[boost] New Version (0.4) of Boost.Application (Aspect Based) available to comments (RFC).

Subject: [boost] New Version (0.4) of Boost.Application (Aspect Based) available to comments (RFC).
From: Renato Forti (re.tf_at_[hidden])
Date: 2013-11-08 06:43:58

>> The problem is to transfer interruption signal to the thread performing
I/O multiplexing, for instance, waiting for new data during select(2) call.
>> Default signal handler will force select(..) to return, but as far as we
want to have a custom one, we need to abort select(..) manually.

>> The tricky solution is to set up an non-blocking pipe and add its read
end to select(2)'s readfds array. Hence select(..) will return immediately
when any data will be written to the pipe's write end. Therefore,
write(selfpipe_write_fd, "", 1); must be called in signal handler after the
termination_signal_received is set to true.

>> The same effect can be achieved with signalfd(2). Unfortunately, this
syscall is linux-specific.

>> Here is a draft of the proposed aspect:

class selfpipe : noncopyable
{
protected:
    void setup() {
        pipe(fd_);
        fcntl(fd_[READ_FD], F_SETFL, fcntl(fd_[READ_FD], F_GETFL) |
O_NONBLOCK);
        fcntl(fd_[WRITE_FD], F_SETFL, fcntl(fd_[WRITE_FD], F_GETFL) |
O_NONBLOCK);
    }

    void teardown() {
        close(fd_[READ_FD];
        close(fd_[WRITE_FD];
    }

public:
    int readfd() const { return fd_[READ_FD]; }
    void poke() { write(fd_[WRITE_FD], "", 1); }

private:
    enum { READ_FD = 0, WRITE_FD = 1 };
    int fd_[2];
};

Thanks a lot for the code, I want  to implement it on lib.  Some questions:
The user need use 'select' to use this aspect? How user will use it? (on
final application code) I can't figure it! I tell this because,  One
question that comes to mind! We have something like that in Windows side? I
must/want provide an 'aspect' with same functionality or interface on both
sides! I need tie all internally on lib, and provide a normalized interface,
but signals are completely different on windows (windows don't have signal)
and posix.
Any idea ?

Thanks a lot.