hashtable.c

   1 /*
   2  * Routines to provide a memory-efficient hashtable.
   3  *
   4  * Copyright (C) 2007-2009 Wayne Davison
   5  *
   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.
  10  *
  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.
  15  *
  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.
  18  */
  19
  20 #include "rsync.h"
  21
  22 #define HASH_LOAD_LIMIT(size) ((size)*3/4)
  23
  24 struct hashtable *hashtable_create(int size, int key64)
  25 {
  26         int req = size;
  27         struct hashtable *tbl;
  28         int node_size = key64 ? sizeof (struct ht_int64_node)
  29                               : sizeof (struct ht_int32_node);
  30
  31         /* Pick a power of 2 that can hold the requested size. */
  32         if (size & (size-1) || size < 16) {
  33                 size = 16;
  34                 while (size < req)
  35                         size *= 2;
  36         }
  37
  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 ? 1 : 0;
  45
  46         if (DEBUG_GTE(HASH, 1)) {
  47                 char buf[32];
  48                 if (req != size)
  49                         snprintf(buf, sizeof buf, "req: %d, ", req);
  50                 else
  51                         *buf = '\0';
  52                 rprintf(FINFO, "[%s] created hashtable %lx (%ssize: %d, keys: %d-bit)\n",
  53                         who_am_i(), (long)tbl, buf, size, key64 ? 64 : 32);
  54         }
  55
  56         return tbl;
  57 }
  58
  59 void hashtable_destroy(struct hashtable *tbl)
  60 {
  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);
  64         }
  65         free(tbl->nodes);
  66         free(tbl);
  67 }
  68
  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)
  72 {
  73         int key64 = tbl->key64;
  74         struct ht_int32_node *node;
  75         uint32 ndx;
  76
  77         if (key64 ? key == 0 : (int32)key == 0) {
  78                 rprintf(FERROR, "Internal hashtable error: illegal key supplied!\n");
  79                 exit_cleanup(RERR_MESSAGEIO);
  80         }
  81
  82         if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
  83                 void *old_nodes = tbl->nodes;
  84                 int size = tbl->size * 2;
  85                 int i;
  86
  87                 if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
  88                         out_of_memory("hashtable_node");
  89                 tbl->size = size;
  90                 tbl->entries = 0;
  91
  92                 if (DEBUG_GTE(HASH, 1)) {
  93                         rprintf(FINFO, "[%s] growing hashtable %lx (size: %d, keys: %d-bit)\n",
  94                                 who_am_i(), (long)tbl, size, key64 ? 64 : 32);
  95                 }
  96
  97                 for (i = size / 2; i-- > 0; ) {
  98                         struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
  99                         int64 move_key = HT_KEY(move_node, key64);
 100                         if (move_key == 0)
 101                                 continue;
 102                         node = hashtable_find(tbl, move_key, 1);
 103                         node->data = move_node->data;
 104                 }
 105
 106                 free(old_nodes);
 107         }
 108
 109         if (!key64) {
 110                 /* Based on Jenkins One-at-a-time hash. */
 111                 uchar buf[4], *keyp = buf;
 112                 int i;
 113
 114                 SIVALu(buf, 0, key);
 115                 for (ndx = 0, i = 0; i < 4; i++) {
 116                         ndx += keyp[i];
 117                         ndx += (ndx << 10);
 118                         ndx ^= (ndx >> 6);
 119                 }
 120                 ndx += (ndx << 3);
 121                 ndx ^= (ndx >> 11);
 122                 ndx += (ndx << 15);
 123         } else {
 124                 /* Based on Jenkins hashword() from lookup3.c. */
 125                 uint32 a, b, c;
 126
 127                 /* Set up the internal state */
 128                 a = b = c = 0xdeadbeef + (8 << 2);
 129
 130 #define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
 131 #if SIZEOF_INT64 >= 8
 132                 b += (uint32)(key >> 32);
 133 #endif
 134                 a += (uint32)key;
 135                 c ^= b; c -= rot(b, 14);
 136                 a ^= c; a -= rot(c, 11);
 137                 b ^= a; b -= rot(a, 25);
 138                 c ^= b; c -= rot(b, 16);
 139                 a ^= c; a -= rot(c, 4);
 140                 b ^= a; b -= rot(a, 14);
 141                 c ^= b; c -= rot(b, 24);
 142 #undef rot
 143                 ndx = c;
 144         }
 145
 146         /* If it already exists, return the node.  If we're not
 147          * allocating, return NULL if the key is not found. */
 148         while (1) {
 149                 int64 nkey;
 150
 151                 ndx &= tbl->size - 1;
 152                 node = HT_NODE(tbl, tbl->nodes, ndx);
 153                 nkey = HT_KEY(node, key64);
 154
 155                 if (nkey == key)
 156                         return node;
 157                 if (nkey == 0) {
 158                         if (!allocate_if_missing)
 159                                 return NULL;
 160                         break;
 161                 }
 162                 ndx++;
 163         }
 164
 165         /* Take over this empty spot and then return the node. */
 166         if (key64)
 167                 ((struct ht_int64_node*)node)->key = key;
 168         else
 169                 node->key = (int32)key;
 170         tbl->entries++;
 171         return node;
 172 }