diff --git a/defer-internal.h b/defer-internal.h
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+/*
+ * Copyright (c) 2009-2012 Niels Provos and Nick Mathewson
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef _DEFER_INTERNAL_H_
+#define _DEFER_INTERNAL_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "event2/event-config.h"
+#include <sys/queue.h>
+
+struct deferred_cb;
+
+typedef void (*deferred_cb_fn)(struct deferred_cb *, void *);
+
+/** A deferred_cb is a callback that can be scheduled to run as part of
+ * an event_base's event_loop, rather than running immediately. */
+struct deferred_cb {
+	/** Links to the adjacent active (pending) deferred_cb objects. */
+	TAILQ_ENTRY (deferred_cb) cb_next;
+	/** True iff this deferred_cb is pending in an event_base. */
+	unsigned queued : 1;
+	/** The function to execute when the callback runs. */
+	deferred_cb_fn cb;
+	/** The function's second argument. */
+	void *arg;
+};
+
+/** A deferred_cb_queue is a list of deferred_cb that we can add to and run. */
+struct deferred_cb_queue {
+	/** Lock used to protect the queue. */
+	void *lock;
+
+	/** How many entries are in the queue? */
+	int active_count;
+
+	/** Function called when adding to the queue from another thread. */
+	void (*notify_fn)(struct deferred_cb_queue *, void *);
+	void *notify_arg;
+
+	/** Deferred callback management: a list of deferred callbacks to
+	 * run active the active events. */
+	TAILQ_HEAD (deferred_cb_list, deferred_cb) deferred_cb_list;
+};
+
+/**
+   Initialize an empty, non-pending deferred_cb.
+
+   @param deferred The deferred_cb structure to initialize.
+   @param cb The function to run when the deferred_cb executes.
+   @param arg The function's second argument.
+ */
+void event_deferred_cb_init(struct deferred_cb *, deferred_cb_fn, void *);
+/**
+   Cancel a deferred_cb if it is currently scheduled in an event_base.
+ */
+void event_deferred_cb_cancel(struct deferred_cb_queue *, struct deferred_cb *);
+/**
+   Activate a deferred_cb if it is not currently scheduled in an event_base.
+ */
+void event_deferred_cb_schedule(struct deferred_cb_queue *, struct deferred_cb *);
+
+#define LOCK_DEFERRED_QUEUE(q)						\
+	EVLOCK_LOCK((q)->lock, 0)
+#define UNLOCK_DEFERRED_QUEUE(q)					\
+	EVLOCK_UNLOCK((q)->lock, 0)
+
+#ifdef __cplusplus
+}
+#endif
+
+void event_deferred_cb_queue_init(struct deferred_cb_queue *);
+struct deferred_cb_queue *event_base_get_deferred_cb_queue(struct event_base *);
+
+#endif /* _EVENT_INTERNAL_H_ */
+