path: root/ecp/src/htable/hashtable.c

/* 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>

#define MAX_LOAD_FACTOR 0.65F

/*****************************************************************************/
struct hashtable *
hashtable_create(unsigned int minsize,
                 unsigned int (*hashf) (void*),
                 int (*eqf) (void*,void*))
{
    struct hashtable *h;
    struct entry **t;
    unsigned int size;
    size = hashtable_prime_size(minsize);
    if (0 == size) return NULL;
    h = (struct hashtable *)malloc(sizeof(struct hashtable));
    if (NULL == h) return NULL; /*oom*/
    t = (struct entry **)malloc(sizeof(struct entry*) * size);
    if (NULL == t) { free(h); return NULL; } /*oom*/
    hashtable_create_static(h,t,size,hashf,eqf);
    return h;
}

/*****************************************************************************/
void
hashtable_create_static(struct hashtable *h, struct entry **t,
                        unsigned int size,
                        unsigned int (*hashf) (void*),
                        int (*eqf) (void*,void*))
{
    memset(t, 0, size * sizeof(struct entry *));
    h->table        = t;
    h->tablelength  = size;
    h->entrycount   = 0;
    h->hashfn       = hashf;
    h->eqfn         = eqf;
    h->loadlimit    = (unsigned int) ceil(size * MAX_LOAD_FACTOR);
}

unsigned int
hashtable_prime_size(unsigned int minsize)
{
    /*
    Credit for primes table: Aaron Krowne
     http://br.endernet.org/~akrowne/
     http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
    */
    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]);
    unsigned int pindex, size = 0;
    /* Check requested hashtable isn't too large */
    if (minsize > (1u << 30)) return 0;
    /* Enforce size as prime */
    for (pindex=0; pindex < prime_table_length; pindex++) {
        if (primes[pindex] >= minsize) { size = primes[pindex]; break; }
    }
    return size;
}

/*****************************************************************************/
/* key      - return the key of the (key,value) pair from hash table entry */
/* value    - return the value of the (key,value) pair from hash table entry */

void *
hashtable_entry_key(struct entry *e)
{ return e->k; }

void *
hashtable_entry_value(struct entry *e)
{ return e->v; }

/*****************************************************************************/
unsigned int
hashtable_hash(struct hashtable *h, void *k)
{
    return h->hashfn(k);
}

/*****************************************************************************/
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;
    newsize = hashtable_prime_size(h->tablelength + 1);
    /* Check we're not hitting max capacity */
    if (0 == newsize) return 0;

    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) 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)
{
    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*/
    hashtable_insert_static(h,e,k,v);
    return -1;
}

void
hashtable_insert_static(struct hashtable *h, struct entry *e, void *k, void *v)
{
    /* This method allows duplicate keys - but they shouldn't be used */
    unsigned int index;
    e->h = hashtable_hash(h,k);
    index = indexFor(h->tablelength,e->h);
    e->k = k;
    e->v = v;
    e->next = h->table[index];
    h->table[index] = e;
}

/*****************************************************************************/
void * /* returns value associated with key */
hashtable_search(struct hashtable *h, void *k)
{
    struct entry *e;
    unsigned int hashvalue, index;
    hashvalue = hashtable_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;
    void *v;
    e = hashtable_remove_static(h,k);
    if (NULL == e) return NULL;
    v = e->v;
    freekey(e->k);
    free(e);
    return v;
}

struct entry * /* returns hash table entry associated with key */
hashtable_remove_static(struct hashtable *h, void *k)
{
    struct entry *e;
    struct entry **pE;
    unsigned int hashvalue, index;
    hashvalue = hashtable_hash(h,k);
    index = indexFor(h->tablelength,hashvalue);
    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--;
            return e;
        }
        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.
*/