add_off_t
offset = add_off_t(offset, bzctrllen);
offset = add_off_t(offset, bzdatalen);
if (add_off_t(newpos, ctrl[0]) > newsize)
if (add_off_t(oldpos, i) < oldsize)
newpos = add_off_t(newpos, ctrl[0]);
oldpos = add_off_t(oldpos, ctrl[0]);
if (add_off_t(newpos, ctrl[1]) > newsize)
newpos = add_off_t(newpos, ctrl[1]);
oldpos = add_off_t(oldpos, ctrl[2]);