Line data Source code
1 : #ifndef _LINUX_LIST_NULLS_H
2 : #define _LINUX_LIST_NULLS_H
3 :
4 : /*
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)
8 : *
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)
15 : */
16 :
17 : struct hlist_nulls_head {
18 : struct hlist_nulls_node *first;
19 : };
20 1 :
21 : struct hlist_nulls_node {
22 : struct hlist_nulls_node *next, **pprev;
23 : };
24 : #define INIT_HLIST_NULLS_HEAD(ptr, nulls) \
25 : ((ptr)->first = (struct hlist_nulls_node *) (1UL | (((long)nulls) << 1)))
26 :
27 : #define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member)
28 : /**
29 : * ptr_is_a_nulls - Test if a ptr is a nulls
30 : * @ptr: ptr to be tested
31 : *
32 : */
33 : static inline int is_a_nulls(const struct hlist_nulls_node *ptr)
34 : {
35 : return ((unsigned long)ptr & 1);
36 : }
37 :
38 : /**
39 : * get_nulls_value - Get the 'nulls' value of the end of chain
40 : * @ptr: end of chain
41 : *
42 : * Should be called only if is_a_nulls(ptr);
43 : */
44 : static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr)
45 : {
46 : return ((unsigned long)ptr) >> 1;
47 : }
48 :
49 : static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h)
50 : {
51 : return !h->pprev;
52 : }
53 :
54 : static inline int hlist_nulls_empty(const struct hlist_nulls_head *h)
55 : {
56 : return is_a_nulls(h->first);
57 : }
58 :
59 : static inline void hlist_nulls_add_head(struct hlist_nulls_node *n,
60 : struct hlist_nulls_head *h)
61 : {
62 : struct hlist_nulls_node *first = h->first;
63 :
64 : n->next = first;
65 : n->pprev = &h->first;
66 : h->first = n;
67 : if (!is_a_nulls(first))
68 : first->pprev = &n->next;
69 : }
70 :
71 : static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
72 : {
73 : struct hlist_nulls_node *next = n->next;
74 : struct hlist_nulls_node **pprev = n->pprev;
75 : *pprev = next;
76 : if (!is_a_nulls(next))
77 : next->pprev = pprev;
78 : }
79 :
80 : static inline void hlist_nulls_del(struct hlist_nulls_node *n)
81 : {
82 : __hlist_nulls_del(n);
83 : n->pprev = LIST_POISON2;
84 : }
85 1 :
86 : /**
87 : * hlist_nulls_for_each_entry - iterate over list of given type
88 : * @tpos: the type * to use as a loop cursor.
89 : * @pos: the &struct hlist_node to use as a loop cursor.
90 : * @head: the head for your list.
91 : * @member: the name of the hlist_node within the struct.
92 : *
93 : */
94 : #define hlist_nulls_for_each_entry(tpos, pos, head, member) \
95 : for (pos = (head)->first; \
96 : (!is_a_nulls(pos)) && \
97 : ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \
98 : pos = pos->next)
99 :
100 : /**
101 : * hlist_nulls_for_each_entry_from - iterate over a hlist continuing from current point
102 : * @tpos: the type * to use as a loop cursor.
103 : * @pos: the &struct hlist_node to use as a loop cursor.
104 : * @member: the name of the hlist_node within the struct.
105 : *
106 : */
107 : #define hlist_nulls_for_each_entry_from(tpos, pos, member) \
108 : for (; (!is_a_nulls(pos)) && \
109 : ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \
110 : pos = pos->next)
111 :
112 : #endif
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