hashtab.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2007, Digium, Inc.
 *
 * Steve Murphy <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
/*! \file
 *
 * \brief code to implement generic hash tables
 *
 * \author Steve Murphy <[email protected]>
 */

/*** MODULEINFO
 <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <ctype.h>

#include "asterisk/lock.h"
#include "asterisk/frame.h"
#include "asterisk/channel.h"
#include "asterisk/cli.h"
#include "asterisk/term.h"
#include "asterisk/utils.h"
#include "asterisk/threadstorage.h"
#include "asterisk/linkedlists.h"
#include "asterisk/hashtab.h"


static void _ast_hashtab_resize(struct ast_hashtab *tab, const char *file, int lineno, const char *func);
#define ast_hashtab_resize(tab) \
 _ast_hashtab_resize(tab, __FILE__, __LINE__, __PRETTY_FUNCTION__)

static void *ast_hashtab_lookup_internal(struct ast_hashtab *tab, const void *obj, unsigned int h);

/* some standard, default routines for general use */

int ast_hashtab_compare_strings(const void *a, const void *b)
{
 return strcmp(a, b);
}

int ast_hashtab_compare_strings_nocase(const void *a, const void *b)
{
 return strcasecmp(a, b);
}

int ast_hashtab_compare_ints(const void *a, const void *b)
{
 int ai = *((int *) a);
 int bi = *((int *) b);

 if (ai < bi)
 return -1;

 return !(ai == bi);
}

int ast_hashtab_compare_shorts(const void *a, const void *b)
{
 short as = *((short *) a);
 short bs = *((short *) b);

 if (as < bs)
 return -1;

 return !(as == bs);
}

int ast_hashtab_resize_java(struct ast_hashtab *tab)
{
 double loadfactor = (double) tab->hash_tab_elements / (double) tab->hash_tab_size;

 return (loadfactor > 0.75);
}

int ast_hashtab_resize_tight(struct ast_hashtab *tab)
{
 return (tab->hash_tab_elements > tab->hash_tab_size); /* this is quicker than division */
}

int ast_hashtab_resize_none(struct ast_hashtab *tab) /* always return 0 -- no resizing */
{
 return 0;
}

int ast_is_prime(int num)
{
 int tnum, limit;

 if (!(num & 0x1)) /* even number -- not prime */
 return 0;

 /* Loop through ODD numbers starting with 3 */

 tnum = 3;
 limit = num;
 while (tnum < limit) {
 if (!(num % tnum))
 return 0;

 /* really, we only need to check sqrt(num) numbers */
 limit = num / tnum;

 /* we only check odd numbers */
 tnum = tnum + 2;
 }

 /* if we made it through the loop, the number is a prime */
 return 1;
}

int ast_hashtab_newsize_java(struct ast_hashtab *tab)
{
 int i = (tab->hash_tab_size << 1); /* multiply by two */

 while (!ast_is_prime(i))
 i++;

 return i;
}

int ast_hashtab_newsize_tight(struct ast_hashtab *tab)
{
 int x = (tab->hash_tab_size << 1);
 int i = (tab->hash_tab_size + x);

 while (!ast_is_prime(i))
 i++;

 return i;
}

int ast_hashtab_newsize_none(struct ast_hashtab *tab) /* always return current size -- no resizing */
{
 return tab->hash_tab_size;
}

unsigned int ast_hashtab_hash_string(const void *obj)
{
 unsigned char *str = (unsigned char *) obj;
 unsigned int total;

 for (total = 0; *str; str++) {
 unsigned int tmp = total;
 total <<= 1; /* multiply by 2 */
 total += tmp; /* multiply by 3 */
 total <<= 2; /* multiply by 12 */
 total += tmp; /* multiply by 13 */

 total += ((unsigned int)(*str));
 }
 return total;
}

unsigned int ast_hashtab_hash_string_sax(const void *obj) /* from Josh */
{
 const unsigned char *str = obj;
 unsigned int total = 0, c = 0;

 while ((c = *str++))
 total ^= (total << 5) + (total >> 2) + (total << 10) + c;

 return total;
}

unsigned int ast_hashtab_hash_string_nocase(const void *obj)
{
 const unsigned char *str = obj;
 unsigned int total;

 for (total = 0; *str; str++) {
 unsigned int tmp = total;
 unsigned int charval = toupper(*str);

