Move common libs to libs/common

libs/common/dogpile/cache/proxy.py

@@ -0,0 +1,95 @@
+"""
+Proxy Backends
+------------------
+
+Provides a utility and a decorator class that allow for modifying the behavior
+of different backends without altering the class itself or having to extend the
+base backend.
+
+.. versionadded:: 0.5.0  Added support for the :class:`.ProxyBackend` class.
+
+"""
+
+from .api import CacheBackend
+
+
+class ProxyBackend(CacheBackend):
+    """A decorator class for altering the functionality of backends.
+
+    Basic usage::
+
+        from dogpile.cache import make_region
+        from dogpile.cache.proxy import ProxyBackend
+
+        class MyFirstProxy(ProxyBackend):
+            def get(self, key):
+                # ... custom code goes here ...
+                return self.proxied.get(key)
+
+            def set(self, key, value):
+                # ... custom code goes here ...
+                self.proxied.set(key)
+
+        class MySecondProxy(ProxyBackend):
+            def get(self, key):
+                # ... custom code goes here ...
+                return self.proxied.get(key)
+
+
+        region = make_region().configure(
+            'dogpile.cache.dbm',
+            expiration_time = 3600,
+            arguments = {
+                "filename":"/path/to/cachefile.dbm"
+            },
+            wrap = [ MyFirstProxy, MySecondProxy ]
+        )
+
+    Classes that extend :class:`.ProxyBackend` can be stacked
+    together.  The ``.proxied`` property will always
+    point to either the concrete backend instance or
+    the next proxy in the chain that a method can be
+    delegated towards.
+
+    .. versionadded:: 0.5.0
+
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.proxied = None
+
+    def wrap(self, backend):
+        ''' Take a backend as an argument and setup the self.proxied property.
+        Return an object that be used as a backend by a :class:`.CacheRegion`
+        object.
+        '''
+        assert(
+            isinstance(backend, CacheBackend) or
+            isinstance(backend, ProxyBackend))
+        self.proxied = backend
+        return self
+
+    #
+    # Delegate any functions that are not already overridden to
+    # the proxies backend
+    #
+    def get(self, key):
+        return self.proxied.get(key)
+
+    def set(self, key, value):
+        self.proxied.set(key, value)
+
+    def delete(self, key):
+        self.proxied.delete(key)
+
+    def get_multi(self, keys):
+        return self.proxied.get_multi(keys)
+
+    def set_multi(self, mapping):
+        self.proxied.set_multi(mapping)
+
+    def delete_multi(self, keys):
+        self.proxied.delete_multi(keys)
+
+    def get_mutex(self, key):
+        return self.proxied.get_mutex(key)