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hashtable: introduce a small and naive hashtable

This hashtable implementation is using hlist buckets to provide a simple hashtable to prevent it from getting reimplemented all over the kernel.

Sasha Levin committed 14 years ago

Commit d9b482c1 parent c660b8f1 file · +192 −0Browse files

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1+/*
2+ * Statically sized hash table implementation
3+ * (C) 2012 Sasha Levin <levinsasha928@gmail.com>
4+ */
5+
6+#ifndef _LINUX_HASHTABLE_H
7+#define _LINUX_HASHTABLE_H
8+
9+#include <linux/list.h>
10+#include <linux/types.h>
11+#include <linux/kernel.h>
12+#include <linux/hash.h>
13+#include <linux/rculist.h>
14+
15+#define DEFINE_HASHTABLE(name, bits) \
16+ struct hlist_head name[1 << (bits)] = \
17+ { [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
18+
19+#define DECLARE_HASHTABLE(name, bits) \
20+ struct hlist_head name[1 << (bits)]
21+
22+#define HASH_SIZE(name) (ARRAY_SIZE(name))
23+#define HASH_BITS(name) ilog2(HASH_SIZE(name))
24+
25+/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
26+#define hash_min(val, bits) \
27+ (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits))
28+
29+static inline void __hash_init(struct hlist_head *ht, unsigned int sz)
30+{
31+ unsigned int i;
32+
33+ for (i = 0; i < sz; i++)
34+ INIT_HLIST_HEAD(&ht[i]);
35+}
36+
37+/**
38+ * hash_init - initialize a hash table
39+ * @hashtable: hashtable to be initialized
40+ *
41+ * Calculates the size of the hashtable from the given parameter, otherwise
42+ * same as hash_init_size.
43+ *
44+ * This has to be a macro since HASH_BITS() will not work on pointers since
45+ * it calculates the size during preprocessing.
46+ */
47+#define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))
48+
49+/**
50+ * hash_add - add an object to a hashtable
51+ * @hashtable: hashtable to add to
52+ * @node: the &struct hlist_node of the object to be added
53+ * @key: the key of the object to be added
54+ */
55+#define hash_add(hashtable, node, key) \
56+ hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
57+
58+/**
59+ * hash_add_rcu - add an object to a rcu enabled hashtable
60+ * @hashtable: hashtable to add to
61+ * @node: the &struct hlist_node of the object to be added
62+ * @key: the key of the object to be added
63+ */
64+#define hash_add_rcu(hashtable, node, key) \
65+ hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
66+
67+/**
68+ * hash_hashed - check whether an object is in any hashtable
69+ * @node: the &struct hlist_node of the object to be checked
70+ */
71+static inline bool hash_hashed(struct hlist_node *node)
72+{
73+ return !hlist_unhashed(node);
74+}
75+
76+static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)
77+{
78+ unsigned int i;
79+
80+ for (i = 0; i < sz; i++)
81+ if (!hlist_empty(&ht[i]))
82+ return false;
83+
84+ return true;
85+}
86+
87+/**
88+ * hash_empty - check whether a hashtable is empty
89+ * @hashtable: hashtable to check
90+ *
91+ * This has to be a macro since HASH_BITS() will not work on pointers since
92+ * it calculates the size during preprocessing.
93+ */
94+#define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))
95+
96+/**
97+ * hash_del - remove an object from a hashtable
98+ * @node: &struct hlist_node of the object to remove
99+ */
100+static inline void hash_del(struct hlist_node *node)
101+{
102+ hlist_del_init(node);
103+}
104+
105+/**
106+ * hash_del_rcu - remove an object from a rcu enabled hashtable
107+ * @node: &struct hlist_node of the object to remove
108+ */
109+static inline void hash_del_rcu(struct hlist_node *node)
110+{
111+ hlist_del_init_rcu(node);
112+}
113+
114+/**
115+ * hash_for_each - iterate over a hashtable
116+ * @name: hashtable to iterate
117+ * @bkt: integer to use as bucket loop cursor
118+ * @node: the &struct list_head to use as a loop cursor for each entry
119+ * @obj: the type * to use as a loop cursor for each entry
120+ * @member: the name of the hlist_node within the struct
121+ */
122+#define hash_for_each(name, bkt, node, obj, member) \
123+ for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\
124+ hlist_for_each_entry(obj, node, &name[bkt], member)
125+
126+/**
127+ * hash_for_each_rcu - iterate over a rcu enabled hashtable
128+ * @name: hashtable to iterate
129+ * @bkt: integer to use as bucket loop cursor
130+ * @node: the &struct list_head to use as a loop cursor for each entry
131+ * @obj: the type * to use as a loop cursor for each entry
132+ * @member: the name of the hlist_node within the struct
133+ */
134+#define hash_for_each_rcu(name, bkt, node, obj, member) \
135+ for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\
136+ hlist_for_each_entry_rcu(obj, node, &name[bkt], member)
137+
138+/**
139+ * hash_for_each_safe - iterate over a hashtable safe against removal of
140+ * hash entry
141+ * @name: hashtable to iterate
142+ * @bkt: integer to use as bucket loop cursor
143+ * @node: the &struct list_head to use as a loop cursor for each entry
144+ * @tmp: a &struct used for temporary storage
145+ * @obj: the type * to use as a loop cursor for each entry
146+ * @member: the name of the hlist_node within the struct
147+ */
148+#define hash_for_each_safe(name, bkt, node, tmp, obj, member) \
149+ for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\
150+ hlist_for_each_entry_safe(obj, node, tmp, &name[bkt], member)
151+
152+/**
153+ * hash_for_each_possible - iterate over all possible objects hashing to the
154+ * same bucket
155+ * @name: hashtable to iterate
156+ * @obj: the type * to use as a loop cursor for each entry
157+ * @node: the &struct list_head to use as a loop cursor for each entry
158+ * @member: the name of the hlist_node within the struct
159+ * @key: the key of the objects to iterate over
160+ */
161+#define hash_for_each_possible(name, obj, node, member, key) \
162+ hlist_for_each_entry(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
163+
164+/**
165+ * hash_for_each_possible_rcu - iterate over all possible objects hashing to the
166+ * same bucket in an rcu enabled hashtable
167+ * in a rcu enabled hashtable
168+ * @name: hashtable to iterate
169+ * @obj: the type * to use as a loop cursor for each entry
170+ * @node: the &struct list_head to use as a loop cursor for each entry
171+ * @member: the name of the hlist_node within the struct
172+ * @key: the key of the objects to iterate over
173+ */
174+#define hash_for_each_possible_rcu(name, obj, node, member, key) \
175+ hlist_for_each_entry_rcu(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
176+
177+/**
178+ * hash_for_each_possible_safe - iterate over all possible objects hashing to the
179+ * same bucket safe against removals
180+ * @name: hashtable to iterate
181+ * @obj: the type * to use as a loop cursor for each entry
182+ * @node: the &struct list_head to use as a loop cursor for each entry
183+ * @tmp: a &struct used for temporary storage
184+ * @member: the name of the hlist_node within the struct
185+ * @key: the key of the objects to iterate over
186+ */
187+#define hash_for_each_possible_safe(name, obj, node, tmp, member, key) \
188+ hlist_for_each_entry_safe(obj, node, tmp, \
189+ &name[hash_min(key, HASH_BITS(name))], member)
190+
191+
192+#endif