pub struct CountingRead<'a, R: 'a + Read> {
    r: &'a mut R,
    count: usize,
}

impl<'a, R: 'a + Read> CountingRead<'a, R> {
    pub fn new(r: &'a mut R) -> Self {
        CountingRead { r: r, count: 0 }
    }

    pub fn count(&self) -> usize {
        self.count
    }

    pub fn reset(&mut self) {
        self.count = 0;
    }
}

impl<'a, R: 'a + Read> Read for CountingRead<'a, R> {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
        match self.r.read(buf) {
            Ok(n) => {
                self.count += n;
                Ok(n)
            }
            err => err,
        }
    }
}