Accessing struct field within another struct

Question

So my data structure is supposed to be a hash table, an array of linked list. Inside each of those linked list holds a linked list. And inside those linked list is a Book. A book contains a book name, and a linked list of library IDs that hold that book.

I'm having trouble searching within the linked list to see if a book->name already exists. I know how to access the so called "shelf" that it's on by:

int index = hashFunction(char* nameOfBook) % this->size;

and then searching within the hash array to find it like this:

this->chain[index]

But how can I access the Book struct once I'm inside the linked list?

In list.h

typedef struct NodeStruct {
    void *data;
    struct NodeStruct* next;
    struct NodeStruct* prev;
} NodeStruct;

typedef struct ListStruct {
    NodeStruct* first;
    NodeStruct* last;
    int elementType;
} ListStruct;

In hash.c:

typedef struct Book {
    ListStruct* libID; // Each book has its own list of library IDs
    char* name; // Each book has a name.
} Book;

// A hashset contains a linked list of books.
typedef struct HashStruct {
    int size;
    int load;
    ListStruct **chain; //An array of Linked Lists.
} HashStruct;

Here are the constructors:

// Constructor for a new book.
Book *newBook(char* name) {
    Book *this = malloc (sizeof (Book));
    assert(this != NULL);
    this->name = name;
    this->libID = malloc(sizeof (ListStruct*));
    this->libID = newList(sizeof(int));
    return this;
}

HashHandle new_hashset(int size) {
    HashHandle tempHash = malloc (sizeof (HashStruct));
    assert (tempHash != NULL);
    tempHash->size = size;
    tempHash->load = 0;
    tempHash->chain = malloc (sizeof (ListStruct));
    assert(tempHash->chain != NULL);
    // Each linked list holds a linked list.
    for (int i = 0; i < size; ++i) {
        tempHash->chain[i] = newList(sizeof(Book));
    }
    return tempHash;
}

EDIT: I think I got it to work. Haven't tested yet.

bool has_hashset (HashHandle this, char *item) { 
    //Finds the index to look at.
    int index = strhash(item) % this->size;

    NodeStruct *cur = this->chain[index]->first;
    while (cur != NULL) {
        Book *tmp = cur->data;
        if (strcmp(tmp->name, item) == 0)
            return true;
        cur = cur->next;
    }
    return false;
}

Sorry if this was very confusing. By the way, the 'data' of a linked list is generic. Thank you!

Answer 1

Because cur->data is a pointer to void , you need to assign it to a pointer of type Book (or cast it to that type). Otherwise, you will not be able to use -> to get a member because void is not a struct.

What you fixed in your edit should work fine.