Function genericZpopCommand

src/t_zset.cpp:3807–3920

This command implements the generic zpop operation, used by: * ZPOPMIN, ZPOPMAX, BZPOPMIN and BZPOPMAX. This function is also used * inside blocked.c in the unblocking stage of BZPOPMIN and BZPOPMAX. * * If 'emitkey' is true also the key name is emitted, useful for the blocking * behavior of BZPOP[MIN|MAX], since we can block into multiple keys. * * The synchronous version instead does not

 * The synchronous version instead does not need to emit the key, but may
 * use the 'count' argument to return multiple items if available. */
void genericZpopCommand(client *c, robj **keyv, int keyc, int where, int emitkey, robj *countarg) {
    int idx;
    robj *key = NULL;
    robj *zobj = NULL;
    sds ele;
    double score;
    long count = 1;

    /* If a count argument as passed, parse it or return an error. */
    if (countarg) {
        if (getLongFromObjectOrReply(c,countarg,&count,NULL) != C_OK)
            return;
        if (count <= 0) {
            addReply(c,shared.emptyarray);
            return;
        }
    }

    /* Check type and break on the first error, otherwise identify candidate. */
    idx = 0;
    while (idx < keyc) {
        key = keyv[idx++];
        zobj = lookupKeyWrite(c->db,key);
        if (!zobj) continue;
        if (checkType(c,zobj,OBJ_ZSET)) return;
        break;
    }

    /* No candidate for zpopping, return empty. */
    if (!zobj) {
        addReply(c,shared.emptyarray);
        return;
    }

    void *arraylen_ptr = addReplyDeferredLen(c);
    long result_count = 0;

    /* We emit the key only for the blocking variant. */
    if (emitkey) addReplyBulk(c,key);

    /* Respond with a single (flat) array in RESP2 or if countarg is not
     * provided (returning a single element). In RESP3, when countarg is
     * provided, use nested array.  */
    int use_nested_array = c->resp > 2 && countarg != NULL;

    /* Remove the element. */
    do {
        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;

            /* Get the first or last element in the sorted set. */
            eptr = ziplistIndex(zl,where == ZSET_MAX ? -2 : 0);
            serverAssertWithInfo(c,zobj,eptr != NULL);
            serverAssertWithInfo(c,zobj,ziplistGet(eptr,&vstr,&vlen,&vlong));