func Readv(fd int, iovs [][]byte) (n int, err error) {
	iovecs := bytes2iovec(iovs)
	n, err = readv(fd, iovecs)
	return n, err
}

//sys	preadv(fd int, iovs []Iovec, off int64) (n int, err error)

func Preadv(fd int, iovs [][]byte, off int64) (n int, err error) {
	iovecs := bytes2iovec(iovs)
	n, err = preadv(fd, iovecs, off)
	return n, err
}