 /* hopefully, the following is faster than multiplication by 7 */
 /* why do I go to this bother? A good compiler will do this
 anyway, if I say total *= 13 */
 /* BTW, tried *= 7, and it doesn't do as well in spreading things around! */
 total <<= 1; /* multiply by 2 */
 total += tmp; /* multiply by 3 */
 total <<= 2; /* multiply by 12 */
 total += tmp; /* multiply by 13 */

 total += (charval);
 }

 return total;
}

unsigned int ast_hashtab_hash_int(const int x)
{
 return x;
}

unsigned int ast_hashtab_hash_short(const short x)
{
 /* hmmmm.... modulus is best < 65535 !! */
 return x;
}

struct ast_hashtab *_ast_hashtab_create(int initial_buckets,
 int (*compare)(const void *a, const void *b),
 int (*resize)(struct ast_hashtab *),
 int (*newsize)(struct ast_hashtab *tab),
 unsigned int (*hash)(const void *obj),
 int do_locking,
 const char *file, int lineno, const char *function
)
{
 struct ast_hashtab *ht;

 ht = __ast_calloc(1, sizeof(*ht), file, lineno, function);
 if (!ht) {
 return NULL;
 }

 while (!ast_is_prime(initial_buckets)) /* make sure this is prime */
 initial_buckets++;

 ht->array = __ast_calloc(initial_buckets, sizeof(*(ht->array)),
 file, lineno, function);
 if (!ht->array) {
 ast_free(ht);
 return NULL;
 }

 ht->hash_tab_size = initial_buckets;
 ht->compare = compare;
 ht->resize = resize;
 ht->newsize = newsize;
 ht->hash = hash;
 ht->do_locking = do_locking;

 if (do_locking)
 ast_rwlock_init(&ht->lock);

 if (!ht->resize)
 ht->resize = ast_hashtab_resize_java;

 if (!ht->newsize)
 ht->newsize = ast_hashtab_newsize_java;

 return ht;
}

struct ast_hashtab *_ast_hashtab_dup(struct ast_hashtab *tab, void *(*obj_dup_func)(const void *obj), const char *file, int lineno, const char *func)
{
 struct ast_hashtab *ht;
 unsigned int i;

 ht = __ast_calloc(1, sizeof(*ht), file, lineno, func);
 if (!ht) {
 return NULL;
 }

 ht->array = __ast_calloc(tab->hash_tab_size, sizeof(*(ht->array)),
 file, lineno, func);
 if (!ht->array) {
 ast_free(ht);
 return NULL;
 }

 ht->hash_tab_size = tab->hash_tab_size;
 ht->compare = tab->compare;
 ht->resize = tab->resize;
 ht->newsize = tab->newsize;
 ht->hash = tab->hash;
 ht->do_locking = tab->do_locking;

 if (ht->do_locking)
 ast_rwlock_init(&ht->lock);

