Simple hashtable in c

hashtable.c

#include <stdlib.h>
#include <stdio.h>

int HASH_SIZE = 10;

struct Node {
  char *key;
  char *value;
  struct Node *next;
};

char *search_list(struct Node *node, char *key)
{
  struct Node *prev = NULL;
  while (node) {
    if (node->key = key) {
      return node->value;
    }
    prev = node;
    node = node->next;
  }
}

int needs_replace(struct Node *node, struct Node *new_node, struct Node *prev, char *key) 
{
  if (node->key == key) {
    // if not a head node, replace the severed connection
    if (prev) {
      prev->next = new_node;
    }
    new_node->next = node->next;
    free(node);
    return 1;
  }
}

struct Node *append(struct Node *head_node, char *key, char *value)
{
  // allocate some memory for node
  struct Node *new_node = malloc(sizeof(struct Node *));
  // set attributes on node
  new_node->key = key;
  new_node->value = value;
  new_node->next = NULL;

  // append to end of list
  struct Node *node = head_node;
  struct Node *prev = NULL;
  if (head_node) {
    while (node->next) {
      if (needs_replace(node, new_node, prev, key)) {
        return head_node;
      }
      prev = node;
      node = node->next;
    }
    /*link the last node to the new node*/
    /*will be head ptr if never entered loop above*/
    if (prev) {
      prev->next = new_node;
    } else {
      if (needs_replace(head_node, new_node, prev, key)) {
        return new_node;
      }
      head_node->next = new_node;
    }
    return head_node;
  } else {
    return new_node;
  }
}

int hash(char *key)
{
  int inter = 0;
  int i;
  for (i = 0; i < 10; i++) {
    int b = key[i];
    if (b == 0) {
      return inter;
    }
    inter += b;
  }
}

struct Node **ptr_array;

void insert(char *key, char *val)
{
  int h = hash(key);
  int bucket = h % HASH_SIZE;
  ptr_array[bucket] = append(ptr_array[bucket], key, val);
}

char *get(char *key)
{
  int h = hash(key);
  int bucket = h % HASH_SIZE;
  struct Node *node = ptr_array[bucket];
  return search_list(node, key);
}

void initialize_buckets()
{
  ptr_array = malloc(sizeof(struct Node *) * HASH_SIZE);
  int i;
  for (i = 0; i < HASH_SIZE; i++) {
    ptr_array[i] = NULL;
  }
}


int main()
{
  initialize_buckets();
  insert("foo\0", "bar\0");
  insert("newb\0", "baz\0");
  insert("nub\0", "bob\0");
  printf("%s\n", get("foo\0"));
  printf("%s\n", get("foo\0"));
  printf("%s\n", get("nub\0"));
  // test replace
  insert("key\0", "foo\0");
  insert("key\0", "fooz\0");
  insert("key\0", "fab\0");
  printf("%s\n", get("key\0"));
  return 0;
}