Cleanup: enable signed/unsigned compare compiler warning
[urcu.git] / doc / examples / rculfhash / cds_lfht_add_replace.c
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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 into a RCU lock-free hash table
14 * with cds_lfht_add_replace(), which replaces existing nodes with the
15 * same key if found.
16 * We use a "seqnum" field to show which node is staying in the hash
17 * table. This hash table requires using a RCU scheme.
18 */
19
20#include <stdio.h>
21#include <stdlib.h>
22#include <time.h>
23
b9050d91 24#include <urcu/urcu-memb.h> /* RCU flavor */
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25#include <urcu/rculfhash.h> /* RCU Lock-free hash table */
26#include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
27#include "jhash.h" /* Example hash function */
28
29/*
30 * Nodes populated into the hash table.
31 */
32struct mynode {
33 int value; /* Node content */
34 int seqnum; /* Our node sequence number */
35 struct cds_lfht_node node; /* Chaining in hash table */
36 struct rcu_head rcu_head; /* For call_rcu() */
37};
38
39static
40int match(struct cds_lfht_node *ht_node, const void *_key)
41{
42 struct mynode *node =
43 caa_container_of(ht_node, struct mynode, node);
83e334d0 44 const int *key = _key;
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45
46 return *key == node->value;
47}
48
49static
50void free_node(struct rcu_head *head)
51{
52 struct mynode *node = caa_container_of(head, struct mynode, rcu_head);
53
54 free(node);
55}
56
57int main(int argc, char **argv)
58{
59 int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */
60 struct cds_lfht *ht; /* Hash table */
61 unsigned int i;
62 int ret = 0, seqnum = 0;
63 uint32_t seed;
64 struct cds_lfht_iter iter; /* For iteration on hash table */
65 struct cds_lfht_node *ht_node;
66 struct mynode *node;
67
68 /*
69 * Each thread need using RCU read-side need to be explicitly
70 * registered.
71 */
b9050d91 72 urcu_memb_register_thread();
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73
74 /* Use time as seed for hash table hashing. */
75 seed = (uint32_t) time(NULL);
76
77 /*
78 * Allocate hash table.
79 */
b9050d91 80 ht = cds_lfht_new_flavor(1, 1, 0,
34b3f359 81 CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING,
b9050d91 82 &urcu_memb_flavor, NULL);
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83 if (!ht) {
84 printf("Error allocating hash table\n");
85 ret = -1;
86 goto end;
87 }
88
89 /*
90 * Add nodes to hash table.
91 */
92 for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
93 unsigned long hash;
94 int value;
95
96 node = malloc(sizeof(*node));
97 if (!node) {
98 ret = -1;
99 goto end;
100 }
101
102 cds_lfht_node_init(&node->node);
103 value = values[i];
104 node->value = value;
105 node->seqnum = seqnum++;
106 hash = jhash(&value, sizeof(value), seed);
107
108 /*
109 * cds_lfht_add() needs to be called from RCU read-side
110 * critical section.
111 */
b9050d91 112 urcu_memb_read_lock();
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113 ht_node = cds_lfht_add_replace(ht, hash, match, &value,
114 &node->node);
115 if (ht_node) {
116 struct mynode *ret_node =
117 caa_container_of(ht_node, struct mynode, node);
118
119 printf("Replaced node (key: %d, seqnum: %d) by (key: %d, seqnum: %d)\n",
120 ret_node->value, ret_node->seqnum,
121 node->value, node->seqnum);
b9050d91 122 urcu_memb_call_rcu(&ret_node->rcu_head, free_node);
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123 } else {
124 printf("Add (key: %d, seqnum: %d)\n",
125 node->value, node->seqnum);
126 }
b9050d91 127 urcu_memb_read_unlock();
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128 }
129
130 /*
131 * Iterate over each hash table node. Those will appear in
132 * random order, depending on the hash seed. Iteration needs to
133 * be performed within RCU read-side critical section.
134 */
135 printf("hash table content (random order):");
b9050d91 136 urcu_memb_read_lock();
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137 cds_lfht_for_each_entry(ht, &iter, node, node) {
138 printf(" (key: %d, seqnum: %d)",
139 node->value, node->seqnum);
140 }
b9050d91 141 urcu_memb_read_unlock();
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142 printf("\n");
143
144end:
b9050d91 145 urcu_memb_unregister_thread();
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146 return ret;
147}
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