Function RM_ZsetRangeNext

app/redis-6.2.6/src/module.c:2921–2980

Go to the next element of the sorted set iterator. Returns 1 if there was * a next element, 0 if we are already at the latest element or the range * does not include any item at all. */

 * a next element, 0 if we are already at the latest element or the range
 * does not include any item at all. */
int RM_ZsetRangeNext(RedisModuleKey *key) {
    if (!key->value || key->value->type != OBJ_ZSET) return 0;
    if (!key->u.zset.type || !key->u.zset.current) return 0; /* No active iterator. */

    if (key->value->encoding == OBJ_ENCODING_ZIPLIST) {
        unsigned char *zl = key->value->ptr;
        unsigned char *eptr = key->u.zset.current;
        unsigned char *next;
        next = ziplistNext(zl,eptr); /* Skip element. */
        if (next) next = ziplistNext(zl,next); /* Skip score. */
        if (next == NULL) {
            key->u.zset.er = 1;
            return 0;
        } else {
            /* Are we still within the range? */
            if (key->u.zset.type == REDISMODULE_ZSET_RANGE_SCORE) {
                /* Fetch the next element score for the
                 * range check. */
                unsigned char *saved_next = next;
                next = ziplistNext(zl,next); /* Skip next element. */
                double score = zzlGetScore(next); /* Obtain the next score. */
                if (!zslValueLteMax(score,&key->u.zset.rs)) {
                    key->u.zset.er = 1;
                    return 0;
                }
                next = saved_next;
            } else if (key->u.zset.type == REDISMODULE_ZSET_RANGE_LEX) {
                if (!zzlLexValueLteMax(next,&key->u.zset.lrs)) {
                    key->u.zset.er = 1;
                    return 0;
                }
            }
            key->u.zset.current = next;
            return 1;
        }
    } else if (key->value->encoding == OBJ_ENCODING_SKIPLIST) {
        zskiplistNode *ln = key->u.zset.current, *next = ln->level[0].forward;
        if (next == NULL) {
            key->u.zset.er = 1;
            return 0;
        } else {
            /* Are we still within the range? */
            if (key->u.zset.type == REDISMODULE_ZSET_RANGE_SCORE &&
                !zslValueLteMax(next->score,&key->u.zset.rs))
            {
                key->u.zset.er = 1;
                return 0;
            } else if (key->u.zset.type == REDISMODULE_ZSET_RANGE_LEX) {
                if (!zslLexValueLteMax(next->ele,&key->u.zset.lrs)) {
                    key->u.zset.er = 1;
                    return 0;
                }
            }
            key->u.zset.current = next;
            return 1;
        }
    } else {
        serverPanic("Unsupported zset encoding");