xor8_buf
if (xor8_buf(block, rsvd0_off, xor_len) != 0xff)
if (xor8_buf(block, 0, sizeof(*block)) != 0xff)
block->ctrl_sig = ~xor8_buf(block, rsvd0_off, ctrl_xor_len);
block->sig = ~xor8_buf(block, 0, sizeof(*block) - 1);
ent->lay->sig = ~xor8_buf(ent->lay, 0, sizeof(*ent->lay));
sig = xor8_buf(ent->lay, 0, sizeof(*ent->lay));