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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 | |
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 | |
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 |
113 |
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