 /* now, dup the objects in the buckets and get them into the table */
 /* the fast way is to use the existing array index, and not have to hash
 the objects again */
 for (i = 0; i < ht->hash_tab_size; i++) {
 struct ast_hashtab_bucket *b = tab->array[i];
 while (b) {
 void *newobj = (*obj_dup_func)(b->object);
 if (newobj) {
 _ast_hashtab_insert_immediate_bucket(ht, newobj, i, file, lineno, func);
 }
 b = b->next;
 }
 }

 return ht;
}

static void tlist_del_item(struct ast_hashtab_bucket **head, struct ast_hashtab_bucket *item)
{
 /* item had better be in the list! or suffer the weirdness that occurs, later! */
 if (*head == item) { /* first item in the list */
 *head = item->tnext;
 if (item->tnext)
 item->tnext->tprev = NULL;
 } else {
 /* short circuit stuff */
 item->tprev->tnext = item->tnext;
 if (item->tnext)
 item->tnext->tprev = item->tprev;
 }
}

static void tlist_add_head(struct ast_hashtab_bucket **head, struct ast_hashtab_bucket *item)
{
 if (*head) {
 item->tnext = *head;
 item->tprev = NULL;
 (*head)->tprev = item;
 *head = item;
 } else {
 /* the list is empty */
 *head = item;
 item->tprev = NULL;
 item->tnext = NULL;
 }
}

/* user-controlled hashtab locking. Create a hashtab without locking, then call the
 following locking routines yourself to lock the table between threads. */

void ast_hashtab_wrlock(struct ast_hashtab *tab)
{
 ast_rwlock_wrlock(&tab->lock);
}

void ast_hashtab_rdlock(struct ast_hashtab *tab)
{
 ast_rwlock_rdlock(&tab->lock);
}

void ast_hashtab_initlock(struct ast_hashtab *tab)
{
 ast_rwlock_init(&tab->lock);
}

void ast_hashtab_destroylock(struct ast_hashtab *tab)
{
 ast_rwlock_destroy(&tab->lock);
}

void ast_hashtab_unlock(struct ast_hashtab *tab)
{
 ast_rwlock_unlock(&tab->lock);
}

void ast_hashtab_destroy(struct ast_hashtab *tab, void (*objdestroyfunc)(void *obj))
{
 /* this func will free the hash table and all its memory. It
 doesn't touch the objects stored in it */
 if (tab) {

 if (tab->do_locking)
 ast_rwlock_wrlock(&tab->lock);

 if (tab->array) {
 /* go thru and destroy the buckets */
 struct ast_hashtab_bucket *t;
 int i;

 while (tab->tlist) {
 t = tab->tlist;
 if (t->object && objdestroyfunc) {
 /* I cast this because I'm not going to MOD it, I'm going to DESTROY
 * it.
 */
 (*objdestroyfunc)((void *) t->object);
 }

 tlist_del_item(&(tab->tlist), tab->tlist);
 ast_free(t);
 }

 for (i = 0; i < tab->hash_tab_size; i++) {
 /* Not totally necessary, but best to destroy old pointers */
 tab->array[i] = NULL;
 }
 ast_free(tab->array);
 }
 if (tab->do_locking) {
 ast_rwlock_unlock(&tab->lock);
 ast_rwlock_destroy(&tab->lock);
 }
 ast_free(tab);
 }
}

int _ast_hashtab_insert_immediate(struct ast_hashtab *tab, const void *obj, const char *file, int lineno, const char *func)
{
 unsigned int h;
 int res=0;

 if (!tab || !obj)
 return res;

 if (tab->do_locking)
 ast_rwlock_wrlock(&tab->lock);

 h = (*tab->hash)(obj) % tab->hash_tab_size;

 res = _ast_hashtab_insert_immediate_bucket(tab, obj, h, file, lineno, func);

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return res;
}

int _ast_hashtab_insert_immediate_bucket(struct ast_hashtab *tab, const void *obj, unsigned int h, const char *file, int lineno, const char *func)
{
 int c;
 struct ast_hashtab_bucket *b;

 if (!tab || !obj)
 return 0;

 for (c = 0, b = tab->array[h]; b; b= b->next)
 c++;

 if (c + 1 > tab->largest_bucket_size)
 tab->largest_bucket_size = c + 1;

 b = __ast_calloc(1, sizeof(*b), file, lineno, func);
 if (!b) {
 return 0;
 }

 b->object = obj;
 b->next = tab->array[h];
 tab->array[h] = b;

