Function isHLLObjectOrReply

app/redis-6.2.6/src/hyperloglog.c:1149–1177

Check if the object is a String with a valid HLL representation. * Return C_OK if this is true, otherwise reply to the client * with an error and return C_ERR. */

 * Return C_OK if this is true, otherwise reply to the client
 * with an error and return C_ERR. */
int isHLLObjectOrReply(client *c, robj *o) {
    struct hllhdr *hdr;

    /* Key exists, check type */
    if (checkType(c,o,OBJ_STRING))
        return C_ERR; /* Error already sent. */

    if (!sdsEncodedObject(o)) goto invalid;
    if (stringObjectLen(o) < sizeof(*hdr)) goto invalid;
    hdr = o->ptr;

    /* Magic should be "HYLL". */
    if (hdr->magic[0] != 'H' || hdr->magic[1] != 'Y' ||
        hdr->magic[2] != 'L' || hdr->magic[3] != 'L') goto invalid;

    if (hdr->encoding > HLL_MAX_ENCODING) goto invalid;

    /* Dense representation string length should match exactly. */
    if (hdr->encoding == HLL_DENSE &&
        stringObjectLen(o) != HLL_DENSE_SIZE) goto invalid;

    /* All tests passed. */
    return C_OK;

invalid:
    addReplyError(c,"-WRONGTYPE Key is not a valid "
               "HyperLogLog string value.");
    return C_ERR;
}

/* PFADD var ele ele ele ... ele => :0 or :1 */
void pfaddCommand(client *c) {