Practicing Ruby C Extension - Linked List using Memory Pool

linked_list.c

#include "ruby.h"

static VALUE cLinkedList;

typedef struct rb_node {
  VALUE data;
  struct rb_node *next;
} Node;

typedef struct rb_linked_list {
  int p_top;
  Node pool[10000];
  Node *head;
  Node *tail;
} LinkedList;

VALUE linked_list_alloc(VALUE rb_self)
{
  LinkedList *list = ALLOC(LinkedList);
  list->p_top = 0;
  memset(list->pool, 0, sizeof(list->pool));
  list->head = NULL;
  list->tail = NULL;
  return Data_Wrap_Struct(cLinkedList,0,free,list);
}

static
Node * create_node(LinkedList *list, VALUE val)
{
  if(list->p_top == sizeof(list->pool)/sizeof(Node)) {
    //list->pool = realloc(list->pool, 1000 * sizeof(Node));
    //if(list->pool == NULL)
    rb_raise(rb_eStandardError, "Allocation Error! %lu", sizeof(list->pool)/sizeof(Node));
  }
  Node *new = &list->pool[list->p_top++];
  new->next = NULL;
  new->data = val;
  return new;
}

static
VALUE rb_linked_list_add(VALUE rb_self, VALUE val)
{
  LinkedList *list;
  Data_Get_Struct(rb_self, LinkedList, list);
  Node *new = create_node(list, val);
  if(list->head == NULL) {
    list->head = list->tail = new;
  } else {
    list->tail = list->tail->next = new;
  }
  return rb_self;
}

static
VALUE rb_linked_list_head(VALUE rb_self)
{
  LinkedList *list;
  Node *n;
  Data_Get_Struct(rb_self, LinkedList, list);
  if(list->head == NULL)
    return Qnil;
  return (VALUE)list->head->data;
}

static
VALUE rb_linked_list_tail(VALUE rb_self)
{
  LinkedList *list;
  Node *n;
  Data_Get_Struct(rb_self, LinkedList, list);
  if(list->tail == NULL)
    return Qnil;
  return (VALUE)list->tail->data;
}

static
VALUE rb_linked_list_each(VALUE rb_self)
{
  LinkedList *list;
  Data_Get_Struct(rb_self, LinkedList, list);

  Node *ptr = list->head;
  while(ptr != NULL){
    rb_yield(ptr->data);
    ptr = ptr->next;
  }

  return rb_self;
}

void Init_linked_list()
{
  cLinkedList = rb_define_class("LinkedList", rb_cObject);
  rb_define_alloc_func(cLinkedList, linked_list_alloc);
  rb_define_method(cLinkedList, "add", rb_linked_list_add, 1);
  rb_define_method(cLinkedList, "head", rb_linked_list_head, 0);
  rb_define_method(cLinkedList, "tail", rb_linked_list_tail, 0);
  rb_define_method(cLinkedList, "each", rb_linked_list_each, 0);
}