Resuming read after timeout

まず rexpect::exp_eof と drain_read_buffer が使用する reader.try_read のパスを調べ、タイムアウト後に何がバッファに残るのかに注目します。「100ms 後に利用可能なものをすべて読み取る」が返すべき内容と、後続の読み取りで以前の出力が再び返されないようにする方法を定義します。段階的に出力を生成する PTY プロセスで動作を検証してください。

I have a

pub session: Option<Arc<Mutex<PtySession>>>,

I want to get the existing output of a process after 100ms. This seemed to work at first:

        let output = {
            let session_mutex = self.session.as_mut().ok_or(anyhow!("No session"))?;
            let mut session = session_mutex.lock()?;
            match session.exp_eof() {
                Ok(output) => output,
                Err(e) => {
                    match e {
                        rexpect::error::Error::Timeout { got, .. } => got
                            .replace("`\\n`\n", "\n")
                            .replace("`\\r`", "\r")
                            .replace("`^`", "\u{1b}"),
                        _ => return Err(e.into()),
                    }
                }
            }
        };

but then I realized that session.exp_eof does not drain the buffer if a timeout is reached, meaning that if I try to read the next chunk, the entire output up to this point is going to be returned yet again. This seems to work:

    fn drain_read_buffer(&mut self) -> ZammResult<String> {
        let mut output = String::new();
        if let Some(session) = self.session.as_mut() {
            let reader = &mut session.lock()?.reader;
            while let Some(chunk) = reader.try_read() {
                output.push(chunk);
            }
        }
        Ok(output)
    }

    ...

        let mut output = String::new();
        loop {
            sleep(Duration::from_millis(100));
            let new_output = self.drain_read_buffer()?;
            if new_output.is_empty() {
                break;
            }
            output.push_str(&new_output);
        }

But I'm wondering, is there a better way to implement "read whatever is available after 100ms" than this?