TNBUF
struct iovec wbuf[TNBUF*2 + NEMPTY];
uint32_t hdr[TNBUF + NEMPTY][3];
pbuf = malloc(DSIZE * TNBUF);
for (i = 1; i < TNBUF; i++)
while (tlen < DSIZE * TNBUF) {
len = read(fd, pbuf + tlen, DSIZE * TNBUF - tlen);