skiplistNode *slInsert(skiplist *sl, double score) {
skiplistNode *update[SKIPLIST_MAXLEVEL];
skiplistNode *node;
node = sl->header;
int i, level;
for ( i = sl->level-1; i >= 0; i--) {
while(node->level[i].forward && node->level[i].forward->score < score) {
node = node->level[i].forward;
}
update[i] = node;
}
level = slRandomLevel();
if (level > sl->level) {
for (i = sl->level; i< level ;i++) {
update[i] = sl->header;
}
sl->level = level;
}
node = slCreateNode(level, score);
for (i = 0; i < level; i++) {
node->level[i].forward = update[i]->level[i].forward;
update[i]->level[i].forward = node;
}
node->backward = (update[0] == sl->header? NULL : update[0]);
if (node->level[0].forward)
node->level[0].forward->backward = node;
else
sl->tail = node;
sl->length++;
return node;
}
skiplistNode *slInsert(skiplist *sl, void *obj)
{
skiplistNode *update[SKIPLIST_MAXLEVEL]={NULL};
skiplistNode *node;
int i, level;
node = sl->header;
/* 从最高层次开始搜索，查找插入的位置。update数组用于记录各层次的插入点 */
for(i=sl->level-1; i>=0; i--){
while(node->forward[i] &&
sl->cmp(node->forward[i]->obj, obj)){
node = node->forward[i];
}
update[i]=node;
}
/* 完全随机决定本次插入的元素所占的层数 */
level = slRandomLevel();
if(level>sl->level){
for(i=sl->level;i<level;i++){
update[i] = sl->header;
}
sl->level = level;
}
node = slCreateNode(level, obj);
/* 分别在每一层执行链表插入动作 */
for(i=0; i<level; i++){
node->forward[i] = update[i]->forward[i];
update[i]->forward[i] = node;
}
sl->length++;
return node;
}
void slInsert(skiplist *sl, double score, slobj *obj) {
skiplistNode *update[SKIPLIST_MAXLEVEL], *x;
unsigned int rank[SKIPLIST_MAXLEVEL];
int i, level;
x = sl->header;
for (i = sl->level-1; i >= 0; i--) {
/* store rank that is crossed to reach the insert position */
rank[i] = i == (sl->level-1) ? 0 : rank[i+1];
while (x->level[i].forward &&
(x->level[i].forward->score < score ||
(x->level[i].forward->score == score &&
compareslObj(x->level[i].forward->obj,obj) < 0))) {
rank[i] += x->level[i].span;
x = x->level[i].forward;
}
update[i] = x;
}
/* we assume the key is not already inside, since we allow duplicated
* scores, and the re-insertion of score and redis object should never
* happen since the caller of slInsert() should test in the hash table
* if the element is already inside or not. */
level = slRandomLevel();
if (level > sl->level) {
for (i = sl->level; i < level; i++) {
rank[i] = 0;
update[i] = sl->header;
update[i]->level[i].span = sl->length;
}
sl->level = level;
}
x = slCreateNode(level,score,obj);
for (i = 0; i < level; i++) {
x->level[i].forward = update[i]->level[i].forward;
update[i]->level[i].forward = x;
/* update span covered by update[i] as x is inserted here */
x->level[i].span = update[i]->level[i].span - (rank[0] - rank[i]);
update[i]->level[i].span = (rank[0] - rank[i]) + 1;
}
/* increment span for untouched levels */
for (i = level; i < sl->level; i++) {
update[i]->level[i].span++;
}
x->backward = (update[0] == sl->header) ? NULL : update[0];
if (x->level[0].forward)
x->level[0].forward->backward = x;
else
sl->tail = x;
sl->length++;
}
entry_t *entryCreate(void)
{
return(entryCreateByLevel(slRandomLevel()));
}
