Function genericZrangebyrankCommand

src/t_zset.cpp:3029–3117

This command implements ZRANGE, ZREVRANGE. */

/* This command implements ZRANGE, ZREVRANGE. */
void genericZrangebyrankCommand(zrange_result_handler *handler,
    robj_roptr zobj, long start, long end, int withscores, int reverse) {

    client *c = handler->client;
    long llen;
    long rangelen;
    size_t result_cardinality;

    /* Sanitize indexes. */
    llen = zsetLength(zobj);
    if (start < 0) start = llen+start;
    if (end < 0) end = llen+end;
    if (start < 0) start = 0;

    handler->beginResultEmission(handler);

    /* Invariant: start >= 0, so this test will be true when end < 0.
     * The range is empty when start > end or start >= length. */
    if (start > end || start >= llen) {
        handler->finalizeResultEmission(handler, 0);
        return;
    }
    if (end >= llen) end = llen-1;
    rangelen = (end-start)+1;
    result_cardinality = rangelen;

    if (zobj->encoding == OBJ_ENCODING_ZIPLIST) {
        unsigned char *zl = (unsigned char*)zobj->m_ptr;
        unsigned char *eptr, *sptr;
        unsigned char *vstr;
        unsigned int vlen;
        long long vlong;
        double score = 0.0;

        if (reverse)
            eptr = ziplistIndex(zl,-2-(2*start));
        else
            eptr = ziplistIndex(zl,2*start);

        serverAssertWithInfo(c,zobj,eptr != NULL);
        sptr = ziplistNext(zl,eptr);

        while (rangelen--) {
            serverAssertWithInfo(c,zobj,eptr != NULL && sptr != NULL);
            serverAssertWithInfo(c,zobj,ziplistGet(eptr,&vstr,&vlen,&vlong));

            if (withscores) /* don't bother to extract the score if it's gonna be ignored. */
                score = zzlGetScore(sptr);

            if (vstr == NULL) {
                handler->emitResultFromLongLong(handler, vlong, score);
            } else {
                handler->emitResultFromCBuffer(handler, vstr, vlen, score);
            }

            if (reverse)
                zzlPrev(zl,&eptr,&sptr);
            else