1 #ifndef _LINUX_LIST_NULLS_H
2 #define _LINUX_LIST_NULLS_H
5 * Special version of lists, where end of list is not a NULL pointer,
6 * but a 'nulls' marker, which can have many different values.
7 * (up to 2^31 different values guaranteed on all platforms)
9 * In the standard hlist, termination of a list is the NULL pointer.
10 * In this special 'nulls' variant, we use the fact that objects stored in
11 * a list are aligned on a word (4 or 8 bytes alignment).
12 * We therefore use the last significant bit of 'ptr' :
13 * Set to 1 : This is a 'nulls' end-of-list marker (ptr >> 1)
14 * Set to 0 : This is a pointer to some object (ptr)
17 struct hlist_nulls_head
{
18 struct hlist_nulls_node
*first
;
21 struct hlist_nulls_node
{
22 struct hlist_nulls_node
*next
, **pprev
;
24 #define INIT_HLIST_NULLS_HEAD(ptr, nulls) \
25 ((ptr)->first = (struct hlist_nulls_node *) (1UL | (((long)nulls) << 1)))
27 #define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member)
29 * ptr_is_a_nulls - Test if a ptr is a nulls
30 * @ptr: ptr to be tested
33 static inline int is_a_nulls(const struct hlist_nulls_node
*ptr
)
35 return ((unsigned long)ptr
& 1);
39 * get_nulls_value - Get the 'nulls' value of the end of chain
42 * Should be called only if is_a_nulls(ptr);
44 static inline unsigned long get_nulls_value(const struct hlist_nulls_node
*ptr
)
46 return ((unsigned long)ptr
) >> 1;
49 static inline int hlist_nulls_unhashed(const struct hlist_nulls_node
*h
)
54 static inline int hlist_nulls_empty(const struct hlist_nulls_head
*h
)
56 return is_a_nulls(h
->first
);
59 static inline void __hlist_nulls_del(struct hlist_nulls_node
*n
)
61 struct hlist_nulls_node
*next
= n
->next
;
62 struct hlist_nulls_node
**pprev
= n
->pprev
;
64 if (!is_a_nulls(next
))
69 * hlist_nulls_for_each_entry - iterate over list of given type
70 * @tpos: the type * to use as a loop cursor.
71 * @pos: the &struct hlist_node to use as a loop cursor.
72 * @head: the head for your list.
73 * @member: the name of the hlist_node within the struct.
76 #define hlist_nulls_for_each_entry(tpos, pos, head, member) \
77 for (pos = (head)->first; \
78 (!is_a_nulls(pos)) && \
79 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \
83 * hlist_nulls_for_each_entry_from - iterate over a hlist continuing from current point
84 * @tpos: the type * to use as a loop cursor.
85 * @pos: the &struct hlist_node to use as a loop cursor.
86 * @member: the name of the hlist_node within the struct.
89 #define hlist_nulls_for_each_entry_from(tpos, pos, member) \
90 for (; (!is_a_nulls(pos)) && \
91 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \
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