问如何有效地使用boost::process::async_pipe进行写入和读取？

EN

#include <boost/asio.hpp>
#include <boost/process.hpp>
#include <iostream>
#include <string>
#include <vector>

typedef std::function<void(const boost::system::error_code & ec, std::size_t n)> Handler;

int main(){
    
    std::vector<char> vread_buffer(4096);
    boost::asio::io_service ios;
    boost::process::async_pipe read_pipe{ios};
    boost::process::async_pipe write_pipe{ios};
    auto child_process = boost::process::child(  "stockfish_12_win_x64/stockfish_20090216_x64.exe" , 
                                                boost::process::std_in  <  write_pipe ,
                                                boost::process::std_out >  read_pipe  );
    

    Handler on_stdout,on_stdin;
    std::string read_string;

    on_stdout = [&](const boost::system::error_code & ec, size_t n){
        std::cout << "I'm reading " << n << " characters from the child process. Can't wait for more!" << std::endl;
        read_string.reserve( read_string.size() + n );
        read_string.insert( read_string.end() , vread_buffer.begin() , vread_buffer.begin() + n );
        if(!ec) boost::asio::async_read( read_pipe , boost::asio::buffer(vread_buffer) , on_stdout );
    };
    on_stdin = [&]( const boost::system::error_code & ec, std::size_t n ){
        std::cout << "I know that " << n << " characters were sent to the process. Yay! " << std::endl;
    };

    // {...} Suppose an undefined amount of time has passed 

    // Expected: To see the initial print from the program calling the on_stdout
    // ... but it doesn't call anything.
    boost::asio::async_read( read_pipe , boost::asio::buffer(vread_buffer) ,  on_stdout );
    ios.poll();
    ios.restart();


    // Expected: To see the "on_stdin" handler being called... and it was!
    std::string write_string = "uci\n";
    boost::asio::async_write( write_pipe , boost::asio::buffer(write_string) ,  on_stdin );
    ios.poll();
    ios.restart();
    
    // Sending a async_read will never do anything unless I close the write_pipe.
    // How can I tell the io_service that last write was done so I can read again?
    boost::asio::async_read( read_pipe , boost::asio::buffer(vread_buffer) ,  on_stdout );
    ios.poll();
    ios.restart();

    
}