+/* Find the rank for an element by both score and key.
+ * Returns 0 when the element cannot be found, rank otherwise.
+ * Note that the rank is 1-based due to the span of zsl->header to the
+ * first element. */
+static unsigned long zslGetRank(zskiplist *zsl, double score, robj *o) {
+ zskiplistNode *x;
+ unsigned long rank = 0;
+ int i;
+
+ x = zsl->header;
+ for (i = zsl->level-1; i >= 0; i--) {
+ while (x->forward[i] &&
+ (x->forward[i]->score < score ||
+ (x->forward[i]->score == score &&
+ compareStringObjects(x->forward[i]->obj,o) <= 0))) {
+ rank += x->span[i];
+ x = x->forward[i];
+ }
+
+ /* x might be equal to zsl->header, so test if obj is non-NULL */
+ if (x->obj && compareStringObjects(x->obj,o) == 0) {
+ return rank;
+ }
+ }
+ return 0;
+}
+