int skiplist_insert(skiplist *list, int key, int value)
{
snode *update[SKIPLIST_MAX_LEVEL+1];
snode *x = list->header;
int i, level;
for (i = list->level; i >= 1; i--) {
while (x->forward[i]->key < key)
x = x->forward[i];
update[i] = x;
}
x = x->forward[1];
if (key == x->key) {
x->value = value;
return 0;
} else {
level = rand_level();
if (level > list->level) {
for (i = list->level+1; i <= level; i++) {
update[i] = list->header;
}
list->level = level;
}
x = (snode *)malloc(sizeof(snode));
x->key = key;
x->value = value;
x->forward = (snode **)malloc(sizeof(snode*) * (level + 1));
for (i = 1; i <= level; i++) {
x->forward[i] = update[i]->forward[i];
update[i]->forward[i] = x;
}
}
return 0;
}
int skiplist_insert_raw(SkipList *list, unsigned char *key, void *value, int(* cmp)(unsigned char *, unsigned char *))
{
Node *update[SKIPLIST_MAX_LEVEL + 1];
Node *x = list->header;
int i, level;
for(i = list->level; i >= 1; i--) {
while(cmp(x->forward[i]->key, key) < 0) {
x = x->forward[i];
}
update[i] = x;
}
x = x->forward[1];
if (cmp(key, x->key) == 0) {
return 1;
}
/*
if (key == x->key) {
free(x->value);
x->value = value;
return 0;
}
*/
else {
level = rand_level();
if (level > list->level) {
for(i = list->level + 1; i <= level; i++) {
update[i] = list->header;
}
list->level = level;
}
x = (Node *)malloc(sizeof(Node));
if (x == NULL) {
printf("Error skiplist_insert_raw, allocate Node failed.\n");
return -1;
}
x->key = key;
x->value = value;
x->forward = (Node **)malloc(sizeof(Node *) * (level + 1));
for(i = 1; i <= level; i++) {
x->forward[i] = update[i]->forward[i];
update[i]->forward[i] = x;
}
}
return 0;
}
/**
* 跳表的插入操作要点
* 1 找到带插入的位置(在当前元素的前向指针的键与元素的键相等或者大于的适合退出)，然后再更新在每个层次的update数组
* 2 随机生成新节点的level
* 3 调整指向，插入新节点
*/
void *skiplist_insert(skiplist_t *l,void *item){
skiplist_node_t *cur=l->head;
skiplist_node_t **update=l->update;
int (*comp)(const void *,const void *);
comp=l->comp;
int i;
/*查找键所属的位置*/
for(i=l->level;i>=0;i--){
while(cur->forward[i]!=NULL &&comp(cur->forward[i]->item,item)<0)
cur=cur->forward[i]; //在当前层次遍历直至前向指针为NULL或者对应的前向指针的元素大于或等于item
update[i]=cur; //更新插入位置的前驱指针
}
cur=cur->forward[0];
if(cur!=NULL&&comp(cur->item,item)==0)
return cur->item; //键值已存在，直接返回原来的节点
int level=rand_level(l->prob,l->max_level); //最大的level控制在max_level
if(level> l->level){ //如果新生成的层数比跳表层数大，更新下标大于i的update数组指向为头结点
for(i=l->level+1;i<=level;i++){ //持续到当前生成的level上
update[i]=l->head;
}
l->level=level; //更新自己的层级数
}
skiplist_node_t *tmp=new_skiplist_node(level,item);
/**
* 调整前向指针的指向，插入新结点
* 问题就出现在这里，注意如果生成的level级别较低，只需要在从0..level的级别进行插入，切记不能使用l->level
* l->level和level是有不同的，除非level大于当前跳表的level时
*/
for(i=0;i<=level;i++){
tmp->forward[i]=update[i]->forward[i];
update[i]->forward[i]=tmp;
}
l->n++;
return NULL;
}
