'n' variable in rust loop undeclared? : I don't understand where this 'n' variable in the below code comes from or what exactly it is, the author says it reads 20 bytes at a time bytes at a time, where is this coming from? My real problem is figuring out how to read from a rust TcpStream, but I think I understand that part and would just like to know where 'n' comes from.

I am trying to implement an HTTP client (sorta) in Rust as my one of my first projects and I'm trying to follow this code:

```rust
fn handle_client(mut stream: TcpStream) {
    // read 20 bytes at a time from stream echoing back to stream
    loop {
        let mut read = [0; 1028];
        match stream.read(&mut read) {
            Ok(n) => {
                if n == 0 { 
                    // connection was closed
                    break;
                }
                stream.write(&read[0..n]).unwrap();
            }
            Err(err) => {
                panic!(err);
            }
        }
    }
}
```

I haven't really tried anything yet because I want to understand before I do.