Improved a couple NEWS items.
[rsync/qnx.git] / hashtable.c
blobd2f5948bea2ac3cfed5364f24a2f4e8bc45335bf
1 /*
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.
20 #include "rsync.h"
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) {
32 int req = size;
33 size = 16;
34 while (size < req)
35 size *= 2;
38 if (!(tbl = new(struct hashtable))
39 || !(tbl->nodes = new_array0(char, size * node_size)))
40 out_of_memory("hashtable_create");
41 tbl->size = size;
42 tbl->entries = 0;
43 tbl->node_size = node_size;
44 tbl->key64 = key64;
46 return tbl;
49 void hashtable_destroy(struct hashtable *tbl)
51 free(tbl->nodes);
52 free(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;
61 uint32 ndx;
63 if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
64 void *old_nodes = tbl->nodes;
65 int size = tbl->size * 2;
66 int i;
68 if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
69 out_of_memory("hashtable_node");
70 tbl->size = size;
71 tbl->entries = 0;
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);
76 if (move_key == 0)
77 continue;
78 node = hashtable_find(tbl, move_key, 1);
79 node->data = move_node->data;
82 free(old_nodes);
85 if (!key64) {
86 /* Based on Jenkins One-at-a-time hash. */
87 uchar buf[4], *keyp = buf;
88 int i;
90 SIVAL(buf, 0, key);
91 for (ndx = 0, i = 0; i < 4; i++) {
92 ndx += keyp[i];
93 ndx += (ndx << 10);
94 ndx ^= (ndx >> 6);
96 ndx += (ndx << 3);
97 ndx ^= (ndx >> 11);
98 ndx += (ndx << 15);
99 } else {
100 /* Based on Jenkins hashword() from lookup3.c. */
101 uint32 a, b, 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);
109 #endif
110 a += (uint32)key;
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);
118 #undef rot
119 ndx = c;
122 /* If it already exists, return the node. If we're not
123 * allocating, return NULL if the key is not found. */
124 while (1) {
125 int64 nkey;
127 ndx &= tbl->size - 1;
128 node = HT_NODE(tbl, tbl->nodes, ndx);
129 nkey = HT_KEY(node, key64);
131 if (nkey == key)
132 return node;
133 if (nkey == 0) {
134 if (!allocate_if_missing)
135 return NULL;
136 break;
138 ndx++;
141 /* Take over this empty spot and then return the node. */
142 if (key64)
143 ((struct ht_int64_node*)node)->key = key;
144 else
145 node->key = key;
146 tbl->entries++;
147 return node;