io - 相当于 Python 的 subprocess.communicate 在 Rust 中？

Question

我正在尝试将这个向辅助进程发送和接收输入的 Python 脚本移植到 Rust:

import subprocess
data = chr(0x3f) * 1024 * 4096
child = subprocess.Popen(['cat'], stdin=subprocess.PIPE,   stdout=subprocess.PIPE)
output, _ = child.communicate(data)
assert output == data

在输入缓冲区超过 64k 之前，我的尝试工作正常，因为大概操作系统的管道缓冲区在输入被写入之前就已经填满了。

use std::io::Write;

const DATA: [u8; 1024 * 4096] = [0x3f; 1024 * 4096];

fn main() {
    let mut child = std::process::Command::new("cat")
                        .stdout(std::process::Stdio::piped())
                        .stdin(std::process::Stdio::piped())
                        .spawn()
                        .unwrap();
    match child.stdin {
        Some(ref mut stdin) => {
            match stdin.write_all(&DATA[..]) {
                Ok(_size) => {}
                Err(err) => panic!(err),
            }
        }
        None => unreachable!(),
    }
    let res = child.wait_with_output();
    assert_eq!(res.unwrap().stdout.len(), DATA.len())
}

Rust 中是否有等效的 subprocess.communicate？也许是一个 select 等价物？可以用mio来解决这个问题吗？另外，似乎没有办法关闭标准输入。

这里的目标是构建一个高性能系统，所以我想避免为每个任务生成一个线程。

Answer 1

好吧，完成这项工作需要大量代码，我需要 mio 和 nix 的组合，因为当它们是管道时，mio 不会将 AsRawFd 项目设置为非阻塞，所以必须这样做首先。

这是结果

extern crate mio;
extern crate bytes;

use mio::*;
use std::io;
use mio::unix::{PipeReader, PipeWriter};
use std::process::{Command, Stdio};
use std::os::unix::io::AsRawFd;
use nix::fcntl::FcntlArg::F_SETFL;
use nix::fcntl::{fcntl, O_NONBLOCK};
extern crate nix;

struct SubprocessClient {
    stdin: PipeWriter,
    stdout: PipeReader,
    output : Vec<u8>,
    input : Vec<u8>,
    input_offset : usize,
    buf : [u8; 65536],
}


// Sends a message and expects to receive the same exact message, one at a time
impl SubprocessClient {
    fn new(stdin: PipeWriter, stdout : PipeReader, data : &[u8]) -> SubprocessClient {
        SubprocessClient {
            stdin: stdin,
            stdout: stdout,
            output : Vec::<u8>::new(),
            buf : [0; 65536],
            input : data.to_vec(),
            input_offset : 0,
        }
    }

    fn readable(&mut self, _event_loop: &mut EventLoop<SubprocessClient>) -> io::Result<()> {
        println!("client socket readable");


        match self.stdout.try_read(&mut self.buf[..]) {
            Ok(None) => {
                println!("CLIENT : spurious read wakeup");
            }
            Ok(Some(r)) => {
                println!("CLIENT : We read {} bytes!", r);
                self.output.extend(&self.buf[0..r]);
            }
            Err(e) => {
                return Err(e);
            }
        };
        return Ok(());
    }

    fn writable(&mut self, event_loop: &mut EventLoop<SubprocessClient>) -> io::Result<()> {
        println!("client socket writable");

        match self.stdin.try_write(&(&self.input)[self.input_offset..]) {
            Ok(None) => {
                println!("client flushing buf; WOULDBLOCK");
            }
            Ok(Some(r)) => {
                println!("CLIENT : we wrote {} bytes!", r);
                self.input_offset += r;
            }
            Err(e) => println!("not implemented; client err={:?}", e)
        }
        if self.input_offset == self.input.len() {
            event_loop.shutdown();
        }
        return Ok(());
    }

}

impl Handler for SubprocessClient {
    type Timeout = usize;
    type Message = ();

    fn ready(&mut self, event_loop: &mut EventLoop<SubprocessClient>, token: Token,
             events: EventSet) {
        println!("ready {:?} {:?}", token, events);
        if events.is_readable() {
            let _x = self.readable(event_loop);
        }
        if events.is_writable() {
            let _y = self.writable(event_loop);
        }
    }
}



pub fn from_nix_error(err: ::nix::Error) -> io::Error {
    io::Error::from_raw_os_error(err.errno() as i32)
}

fn set_nonblock(s: &AsRawFd) -> io::Result<()> {
    fcntl(s.as_raw_fd(), F_SETFL(O_NONBLOCK)).map_err(from_nix_error)
                                             .map(|_| ())
}


const TEST_DATA : [u8; 1024 * 4096] = [40; 1024 * 4096];
pub fn echo_server() {
    let mut event_loop = EventLoop::<SubprocessClient>::new().unwrap();
    let process =
           Command::new("cat")
           .stdin(Stdio::piped())
           .stdout(Stdio::piped())
           .spawn().unwrap();
    let raw_stdin_fd;
    match process.stdin {
      None => unreachable!(),
      Some(ref item) => {
          let err = set_nonblock(item);
          match err {
             Ok(()) => {},
             Err(e) => panic!(e),
          }
          raw_stdin_fd = item.as_raw_fd();
      },
    }
    let raw_stdout_fd;
    match process.stdout {
      None => unreachable!(),
      Some(ref item) => {
          let err = set_nonblock(item);
          match err {
             Ok(()) => {},
             Err(e) => panic!(e),
          }
          raw_stdout_fd = item.as_raw_fd();},
    }
    //println!("listen for connections {:?} {:?}", , process.stdout.unwrap().as_raw_fd());
    let mut subprocess = SubprocessClient::new(PipeWriter::from(Io::from_raw_fd(raw_stdin_fd)),
                                               PipeReader::from(Io::from_raw_fd(raw_stdout_fd)),
                                               &TEST_DATA[..]);
    let stdout_token : Token = Token(0);
    let stdin_token : Token = Token(1);
    event_loop.register(&subprocess.stdout, stdout_token, EventSet::readable(),
                        PollOpt::level()).unwrap();

    // Connect to the server
    event_loop.register(&subprocess.stdin, stdin_token, EventSet::writable(),
                        PollOpt::level()).unwrap();

    // Start the event loop
    event_loop.run(&mut subprocess).unwrap();
    let res = process.wait_with_output();
    match res {
       Err(e) => {panic!(e);},
       Ok(output) => {
          subprocess.output.extend(&output.stdout);
          println!("Final output was {:}\n", output.stdout.len());
       },
    }
    println!("{:?}\n", subprocess.output.len());
}

fn main() {
  echo_server();
}

基本上，关闭标准输入的唯一方法是调用 process.wait_with_output，因为标准输入没有关闭原语

一旦发生这种情况，剩余的输入可以扩展输出数据向量。

现在有一个箱子可以做到这一点

https://crates.io/crates/subprocess-communicate