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rusttcp

If BufReader takes ownership of a stream, how can I read and write lines on it?

I want to read a line from a TCPStream, write another line to it, and then repeat. The issue is that BufReader::new takes ownership of my TCPStream variable:

let stream = ...; // TCPStream

let reader = BufReader::new(stream); // moved its value

// can't use stream here anymore

What is a simple solution to this?

Solution

  • Solution: use references.

    let mut stream = ...;
let reader = BufReader::new(&stream);
let writer = BufWriter::new(&stream);

    Explanation

    If we take a closer look at BufReader::new, we see that it takes an argument inner of type R, where R is just any type that implements Read:

    impl<R: Read> BufReader<R> {
    pub fn new(inner: R) -> BufReader<R> { ... }
}

    We then take a look at Read and see this implementation:

    impl<'a> Read for &'a TcpStream

    So we can just pass a reference to the new function, like so:

    let reader = BufReader::new(&stream);

    We will do the same for BufWriter and Write and will see that indeed there is this implementation:

    impl<'a> Write for &'a TcpStream

    So we can, again, use an immutable reference to create the BufWriter.