read_vectored in libstd

main.rs

use std::fs;
use std::io::{self, IoSliceMut, Read, Write, Seek, SeekFrom};

fn main() -> io::Result<()> {
    let mut f = fs::OpenOptions::new()
        .read(true)
        .write(true)
        .create(true)
        .truncate(true)
        .open("test.txt")?;
    f.write_all(b"Hello!")?;
    f.seek(SeekFrom::Start(0))?;
    
    let buffer = &mut [0u8; 6];
    let (mut first, mut second) = buffer.split_at_mut(3);
    let iovecs = &mut [IoSliceMut::new(&mut first), IoSliceMut::new(&mut second)];
    f.read_vectored(iovecs)?;
    
    assert_eq!(b"Hello!", buffer, "buffers should be equal");
    
    Ok(())
}

output on Windows

thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `[72, 101, 108, 108, 111, 33]`,
  right: `[72, 101, 108, 0, 0, 0]`: buffers should be equal', src\main.rs:19:5