1 files changed, 58 insertions, 0 deletions
diff --git a/python/gevent/_ffi/callback.py b/python/gevent/_ffi/callback.py
new file mode 100644
index 0000000..df59a9f
--- /dev/null
+++ b/python/gevent/_ffi/callback.py
@@ -0,0 +1,58 @@
+from __future__ import absolute_import, print_function
+
+__all__ = [
+    'callback',
+]
+
+
+# For times when *args is captured but often not passed (empty),
+# we can avoid keeping the new tuple that was created for *args
+# around by using a constant.
+_NOARGS = ()
+
+
+class callback(object):
+
+    __slots__ = ('callback', 'args')
+
+    def __init__(self, cb, args):
+        self.callback = cb
+        self.args = args or _NOARGS
+
+    def stop(self):
+        self.callback = None
+        self.args = None
+
+    close = stop
+
+    # Note that __nonzero__ and pending are different
+    # bool() is used in contexts where we need to know whether to schedule another callback,
+    # so it's true if it's pending or currently running
+    # 'pending' has the same meaning as libev watchers: it is cleared before actually
+    # running the callback
+
+    def __nonzero__(self):
+        # it's nonzero if it's pending or currently executing
+        # NOTE: This depends on loop._run_callbacks setting the args property
+        # to None.
+        return self.args is not None
+    __bool__ = __nonzero__
+
+    @property
+    def pending(self):
+        return self.callback is not None
+
+    def _format(self):
+        return ''
+
+    def __repr__(self):
+        result = "<%s at 0x%x" % (self.__class__.__name__, id(self))
+        if self.pending:
+            result += " pending"
+        if self.callback is not None:
+            result += " callback=%r" % (self.callback, )
+        if self.args is not None:
+            result += " args=%r" % (self.args, )
+        if self.callback is None and self.args is None:
+            result += " stopped"
+        return result + ">"