[Zope-Checkins] CVS: ZODB3/ZODB - FileStorage.py:1.105.2.5

[Jeremy Hylton]

Update of /cvs-repository/ZODB3/ZODB
In directory cvs.zope.org:/tmp/cvs-serv7348/ZODB

Modified Files:
      Tag: ZODB3-3_1-branch
	FileStorage.py 
Log Message:
Backport: Better fix for George Bailey events.


=== ZODB3/ZODB/FileStorage.py 1.105.2.4 => 1.105.2.5 ===
--- ZODB3/ZODB/FileStorage.py:1.105.2.4	Mon Oct 21 11:15:55 2002
+++ ZODB3/ZODB/FileStorage.py	Tue Nov  5 16:21:44 2002
@@ -1045,18 +1045,20 @@
 
     def _getVersion(self, oid, pos):
         self._file.seek(pos)
-        read=self._file.read
-        h=read(DATA_HDR_LEN)
-        doid,serial,sprev,stloc,vlen,splen = unpack(DATA_HDR, h)
+        h = self._file.read(DATA_HDR_LEN)
+        doid, serial, sprev, stloc, vlen, splen = unpack(DATA_HDR, h)
+        assert doid == oid
         if vlen:
-            h=read(16)
-            return read(vlen), h[:8]
+            h = self._file.read(16)
+            return self._file.read(vlen), h[:8]
         else:
-            return '',''
+            return '', ''
 
     def _getSerial(self, oid, pos):
-        self._file.seek(pos+8)
-        return self._file.read(8)
+        self._file.seek(pos)
+        h = self._file.read(16)
+        assert oid == h[:8]
+        return h[8:]
 
     def _transactionalUndoRecord(self, oid, pos, serial, pre, version):
         """Get the indo information for a data record
@@ -1068,6 +1070,8 @@
         """
 
         copy=1 # Can we just copy a data pointer
+
+        # First check if it is possible to undo this record.
         tpos=self._tindex.get(oid, 0)
         ipos=self._index.get(oid, 0)
         tipos=tpos or ipos
@@ -1102,6 +1106,12 @@
                     # LoadBack gave us a key error. Bail.
                     raise UndoError
 
+        # Return the data that should be written in the undo record.
+        if not pre:
+            # There is no previous revision, because the object creation
+            # is being undone.
+            return '', 0, '', '', ipos
+
         version, snv = self._getVersion(oid, pre)
         if copy:
             # we can just copy our previous-record pointer forward
@@ -1261,7 +1271,7 @@
                 tindex[oid] = here
                 here += odlen
 
-            pos=pos+dlen
+            pos += dlen
             if pos > tend:
                 raise UndoError, 'non-undoable transaction'
 
@@ -2138,6 +2148,7 @@
     while 1:
         old = U64(back)
         if not old:
+            # If the backpointer is 0, the object does not currently exist.
             raise POSKeyError(oid)
         file.seek(old)
         h = file.read(DATA_HDR_LEN)
@@ -2386,7 +2397,6 @@
             prev = U64(sprev)
             tloc = U64(stloc)
             plen = U64(splen)
-
             dlen = DATA_HDR_LEN + (plen or 8)
 
             if vlen: