#ifndef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif

struct sl {
	struct sl *next;
};

#define SL_INIT(x)	{ .next = x, }
#define SL_DECLARE(x)	struct sl x = SL_INIT(&x)

#define sl_init(pos) \
	(pos)->next = (pos)

#define sl_next(pos) \
	((pos)->next)

#define sl_empty(pos) \
	(sl_next(pos) == (pos))

#define sl_entry(ptr, type, member) ({ \
	const struct sl * __mptr = (const struct sl *)(ptr);	\
	(type *)((char *)__mptr - offsetof(type, member)); })

#define sl_for_each(pos, head) \
	for (pos = sl_next(head); pos != (head); pos = sl_next(pos))

#define sl_for_each_safe(pos, npos, head) \
	for (pos = sl_next(head), npos = sl_next(pos); \
			pos != (head); pos = npos, npos = sl_next(pos))

static inline void sl_link(struct sl *entry, struct sl *prev)
{
	entry->next = prev->next;
	prev->next = entry;
}

static inline void sl_unlink(struct sl *entry, struct sl *prev)
{
	prev->next = entry->next;
	entry->next = (void*)0xdeadbeef; /* poisoning */
}