c – Boost.Asio – 轮询命名管道

我正在尝试在命名管道上侦听输入.我在 Linux下使用Boost.Asio的 stream_descriptor和 async_read.问题是,对io_service :: run()的调用仅阻止我想要它直到第一次读取.之后,即使我尝试将更多的async_reads附加到它,它仍然会立即使用“文件结束”错误调用处理程序.我的代码相当于以下内容：

boost::asio::io_service io_service;
int fifo_d = open("/tmp/fifo",O_RDONLY);
boost::asio::posix::stream_descriptor fifo(io_service,fifo_d);
while (true)
{
    // buffer and handler probably aren't important for the purposes of this question
    boost::asio::async_read(fifo,buffer,handler);
    io_service.run();
}

只有第一个async_read按预期工作.后续的async_reads只是立即返回.我发现让它像我想要的那样工作的唯一方法是关闭并重新打开命名管道,但它似乎是一个黑客：

boost::asio::io_service io_service;
while (true)
{
    int fifo_d = open("/tmp/fifo",O_RDONLY);
    boost::asio::posix::stream_descriptor fifo(io_service,fifo_d);
    boost::asio::async_read(fifo,handler);
    io_service.run();
    close(fifo_d);
}

谁能告诉我我做错了什么？

更新：这是一个简单的“读取”版本,允许一些代码简化,问题仍然是相同的：

int fifo_d = open("/tmp/fifo",fifo_d);
while (true) {
    try {
        boost::asio::read(fifo,boost::asio::buffer(buffer));
    }
    catch (boost::system::system_error& err) {
        // It loops here with "read: End of file" error
        std::cout << err.what() << std::endl;
    }
}

#include <iostream>
#include <fstream>

int main() {
    std::ifstream fifo("/tmp/fifo");

    std::string word;
    size_t lineno = 0;
    while (fifo >> word) {
        std::cout << "word: " << ++lineno << "t" << word << "n";
    }
}

#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream.hpp>
#include <iostream>
#include <fcntl.h>

int main() {
    namespace io = boost::iostreams;
    using src = io::file_descriptor_source;
    io::stream<src> fifo(src(open("./fifo",O_RDONLY),io::file_descriptor_flags::close_handle));

    std::string word;
    size_t number = 0;
    while (fifo >> word) {
        std::cout << "word: " << ++number << "t" << word << "n";
    }
}

word: 1 hello
word: 2 world