DSIZE
pad = malloc(DSIZE*MAXBLOCKS);
memset(pad, 0xff, DSIZE*MAXBLOCKS);
npad *= DSIZE;
wbuf[vec++].iov_len = DSIZE;
pbuf = malloc(DSIZE * TNBUF);
pkt->mode.stream.len = DSIZE + sizeof(struct ciphdr);
while (tlen < DSIZE * TNBUF) {
len = read(fd, pbuf + tlen, DSIZE * TNBUF - tlen);
dv = (struct dvdbc *)(pbuf + offset * DSIZE);
wbuf[vec++].iov_len = DSIZE;
if (offset * DSIZE < tlen)