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zskiplistNode *zslInsert(zskiplist *zsl, double score, sds ele) {
zskiplistNode *update[ZSKIPLIST_MAXLEVEL], *x; unsigned int rank[ZSKIPLIST_MAXLEVEL]; int i, level;
serverAssert(!isnan(score));
x = zsl->header; for (i = zsl->level-1; i >= 0; i--) { rank[i] = i == (zsl->level-1) ? 0 : rank[i+1]; while (x->level[i].forward && (x->level[i].forward->score < score || (x->level[i].forward->score == score && sdscmp(x->level[i].forward->ele,ele) < 0))) { rank[i] += x->level[i].span; x = x->level[i].forward; } update[i] = x; }
level = zslRandomLevel(); if (level > zsl->level) { for (i = zsl->level; i < level; i++) { rank[i] = 0; update[i] = zsl->header; update[i]->level[i].span = zsl->length; } zsl->level = level; }
x = zslCreateNode(level,score,ele); for (i = 0; i < level; i++) {
x->level[i].forward = update[i]->level[i].forward; update[i]->level[i].forward = x;
x->level[i].span = update[i]->level[i].span - (rank[0] - rank[i]); update[i]->level[i].span = (rank[0] - rank[i]) + 1; }
for (i = level; i < zsl->level; i++) { update[i]->level[i].span++; }
x->backward = (update[0] == zsl->header) ? NULL : update[0]; if (x->level[0].forward) x->level[0].forward->backward = x; else zsl->tail = x; zsl->length++; return x; }
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