crossthread.posix.cc

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#include <poll.h>

CrossThreadChannel::CrossThreadChannel (bool non_blocking)
        : receive_channel (0)
{
        fds[0] = -1;
        fds[1] = -1;

        if (pipe (fds)) {
                error << "cannot create x-thread pipe for read (%2)" << ::strerror (errno) << endmsg;
                return;
        }

        if (non_blocking) {
                if (fcntl (fds[0], F_SETFL, O_NONBLOCK)) {
                        error << "cannot set non-blocking mode for x-thread pipe (read) (" << ::strerror (errno) << ')' << endmsg;
                        return;
                }
                
                if (fcntl (fds[1], F_SETFL, O_NONBLOCK)) {
                        error << "cannot set non-blocking mode for x-thread pipe (write) (%2)" << ::strerror (errno) << ')' << endmsg;
                        return;
                }
        }

        receive_channel = g_io_channel_unix_new (fds[0]);
}

CrossThreadChannel::~CrossThreadChannel ()
{
        if (receive_channel) {
                g_io_channel_unref (receive_channel);
        }

        if (fds[0] >= 0) {
                close (fds[0]);
                fds[0] = -1;
        } 

        if (fds[1] >= 0) {
                close (fds[1]);
                fds[1] = -1;
        } 
}

void
CrossThreadChannel::wakeup ()
{
        char c = 0;
        (void) ::write (fds[1], &c, 1);
}

void
CrossThreadChannel::drain ()
{
        char buf[64];
        while (::read (fds[0], buf, sizeof (buf)) > 0) {};
}

int
CrossThreadChannel::deliver (char msg)
{
        return ::write (fds[1], &msg, 1);
}

bool
CrossThreadChannel::poll_for_request()
{
        struct pollfd pfd[1];
        pfd[0].fd = fds[0];
        pfd[0].events = POLLIN|POLLERR|POLLHUP;
        while(true) {
                if (poll (pfd, 1, -1) < 0) {
                        if (errno == EINTR) {
                                continue;
                        }
                        break;
                }
                if (pfd[0].revents & ~POLLIN) {
                        break;
                }

                if (pfd[0].revents & POLLIN) {
                        return true;
                }
        }
        return false;
}

int 
CrossThreadChannel::receive (char& msg, bool wait)
{
        if (wait) {
                if (!poll_for_request ()) {
                        return -1;
                }
        }
        return ::read (fds[0], &msg, 1);
}