1 files changed, 92 insertions, 0 deletions
diff --git a/dogpile/core/nameregistry.py b/dogpile/core/nameregistry.py
new file mode 100644
index 0000000..ab3ad7b
--- /dev/null
+++ b/dogpile/core/nameregistry.py
@@ -0,0 +1,92 @@
+from util import threading
+import weakref
+
+class NameRegistry(object):
+    """Generates and return an object, keeping it as a
+    singleton for a certain identifier for as long as its 
+    strongly referenced.
+    
+    e.g.::
+    
+        class MyFoo(object):
+            "some important object."
+            def __init__(self, identifier):
+                self.identifier = identifier
+
+        registry = NameRegistry(MyFoo)
+
+        # thread 1:
+        my_foo = registry.get("foo1")
+        
+        # thread 2
+        my_foo = registry.get("foo1")
+    
+    Above, ``my_foo`` in both thread #1 and #2 will
+    be *the same object*.   The constructor for
+    ``MyFoo`` will be called once, passing the 
+    identifier ``foo1`` as the argument.
+    
+    When thread 1 and thread 2 both complete or 
+    otherwise delete references to ``my_foo``, the
+    object is *removed* from the :class:`.NameRegistry` as 
+    a result of Python garbage collection.
+    
+    :class:`.NameRegistry` is a utility object that
+    is used to maintain new :class:`.Dogpile` objects
+    against a certain key, for as long as that particular key
+    is referenced within the application.   An application
+    can deal with an arbitrary number of keys, ensuring that
+    all threads requesting a certain key use the same
+    :class:`.Dogpile` object, without the need to maintain
+    each :class:`.Dogpile` object persistently in memory.
+
+    :param creator: A function that will create a new
+     value, given the identifier passed to the :meth:`.NameRegistry.get`
+     method.
+
+    """
+    _locks = weakref.WeakValueDictionary()
+    _mutex = threading.RLock()
+
+    def __init__(self, creator):
+        """Create a new :class:`.NameRegistry`.
+        
+         
+        """
+        self._values = weakref.WeakValueDictionary()
+        self._mutex = threading.RLock()
+        self.creator = creator
+
+    def get(self, identifier, *args, **kw):
+        """Get and possibly create the value.
+        
+        :param identifier: Hash key for the value.
+         If the creation function is called, this identifier
+         will also be passed to the creation function.
+        :param \*args, \**kw: Additional arguments which will
+         also be passed to the creation function if it is 
+         called.
+        
+        """
+        try:
+            if identifier in self._values:
+                return self._values[identifier]
+            else:
+                return self._sync_get(identifier, *args, **kw)
+        except KeyError:
+            return self._sync_get(identifier, *args, **kw)
+
+    def _sync_get(self, identifier, *args, **kw):
+        self._mutex.acquire()
+        try:
+            try:
+                if identifier in self._values:
+                    return self._values[identifier]
+                else:
+                    self._values[identifier] = value = self.creator(identifier, *args, **kw)
+                    return value
+            except KeyError:
+                self._values[identifier] = value = self.creator(identifier, *args, **kw)
+                return value
+        finally:
+            self._mutex.release()