New mix-in class for database connection wrappers that implements

coordination of Zope and external transaction managers.  See the
gadfly DA (class DB in db.py) for an example of use.

lib/python/Shared/DC/ZRDB/TM.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.
+# 
+##############################################################################
+"""Provide support for linking an external transaction manager with Zope's
+"""
+
+class TM:
+    """Mix-in class that provides transaction management support
+
+    A base class should call self._register() whenever it performs
+    any transaction-dependent operations (e.g. sql statements).
+
+    The base class may need to override tpc_finish and tpc_abort.
+    """
+
+    _registered=None
+
+    #class _p_jar:
+    #    # This is place holder for new transaction machinery 2pc
+    #    # I don't think this is needed.
+    #    def __init__(self, db=None): self.db=db
+    #    def begin_commit(self, *args): pass
+    #    def finish_commit(self, *args): pass
+    #
+    #_p_jar=_p_jar(_p_jar())
+
+    def _register(self):
+        if not self._registered:
+            try:
+                get_transaction().register(Surrogate(self))
+                self._registered=1
+            except: pass
+
+    def tpc_begin(self, *ignored): pass
+    commit=abort=tpc_begin
+
+    def tpc_finish(self, *ignored):
+        self.db.commit()
+        self._registered=0
+
+    def tpc_abort(self, *ignored):
+        self.db.rollback()
+        self.db.checkpoint()
+        self._registered=0
+
+class Surrogate:
+
+    def __init__(self, db):
+        self._p_jar=db
+        self.__inform_commit__=db.tpc_commit
+        self.__inform_abort__=db.tpc_abort