int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
{
    int ret = 1;

    drbg->state = DRBG_UNINITIALISED;
    drbg->flags = flags;
    drbg->nid = nid;

    switch (nid) {
    default:
        RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
        return -2;
    case 0:
        /* Uninitialized; that's okay. */
        return 1;
    case NID_aes_128_ctr:
    case NID_aes_192_ctr:
    case NID_aes_256_ctr:
        ret = ctr_init(drbg);
        break;
    }

    if (ret < 0)
        RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
    return ret;
}