dec_do
dec_do(&dev_dec,
dec_do(&s->conv, in, s->convbuf, icnt);
void dec_do(struct conv *, unsigned char *, unsigned char *, int);
dec_do(&s->mix.dec, (void *)in, s->mix.decbuf, s->round);
dec_do(&d->dec, d->decbuf, (unsigned char *)d->rbuf, d->round);
void dec_do(struct conv *, unsigned char *, unsigned char *, int);