Added license header

Added module doc string

Imported POSException

Parameterized MAXTEMPFSIZE

Added exception classes

Added docstring to _dbnames explaining what each database is.

Made all struct.pack and struct.unpack calls which deal with integers use signed integer representations.

Added exception handling for out of temp space.

Added workaround for import which defers adding a new object to the "zeroes" directory "out of the gate".  This fixes import (it was broken).

Added a pack method.

lib/python/BDBStorage/Packless.py

+##############################################################################
+# 
+# Zope Public License (ZPL) Version 1.0
+# -------------------------------------
+# 
+# Copyright (c) Digital Creations.  All rights reserved.
+# 
+# This license has been certified as Open Source(tm).
+# 
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+# 
+# 1. Redistributions in source code must retain the above copyright
+#    notice, this list of conditions, and the following disclaimer.
+# 
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions, and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 
+# 3. Digital Creations requests that attribution be given to Zope
+#    in any manner possible. Zope includes a "Powered by Zope"
+#    button that is installed by default. While it is not a license
+#    violation to remove this button, it is requested that the
+#    attribution remain. A significant investment has been put
+#    into Zope, and this effort will continue if the Zope community
+#    continues to grow. This is one way to assure that growth.
+# 
+# 4. All advertising materials and documentation mentioning
+#    features derived from or use of this software must display
+#    the following acknowledgement:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    In the event that the product being advertised includes an
+#    intact Zope distribution (with copyright and license included)
+#    then this clause is waived.
+# 
+# 5. Names associated with Zope or Digital Creations must not be used to
+#    endorse or promote products derived from this software without
+#    prior written permission from Digital Creations.
+# 
+# 6. Modified redistributions of any form whatsoever must retain
+#    the following acknowledgment:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    Intact (re-)distributions of any official Zope release do not
+#    require an external acknowledgement.
+# 
+# 7. Modifications are encouraged but must be packaged separately as
+#    patches to official Zope releases.  Distributions that do not
+#    clearly separate the patches from the original work must be clearly
+#    labeled as unofficial distributions.  Modifications which do not
+#    carry the name Zope may be packaged in any form, as long as they
+#    conform to all of the clauses above.
+# 
+# 
+# Disclaimer
+# 
+#   THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS ``AS IS'' AND ANY
+#   EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+#   PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DIGITAL CREATIONS OR ITS
+#   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+#   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+#   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+#   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+#   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+#   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+#   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+#   SUCH DAMAGE.
+# 
+# 
+# This software consists of contributions made by Digital Creations and
+# many individuals on behalf of Digital Creations.  Specific
+# attributions are listed in the accompanying credits file.
+# 
+##############################################################################
+"""
+An implementation of a BerkeleyDB-backed storage that uses a reference-
+counting garbage-collection strategy which necessitates packing only when
+the stored data has cyclically-referenced garbage.
+"""
+
+__version__ ='$Revision: 1.3 $'[11:-2]
+
 from base import Base
 from bsddb3 import db
 from struct import pack, unpack
 from ZODB.referencesf import referencesf
+from ZODB import POSException
+
+MAXTEMPFSIZE = 999999
+
+class ReferenceCountError(POSException.POSError):
+    """ An error occured while decrementing a reference to an object in
+    the commit phase. The object's reference count was below zero."""
+
+class TemporaryLogCorruptedError(POSException.POSError):
+    """ An error occurred due to temporary log file corruption. """
+
+class OutOfTempSpaceError(POSException.POSError):
+    """ An out-of-disk-space error occured when writing a temporary log
+    file. """
 
 class Packless(Base):
 
@@ -13,6 +119,12 @@ class Packless(Base):
         self._setupDB('opickle')
 
     def _dbnames(self):
+        """
+        current -- mapping of oid to current serial
+        referenceCount -- mapping of oid to count
+        oreferences -- mapping of oid to a sequence of its referenced oids
+        opickle -- mapping of oid to pickle
+        """
         return 'current', 'referenceCount', 'oreferences', 'opickle'
 
     def load(self, oid, version):
@@ -26,7 +138,6 @@ class Packless(Base):
     def store(self, oid, serial, data, version, transaction):
         if transaction is not self._transaction:
             raise POSException.StorageTransactionError(self, transaction)
-
         if version:
             raise POSException.Unsupported, "Versions aren't supported"
 
