2 * Routines to provide a memory-efficient hashtable.
4 * Copyright (C) 2007 Wayne Davison
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 3 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License along
17 * with this program; if not, visit the http://fsf.org website.
22 #define HASH_LOAD_LIMIT(size) ((size)*3/4)
24 struct hashtable *hashtable_create(int size, int key64)
26 struct hashtable *tbl;
27 int node_size = key64 ? sizeof (struct ht_int64_node )
28 : sizeof (struct ht_int32_node);
30 /* Pick a power of 2 that can hold the requested size. */
31 if (size & (size-1) || size < 16) {
38 if (!(tbl = new(struct hashtable))
39 || !(tbl->nodes = new_array0(char, size * node_size)))
40 out_of_memory("hashtable_create");
43 tbl->node_size = node_size;
48 void hashtable_destroy(struct hashtable *tbl)
54 /* This returns the node for the indicated key, either newly created or
55 * already existing. Returns NULL if not allocating and not found. */
56 void *hashtable_find(struct hashtable *tbl, int64 key, int allocate_if_missing)
58 int key64 = (tbl->node_size > sizeof (struct ht_int32_node));
59 struct ht_int32_node *node;
62 if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
63 void *old_nodes = tbl->nodes;
64 int size = tbl->size * 2;
67 if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
68 out_of_memory("hashtable_node");
72 for (i = size / 2; i-- > 0; ) {
73 struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
74 int64 move_key = HT_KEY(move_node, key64);
77 node = hashtable_find(tbl, move_key, 1);
78 node->data = move_node->data;
85 /* Based on Jenkins One-at-a-time hash. */
86 uchar buf[4], *keyp = buf;
90 for (ndx = 0, i = 0; i < 4; i++) {
99 /* Based on Jenkins hashword() from lookup3.c. */
102 /* Set up the internal state */
103 a = b = c = 0xdeadbeef + (8 << 2);
105 #define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
106 b += (uint32)(key >> 32);
108 c ^= b; c -= rot(b, 14);
109 a ^= c; a -= rot(c, 11);
110 b ^= a; b -= rot(a, 25);
111 c ^= b; c -= rot(b, 16);
112 a ^= c; a -= rot(c, 4);
113 b ^= a; b -= rot(a, 14);
114 c ^= b; c -= rot(b, 24);
119 /* If it already exists, return the node. If we're not
120 * allocating, return NULL if the key is not found. */
124 ndx &= tbl->size - 1;
125 node = HT_NODE(tbl, tbl->nodes, ndx);
126 nkey = HT_KEY(node, key64);
131 if (!allocate_if_missing)
138 /* Take over this empty spot and then return the node. */
140 ((struct ht_int64_node*)node)->key = key;