/* SPDX-License-Identifier: MIT */
/**
 * utils.h - useful macros for compile-time magic
 *
 * Inspired by similar macros in the Linux Kernel.
 *
 * Copyright (c) 2023 - Yaroslav de la Peña Smirnov
 */
#ifndef CWARE_UTILS_H
#define CWARE_UTILS_H

#include <stddef.h>

#ifndef static_assert
#define static_assert(exp, msg) _Static_assert(exp, msg)
#endif

/**
 * BUILD_BUG_ON_ZERO - throws compilation error if true, expressions returns 0.
 * @cond:	condition
 *
 * Force a compilation error if condition is true, but also produce a
 * result (of value 0 and type int), so the expression can be used
 * e.g. in a structure initializer (or where-ever else comma expressions
 * aren't permitted).
 */
#define BUILD_BUG_ON_ZERO(cond) ((int)(sizeof(struct { int : (-!!(cond)); })))

#define same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))

#define container_of(ptr, T, member)                      \
	({                                                    \
		static_assert(same_type(*(ptr), ((T *)0)->member) \
							  || same_type(*(ptr), void), \
					  "type mismatch in container_of()"); \
		(T *)((void *)(ptr)-offsetof(T, member));         \
	})

/**
 * __ASSERT_IS_ARRAY - throw a compilation error if @arr is not an array.
 * @arr:	variable to check.
 */
#define __ASSERT_IS_ARRAY(arr) BUILD_BUG_ON_ZERO(same_type((arr), &(arr)[0]))

/**
 * ARRAY_SIZE - return the number of elements in @arr.
 * @arr:	array of any type.
 */
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(*arr) + __ASSERT_IS_ARRAY(arr))

#endif