2 * Routines to provide a memory-efficient hashtable.
4 * Copyright (C) 2007-2008 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
;
49 void hashtable_destroy(struct hashtable
*tbl
)
55 /* This returns the node for the indicated key, either newly created or
56 * already existing. Returns NULL if not allocating and not found. */
57 void *hashtable_find(struct hashtable
*tbl
, int64 key
, int allocate_if_missing
)
59 int key64
= tbl
->key64
;
60 struct ht_int32_node
*node
;
63 if (allocate_if_missing
&& tbl
->entries
> HASH_LOAD_LIMIT(tbl
->size
)) {
64 void *old_nodes
= tbl
->nodes
;
65 int size
= tbl
->size
* 2;
68 if (!(tbl
->nodes
= new_array0(char, size
* tbl
->node_size
)))
69 out_of_memory("hashtable_node");
73 for (i
= size
/ 2; i
-- > 0; ) {
74 struct ht_int32_node
*move_node
= HT_NODE(tbl
, old_nodes
, i
);
75 int64 move_key
= HT_KEY(move_node
, key64
);
78 node
= hashtable_find(tbl
, move_key
, 1);
79 node
->data
= move_node
->data
;
86 /* Based on Jenkins One-at-a-time hash. */
87 uchar buf
[4], *keyp
= buf
;
91 for (ndx
= 0, i
= 0; i
< 4; i
++) {
100 /* Based on Jenkins hashword() from lookup3.c. */
103 /* Set up the internal state */
104 a
= b
= c
= 0xdeadbeef + (8 << 2);
106 #define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
107 #if SIZEOF_INT64 >= 8
108 b
+= (uint32
)(key
>> 32);
111 c
^= b
; c
-= rot(b
, 14);
112 a
^= c
; a
-= rot(c
, 11);
113 b
^= a
; b
-= rot(a
, 25);
114 c
^= b
; c
-= rot(b
, 16);
115 a
^= c
; a
-= rot(c
, 4);
116 b
^= a
; b
-= rot(a
, 14);
117 c
^= b
; c
-= rot(b
, 24);
122 /* If it already exists, return the node. If we're not
123 * allocating, return NULL if the key is not found. */
127 ndx
&= tbl
->size
- 1;
128 node
= HT_NODE(tbl
, tbl
->nodes
, ndx
);
129 nkey
= HT_KEY(node
, key64
);
134 if (!allocate_if_missing
)
141 /* Take over this empty spot and then return the node. */
143 ((struct ht_int64_node
*)node
)->key
= key
;