hashtable.c

/*
  Copyright (c) 2002, 2004, 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.
*/

#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.
*/