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git.ipfire.org Git - thirdparty/rsync.git/blob - hashtable.c
2 * Routines to provide a memory-efficient hashtable.
4 * Copyright (C) 2007-2009 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
)
27 struct hashtable
*tbl
;
28 int node_size
= key64
? sizeof (struct ht_int64_node
)
29 : sizeof (struct ht_int32_node
);
31 /* Pick a power of 2 that can hold the requested size. */
32 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
;
44 tbl
->key64
= (short)key64
;
46 if (DEBUG_GTE(HASH
, 1)) {
49 snprintf(buf
, sizeof buf
, "req: %d, ", req
);
52 rprintf(FINFO
, "[%s] created hashtable %lx (%ssize: %d, keys: %d-bit)\n",
53 who_am_i(), (long)tbl
, buf
, size
, key64
? 64 : 32);
59 void hashtable_destroy(struct hashtable
*tbl
)
61 if (DEBUG_GTE(HASH
, 1)) {
62 rprintf(FINFO
, "[%s] destroyed hashtable %lx (size: %d, keys: %d-bit)\n",
63 who_am_i(), (long)tbl
, tbl
->size
, tbl
->key64
? 64 : 32);
69 /* This returns the node for the indicated key, either newly created or
70 * already existing. Returns NULL if not allocating and not found. */
71 void *hashtable_find(struct hashtable
*tbl
, int64 key
, int allocate_if_missing
)
73 int key64
= tbl
->key64
;
74 struct ht_int32_node
*node
;
77 if (allocate_if_missing
&& tbl
->entries
> HASH_LOAD_LIMIT(tbl
->size
)) {
78 void *old_nodes
= tbl
->nodes
;
79 int size
= tbl
->size
* 2;
82 if (!(tbl
->nodes
= new_array0(char, size
* tbl
->node_size
)))
83 out_of_memory("hashtable_node");
87 if (DEBUG_GTE(HASH
, 1)) {
88 rprintf(FINFO
, "[%s] growing hashtable %lx (size: %d, keys: %d-bit)\n",
89 who_am_i(), (long)tbl
, size
, key64
? 64 : 32);
92 for (i
= size
/ 2; i
-- > 0; ) {
93 struct ht_int32_node
*move_node
= HT_NODE(tbl
, old_nodes
, i
);
94 int64 move_key
= HT_KEY(move_node
, key64
);
97 node
= hashtable_find(tbl
, move_key
, 1);
98 node
->data
= move_node
->data
;
105 /* Based on Jenkins One-at-a-time hash. */
106 uchar buf
[4], *keyp
= buf
;
110 for (ndx
= 0, i
= 0; i
< 4; i
++) {
119 /* Based on Jenkins hashword() from lookup3.c. */
122 /* Set up the internal state */
123 a
= b
= c
= 0xdeadbeef + (8 << 2);
125 #define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
126 #if SIZEOF_INT64 >= 8
127 b
+= (uint32
)(key
>> 32);
130 c
^= b
; c
-= rot(b
, 14);
131 a
^= c
; a
-= rot(c
, 11);
132 b
^= a
; b
-= rot(a
, 25);
133 c
^= b
; c
-= rot(b
, 16);
134 a
^= c
; a
-= rot(c
, 4);
135 b
^= a
; b
-= rot(a
, 14);
136 c
^= b
; c
-= rot(b
, 24);
141 /* If it already exists, return the node. If we're not
142 * allocating, return NULL if the key is not found. */
146 ndx
&= tbl
->size
- 1;
147 node
= HT_NODE(tbl
, tbl
->nodes
, ndx
);
148 nkey
= HT_KEY(node
, key64
);
153 if (!allocate_if_missing
)
160 /* Take over this empty spot and then return the node. */
162 ((struct ht_int64_node
*)node
)->key
= key
;
164 node
->key
= (int32
)key
;