrap a ClientStorage
+    # in DemoStorage.  The least we can do to help support that case is
+    # to arrange for invalidations to get delivered to the base storage.
+    def registerDB(self, db, limit):
+        if self._base is not None: # delegate
+            self._base.registerDB(db, limit)
+
+    # When DemoStorage needs to create a new oid, and there is a base
+    # storage, it must use that storage's new_oid() method.  Else
+    # DemoStorage may end up assigning "new" oids that are already in use
+    # by the base storage, leading to a variety of "impossible" problems.
+    def new_oid(self):
+        if self._base is None:
+            return BaseStorage.new_oid(self)
+        else:
+            return self._base.new_oid()
 
     def __len__(self):
         base=self._base