From cd1b95aea34de3415fc4a33ecc73e9ebfdbaaa3a Mon Sep 17 00:00:00 2001
From: "Justin R. Cutler" <justin.r.cutler@gmail.com>
Date: Fri, 8 Apr 2016 21:16:07 -0400
Subject: [PATCH] Add container_of macro

---
 threadless/container_of.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 threadless/container_of.h

diff --git a/threadless/container_of.h b/threadless/container_of.h
new file mode 100644
index 0000000..9bd65a8
--- /dev/null
+++ b/threadless/container_of.h
@@ -0,0 +1,27 @@
+/* threadless.io
+ * Copyright (c) 2016 Justin R. Cutler
+ * Licensed under the MIT License. See LICENSE file in the project root for
+ * full license information.
+ */
+/** @file
+ * container_of macro definition
+ * @author Justin R. Cutler <justin.r.cutler@gmail.com>
+ */
+#ifndef THREADLESS_CONTAINER_OF_H
+#define THREADLESS_CONTAINER_OF_H
+
+/* offsetof */
+#include <stddef.h>
+
+/** Get a pointer to the containing structure of a member
+ * @param ptr    address of @p member within a @p type
+ * @param type   type of container
+ * @param member name of the member in @p type
+ * @returns pointer to containing @p type
+ */
+#define container_of(ptr, type, member) ( \
+    (type *)((char *)(1 ? (ptr) : &((type *)0)->member) \
+        - offsetof(type, member)) \
+)
+
+#endif /* THREADLESS_CONTAINER_OF_H */