/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_CONTAINER_OF_H
#define _LINUX_CONTAINER_OF_H

#include <linux/build_bug.h>
#include <linux/stddef.h>

#define typeof_member(T, m)    typeof(((T*)0)->m)

/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:    the pointer to the member.
 * @type:    the type of the container struct this is embedded in.
 * @member:    the name of the member within the struct.
 *
 * WARNING: any const qualifier of @ptr is lost.
 */
#define container_of(ptr, type, member) ({                \
    void *__mptr = (void *)(ptr);                    \
    static_assert(__same_type(*(ptr), ((type *)0)->member) ||    \
              __same_type(*(ptr), void),            \
              "pointer type mismatch in container_of()");    \
    ((type *)(__mptr - offsetof(type, member))); })

/**
 * container_of_const - cast a member of a structure out to the containing
 *            structure and preserve the const-ness of the pointer
 * @ptr:        the pointer to the member
 * @type:        the type of the container struct this is embedded in.
 * @member:        the name of the member within the struct.
 */
#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    /* _LINUX_CONTAINER_OF_H */