Introduce finalizer module to manage finalization of C resources.

llvm/_utils/finalizer.py

@@ -0,0 +1,58 @@
+'''
+Modified C-level finalizer by Benjamin Peterson <benjamin@python.org>
+Available at http://code.activestate.com/recipes/577242-calling-c-level-finalizers-without-__del__/
+'''
+import sys
+import traceback
+import weakref
+
+class OwnerRef(weakref.ref):
+    """A simple weakref.ref subclass, so attributes can be added."""
+    pass
+
+def _run_finalizer(ref):
+    """Internal weakref callback to run finalizers"""
+    del _finalize_refs[ref.owner]
+    for item, finalizer in ref.items:
+        try:
+            finalizer(item)
+        except Exception:
+            print>>sys.stderr, "Exception running {}:".format(finalizer)
+            traceback.print_exc()
+
+_finalize_refs = {}
+
+def track(owner, item, finalizer):
+    """Register an object for finalization.
+
+        ``owner`` is the the object which is responsible for ``item``.
+        ``finalizer`` will be called with ``item`` as its only argument when
+        ``owner`` is destroyed by the garbage collector.
+        """
+    if id(owner) in _finalize_refs:
+        ref = _finalize_refs[id(owner)]
+    else:
+        ref = OwnerRef(owner, _run_finalizer)
+        ref.owner = id(owner)
+        ref.items = []
+    ref.items.append((item, finalizer))
+    _finalize_refs[id(owner)] = ref
+
+def untrack(owner, item):
+    ref = _finalize_refs[id(owner)]
+    # search and remove the item from the ref
+    for i, (item_i, _) in enumerate(ref.items):
+        if item_i is item:
+            del ref.items[i]
+    # remove the ref if it is empty
+    if not ref.items:
+        del _finalize_refs[id(owner)]
+
+class OwnerMixin(object):
+    def _finalizer_track(self, item):
+        if not hasattr(self, '_finalize'):
+            raise AttributeError("%s must define a _finalize method" % self)
+        track(self, item, type(self)._finalize)
+
+    def _finalizer_untrack(self, item):
+        untrack(self, item)