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/* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */
#include "hashtable.h"
#include "hashtable_private.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
/*
Credit for primes table: Aaron Krowne
http://br.endernet.org/~akrowne/
http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
*/
static const unsigned int primes[] = {
53, 97, 193, 389,
769, 1543, 3079, 6151,
12289, 24593, 49157, 98317,
196613, 393241, 786433, 1572869,
3145739, 6291469, 12582917, 25165843,
50331653, 100663319, 201326611, 402653189,
805306457, 1610612741
};
const unsigned int prime_table_length = sizeof(primes)/sizeof(primes[0]);
const float max_load_factor = 0.65;
/*****************************************************************************/
struct hashtable *
create_hashtable(unsigned int minsize,
unsigned int (*hashf) (void*),
int (*eqf) (void*,void*))
{
struct hashtable *h;
unsigned int pindex, size = primes[0];
/* Check requested hashtable isn't too large */
if (minsize > (1u << 30)) return NULL;
/* Enforce size as prime */
for (pindex=0; pindex < prime_table_length; pindex++) {
if (primes[pindex] > minsize) { size = primes[pindex]; break; }
}
h = (struct hashtable *)malloc(sizeof(struct hashtable));
if (NULL == h) return NULL; /*oom*/
h->table = (struct entry **)malloc(sizeof(struct entry*) * size);
if (NULL == h->table) { free(h); return NULL; } /*oom*/
memset(h->table, 0, size * sizeof(struct entry *));
h->tablelength = size;
h->primeindex = pindex;
h->entrycount = 0;
h->hashfn = hashf;
h->eqfn = eqf;
h->loadlimit = (unsigned int) ceil(size * max_load_factor);
return h;
}
/*****************************************************************************/
unsigned int
hash(struct hashtable *h, void *k)
{
/* Aim to protect against poor hash functions by adding logic here
* - logic taken from java 1.4 hashtable source */
unsigned int i = h->hashfn(k);
i += ~(i << 9);
i ^= ((i >> 14) | (i << 18)); /* >>> */
i += (i << 4);
i ^= ((i >> 10) | (i << 22)); /* >>> */
return i;
}
/*****************************************************************************/
static int
hashtable_expand(struct hashtable *h)
{
/* Double the size of the table to accomodate more entries */
struct entry **newtable;
struct entry *e;
struct entry **pE;
unsigned int newsize, i, index;
/* Check we're not hitting max capacity */
if (h->primeindex == (prime_table_length - 1)) return 0;
newsize = primes[++(h->primeindex)];
newtable = (struct entry **)malloc(sizeof(struct entry*) * newsize);
if (NULL != newtable)
{
memset(newtable, 0, newsize * sizeof(struct entry *));
/* This algorithm is not 'stable'. ie. it reverses the list
* when it transfers entries between the tables */
for (i = 0; i < h->tablelength; i++) {
while (NULL != (e = h->table[i])) {
h->table[i] = e->next;
index = indexFor(newsize,e->h);
e->next = newtable[index];
newtable[index] = e;
}
}
free(h->table);
h->table = newtable;
}
/* Plan B: realloc instead */
else
{
newtable = (struct entry **)
realloc(h->table, newsize * sizeof(struct entry *));
if (NULL == newtable) { (h->primeindex)--; return 0; }
h->table = newtable;
memset(newtable[h->tablelength], 0, newsize - h->tablelength);
for (i = 0; i < h->tablelength; i++) {
for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) {
index = indexFor(newsize,e->h);
if (index == i)
{
pE = &(e->next);
}
else
{
*pE = e->next;
e->next = newtable[index];
newtable[index] = e;
}
}
}
}
h->tablelength = newsize;
h->loadlimit = (unsigned int) ceil(newsize * max_load_factor);
return -1;
}
/*****************************************************************************/
unsigned int
hashtable_count(struct hashtable *h)
{
return h->entrycount;
}
/*****************************************************************************/
int
hashtable_insert(struct hashtable *h, void *k, void *v)
{
/* This method allows duplicate keys - but they shouldn't be used */
unsigned int index;
struct entry *e;
if (++(h->entrycount) > h->loadlimit)
{
/* Ignore the return value. If expand fails, we should
* still try cramming just this value into the existing table
* -- we may not have memory for a larger table, but one more
* element may be ok. Next time we insert, we'll try expanding again.*/
hashtable_expand(h);
}
e = (struct entry *)malloc(sizeof(struct entry));
if (NULL == e) { --(h->entrycount); return 0; } /*oom*/
e->h = hash(h,k);
index = indexFor(h->tablelength,e->h);
e->k = k;
e->v = v;
e->next = h->table[index];
h->table[index] = e;
return -1;
}
/*****************************************************************************/
void * /* returns value associated with key */
hashtable_search(struct hashtable *h, void *k)
{
struct entry *e;
unsigned int hashvalue, index;
hashvalue = hash(h,k);
index = indexFor(h->tablelength,hashvalue);
e = h->table[index];
while (NULL != e)
{
/* Check hash value to short circuit heavier comparison */
if ((hashvalue == e->h) && (h->eqfn(k, e->k))) return e->v;
e = e->next;
}
return NULL;
}
/*****************************************************************************/
void * /* returns value associated with key */
hashtable_remove(struct hashtable *h, void *k)
{
/* TODO: consider compacting the table when the load factor drops enough,
* or provide a 'compact' method. */
struct entry *e;
struct entry **pE;
void *v;
unsigned int hashvalue, index;
hashvalue = hash(h,k);
index = indexFor(h->tablelength,hash(h,k));
pE = &(h->table[index]);
e = *pE;
while (NULL != e)
{
/* Check hash value to short circuit heavier comparison */
if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
{
*pE = e->next;
h->entrycount--;
v = e->v;
freekey(e->k);
free(e);
return v;
}
pE = &(e->next);
e = e->next;
}
return NULL;
}
/*****************************************************************************/
/* destroy */
void
hashtable_destroy(struct hashtable *h, int free_values)
{
unsigned int i;
struct entry *e, *f;
struct entry **table = h->table;
if (free_values)
{
for (i = 0; i < h->tablelength; i++)
{
e = table[i];
while (NULL != e)
{ f = e; e = e->next; freekey(f->k); free(f->v); free(f); }
}
}
else
{
for (i = 0; i < h->tablelength; i++)
{
e = table[i];
while (NULL != e)
{ f = e; e = e->next; freekey(f->k); free(f); }
}
}
free(h->table);
free(h);
}
/*
* Copyright (c) 2002, Christopher Clark
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of the original author; nor the names of any contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
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