Proper Memory allocation

Question

I have the following construction:

typedef struct bucket {
    char *key;
    ENTRY *data;
    struct bucket *next;
} bucket;

typedef struct {
    size_t size;
    bucket **table;
} hash_table;

But I have no idea how to allocate memory for that. I tried:

hash_table* ht = malloc(sizeof(hash_table)*101);

in order to create a hashtable for 101 entries but it din't work! Can anyone help me? I would really appreciate it!

Answer 1

Not quite. Assuming this is C, you probably want to make a function:

 hash_table* init_table(size_t size) {
     size_t i;
     hash_table* ht = (hash_table*)malloc(sizeof(hash_table));
     if (ht == NULL) return NULL;
     ht->size = size;
     ht->table = (bucket**)malloc(sizeof(bucket*)*size);
     if (ht->table == NULL) {
         free(ht);
         return NULL;
     }
     for (i = 0; i < size; ++i) {
         ht->table[i] = NULL;
     }
     return ht;
 }

You might need some other fields in that struct.

If you wanted to be tricky, and never realloc the bucket, you can do this:

 hash_table* init_table(size_t size) {
     hash_table* ht = (hash_table*)malloc(sizeof(hash_table)+sizeof(bucket)*size);
     if (ht == NULL) return NULL;
     ht->size = size;
     ht->table = (bucket**)(ht+1);
     for (i = 0; i < size; ++i) {
         ht->table[i] = NULL;
     }
     return ht;
 }

EDIT: I fixed my bucket* table's to bucket**

EDIT2: I've gotten rid of the memsets and added error checking for malloc.