boost::coroutine2 + ::select = ???

coselect.cpp

#include <stdio.h>
#include <boost/coroutine2/coroutine.hpp>
#include <sys/select.h>
#include <list>
#include <utility>

namespace coselect {

struct tri_fd_set {
    fd_set read, write, except;
    tri_fd_set () {
        FD_ZERO(&read);
        FD_ZERO(&write);
        FD_ZERO(&except);
    }
};

using coro_t = boost::coroutines2::coroutine<tri_fd_set>;
using handle_t = coro_t::push_type;
using pull_handle_t = coro_t::pull_type;

void select(handle_t &handle, tri_fd_set &set) {
    handle(set);
    struct timeval tv { 0, 0 };
    ::select(FD_SETSIZE, &set.read, &set.write,
            &set.except, &tv);
}

bool operator && (const fd_set &lhs, const fd_set &rhs) {
    for(int i = 0; i < FD_SETSIZE; i++)
        if(FD_ISSET(i, &lhs) && FD_ISSET(i, &rhs))
            return true;
    return false;
}

bool operator && (const tri_fd_set &lhs, const tri_fd_set &rhs) {
    return (lhs.read && rhs.read) || 
            (lhs.write && rhs.write) ||
            (lhs.except && rhs.except);
}

fd_set &operator |= (fd_set &lhs, const fd_set &rhs) {
    for(int i = 0; i < FD_SETSIZE; i++)
        if(FD_ISSET(i, &rhs))
            FD_SET(i, &lhs);
    return lhs;
}

tri_fd_set &operator |= (tri_fd_set &lhs, const tri_fd_set &rhs) {
    lhs.read |= rhs.read;
    lhs.write |= rhs.write;
    lhs.except |= rhs.except;
    return lhs;
}

void select_loop(std::list<pull_handle_t> handles) {
    for(auto it = handles.begin(); it != handles.end();)
        if(*it)
            ++it;
        else
            it = handles.erase(it);

    while(!handles.empty()) {
        tri_fd_set set;
        for(pull_handle_t &handle : handles)
            set |= handle.get();
        int result = ::select(FD_SETSIZE,
                &set.read, &set.write, &set.except, nullptr);
        if(result < 0) {
            ::perror("select");
            continue; // XXX what to do
        }
        for(auto it = handles.begin(); it != handles.end(); )
            if((set && it->get()) && !(*it)())
                it = handles.erase(it);
            else
                ++it;
    }
}

}

int main() {
    std::list<coselect::pull_handle_t> handles;
    handles.emplace_back(
            [](coselect::handle_t &handle) {
                while(true) {
                    {
                        coselect::tri_fd_set set;
                        FD_SET(STDIN_FILENO, &set.read);
                        coselect::select(handle, set);
                    }
                    char buf[4096];
                    ssize_t sz = read(STDIN_FILENO, buf, 4096);
                    if(sz < 0) {
                        perror("read");
                        continue;
                    }
                    if(sz == 0)
                        break;
                    {
                        coselect::tri_fd_set set;
                        FD_SET(STDOUT_FILENO, &set.write);
                        coselect::select(handle, set);
                    }
                    if(write(STDOUT_FILENO, buf, sz) < 0)
                        perror("write");
                }
            });
    handles.emplace_back([](coselect::handle_t &) {});
    // TODO add more handles
    coselect::select_loop(std::move(handles));
}