secbyt
#define blkoff(fs, b) (secbyt(fs, (fs)->lsndta) + \
max_offset_in_fat = secbyt(fs, (daddr_t)fs->spf);
off += secbyt(f->fs, f->fs->lsndir);
fs->bsize = secbyt(fs, fs->spc);
fs->dshift = ffs(secbyt(fs, 1) / sizeof (DOS_DE)) - 1;
(secbyt(fs, 1) - 1)) / secbyt(fs, 1);
sc = (secbyt(fs, fs->spf) << 1) / (fs->fatsz >> 2) - 1;
secbyt(fs, 1))))
if (offset + nbyte > secbyt(fs, fs->spf))
secsiz = secbyt(fs, 1);
lsec = secbyt(fs, lsec) >> 9;