 if (b->next)
 b->next->prev = b;

 tlist_add_head(&(tab->tlist), b);
 tab->hash_tab_elements++;

 if ((*tab->resize)(tab))
 ast_hashtab_resize(tab);

 return 1;
}

int _ast_hashtab_insert_safe(struct ast_hashtab *tab, const void *obj, const char *file, int lineno, const char *func)
{
 /* check to see if the element is already there; insert only if
 it is not there. */
 /* will force a resize if the resize func returns 1 */
 /* returns 1 on success, 0 if there's a problem, or it's already there. */
 unsigned int bucket = 0;

 if (tab->do_locking)
 ast_rwlock_wrlock(&tab->lock);

 if (!ast_hashtab_lookup_bucket(tab, obj, &bucket)) {
 int ret2 = _ast_hashtab_insert_immediate_bucket(tab, obj, bucket, file, lineno, func);

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return ret2;
 }

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return 0;
}

void *ast_hashtab_lookup(struct ast_hashtab *tab, const void *obj)
{
 /* lookup this object in the hash table. return a ptr if found, or NULL if not */
 unsigned int h;
 void *ret;

 if (!tab || !obj)
 return 0;

 if (tab->do_locking)
 ast_rwlock_rdlock(&tab->lock);

 h = (*tab->hash)(obj) % tab->hash_tab_size;

 ret = ast_hashtab_lookup_internal(tab,obj,h);

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return ret;
}


void *ast_hashtab_lookup_with_hash(struct ast_hashtab *tab, const void *obj, unsigned int hashval)
{
 /* lookup this object in the hash table. return a ptr if found, or NULL if not */
 unsigned int h;
 void *ret;

 if (!tab || !obj)
 return 0;

 if (tab->do_locking)
 ast_rwlock_rdlock(&tab->lock);

 h = hashval % tab->hash_tab_size;

 ret = ast_hashtab_lookup_internal(tab,obj,h);

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return ret;
}

void *ast_hashtab_lookup_bucket(struct ast_hashtab *tab, const void *obj, unsigned int *bucket)
{
 /* lookup this object in the hash table. return a ptr if found, or NULL if not */
 unsigned int h;
 void *ret;

 if (!tab || !obj)
 return 0;

 h = (*tab->hash)(obj) % tab->hash_tab_size;

 ret = ast_hashtab_lookup_internal(tab,obj,h);

 *bucket = h;

 return ret;
}

static void *ast_hashtab_lookup_internal(struct ast_hashtab *tab, const void *obj, unsigned int h)
{
 struct ast_hashtab_bucket *b;

 for (b = tab->array[h]; b; b = b->next) {
 if (!(*tab->compare)(obj,b->object)) {
 /* I can't touch obj in this func, but the outside world is welcome to */
 return (void*) b->object;
 }
 }

 return NULL;
}

void ast_hashtab_get_stats(struct ast_hashtab *tab, int *biggest_bucket_size, int *resize_count, int *num_objects, int *num_buckets)
{
 /* returns key stats for the table */
 if (tab->do_locking)
 ast_rwlock_rdlock(&tab->lock);
 *biggest_bucket_size = tab->largest_bucket_size;
 *resize_count = tab->resize_count;
 *num_objects = tab->hash_tab_elements;
 *num_buckets = tab->hash_tab_size;
 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);
}

/* this function returns the number of elements stored in the hashtab */
int ast_hashtab_size(struct ast_hashtab *tab)
{
 return tab->hash_tab_elements;
}

/* this function returns the size of the bucket array in the hashtab */
int ast_hashtab_capacity( struct ast_hashtab *tab)
{
 return tab->hash_tab_size;
}

