Function genericZrangebylexCommand

app/redis-6.2.6/src/t_zset.c:3433–3545

This command implements ZRANGEBYLEX, ZREVRANGEBYLEX. */

/* This command implements ZRANGEBYLEX, ZREVRANGEBYLEX. */
void genericZrangebylexCommand(zrange_result_handler *handler,
    zlexrangespec *range, robj *zobj, int withscores, long offset, long limit,
    int reverse)
{
    client *c = handler->client;
    unsigned long rangelen = 0;

    handler->beginResultEmission(handler);

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

        /* If reversed, get the last node in range as starting point. */
        if (reverse) {
            eptr = zzlLastInLexRange(zl,range);
        } else {
            eptr = zzlFirstInLexRange(zl,range);
        }

        /* Get score pointer for the first element. */
        if (eptr)
            sptr = ziplistNext(zl,eptr);

        /* If there is an offset, just traverse the number of elements without
         * checking the score because that is done in the next loop. */
        while (eptr && offset--) {
            if (reverse) {
                zzlPrev(zl,&eptr,&sptr);
            } else {
                zzlNext(zl,&eptr,&sptr);
            }
        }

        while (eptr && limit--) {
            double score = 0;
            if (withscores) /* don't bother to extract the score if it's gonna be ignored. */
                score = zzlGetScore(sptr);

            /* Abort when the node is no longer in range. */
            if (reverse) {
                if (!zzlLexValueGteMin(eptr,range)) break;
            } else {
                if (!zzlLexValueLteMax(eptr,range)) break;
            }

            /* We know the element exists, so ziplistGet should always
             * succeed. */
            serverAssertWithInfo(c,zobj,ziplistGet(eptr,&vstr,&vlen,&vlong));

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