2 * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
5 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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.
13 * This example shows how to lookup keys within a RCU lock-free hash
14 * table. This hash table requires using a RCU scheme.
21 #include <urcu/urcu-memb.h> /* RCU flavor */
22 #include <urcu/rculfhash.h> /* RCU Lock-free hash table */
23 #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
24 #include "jhash.h" /* Example hash function */
27 * Nodes populated into the hash table.
30 int value
; /* Node content */
31 int seqnum
; /* Our node sequence number */
32 struct cds_lfht_node node
; /* Chaining in hash table */
36 int match(struct cds_lfht_node
*ht_node
, const void *_key
)
39 caa_container_of(ht_node
, struct mynode
, node
);
40 const int *key
= _key
;
42 return *key
== node
->value
;
47 int values
[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */
48 int lookup_values
[] = { 42, 200, 36, };
49 struct cds_lfht
*ht
; /* Hash table */
51 int ret
= 0, seqnum
= 0;
53 struct cds_lfht_iter iter
; /* For iteration on hash table */
54 struct cds_lfht_node
*ht_node
;
58 * Each thread need using RCU read-side need to be explicitly
61 urcu_memb_register_thread();
63 /* Use time as seed for hash table hashing. */
64 seed
= (uint32_t) time(NULL
);
67 * Allocate hash table.
69 ht
= cds_lfht_new_flavor(1, 1, 0,
70 CDS_LFHT_AUTO_RESIZE
| CDS_LFHT_ACCOUNTING
,
71 &urcu_memb_flavor
, NULL
);
73 printf("Error allocating hash table\n");
79 * Add nodes to hash table.
81 for (i
= 0; i
< CAA_ARRAY_SIZE(values
); i
++) {
85 node
= malloc(sizeof(*node
));
91 cds_lfht_node_init(&node
->node
);
94 node
->seqnum
= seqnum
++;
95 hash
= jhash(&value
, sizeof(value
), seed
);
98 * cds_lfht_add() needs to be called from RCU read-side
101 urcu_memb_read_lock();
102 cds_lfht_add(ht
, hash
, &node
->node
);
103 printf("Add (key: %d, seqnum: %d)\n",
104 node
->value
, node
->seqnum
);
105 urcu_memb_read_unlock();
109 * Iterate over each hash table node. Those will appear in
110 * random order, depending on the hash seed. Iteration needs to
111 * be performed within RCU read-side critical section.
113 printf("hash table content (random order):");
114 urcu_memb_read_lock();
115 cds_lfht_for_each_entry(ht
, &iter
, node
, node
) {
116 printf(" (key: %d, seqnum: %d)",
117 node
->value
, node
->seqnum
);
119 urcu_memb_read_unlock();
123 * Lookup queries. Note that which node (seqnum) within
124 * duplicates will be found by lookup is random.
126 printf("Lookups:\n");
127 for (i
= 0; i
< CAA_ARRAY_SIZE(lookup_values
); i
++) {
128 int value
= lookup_values
[i
];
129 unsigned long hash
= jhash(&value
, sizeof(value
), seed
);
131 urcu_memb_read_lock();
132 cds_lfht_lookup(ht
, hash
, match
, &value
, &iter
);
133 ht_node
= cds_lfht_iter_get_node(&iter
);
135 printf("Key %d not found\n", value
);
137 node
= caa_container_of(ht_node
, struct mynode
, node
);
138 printf("(key %d, seqnum %d) found\n",
139 node
->value
, node
->seqnum
);
141 urcu_memb_read_unlock();
145 urcu_memb_unregister_thread();
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