/* the insert operation calls this, and is wrlock'd when it does. */
/* if you want to call it, you should set the wrlock yourself */

static void _ast_hashtab_resize(struct ast_hashtab *tab, const char *file, int lineno, const char *func)
{
 /* this function is called either internally, when the resize func returns 1, or
 externally by the user to force a resize of the hash table */
 int newsize = (*tab->newsize)(tab), i, c;
 unsigned int h;
 struct ast_hashtab_bucket *b,*bn;

 /* Since we keep a DLL of all the buckets in tlist,
 all we have to do is free the array, malloc a new one,
 and then go thru the tlist array and reassign them into
 the bucket arrayj.
 */
 for (i = 0; i < tab->hash_tab_size; i++) { /* don't absolutely have to do this, but
 why leave ptrs laying around */
 tab->array[i] = 0; /* erase old ptrs */
 }
 ast_free(tab->array);
 tab->array = __ast_calloc(newsize, sizeof(*(tab->array)), file, lineno, func);
 if (!tab->array) {
 return;
 }

 /* now sort the buckets into their rightful new slots */
 tab->resize_count++;
 tab->hash_tab_size = newsize;
 tab->largest_bucket_size = 0;

 for (b = tab->tlist; b; b = bn) {
 b->prev = 0;
 bn = b->tnext;
 h = (*tab->hash)(b->object) % tab->hash_tab_size;
 b->next = tab->array[h];
 if (b->next)
 b->next->prev = b;
 tab->array[h] = b;
 }
 /* recalc the largest bucket size */
 for (i = 0; i < tab->hash_tab_size; i++) {
 for (c = 0, b = tab->array[i]; b; b = b->next)
 c++;
 if (c > tab->largest_bucket_size)
 tab->largest_bucket_size = c;
 }
}

struct ast_hashtab_iter *_ast_hashtab_start_traversal(struct ast_hashtab *tab, const char *file, int lineno, const char *func)
{
 /* returns an iterator */
 struct ast_hashtab_iter *it;

 it = __ast_calloc(1, sizeof(*it), file, lineno, func);
 if (!it) {
 return NULL;
 }

 it->next = tab->tlist;
 it->tab = tab;
 if (tab->do_locking)
 ast_rwlock_rdlock(&tab->lock);

 return it;
}

/* use this function to get a write lock */
struct ast_hashtab_iter *_ast_hashtab_start_write_traversal(struct ast_hashtab *tab, const char *file, int lineno, const char *func)
{
 /* returns an iterator */
 struct ast_hashtab_iter *it;

 it = __ast_calloc(1, sizeof(*it), file, lineno, func);
 if (!it) {
 return NULL;
 }

 it->next = tab->tlist;
 it->tab = tab;
 if (tab->do_locking)
 ast_rwlock_wrlock(&tab->lock);

 return it;
}

void ast_hashtab_end_traversal(struct ast_hashtab_iter *it)
{
 if (!it)
 return;
 if (it->tab->do_locking)
 ast_rwlock_unlock(&it->tab->lock);
 ast_free(it);
}

void *ast_hashtab_next(struct ast_hashtab_iter *it)
{
 /* returns the next object in the list, advances iter one step */
 struct ast_hashtab_bucket *retval;

 if (it && it->next) { /* there's a next in the bucket list */
 retval = it->next;
 it->next = retval->tnext;
 return (void *) retval->object;
 }

 return NULL;
}

static void *ast_hashtab_remove_object_internal(struct ast_hashtab *tab, struct ast_hashtab_bucket *b, int h)
{
 const void *obj2;

 if (b->prev)
 b->prev->next = b->next;
 else
 tab->array[h] = b->next;

 if (b->next)
 b->next->prev = b->prev;

 tlist_del_item(&(tab->tlist), b);

