switch_hashtable.c

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/*
 * 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.
 */

#include "switch.h"
#include "private/switch_hashtable_private.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 = 0.65f;

/*****************************************************************************/
SWITCH_DECLARE(switch_status_t)
switch_create_hashtable(switch_hashtable_t **hp, unsigned int minsize,
                                                unsigned int (*hashf) (void*),
                                                int (*eqf) (void*,void*))
{
        switch_hashtable_t *h;
        unsigned int pindex, size = primes[0];

        /* Check requested hashtable isn't too large */
        if (minsize > (1u << 30)) {*hp = NULL; return SWITCH_STATUS_FALSE;}
        /* Enforce size as prime */
        for (pindex=0; pindex < prime_table_length; pindex++) {
                if (primes[pindex] > minsize) { 
                        size = primes[pindex]; 
                        break; 
                }
        }
        h = (switch_hashtable_t *) malloc(sizeof(switch_hashtable_t));

        if (NULL == h) abort(); /*oom*/

        h->table = (struct entry **)malloc(sizeof(struct entry*) * size);

        if (NULL == h->table) abort(); /*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);

        *hp = h;
        return SWITCH_STATUS_SUCCESS;
}

/*****************************************************************************/
static int
hashtable_expand(switch_hashtable_t *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;
                                }
                        }
                        switch_safe_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;
}

/*****************************************************************************/
SWITCH_DECLARE(unsigned int)
switch_hashtable_count(switch_hashtable_t *h)
{
        return h->entrycount;
}

static void * _switch_hashtable_remove(switch_hashtable_t *h, void *k, unsigned int hashvalue, unsigned int index) {
        /* TODO: consider compacting the table when the load factor drops enough,
         *       or provide a 'compact' method. */

        struct entry *e;
        struct entry **pE;
        void *v;


        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;
                        if (e->flags & HASHTABLE_FLAG_FREE_KEY) {
                                freekey(e->k);
                        }
                        if (e->flags & HASHTABLE_FLAG_FREE_VALUE) {
                                switch_safe_free(e->v); 
                                v = NULL;
                        } else if (e->destructor) {
                                e->destructor(e->v);
                                v = e->v = NULL;
                        }
                        switch_safe_free(e);
                        return v;
                }
                pE = &(e->next);
                e = e->next;
        }
        return NULL;
}

/*****************************************************************************/
SWITCH_DECLARE(int)
switch_hashtable_insert_destructor(switch_hashtable_t *h, void *k, void *v, hashtable_flag_t flags, hashtable_destructor_t destructor)
{
        struct entry *e;
        unsigned int hashvalue = hash(h, k);
        unsigned index = indexFor(h->tablelength, hashvalue);

        if (flags & HASHTABLE_DUP_CHECK) {
                _switch_hashtable_remove(h, k, hashvalue, index);
        }

        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);
                        index = indexFor(h->tablelength, hashvalue);
                }
        e = (struct entry *)malloc(sizeof(struct entry));
        if (NULL == e) { --(h->entrycount); return 0; } /*oom*/
        e->h = hashvalue;
        e->k = k;
        e->v = v;
        e->flags = flags;
        e->destructor = destructor;
        e->next = h->table[index];
        h->table[index] = e;
        return -1;
}

/*****************************************************************************/
SWITCH_DECLARE(void *) /* returns value associated with key */
switch_hashtable_search(switch_hashtable_t *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;
}

/*****************************************************************************/
SWITCH_DECLARE(void *) /* returns value associated with key */
switch_hashtable_remove(switch_hashtable_t *h, void *k)
{
        unsigned int hashvalue = hash(h,k);
        return _switch_hashtable_remove(h, k, hashvalue, indexFor(h->tablelength,hashvalue));
}

/*****************************************************************************/
/* destroy */
SWITCH_DECLARE(void)
switch_hashtable_destroy(switch_hashtable_t **h)
{
        unsigned int i;
        struct entry *e, *f;
        struct entry **table = (*h)->table;

        for (i = 0; i < (*h)->tablelength; i++) {
                e = table[i];
                while (NULL != e) {
                        f = e; e = e->next; 

                        if (f->flags & HASHTABLE_FLAG_FREE_KEY) {
                                freekey(f->k); 
                        }
                        
                        if (f->flags & HASHTABLE_FLAG_FREE_VALUE) {
                                switch_safe_free(f->v); 
                        } else if (f->destructor) {
                                f->destructor(f->v);
                                f->v = NULL;
                        }
                        switch_safe_free(f); 
                }
        }

        switch_safe_free((*h)->table);
        free(*h);
        *h = NULL;
}

SWITCH_DECLARE(switch_hashtable_iterator_t *) switch_hashtable_next(switch_hashtable_iterator_t **iP)
{

        switch_hashtable_iterator_t *i = *iP;
        
        if (i->e) {
                if ((i->e = i->e->next) != 0) { 
                        return i;
                } else {
                        i->pos++;
                }
        }

        while(i->pos < i->h->tablelength && !i->h->table[i->pos]) {
                i->pos++;
        }
        
        if (i->pos >= i->h->tablelength) {
                goto end;
        }
        
        if ((i->e = i->h->table[i->pos]) != 0) { 
                return i;
        }

 end:

        free(i);
        *iP = NULL;

        return NULL;
}

SWITCH_DECLARE(switch_hashtable_iterator_t *) switch_hashtable_first_iter(switch_hashtable_t *h, switch_hashtable_iterator_t *it)
{
        switch_hashtable_iterator_t *iterator;

        if (it) {
                iterator = it;
        } else {
                switch_zmalloc(iterator, sizeof(*iterator));
        }

        switch_assert(iterator);

        iterator->pos = 0;
        iterator->e = NULL;
        iterator->h = h;

        return switch_hashtable_next(&iterator);
}

SWITCH_DECLARE(void) switch_hashtable_this_val(switch_hashtable_iterator_t *i, void *val)
{
        if (i->e) {
                i->e->v = val;
        }
}

SWITCH_DECLARE(void) switch_hashtable_this(switch_hashtable_iterator_t *i, const void **key, switch_ssize_t *klen, void **val)
{
        if (i->e) {
                if (key) {
                        *key = i->e->k;
                }
                if (klen) {
                        *klen = (int)strlen(i->e->k);
                }
                if (val) {
                        *val = i->e->v;
                }
        } else {
                if (key) {
                        *key = NULL;
                }
                if (klen) {
                        *klen = 0;
                }
                if (val) {
                        *val = NULL;
                }
        }
}


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