Add SafeMapping class, for use when mappings (or MultiMappings) need to be...

Add SafeMapping class, for use when mappings (or MultiMappings) need to be exposed to restricted code.

lib/python/RestrictedPython/SafeMapping.py

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+##############################################################################
+__doc__='''Read-only Mapping class based on MultiMapping
+
+$Id: SafeMapping.py,v 1.1 2001/05/08 18:15:36 evan Exp $'''
+__version__='$Revision: 1.1 $'[11:-2]
+
+from MultiMapping import MultiMapping
+
+_marker = []
+
+class SafeMapping(MultiMapping):
+    '''Mapping with security declarations and limited method exposure.
+
+    Since it subclasses MultiMapping, this class can be used to wrap
+    one or more mapping objects.  Restricted Python code will not be
+    able to mutate the SafeMapping or the wrapped mappings, but will be
+    able to read any value.
+    '''
+    __allow_access_to_unprotected_subobjects__ = 1
+    push = pop = None
+    def _push(self, ob):
+        MultiMapping.push(self, ob)
+    def _pop(self, *args):
+        if args:
+            return apply(MultiMapping.pop, (self,) + args)
+        else:
+            return MultiMapping.pop(self)
+    def has_get(self, key):
+        v = self.get(key, _marker)
+        if v is _marker:
+            return 0, None
+        else:
+            return 1, v