--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_utils/property.py	Thu Feb 19 00:46:48 2015 +0100
@@ -0,0 +1,105 @@
+#
+# Copyright (c) 2008-2015 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+
+# import standard library
+
+# import interfaces
+
+# import packages
+from pyams_utils.request import check_request, get_request_data, set_request_data
+from pyams_utils.session import get_session_data, set_session_data
+
+
+class cached(object):
+    """Custom property decorator to define a property or function
+    which is calculated only once
+       
+    When applied on a function, caching is based on input arguments
+    """
+
+    def __init__(self, function):
+        self._function = function
+        self._cache = {}
+
+    def __call__(self, *args):
+        try:
+            return self._cache[args]
+        except KeyError:
+            self._cache[args] = self._function(*args)
+            return self._cache[args]
+
+    def expire(self, *args):
+        del self._cache[args]
+
+
+class cached_property(object):
+    """A read-only @property decorator that is only evaluated once. The value is cached
+    on the object itself rather than the function or class; this should prevent
+    memory leakage.
+    """
+    def __init__(self, fget, doc=None):
+        self.fget = fget
+        self.__doc__ = doc or fget.__doc__
+        self.__name__ = fget.__name__
+        self.__module__ = fget.__module__
+
+    def __get__(self, obj, cls):
+        if obj is None:
+            return self
+        obj.__dict__[self.__name__] = result = self.fget(obj)
+        return result
+
+
+_marker = object()
+
+class request_property(object):
+    """Define a property stored in request annotations"""
+
+    def __init__(self, fget, key=None):
+        self.fget = fget
+        if key is None:
+            key = "%s.%s" % (fget.__module__, fget.__name__)
+        self.key = key
+
+    def __get__(self, obj, cls):
+        if obj is None:
+            return self
+        request = check_request()
+        data = get_request_data(request, self.key, _marker)
+        if data is _marker:
+            data = self.fget(obj)
+            set_request_data(request, self.key, data)
+        return data
+
+
+class session_property(object):
+    """Define a property stored into session"""
+
+    def __init__(self, fget, app, key=None):
+        self.fget = fget
+        self.app = app
+        if key is None:
+            key = "%s.%s" % (fget.__module__, fget.__name__)
+        self.key = key
+
+    def __get__(self, obj, cls):
+        if obj is None:
+            return self
+        request = check_request()
+        data = get_session_data(request, self.app, self.key, _marker)
+        if data is _marker:
+            data = self.fget(obj)
+            set_session_data(request, self.app, self.key, data)
+        return data