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#![feature(
    buf_read_has_data_left,
    can_vector,
    core_io_borrowed_buf,
    read_buf,
    write_all_vectored
)]

use std::fmt;
use std::io::{self, BorrowedCursor, BufRead, IoSlice, Read, Write};

#[derive(Copy, Clone, Debug, Default)]
pub struct Empty;

impl Read for Empty {
    #[inline]
    fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
        Ok(0)
    }

#[inline]
    fn read_buf(&mut self, _buf: BorrowedCursor<'_>) -> io::Result<()> {
        Ok(())
    }
}

impl BufRead for Empty {
    #[inline]
    fn fill_buf(&mut self) -> io::Result<&[u8]> {
        Ok(&[])
    }

#[inline]
    fn consume(&mut self, _n: usize) {}
}

impl Write for Empty {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        Ok(buf.len())
    }

#[inline]
    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
        let total_len = bufs.iter().map(|b| b.len()).sum();
        Ok(total_len)
    }

#[inline]
    fn is_write_vectored(&self) -> bool {
        true
    }

#[inline]
    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

// Read
pub fn read_to_end(buf: &mut Vec<u8>) -> io::Result<usize> {
    Empty.read_to_end(buf)
}
pub fn read_to_string(buf: &mut String) -> io::Result<usize> {
    Empty.read_to_string(buf)
}
pub fn read_exact(buf: &mut [u8]) -> io::Result<()> {
    Empty.read_exact(buf)
}
pub fn read_buf_exact(buf: BorrowedCursor<'_>) -> io::Result<()> {
    Empty.read_buf_exact(buf)
}

// BufRead
pub fn has_data_left() -> io::Result<bool> {
    Empty.has_data_left()
}
pub fn read_until(byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
    Empty.read_until(byte, buf)
}
pub fn skip_until(byte: u8) -> io::Result<usize> {
    Empty.skip_until(byte)
}
pub fn read_line(buf: &mut String) -> io::Result<usize> {
    Empty.read_line(buf)
}

// Write
pub fn write_all(buf: &[u8]) -> io::Result<()> {
    Empty.write_all(buf)
}
pub fn write_all_vectored(bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
    Empty.write_all_vectored(bufs)
}
// pub fn write_fmt(fmt: fmt::Arguments<'_>) -> io::Result<()> {
//     Empty.write_fmt(fmt)
// }