Thread: HashTable help?

for example make your HashTableLookUp return list_ptr, in this case you will have no problem to update list_ptr->value

Originally Posted by -EquinoX-

if it returns an address to the old value then changing that address wouldn't work right because the list->value still points to the old address

if you write

list->value = <new value> ; it will defiitely not point to the old address.

so what do you mean?

deleted

probably cstr.h - look at your warnings about explicitely defined functions to be sure

You should not include one c file into another
but you should compile them together

1. new_list is used only in else - but allocated anyway - you get memory leak in the if case
2. if this->table[hashval] was not NULL in the else case - you effectivly loosing this value

so you should allocate new_list only in the else branch - becase when the key is found - you do not need to create the new node - instead you are replacing value of the existing node

I see and that would solve problem no.1 that you mentioned above right? but how about number 2? I don't get what you mean

what about now:

Code:

boolean HashTableInsert(HashTable *this, const char* key, const char* value)
{
  list_t *temp;

  int_u4 hashval = StringHash(key) % this->length;

  /* Does item already exist? */
  if (HashTableContains(this, key) == true){
    for (temp = this->table[hashval]; temp!= NULL; temp = temp->next){
      if (strcmp(key, temp->key) == 0){
        StringDestruct(temp->value);
        temp->value = StringConstruct(value);
        return false;
      }
    }
  }
  else if (temp == NULL){
  /* Insert into list */
    list_t *new_list;
    if ((new_list = malloc(sizeof(list_t))) == NULL)
      outOfMemory_(__LINE__, __FILE__, "struct node creation");
    new_list->key = StringConstruct(key);
    new_list->value = StringConstruct(value);
    new_list->next = this->table[hashval];
    this->table[hashval] = new_list;
    this->length = this->length + 1;
    return true;
  }
}

in your else branch you could have already several links connected to the same have entry
so the list could be not empty.

How would you go about adding new node to the list if you know that the new node is pointed by new_list pointer and list head is stored in the this->table[hashval] pointer?