 obj2 = b->object;
 b->object = b->next = (void*)2;
 ast_free(b); /* free up the hashbucket */
 tab->hash_tab_elements--;
#ifdef DEBUG
 {
 int c2;
 struct ast_hashtab_bucket *b2;
 /* do a little checking */
 for (c2 = 0, b2 = tab->tlist; b2; b2 = b2->tnext) {
 c2++;
 }
 if (c2 != tab->hash_tab_elements) {
 printf("Hey! we didn't delete right! there are %d elements in the list, and we expected %d\n",
 c2, tab->hash_tab_elements);
 }
 for (c2 = 0, b2 = tab->tlist; b2; b2 = b2->tnext) {
 unsigned int obj3 = (unsigned long) obj2;
 unsigned int b3 = (unsigned long) b;
 if (b2->object == obj2)
 printf("Hey-- you've still got a bucket pointing at ht_element %x\n", obj3);
 if (b2->next == b)
 printf("Hey-- you've still got a bucket with next ptr pointing to deleted bucket %x\n", b3);
 if (b2->prev == b)
 printf("Hey-- you've still got a bucket with prev ptr pointing to deleted bucket %x\n", b3);
 if (b2->tprev == b)
 printf("Hey-- you've still got a bucket with tprev ptr pointing to deleted bucket %x\n", b3);
 if (b2->tnext == b)
 printf("Hey-- you've still got a bucket with tnext ptr pointing to deleted bucket %x\n", b3);
 }
 }
#endif
 return (void *) obj2; /* inside this code, the obj's are untouchable, but outside, they aren't */
}

void *ast_hashtab_remove_object_via_lookup(struct ast_hashtab *tab, void *obj)
{
 /* looks up the object; removes the corresponding bucket */
 const void *obj2;

 if (!tab || !obj)
 return 0;

 if (tab->do_locking)
 ast_rwlock_wrlock(&tab->lock);

 obj2 = ast_hashtab_remove_object_via_lookup_nolock(tab,obj);

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return (void *)obj2;
}

void *ast_hashtab_remove_object_via_lookup_nolock(struct ast_hashtab *tab, void *obj)
{
 /* looks up the object; removes the corresponding bucket */
 unsigned int h;
 struct ast_hashtab_bucket *b;

 if (!tab || !obj)
 return 0;

 h = (*tab->hash)(obj) % tab->hash_tab_size;
 for (b = tab->array[h]; b; b = b->next) {

 if (!(*tab->compare)(obj, b->object)) {
 const void *obj2;

 obj2 = ast_hashtab_remove_object_internal(tab, b, h);

 return (void *) obj2; /* inside this code, the obj's are untouchable, but outside, they aren't */
 }
 }

 return 0;
}

void *ast_hashtab_remove_this_object(struct ast_hashtab *tab, void *obj)
{
 /* looks up the object by hash and then comparing pts in bucket list instead of
 calling the compare routine; removes the bucket -- a slightly cheaper operation */
 /* looks up the object; removes the corresponding bucket */
 const void *obj2;

 if (!tab || !obj)
 return 0;

 if (tab->do_locking)
 ast_rwlock_wrlock(&tab->lock);

 obj2 = ast_hashtab_remove_this_object_nolock(tab,obj);

 if (tab->do_locking)
 ast_rwlock_unlock(&tab->lock);

 return (void *)obj2;
}

void *ast_hashtab_remove_this_object_nolock(struct ast_hashtab *tab, void *obj)
{
 /* looks up the object by hash and then comparing pts in bucket list instead of
 calling the compare routine; removes the bucket -- a slightly cheaper operation */
 /* looks up the object; removes the corresponding bucket */
 unsigned int h;
 struct ast_hashtab_bucket *b;

 if (!tab || !obj)
 return 0;

 h = (*tab->hash)(obj) % tab->hash_tab_size;
 for (b = tab->array[h]; b; b = b->next) {

 if (obj == b->object) {
 const void *obj2;
 obj2 = ast_hashtab_remove_object_internal(tab, b, h);

 return (void *) obj2; /* inside this code, the obj's are untouchable, but outside, they aren't */
 }
 }

 return 0;
}