asynchronous I/O?

async_io.cpp

#include <iostream>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/select.h>

int
async_open(const char * filename, int flags)
{
	// create pipe
	int fds[2] = {0};
	if (::socketpair(AF_UNIX, SOCK_STREAM, 0, fds) < 0)
	{
		std::cerr << "unable to create socket pair" << std::endl;
		return -1;
	}
	pid_t pid = ::fork();
	if (pid == 0)
	{
		int open_file = open(filename, flags);
		char buf[16] = {'1', 0};
		if (write(fds[1], buf, 1) != 1)
		{
			std::cerr << "unable to write ready signal to a pipe" << std::endl;
		}
		::close(fds[1]);
		::close(open_file);
		std::exit(0);
	}
	else if (pid > 0)
	{
		return fds[0];
	}
	else
	{
		return -1;
	}
}

int
main()
{
	int fd = async_open("/dev/urandom", O_RDONLY);
	fd_set fds;
	FD_ZERO(&fds);
	FD_SET(fd, &fds);
	struct timeval tv = {0};
	tv.tv_sec = 1;
	while (true)
	{
		int result = ::select(fd + 1, &fds, NULL, NULL, &tv);
		if (result < 0)
		{
			std::cerr << "select error" << std::endl;
			break;
		}
		if (result == 0)
		{
			std::cout << "no data received" << std::endl;
			continue;
		}
		if (FD_ISSET(fd, &fds))
		{
			std::cout << "tak" << std::endl;
			FD_CLR(fd, &fds);
		}
	}
	close(fd);
}