Add lab04

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/lab04/container_of.h b/lab04/container_of.h
new file mode 100644
index 0000000..bffe7b7
--- /dev/null
+++ b/lab04/container_of.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/**
+ * @file container_of.h
+ * @brief Provides type-aware container and member offset macros.
+ */
+#ifndef _CONTAINER_OF_H
+#define _CONTAINER_OF_H
+
+#include <stddef.h>
+
+/** @brief Checks whether two expressions have compatible types. */
+#define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
+
+/** @brief Computes a member offset using the compiler builtin. */
+#undef offsetof
+#define offsetof(TYPE, MEMBER)	__builtin_offsetof(TYPE, MEMBER)
+
+/** @brief Obtains the type of a member of a structure type. */
+#define typeof_member(T, m)   typeof(((T*)0)->m)
+
+/**
+ * @brief Converts a pointer to a structure member to its containing object.
+ * @param ptr A pointer to the member.
+ * @param type The type of the containing structure.
+ * @param member The member name within `type`.
+ *
+ * The macro performs a compile-time type compatibility check before applying
+ * the member offset.
+ */
+#define container_of(ptr, type, member) ({                         \
+    _Static_assert(__same_type(*(ptr), typeof_member(type, member)) || \
+                   __same_type(*(ptr), void),                      \
+                   "pointer type mismatch in container_of()");     \
+    (type *)((void *)(ptr) - offsetof(type, member)); })
+
+
+/**
+ * @brief Converts a member pointer while preserving its const qualification.
+ * @param ptr A pointer to the member.
+ * @param type The type of the containing structure.
+ * @param member The member name within `type`.
+ */
+#define container_of_const(ptr, type, member)				\
+	_Generic(ptr,							\
+		const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
+		default: ((type *)container_of(ptr, type, member))	\
+	)
+
+#endif /* _CONTAINER_OF_H */