@@ -37,8 +148,13 @@ class Packless(Base):
                 if serial != oserial: raise POSException.ConflictError
                 
             serial=self._serial
-            self._tmp.write(oid+pack(">I", len(data)))
-            self._tmp.write(data)
+            try:
+                # write the metadata to the temp log
+                self._tmp.write(oid+pack(">i", len(data)))
+                # write the pickle to the temp log
+                self._tmp.write(data)
+            except IOError:
+                raise OutOfTempSpaceError, self._tempdir
         finally: self._lock_release()
 
         return serial
@@ -56,12 +172,15 @@ class Packless(Base):
             opickle_put=self._opickle.put
             serial=self._serial
             tmp=self._tmp
-            s=tmp.tell()
+            oidlen=8 # length in bytes of oid string rep
+            intlen=4 # length in bytes of struct.packed integer string rep
+            fsize=tmp.tell()
             tmp.seek(0)
             read=tmp.read
             l=0
-            while l < s:
-                oid, ldata = unpack(">8sI", read(12))
+            while l < fsize:
+                sdata = read(oidlen+intlen)
+                oid, ldata = unpack(">%ssi" % oidlen, sdata)
                 data=read(ldata)
 
                 # get references
@@ -73,9 +192,15 @@ class Packless(Base):
 
                 # Create refcnt
                 if not referenceCount_get(oid, txn):
-                    referenceCount_put(oid, '\0\0\0\0', txn)
-                    zeros[oid]=1
-                
+                    referenceCount_put(oid, '\0'*intlen, txn)
+                    # zeros[oid]=1
+                    # ^^^^^^^^^^^^
+                    # this should happen when ZODB import is fixed
+                    # to commit an import in a subtransaction.  we rely
+                    # on pack to get rid of unreferenced objects added
+                    # via an aborted import now.  this is only slightly
+                    # lame.
+                    
                 # update stored references
                 c=oreferences.cursor(txn)
                 try:
@@ -98,7 +223,9 @@ class Packless(Base):
                                 rc=rc-1
                                 if rc < 0:
                                     # This should never happen
-                                    raise "Bad reference count, %s" % (rc+1)
+                                     raise ReferenceCountError, (
+                                        "Oid %s had refcount %s" % (`roid`,rc)
+                                        )
                                 referenceCount_put(roid, pack(">i", rc), txn)
                                 if rc==0: zeros[roid]=1
                             roid=c.get(db.DB_NEXT_DUP)
@@ -118,11 +245,12 @@ class Packless(Base):
                             except: pass
                         referenceCount_put(roid, pack(">i", rc+1), txn)
                     else:
-                        referenceCount_put(roid, '\0\0\0\1', txn)
+                        referenceCount_put(roid, pack(">i", 1), txn)
                 
-                l=l+ldata+12
-                if ldata > s:
-                    raise 'Temporary file corrupted'
+                l=l+ldata+oidlen+intlen
+                if ldata > fsize:
+                    # this should never happen.
+                    raise TemporaryLogCorruptedError
                 serial_put(oid, serial, txn)
                 opickle_put(oid, data, txn)
 
@@ -132,8 +260,8 @@ class Packless(Base):
                     self._takeOutGarbage(oid, txn)
                     
             tmp.seek(0)
-            if s > 999999: tmp.truncate()
-            
+            if fsize > MAXTEMPFSIZE: tmp.truncate()
+
         except:
             txn.abort()
             raise
@@ -165,7 +293,9 @@ class Packless(Base):
                     if rc:
                         rc=unpack(">i", rc)[0]-1
                         if rc < 0:
-                            raise "Bad reference count, %s" % (rc+1)
+                            raise ReferenceCountError, (
+                                "Oid %s had refcount %s" % (`roid`,rc)
+                                )
                         if rc==0: self._takeOutGarbage(roid, txn)
                         else: referenceCount_put(roid, pack(">i", rc), txn)
 
@@ -174,13 +304,36 @@ class Packless(Base):
 
         if self._len > 0: self._len=self._len-1
 
-
     def pack(self, t, referencesf):
-        
         self._lock_acquire()
         try:
-            pass
-            # TBD
-        finally: self._lock_release()
+            try:
+                txn = self._env.txn_begin()
+                rindex={}
+                referenced=rindex.has_key
+                rootl=['\0\0\0\0\0\0\0\0']
+
+                # mark referenced objects
+                while rootl:
+                    oid=rootl.pop()
+                    if referenced(oid): continue
+                    p = self._opickle[oid]
+                    referencesf(p, rootl)
+                    rindex[oid] = None
+                    
+                # sweep unreferenced objects
+                for oid in self._index.keys():
+                    if not referenced(oid):
+                        self._takeOutGarbage(oid, txn)
+            except:
+                txn.abort()
+                raise
+            else:
+                txn.commit()
+        finally:
+            self._lock_release()
+
+
 
+