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/*
* Routines to provide a memory-efficient hashtable.
*
* Copyright (C) 2007-2008 Wayne Davison
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, visit the http://fsf.org website.
*/
#include "rsync.h"
#define HASH_LOAD_LIMIT(size) ((size)*3/4)
struct hashtable *hashtable_create(int size, int key64)
{
struct hashtable *tbl;
int node_size = key64 ? sizeof (struct ht_int64_node)
: sizeof (struct ht_int32_node);
/* Pick a power of 2 that can hold the requested size. */
if (size & (size-1) || size < 16) {
int req = size;
size = 16;
while (size < req)
size *= 2;
}
if (!(tbl = new(struct hashtable))
|| !(tbl->nodes = new_array0(char, size * node_size)))
out_of_memory("hashtable_create");
tbl->size = size;
tbl->entries = 0;
tbl->node_size = node_size;
tbl->key64 = key64;
return tbl;
}
void hashtable_destroy(struct hashtable *tbl)
{
free(tbl->nodes);
free(tbl);
}
/* This returns the node for the indicated key, either newly created or
* already existing. Returns NULL if not allocating and not found. */
void *hashtable_find(struct hashtable *tbl, int64 key, int allocate_if_missing)
{
int key64 = tbl->key64;
struct ht_int32_node *node;
uint32 ndx;
if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
void *old_nodes = tbl->nodes;
int size = tbl->size * 2;
int i;
if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
out_of_memory("hashtable_node");
tbl->size = size;
tbl->entries = 0;
for (i = size / 2; i-- > 0; ) {
struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
int64 move_key = HT_KEY(move_node, key64);
if (move_key == 0)
continue;
node = hashtable_find(tbl, move_key, 1);
node->data = move_node->data;
}
free(old_nodes);
}
if (!key64) {
/* Based on Jenkins One-at-a-time hash. */
uchar buf[4], *keyp = buf;
int i;
SIVAL(buf, 0, key);
for (ndx = 0, i = 0; i < 4; i++) {
ndx += keyp[i];
ndx += (ndx << 10);
ndx ^= (ndx >> 6);
}
ndx += (ndx << 3);
ndx ^= (ndx >> 11);
ndx += (ndx << 15);
} else {
/* Based on Jenkins hashword() from lookup3.c. */
uint32 a, b, c;
/* Set up the internal state */
a = b = c = 0xdeadbeef + (8 << 2);
#define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
b += (uint32)(key >> 32);
a += (uint32)key;
c ^= b; c -= rot(b, 14);
a ^= c; a -= rot(c, 11);
b ^= a; b -= rot(a, 25);
c ^= b; c -= rot(b, 16);
a ^= c; a -= rot(c, 4);
b ^= a; b -= rot(a, 14);
c ^= b; c -= rot(b, 24);
#undef rot
ndx = c;
}
/* If it already exists, return the node. If we're not
* allocating, return NULL if the key is not found. */
while (1) {
int64 nkey;
ndx &= tbl->size - 1;
node = HT_NODE(tbl, tbl->nodes, ndx);
nkey = HT_KEY(node, key64);
if (nkey == key)
return node;
if (nkey == 0) {
if (!allocate_if_missing)
return NULL;
break;
}
ndx++;
}
/* Take over this empty spot and then return the node. */
if (key64)
((struct ht_int64_node*)node)->key = key;
else
node->key = key;
tbl->entries++;
return node;
}
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