provide simple caching

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@3449 fd906abe-77d9-0310-91a1-e0d9ade77398

util/cache.py

@@ -0,0 +1,68 @@
+#
+#  Copyright (c) 2009 Helmut Merz helmutm@cy55.de
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+A simple caching mechanism.
+
+$Id$
+"""
+
+from cybertools.util.date import getTimeStamp
+
+INVALID = object()
+
+
+class CacheManager(dict):
+
+    pass
+
+manager = CacheManager()
+
+
+class CacheItem(object):
+
+    def __init__(self, identifier, value=INVALID, lifetime=3600):
+        self.identifier = identifier
+        self.lifetime = lifetime
+        self.set(value)
+
+    def set(self, value):
+        self.value = value
+        self.modified = getTimeStamp()
+
+    def get(self):
+        self.check()
+        return self.value
+
+    def check(self):
+        if getTimeStamp() - self.modified > self.lifetime:
+            self.value = INVALID
+
+
+def cache(getIdentifier, lifetime=3600):
+    def _cache(fct):
+        def __cache(*args, **kw):
+            id = getIdentifier(*args)
+            item = manager.setdefault(id, CacheItem(id, lifetime=lifetime))
+            value = item.get()
+            if value is INVALID:
+                value = fct(*args, **kw)
+                item.set(value)
+            return value
+        return __cache
+    return _cache

util/cache.txt

@@ -0,0 +1,41 @@
+============
+Data Caching
+============
+
+$Id$
+
+  >>> from cybertools.util.cache import cache
+
+  >>> @cache(lambda *args: 'calc')
+  ... def calculate():
+  ...     print 'calculating'
+  ...     return 42
+
+  >>> calculate()
+  calculating
+  42
+  >>> calculate()
+  42
+
+  >>> class Demo(object):
+  ...     id = '4711'
+  ...     def getId(self, *args):
+  ...         return self.id
+  ...     @cache(getId)
+  ...     def calculate(self):
+  ...         print 'calculating'
+  ...         return 42
+
+  >>> demo = Demo()
+  >>> demo.calculate()
+  calculating
+  42
+  >>> demo.calculate()
+  42
+
+  >>> demo.id = '4712'
+  >>> demo.calculate()
+  calculating
+  42
+  >>> demo.calculate()
+  42

util/tests.py

@@ -20,6 +20,7 @@ def test_suite():
         #doctest.DocTestSuite(cybertools.util.property, optionflags=flags),
         doctest.DocFileSuite('adapter.txt', optionflags=flags),
         doctest.DocFileSuite('aop.txt', optionflags=flags),
+        doctest.DocFileSuite('cache.txt', optionflags=flags),
         doctest.DocFileSuite('config.txt', optionflags=flags),
         doctest.DocFileSuite('defer.txt', optionflags=flags),
         doctest.DocFileSuite('format.txt', optionflags=flags),