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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 iterate on duplicate keys within a RCU
14 * lock-free hash 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 */
57 * Each thread need using RCU read-side need to be explicitly
60 urcu_memb_register_thread();
62 /* Use time as seed for hash table hashing. */
63 seed
= (uint32_t) time(NULL
);
66 * Allocate hash table.
68 ht
= cds_lfht_new_flavor(1, 1, 0,
69 CDS_LFHT_AUTO_RESIZE
| CDS_LFHT_ACCOUNTING
,
70 &urcu_memb_flavor
, NULL
);
72 printf("Error allocating hash table\n");
78 * Add nodes to hash table.
80 for (i
= 0; i
< CAA_ARRAY_SIZE(values
); i
++) {
84 node
= malloc(sizeof(*node
));
90 cds_lfht_node_init(&node
->node
);
93 node
->seqnum
= seqnum
++;
94 hash
= jhash(&value
, sizeof(value
), seed
);
97 * cds_lfht_add() needs to be called from RCU read-side
100 urcu_memb_read_lock();
101 cds_lfht_add(ht
, hash
, &node
->node
);
102 printf("Add (key: %d, seqnum: %d)\n",
103 node
->value
, node
->seqnum
);
104 urcu_memb_read_unlock();
108 * Iterate over each hash table node. Those will appear in
109 * random order, depending on the hash seed. Iteration needs to
110 * be performed within RCU read-side critical section.
112 printf("hash table content (random order):");
113 urcu_memb_read_lock();
114 cds_lfht_for_each_entry(ht
, &iter
, node
, node
) {
115 printf(" (key: %d, seqnum: %d)",
116 node
->value
, node
->seqnum
);
118 urcu_memb_read_unlock();
122 * Lookup queries. Note that which node (seqnum) within
123 * duplicates will be found by lookup is random.
125 printf("Lookups, with iteration on duplicates:\n");
126 for (i
= 0; i
< CAA_ARRAY_SIZE(lookup_values
); i
++) {
127 int value
= lookup_values
[i
];
128 unsigned long hash
= jhash(&value
, sizeof(value
), seed
);
130 printf("lookup key: %d\n", value
);
131 urcu_memb_read_lock();
132 cds_lfht_for_each_entry_duplicate(ht
, hash
, match
,
133 &value
, &iter
, node
, node
) {
134 printf(" (key %d, seqnum %d) found\n",
135 node
->value
, node
->seqnum
);
137 urcu_memb_read_unlock();
141 urcu_memb_unregister_thread();
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