如何在Rust中选择未来和流？

Question

我刚开始在Rust尝试期货/ tokio.我可以用期货或只用流来做基本的事情.我想知道如何在未来和流之间进行选择.

如何将tokio文档中的玩具问题扩展到用于tokio_timer::Timer执行定时HTTPS请求？

extern crate futures;
extern crate native_tls;
extern crate tokio_core;
extern crate tokio_io;
extern crate tokio_tls;

use std::io;
use std::net::ToSocketAddrs;

use futures::Future;
use native_tls::TlsConnector;
use tokio_core::net::TcpStream;
use tokio_core::reactor::Core;
use tokio_tls::TlsConnectorExt;

fn main() {
    let mut core = Core::new().unwrap();
    let handle = core.handle();
    let addr = "www.rust-lang.org:443".to_socket_addrs().unwrap().next().unwrap();

    let cx = TlsConnector::builder().unwrap().build().unwrap();
    let socket = TcpStream::connect(&addr, &handle);

    let tls_handshake = socket.and_then(|socket| {
        let tls = cx.connect_async("www.rust-lang.org", socket);
        tls.map_err(|e| {
            io::Error::new(io::ErrorKind::Other, e)
        })
    });
    let request = tls_handshake.and_then(|socket| {
        tokio_io::io::write_all(socket, "\
            GET / HTTP/1.0\r\n\
            Host: www.rust-lang.org\r\n\
            \r\n\
        ".as_bytes())
    });
    let response = request.and_then(|(socket, _request)| {
        tokio_io::io::read_to_end(socket, Vec::new())
    });

    let (_socket, data) = core.run(response).unwrap();
    println!("{}", String::from_utf8_lossy(&data));
}

Answer 1

您可以将a转换Future为a Stream,然后在两个流上进行选择:

extern crate futures; // 0.1.21

use futures::{Future, Stream};

fn select_stream_or_future_as_stream<S, F>(
    stream: S,
    future: F,
) -> impl Stream<Item = S::Item, Error = S::Error>
where
    S: Stream + 'static,
    F: Future<Item = S::Item, Error = S::Error> + 'static,
{
    future.into_stream().select(stream)
}