C - Trying to make an array of LinkedList pointers - c

Question

I'm trying to create a HashTable in C where each 'bucket' is a pointer to a LinkedList. That is, I need to create an array of LinkedList pointers.
As of now, SomeHashTable->Buckets[i] is returning a non-pointer LinkedList. I've been looking for answers everywhere and I just can't find anything. Perhaps I'm overlooking something? I've given my current code below.
HashTable.h
#include "LinkedList.h"
typedef struct HashTable
{
LinkedList* Buckets[1009];
} HashTable;
//Creates new hashtable
HashTable* HashTable_new();
//Hashes and adds a new entry
void HashTable_add(HashTable* Table, int data);
HashTable.c
#include "HashTable.h"
HashTable* HashTable_new()
{
HashTable* newTable = (HashTable*)malloc(sizeof(HashTable));
newTable->Buckets = malloc(1009 * sizeof(LinkedList*));
//Create linked lists
for (int i = 0; i < 1009; i++)
{
newTable->Buckets[i] = LinkedList_new();
}
return newTable;
}
void HashTable_add(HashTable* Table, int data)
{
int index = data % 1009;
//Get bucket to hash to
LinkedList* BucketHead = (Table->Buckets[index]);
//Hash it iiinnnn real good
LinkedList_add_at_end(BucketHead, data);
}
The linked List structs for reference:
typedef struct LinkedListNode {
int data;
struct LinkedListNode *next;
struct LinkedListNode *prev;
} LinkedListNode;
typedef struct LinkedList {
struct LinkedListNode *first;
struct LinkedListNode *last;
} LinkedList;

Answer 1

As H.S.'s comment mentions, there is no need to dynamically --and-- statically allocate the Buckets array.
This line:
newTable->Buckets = malloc(1009 * sizeof(LinkedList*));
is overwriting the pointer to the statically allocated array, which is probably not what you want. For scalability, I would ditch the static array and stick with malloc(). That way you could use an argument to HashTable_new() to specify the size of the buckets array, like so:
HashTable* HashTable_new(int nBuckets)
{
HashTable* newTable = (HashTable*)malloc(sizeof(HashTable));
newTable->Buckets = malloc(nBuckets * sizeof(LinkedList*));
newTable->nBuckets = nBuckets;
//Create linked lists
for (int i = 0; i < nBuckets; i++)
{
newTable->Buckets[i] = LinkedList_new();
}
return newTable;
}
Notice that newTable->Buckets is being allocated as a pointer to a pointer to LinkedList (LinkedList**). You'll need to keep track to the size of Buckets[], so add the variable to the struct as follows:
typedef struct HashTable
{
int nBuckets;
LinkedList **Buckets;
} HashTable;
You should be good as long as LinkedList_new()'s return type is LinkedList*, and don't forget to free() it all when you're done.