//TODO: Switch to a more robust error handling policy
extern skip_t skip_init(free_func_t free_func)
{
int i;
skip_list *new_skip;
new_skip = malloc(sizeof(*new_skip));
check_hard(new_skip, "Couldn't find memory for a new skip list.");
// data structure callbacks
new_skip->free_func = (free_func == NULL) ? default_free : free_func;
// init our random generator
srand(time(NULL));
new_skip->level = 1; // following algorithm to the letter
new_skip->length = 0;
new_skip->header = create_skip_node(SKIP_MAX, 0, NULL);
for (i = 0; i < SKIP_MAX; i++) {
new_skip->finger[i] = NULL;
new_skip->header->level[i].forward = NULL;
}
return new_skip;
}
bool skip_list<T>::insert_node(int key, T value)
{
//find in every level in the past skip list
//which node is the last smaller than key
skip_node<T> *last_smaller_in_level[MAX_LEVEL];
skip_node<T> *tmp = header;
for(int i = 0; i <= level; i++)
{
while(tmp->next_in_level[i] != NULL)
{
if(tmp->next_in_level[i]->key == key)
{
printf("can't insert same key\n");
return false;
}
if(tmp->next_in_level[i]->key > key)
break;
else
tmp = tmp->next_in_level[i];
}
last_smaller_in_level[i] = tmp;
}
//random how much level to inserit
//build a new skip list
int insert_level = get_random_level();
printf("key %d insert_level %d\n", key, insert_level);
skip_node<T> *p = create_skip_node(key, value);
if(insert_level > level)
{
for(int i = 0; i <= level; i++)
{
skip_node<T> *tmp2 = last_smaller_in_level[i]->next_in_level[i];
last_smaller_in_level[i]->next_in_level[i] = p;
p->next_in_level[i] = tmp2;
}
for(int i = level + 1; i <= insert_level; i++)
{
header->next_in_level[i] = p;
}
level = insert_level;
}
else
{
for(int i = 0; i <= insert_level; i++)
{
skip_node<T> *tmp2 = last_smaller_in_level[i]->next_in_level[i];
last_smaller_in_level[i]->next_in_level[i] = p;
p->next_in_level[i] = tmp2;
}
}
return true;
}
//TODO: Switch to a more robust error handling policy
extern int skip_insert(skip_t sl, unsigned int key, void *payload)
{
int i, rand_level;
skip_node *x, *update[SKIP_MAX];
check_hard(sl, "Invalid Skip List");
check_hard(key, "Invalid Key");
check_hard(payload, " Empty payload");
x = sl->header;
for (i = sl->level - 1; i >= 0; i--) {
while (x->level[i].forward && // not end NULL
default_compare(x->level[i].forward->key, key)) {
x = x->level[i].forward;
// log_warn("still in whleLoop");
}
update[i] = x;
sl->finger[i] = x;
//log_warn("still in ForLoop");
}
// make sure were not nulled
x = (x->level[0].forward) ? x->level[0].forward : x;
//TODO: Decide if we should warn, or reject an overwrite,
//log_info(" %u, %u", x->key, key);
if (x->key == key) {
sl->free_func(x->payload);
x->payload = payload;
//log_warn("Key overwrite");
return 2;
} else {
rand_level = random_level();
if (rand_level > sl->level) {
for (i = sl->level; i < rand_level; i++) {
update[i] = sl->header;
sl->finger[i] = sl->header;
}
sl->level = rand_level;
//log_info("Lvl: %d",sl->level);
}
x = create_skip_node(rand_level, key, payload);
for (i = 0 ; i < rand_level; i++) {
x->level[i].forward = update[i]->level[i].forward;
update[i]->level[i].forward = x;
}
//log_success("inserted key %u and data", key);
sl->length++;
return 1;
}
}
