/* * 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 iterate on duplicate keys within a RCU * lock-free hash table. This hash table requires using a RCU scheme. */ #include <stdio.h> #include <stdlib.h> #include <time.h> #include <urcu/urcu-memb.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 */ }; static int match(struct cds_lfht_node *ht_node, const void *_key) { struct mynode *node = caa_container_of(ht_node, struct mynode, node); const int *key = _key; return *key == node->value; } int main(void) { int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */ int lookup_values[] = { 42, 200, 36, }; 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 mynode *node; /* * Each thread need using RCU read-side need to be explicitly * registered. */ urcu_memb_register_thread(); /* Use time as seed for hash table hashing. */ seed = (uint32_t) time(NULL); /* * Allocate hash table. */ ht = cds_lfht_new_flavor(1, 1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, &urcu_memb_flavor, 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. */ urcu_memb_read_lock(); cds_lfht_add(ht, hash, &node->node); printf("Add (key: %d, seqnum: %d)\n", node->value, node->seqnum); urcu_memb_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):"); urcu_memb_read_lock(); cds_lfht_for_each_entry(ht, &iter, node, node) { printf(" (key: %d, seqnum: %d)", node->value, node->seqnum); } urcu_memb_read_unlock(); printf("\n"); /* * Lookup queries. Note that which node (seqnum) within * duplicates will be found by lookup is random. */ printf("Lookups, with iteration on duplicates:\n"); for (i = 0; i < CAA_ARRAY_SIZE(lookup_values); i++) { int value = lookup_values[i]; unsigned long hash = jhash(&value, sizeof(value), seed); printf("lookup key: %d\n", value); urcu_memb_read_lock(); cds_lfht_for_each_entry_duplicate(ht, hash, match, &value, &iter, node, node) { printf(" (key %d, seqnum %d) found\n", node->value, node->seqnum); } urcu_memb_read_unlock(); } end: urcu_memb_unregister_thread(); return ret; }