1 files changed, 56 insertions, 0 deletions
diff --git a/BitTorrent/defer.py b/BitTorrent/defer.py
new file mode 100644
index 0000000..4531271
--- /dev/null
+++ b/BitTorrent/defer.py
@@ -0,0 +1,56 @@
+# The contents of this file are subject to the BitTorrent Open Source License
+# Version 1.1 (the License).  You may not copy or use this file, in either
+# source code or executable form, except in compliance with the License.  You
+# may obtain a copy of the License at http://www.bittorrent.com/license/.
+#
+# Software distributed under the License is distributed on an AS IS basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the License
+# for the specific language governing rights and limitations under the
+# License.
+
+class Deferred(object):
+    def __init__(self):
+        self.callbacks = []
+        self.errbacks = []
+        self.calledBack = False
+        self.erredBack = False
+        self.results = []
+        self.failures = []
+        
+    def addCallback(self, cb, args=(), kwargs={}):
+        assert callable(cb)
+        self.callbacks.append((cb, args, kwargs))
+        if self.calledBack:
+            self.doCallbacks(self.results, [(cb, args, kwargs)])
+        return self
+
+    def addErrback(self, cb, args=(), kwargs={}):
+        assert callable(cb)
+        self.errbacks.append((cb, args, kwargs))
+        if self.erredBack:
+            self.doCallbacks(self.failures, [(cb, args, kwargs)])
+        return self
+
+    def addCallbacks(self, cb, eb, args=(), kwargs={},
+                     ebargs=(), ebkwargs={}):
+        assert callable(cb)
+        assert callable(eb)
+        self.addCallback(cb, args, kwargs)
+        self.addErrback(eb, ebargs, ebkwargs)
+
+    def callback(self, result):
+        self.results.append(result)
+        self.calledBack = True
+        if self.callbacks:
+            self.doCallbacks([result], self.callbacks)
+        
+    def errback(self, failed):
+        self.failures.append(failed)
+        self.erredBack = True
+        if self.errbacks:
+            self.doCallbacks([failed], self.errbacks)
+        
+    def doCallbacks(self, results, callbacks):
+        for result in results:
+            for cb, args, kwargs in callbacks:
+                result = cb(result, *args, **kwargs)