PT3_BUF_CANARY
p[ofs] = PT3_BUF_CANARY;
if (adap->buffer[idx].data[ofs] == PT3_BUF_CANARY)
while (*next_unit(adap, &idx, &ofs) != PT3_BUF_CANARY) {
*p = PT3_BUF_CANARY;