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use std::io;
use std::fs::File;

trait Trunc {
    fn trunc(&mut self, size: u64) -> io::Result<()>;
}

impl Trunc for File {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        self.set_len(size)
    }
}

impl<'a> Trunc for &'a File {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        self.set_len(size)
    }
}

impl<R: Trunc + io::Read> Trunc for io::BufReader<R> {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        self.get_mut().trunc(size)
    }
}

impl<W: Trunc + io::Write> Trunc for io::BufWriter<W> {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        self.get_mut().trunc(size)
    }
}

impl Trunc for Vec<u8> {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        Ok(self.resize(size as usize, 0))
    }
}

impl Trunc for io::Cursor<Vec<u8>> {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        Ok(self.get_mut().resize(size as usize, 0))
    }
}

impl<'a, T: Trunc + ?Sized> Trunc for &'a mut T {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        (**self).trunc(size)
    }
}

impl<'a, T: Trunc + ?Sized> Trunc for Box<T> {
    fn trunc(&mut self, size: u64) -> io::Result<()> {
        (**self).trunc(size)
    }
}