doc/examples: cds_lfht_add/cds_lfht_del
[urcu.git] / doc / examples / rculfhash / cds_lfht_add.c
1 /*
2 * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
3 *
4 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
5 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
6 *
7 * Permission is hereby granted to use or copy this program for any
8 * purpose, provided the above notices are retained on all copies.
9 * Permission to modify the code and to distribute modified code is
10 * granted, provided the above notices are retained, and a notice that
11 * the code was modified is included with the above copyright notice.
12 *
13 * This example shows how to add nodes (allowing duplicate keys) into a
14 * RCU lock-free hash table.
15 * This hash table requires using a RCU scheme.
16 */
17
18 #include <stdio.h>
19 #include <stdlib.h>
20 #include <time.h>
21
22 #include <urcu.h> /* RCU flavor */
23 #include <urcu/rculfhash.h> /* RCU Lock-free hash table */
24 #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
25 #include "jhash.h" /* Example hash function */
26
27 /*
28 * Nodes populated into the hash table.
29 */
30 struct mynode {
31 int value; /* Node content */
32 struct cds_lfht_node node; /* Chaining in hash table */
33 };
34
35 int main(int argc, char **argv)
36 {
37 int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */
38 struct cds_lfht *ht; /* Hash table */
39 unsigned int i;
40 int ret = 0;
41 uint32_t seed;
42 struct cds_lfht_iter iter; /* For iteration on hash table */
43 struct mynode *node;
44
45 /*
46 * Each thread need using RCU read-side need to be explicitly
47 * registered.
48 */
49 rcu_register_thread();
50
51 /* Use time as seed for hash table hashing. */
52 seed = (uint32_t) time(NULL);
53
54 /*
55 * Allocate hash table.
56 */
57 ht = cds_lfht_new(1, 1, 0,
58 CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING,
59 NULL);
60 if (!ht) {
61 printf("Error allocating hash table\n");
62 ret = -1;
63 goto end;
64 }
65
66 /*
67 * Add nodes to hash table.
68 */
69 for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
70 unsigned long hash;
71
72 node = malloc(sizeof(*node));
73 if (!node) {
74 ret = -1;
75 goto end;
76 }
77
78 cds_lfht_node_init(&node->node);
79 node->value = values[i];
80 hash = jhash(&values[i], sizeof(values[i]), seed);
81
82 /*
83 * cds_lfht_add() needs to be called from RCU read-side
84 * critical section.
85 */
86 rcu_read_lock();
87 cds_lfht_add(ht, hash, &node->node);
88 rcu_read_unlock();
89 }
90
91 /*
92 * Iterate over each hash table node. Those will appear in
93 * random order, depending on the hash seed. Iteration needs to
94 * be performed within RCU read-side critical section.
95 */
96 printf("hash table content (random order):");
97 rcu_read_lock();
98 cds_lfht_for_each_entry(ht, &iter, node, node) {
99 printf(" %d", node->value);
100 }
101 rcu_read_unlock();
102 printf("\n");
103 end:
104 rcu_unregister_thread();
105 return ret;
106 }
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