--- /dev/null
+# Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+#
+# THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+# OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
+#
+# Permission is hereby granted to use or copy this program for any
+# purpose, provided the above notices are retained on all copies.
+# Permission to modify the code and to distribute modified code is
+# granted, provided the above notices are retained, and a notice that
+# the code was modified is included with the above copyright notice.
+#
+# This makefile is purposefully kept simple to support GNU and BSD make.
+
+EXAMPLE_NAME = cds_lfht_add_unique
+
+SOURCES = $(EXAMPLE_NAME).c
+DEPS = jhash.h
+OBJECTS = $(EXAMPLE_NAME).o
+BINARY = $(EXAMPLE_NAME)
+LIBS = -lurcu-cds -lurcu
+
+include ../Makefile.examples.template
--- /dev/null
+/*
+ * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program for any
+ * purpose, provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is
+ * granted, provided the above notices are retained, and a notice that
+ * the code was modified is included with the above copyright notice.
+ *
+ * This example shows how to add unique nodes into a RCU lock-free hash
+ * table. We use a "seqnum" field to show which node is staying in the
+ * hash table. This hash table requires using a RCU scheme.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include <urcu.h> /* RCU flavor */
+#include <urcu/rculfhash.h> /* RCU Lock-free hash table */
+#include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
+#include "jhash.h" /* Example hash function */
+
+/*
+ * Nodes populated into the hash table.
+ */
+struct mynode {
+ int value; /* Node content */
+ int seqnum; /* Our node sequence number */
+ struct cds_lfht_node node; /* Chaining in hash table */
+};
+
+int match(struct cds_lfht_node *ht_node, const void *_key)
+{
+ struct mynode *node =
+ caa_container_of(ht_node, struct mynode, node);
+ const unsigned int *key = _key;
+
+ return *key == node->value;
+}
+
+int main(int argc, char **argv)
+{
+ int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */
+ struct cds_lfht *ht; /* Hash table */
+ unsigned int i;
+ int ret = 0, seqnum = 0;
+ uint32_t seed;
+ struct cds_lfht_iter iter; /* For iteration on hash table */
+ struct cds_lfht_node *ht_node;
+ struct mynode *node;
+
+ /*
+ * Each thread need using RCU read-side need to be explicitly
+ * registered.
+ */
+ rcu_register_thread();
+
+ /* Use time as seed for hash table hashing. */
+ seed = (uint32_t) time(NULL);
+
+ /*
+ * Allocate hash table.
+ */
+ ht = cds_lfht_new(1, 1, 0,
+ CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING,
+ NULL);
+ if (!ht) {
+ printf("Error allocating hash table\n");
+ ret = -1;
+ goto end;
+ }
+
+ /*
+ * Add nodes to hash table.
+ */
+ for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
+ unsigned long hash;
+ int value;
+
+ node = malloc(sizeof(*node));
+ if (!node) {
+ ret = -1;
+ goto end;
+ }
+
+ cds_lfht_node_init(&node->node);
+ value = values[i];
+ node->value = value;
+ node->seqnum = seqnum++;
+ hash = jhash(&value, sizeof(value), seed);
+
+ /*
+ * cds_lfht_add() needs to be called from RCU read-side
+ * critical section.
+ */
+ rcu_read_lock();
+ ht_node = cds_lfht_add_unique(ht, hash, match, &value,
+ &node->node);
+ /*
+ * cds_lfht_add_unique() returns the added node if not
+ * already present, else returns the node matching the
+ * key.
+ */
+ if (ht_node != &node->node) {
+ /*
+ * We found a match. Therefore, to ensure we
+ * don't add duplicates, cds_lfht_add_unique()
+ * acted as a RCU lookup, returning the found
+ * match. It did not add the new node to the
+ * hash table, so we can free it on the spot.
+ */
+ printf("Not adding duplicate key: %d, seqnum: %d\n",
+ node->value, node->seqnum);
+ free(node);
+ } else {
+ printf("Add key: %d, seqnum: %d\n",
+ node->value, node->seqnum);
+ }
+ rcu_read_unlock();
+ }
+
+ /*
+ * Iterate over each hash table node. Those will appear in
+ * random order, depending on the hash seed. Iteration needs to
+ * be performed within RCU read-side critical section.
+ */
+ printf("hash table content (random order):");
+ rcu_read_lock();
+ cds_lfht_for_each_entry(ht, &iter, node, node) {
+ printf(" (key: %d, seqnum: %d)",
+ node->value, node->seqnum);
+ }
+ rcu_read_unlock();
+ printf("\n");
+
+end:
+ rcu_unregister_thread();
+ return ret;
+}
projects / urcu.git / commitdiff
