SECSIZ
if ((err = !(fs->buf = alloc(SECSIZ)) ? errno : 0) ||
dealloc(fs->buf, SECSIZ);
if (getushort(bs->bpb.bpbBytesPerSec) != SECSIZ)
if ((off = offset & (SECSIZ - 1))) {
offset += SECSIZ;
if ((n = SECSIZ - off) > nbyte)
n = nbyte & (SECSIZ - 1);