Function zsetInitLexRange

app/redis-6.2.6/src/module.c:2837–2866

Helper function for RM_ZsetFirstInLexRange() and RM_ZsetLastInLexRange(). * Setup the sorted set iteration according to the specified lexicographical * range (see the functions calling it for more info). If 'first' is true the * first element in the range is used as a starting point for the iterator * otherwise the last. Return REDISMODULE_OK on success otherwise * REDISMODULE_ERR. * * Note

 * Note that this function takes 'min' and 'max' in the same form of the
 * Redis ZRANGEBYLEX command. */
int zsetInitLexRange(RedisModuleKey *key, RedisModuleString *min, RedisModuleString *max, int first) {
    if (!key->value || key->value->type != OBJ_ZSET) return REDISMODULE_ERR;

    RM_ZsetRangeStop(key);
    key->u.zset.er = 0;

    /* Setup the range structure used by the sorted set core implementation
     * in order to seek at the specified element. */
    zlexrangespec *zlrs = &key->u.zset.lrs;
    if (zslParseLexRange(min, max, zlrs) == C_ERR) return REDISMODULE_ERR;

    /* Set the range type to lex only after successfully parsing the range,
     * otherwise we don't want the zlexrangespec to be freed. */
    key->u.zset.type = REDISMODULE_ZSET_RANGE_LEX;

    if (key->value->encoding == OBJ_ENCODING_ZIPLIST) {
        key->u.zset.current = first ? zzlFirstInLexRange(key->value->ptr,zlrs) :
                                      zzlLastInLexRange(key->value->ptr,zlrs);
    } else if (key->value->encoding == OBJ_ENCODING_SKIPLIST) {
        zset *zs = key->value->ptr;
        zskiplist *zsl = zs->zsl;
        key->u.zset.current = first ? zslFirstInLexRange(zsl,zlrs) :
                                      zslLastInLexRange(zsl,zlrs);
    } else {
        serverPanic("Unsupported zset encoding");
    }
    if (key->u.zset.current == NULL) key->u.zset.er = 1;

    return REDISMODULE_OK;
}

/* Setup a sorted set iterator seeking the first element in the specified
 * lexicographical range. Returns REDISMODULE_OK if the iterator was correctly