Make sure we produce canonical pickles

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@998 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/XMLExportImport.py

@@ -31,11 +31,35 @@ from Acquisition import aq_base, aq_inner
 from cStringIO import StringIO
 from email.MIMEBase import MIMEBase
 from email import Encoders
-import pickle
+from pickle import Pickler
 from xml.sax.saxutils import escape, unescape
 
 from zLOG import LOG
 
+class OrderedPickler(Pickler):
+  
+    def save_dict(self, obj):
+        write = self.write
+
+        if self.bin:
+            write(EMPTY_DICT)
+        else:   # proto 0 -- can't use EMPTY_DICT
+            write(MARK + DICT)
+
+        self.memoize(obj)
+        key_list = obj.keys()
+        key_list.sort() # Order keys
+        obj_items = map(lambda x: (x, obj[x]), obj) # XXX Make it lazy in the future
+        self._batch_setitems(obj_items)
+
+  
+# ERP5 specific pickle function - produces ordered pickles
+def dumps(obj, protocol=None, bin=None):
+    file = StringIO()
+    OrderedPickler(file, protocol, bin).dump(obj)
+    return file.getvalue()
+
+
 def Base_asXML(object, ident=0):
   """
       Generate an xml text corresponding to the content of this object