???
git-svn-id: http://svn.eurecom.fr/openair4G/trunk@4660 818b1a75-f10b-46b9-bf7c-635c3b92a50f
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Lionel Gauthier
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/* from: http://en.literateprograms.org/Hash_table_%28C%29#chunk%20def:node
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*
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*/
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "obj_hashtable.h"
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* Default hash function
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* def_hashfunc() is the default used by hashtable_create() when the user didn't specify one.
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* This is a simple/naive hash function which adds the key's ASCII char values. It will probably generate lots of collisions on large hash tables.
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*/
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static hash_size_t def_hashfunc(const void *keyP, int key_sizeP)
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{
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hash_size_t hash=0;
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while(key_sizeP) hash^=((unsigned char*)keyP)[key_sizeP --];
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return hash;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* Initialisation
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* hashtable_create() sets up the initial structure of the hash table. The user specified size will be allocated and initialized to NULL.
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* The user can also specify a hash function. If the hashfunc argument is NULL, a default hash function is used.
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* If an error occurred, NULL is returned. All other values in the returned obj_hash_table_t pointer should be released with hashtable_destroy().
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*/
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obj_hash_table_t *obj_hashtable_create(hash_size_t sizeP, hash_size_t (*hashfuncP)(const void*, int ), void (*freekeyfuncP)(void*), void (*freedatafuncP)(void*))
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{
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obj_hash_table_t *hashtbl;
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if(!(hashtbl=malloc(sizeof(obj_hash_table_t)))) return NULL;
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if(!(hashtbl->nodes=calloc(sizeP, sizeof(obj_hash_node_t*)))) {
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free(hashtbl);
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return NULL;
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}
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hashtbl->size=sizeP;
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if(hashfuncP) hashtbl->hashfunc=hashfuncP;
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else hashtbl->hashfunc=def_hashfunc;
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if(freekeyfuncP) hashtbl->freekeyfunc=freekeyfuncP;
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else hashtbl->freekeyfunc=free;
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if(freedatafuncP) hashtbl->freedatafunc=freedatafuncP;
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else hashtbl->freedatafunc=free;
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return hashtbl;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* Cleanup
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* The hashtable_destroy() walks through the linked lists for each possible hash value, and releases the elements. It also releases the nodes array and the obj_hash_table_t.
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*/
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hashtable_rc_t obj_hashtable_destroy(obj_hash_table_t *hashtblP)
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{
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hash_size_t n;
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obj_hash_node_t *node, *oldnode;
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for(n=0; n<hashtblP->size; ++n) {
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node=hashtblP->nodes[n];
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while(node) {
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oldnode=node;
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node=node->next;
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hashtblP->freekeyfunc(oldnode->key);
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hashtblP->freedatafunc(oldnode->data);
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free(oldnode);
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}
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}
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free(hashtblP->nodes);
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free(hashtblP);
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return HASH_TABLE_OK;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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hashtable_rc_t obj_hashtable_is_key_exists (obj_hash_table_t *hashtblP, void* keyP, int key_sizeP)
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//-------------------------------------------------------------------------------------------------------------------------------
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{
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obj_hash_node_t *node;
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hash_size_t hash;
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if (hashtblP == NULL) {
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return HASH_TABLE_BAD_PARAMETER_HASHTABLE;
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}
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hash=hashtblP->hashfunc(keyP, key_sizeP)%hashtblP->size;
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node=hashtblP->nodes[hash];
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while(node) {
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if(node->key == keyP) {
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return HASH_TABLE_OK;
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}
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node=node->next;
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}
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return HASH_TABLE_KEY_NOT_EXISTS;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* Adding a new element
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* To make sure the hash value is not bigger than size, the result of the user provided hash function is used modulo size.
