1 files changed, 72 insertions, 0 deletions
diff --git a/paramiko/resource.py b/paramiko/resource.py
new file mode 100644
index 0000000..a089754
--- /dev/null
+++ b/paramiko/resource.py
@@ -0,0 +1,72 @@
+# Copyright (C) 2003-2007  Robey Pointer <robey@lag.net>
+#
+# This file is part of paramiko.
+#
+# Paramiko is free software; you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation; either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# Paramiko is distrubuted 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 Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+
+"""
+Resource manager.
+"""
+
+import weakref
+
+
+class ResourceManager (object):
+    """
+    A registry of objects and resources that should be closed when those
+    objects are deleted.
+    
+    This is meant to be a safer alternative to python's C{__del__} method,
+    which can cause reference cycles to never be collected.  Objects registered
+    with the ResourceManager can be collected but still free resources when
+    they die.
+    
+    Resources are registered using L{register}, and when an object is garbage
+    collected, each registered resource is closed by having its C{close()}
+    method called.  Multiple resources may be registered per object, but a
+    resource will only be closed once, even if multiple objects register it.
+    (The last object to register it wins.)
+    """
+    
+    def __init__(self):
+        self._table = {}
+        
+    def register(self, obj, resource):
+        """
+        Register a resource to be closed with an object is collected.
+        
+        When the given C{obj} is garbage-collected by the python interpreter,
+        the C{resource} will be closed by having its C{close()} method called.
+        Any exceptions are ignored.
+        
+        @param obj: the object to track
+        @type obj: object
+        @param resource: the resource to close when the object is collected
+        @type resource: object
+        """
+        def callback(ref):
+            try:
+                resource.close()
+            except:
+                pass
+            del self._table[id(resource)]
+
+        # keep the weakref in a table so it sticks around long enough to get
+        # its callback called. :)
+        self._table[id(resource)] = weakref.ref(obj, callback)
+
+
+# singleton
+ResourceManager = ResourceManager()