res = blocks * blk_sz;
if (iflag.zero && iflag.ff && (blk_sz >= 4)) {
uint32_t pos = (uint32_t)skip;
uint off;
uint32_t off;
for (k = 0, off = 0; k < blocks; ++k, off += blk_sz, ++pos) {
for (j = 0; j < (blk_sz - 3); j += 4)