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*/
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hashtable_rc_t obj_hashtable_insert(obj_hash_table_t *hashtblP, void* keyP, int key_sizeP, void *dataP)
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{
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obj_hash_node_t *node;
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hash_size_t hash;
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if (hashtblP == NULL) {
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return HASH_TABLE_BAD_PARAMETER_HASHTABLE;
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}
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hash=hashtblP->hashfunc(keyP, key_sizeP)%hashtblP->size;
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node=hashtblP->nodes[hash];
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while(node) {
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if(node->key == keyP) {
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if (node->data) {
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hashtblP->freedatafunc(node->data);
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}
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node->data=dataP;
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// waste of memory here (keyP is lost) we should free it now
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return HASH_TABLE_INSERT_OVERWRITTEN_DATA;
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}
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node=node->next;
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}
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if(!(node=malloc(sizeof(obj_hash_node_t)))) return -1;
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node->key=keyP;
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node->data=dataP;
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if (hashtblP->nodes[hash]) {
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node->next=hashtblP->nodes[hash];
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} else {
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node->next = NULL;
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}
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hashtblP->nodes[hash]=node;
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return HASH_TABLE_OK;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* To remove an element from the hash table, we just search for it in the linked list for that hash value,
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* and remove it if it is found. If it was not found, it is an error and -1 is returned.
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*/
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hashtable_rc_t obj_hashtable_remove(obj_hash_table_t *hashtblP, const void* keyP, int key_sizeP)
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{
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obj_hash_node_t *node, *prevnode=NULL;
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hash_size_t hash;
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if (hashtblP == NULL) {
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return HASH_TABLE_BAD_PARAMETER_HASHTABLE;
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}
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hash=hashtblP->hashfunc(keyP, key_sizeP)%hashtblP->size;
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node=hashtblP->nodes[hash];
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while(node) {
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if(node->key == keyP) {
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if(prevnode) {
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prevnode->next=node->next;
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} else {
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hashtblP->nodes[hash]=node->next;
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}
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hashtblP->freekeyfunc(node->key);
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hashtblP->freedatafunc(node->data);
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free(node);
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return HASH_TABLE_OK;
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}
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prevnode=node;
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node=node->next;
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}
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return HASH_TABLE_KEY_NOT_EXISTS;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* Searching for an element is easy. We just search through the linked list for the corresponding hash value.
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* NULL is returned if we didn't find it.
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*/
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hashtable_rc_t obj_hashtable_get(obj_hash_table_t *hashtblP, const void* keyP, int key_sizeP, void** dataP)
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{
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obj_hash_node_t *node;
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hash_size_t hash;
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if (hashtblP == NULL) {
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*dataP = NULL;
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return HASH_TABLE_BAD_PARAMETER_HASHTABLE;
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}
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hash=hashtblP->hashfunc(keyP, key_sizeP)%hashtblP->size;
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node=hashtblP->nodes[hash];
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while(node) {
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if(node->key == keyP) {
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*dataP = node->data;
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return HASH_TABLE_OK;
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}
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node=node->next;
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}
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*dataP = NULL;
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return HASH_TABLE_KEY_NOT_EXISTS;
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}
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//-------------------------------------------------------------------------------------------------------------------------------
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/*
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* Resizing
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* The number of elements in a hash table is not always known when creating the table.
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* If the number of elements grows too large, it will seriously reduce the performance of most hash table operations.
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* If the number of elements are reduced, the hash table will waste memory. That is why we provide a function for resizing the table.
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* Resizing a hash table is not as easy as a realloc(). All hash values must be recalculated and each element must be inserted into its new position.
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* We create a temporary obj_hash_table_t object (newtbl) to be used while building the new hashes.
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* This allows us to reuse hashtable_insert() and hashtable_remove(), when moving the elements to the new table.
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* After that, we can just free the old table and copy the elements from newtbl to hashtbl.
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*/
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hashtable_rc_t obj_hashtable_resize(obj_hash_table_t *hashtblP, hash_size_t sizeP)
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{
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obj_hash_table_t newtbl;
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hash_size_t n;
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obj_hash_node_t *node,*next;
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if (hashtblP == NULL) {
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return HASH_TABLE_BAD_PARAMETER_HASHTABLE;
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}
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newtbl.size = sizeP;
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newtbl.hashfunc = hashtblP->hashfunc;
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if(!(newtbl.nodes=calloc(sizeP, sizeof(obj_hash_node_t*)))) return -1;
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for(n=0; n<hashtblP->size; ++n) {
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for(node=hashtblP->nodes[n]; node; node=next) {
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next = node->next;
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obj_hashtable_insert(&newtbl, node->key, node->key_size, node->data);
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//WARNING Lionel GAUTHIER: BAD CODE TO BE REWRITTEN
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obj_hashtable_remove(hashtblP, node->key, node->key_size);
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}
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}
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free(hashtblP->nodes);
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hashtblP->size=newtbl.size;
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hashtblP->nodes=newtbl.nodes;
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return HASH_TABLE_OK;
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}
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