You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: peekable.rs
    path of file: ./repos/Rocket/core/lib/src/data
    
    the code of the file until where you have to start completion: use tokio::io::{AsyncRead, AsyncReadExt};

pub struct Peekable<const N: usize, R> {
    pub(crate) buffer: Vec<u8>,
    pub(crate) complete: bool,
    pub(crate) reader: R,
}

impl<const N: usize, R: AsyncRead + Unpin> Peekable<N, R> {
    pub fn new(reader: R) -> Self {
        Self { buffer: Vec::new(), complete: fal
    
    pub async fn peek(&mut self, num: usize) -> &[u8] {
        if self.complete {
            return self.buffer.as_slice();
        }

        let to_read = std::cmp::min(N, num);
        if self.buffer.len() >= to_read {
            return &self.buffer.as_slice();
        }

        if self.buffer.capacity() == 0 {
            self.buffer.reserve(N);
        }

        while self.buffer.len() < to_read {
            match self.reader.read_buf::<Vec<u8>>(&mut self.buffer).await {
                Ok(0) => {
                    self.complete = self.buffer.capacity() > self.buffer.len();
                    break;
                },
                Ok(_) => { /* continue */ },
                Err(e) => {
                    error_!("Failed to read into peek buffer: {:?}.", e);
                    break;
                }
            }
        }

        self.buffer.as_slice()
    }