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1644 | .PD |
1644 | .PD |
1645 | Initialises and configures the prepare or check watcher \- they have no |
1645 | Initialises and configures the prepare or check watcher \- they have no |
1646 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
1646 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
1647 | macros, but using them is utterly, utterly and completely pointless. |
1647 | macros, but using them is utterly, utterly and completely pointless. |
1648 | .PP |
1648 | .PP |
1649 | Example: To include a library such as adns, you would add \s-1IO\s0 watchers |
1649 | There are a number of principal ways to embed other event loops or modules |
1650 | and a timeout watcher in a prepare handler, as required by libadns, and |
1650 | into libev. Here are some ideas on how to include libadns into libev |
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1651 | (there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could |
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1652 | use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR |
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1653 | embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 |
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1654 | into the Glib event loop). |
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1655 | .PP |
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1656 | Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, |
1651 | in a check watcher, destroy them and call into libadns. What follows is |
1657 | and in a check watcher, destroy them and call into libadns. What follows |
1652 | pseudo-code only of course: |
1658 | is pseudo-code only of course. This requires you to either use a low |
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1659 | priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as |
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1660 | the callbacks for the IO/timeout watchers might not have been called yet. |
1653 | .PP |
1661 | .PP |
1654 | .Vb 2 |
1662 | .Vb 2 |
1655 | \& static ev_io iow [nfd]; |
1663 | \& static ev_io iow [nfd]; |
1656 | \& static ev_timer tw; |
1664 | \& static ev_timer tw; |
1657 | .Ve |
1665 | .Ve |
1658 | .PP |
1666 | .PP |
1659 | .Vb 9 |
1667 | .Vb 4 |
1660 | \& static void |
1668 | \& static void |
1661 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
1669 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
1662 | \& { |
1670 | \& { |
1663 | \& // set the relevant poll flags |
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1664 | \& // could also call adns_processreadable etc. here |
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1665 | \& struct pollfd *fd = (struct pollfd *)w->data; |
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1666 | \& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
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1667 | \& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
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1668 | \& } |
1671 | \& } |
1669 | .Ve |
1672 | .Ve |
1670 | .PP |
1673 | .PP |
1671 | .Vb 8 |
1674 | .Vb 8 |
1672 | \& // create io watchers for each fd and a timer before blocking |
1675 | \& // create io watchers for each fd and a timer before blocking |
… | |
… | |
1684 | \& ev_timer_init (&tw, 0, timeout * 1e-3); |
1687 | \& ev_timer_init (&tw, 0, timeout * 1e-3); |
1685 | \& ev_timer_start (loop, &tw); |
1688 | \& ev_timer_start (loop, &tw); |
1686 | .Ve |
1689 | .Ve |
1687 | .PP |
1690 | .PP |
1688 | .Vb 6 |
1691 | .Vb 6 |
1689 | \& // create on ev_io per pollfd |
1692 | \& // create one ev_io per pollfd |
1690 | \& for (int i = 0; i < nfd; ++i) |
1693 | \& for (int i = 0; i < nfd; ++i) |
1691 | \& { |
1694 | \& { |
1692 | \& ev_io_init (iow + i, io_cb, fds [i].fd, |
1695 | \& ev_io_init (iow + i, io_cb, fds [i].fd, |
1693 | \& ((fds [i].events & POLLIN ? EV_READ : 0) |
1696 | \& ((fds [i].events & POLLIN ? EV_READ : 0) |
1694 | \& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1697 | \& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1695 | .Ve |
1698 | .Ve |
1696 | .PP |
1699 | .PP |
1697 | .Vb 5 |
1700 | .Vb 4 |
1698 | \& fds [i].revents = 0; |
1701 | \& fds [i].revents = 0; |
1699 | \& iow [i].data = fds + i; |
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1700 | \& ev_io_start (loop, iow + i); |
1702 | \& ev_io_start (loop, iow + i); |
1701 | \& } |
1703 | \& } |
1702 | \& } |
1704 | \& } |
1703 | .Ve |
1705 | .Ve |
1704 | .PP |
1706 | .PP |
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1708 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1710 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1709 | \& { |
1711 | \& { |
1710 | \& ev_timer_stop (loop, &tw); |
1712 | \& ev_timer_stop (loop, &tw); |
1711 | .Ve |
1713 | .Ve |
1712 | .PP |
1714 | .PP |
1713 | .Vb 2 |
1715 | .Vb 8 |
1714 | \& for (int i = 0; i < nfd; ++i) |
1716 | \& for (int i = 0; i < nfd; ++i) |
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1717 | \& { |
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1718 | \& // set the relevant poll flags |
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1719 | \& // could also call adns_processreadable etc. here |
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1720 | \& struct pollfd *fd = fds + i; |
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1721 | \& int revents = ev_clear_pending (iow + i); |
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1722 | \& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
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1723 | \& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
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1724 | .Ve |
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1725 | .PP |
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1726 | .Vb 3 |
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1727 | \& // now stop the watcher |
1715 | \& ev_io_stop (loop, iow + i); |
1728 | \& ev_io_stop (loop, iow + i); |
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1729 | \& } |
1716 | .Ve |
1730 | .Ve |
1717 | .PP |
1731 | .PP |
1718 | .Vb 2 |
1732 | .Vb 2 |
1719 | \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1733 | \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
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1734 | \& } |
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1735 | .Ve |
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1736 | .PP |
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1737 | Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR |
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1738 | in the prepare watcher and would dispose of the check watcher. |
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1739 | .PP |
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1740 | Method 3: If the module to be embedded supports explicit event |
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1741 | notification (adns does), you can also make use of the actual watcher |
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1742 | callbacks, and only destroy/create the watchers in the prepare watcher. |
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1743 | .PP |
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1744 | .Vb 5 |
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1745 | \& static void |
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1746 | \& timer_cb (EV_P_ ev_timer *w, int revents) |
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1747 | \& { |
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1748 | \& adns_state ads = (adns_state)w->data; |
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1749 | \& update_now (EV_A); |
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1750 | .Ve |
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1751 | .PP |
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1752 | .Vb 2 |
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1753 | \& adns_processtimeouts (ads, &tv_now); |
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1754 | \& } |
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1755 | .Ve |
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1756 | .PP |
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1757 | .Vb 5 |
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1758 | \& static void |
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1759 | \& io_cb (EV_P_ ev_io *w, int revents) |
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1760 | \& { |
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1761 | \& adns_state ads = (adns_state)w->data; |
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1762 | \& update_now (EV_A); |
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1763 | .Ve |
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1764 | .PP |
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1765 | .Vb 3 |
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1766 | \& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
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1767 | \& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
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1768 | \& } |
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1769 | .Ve |
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1770 | .PP |
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1771 | .Vb 1 |
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1772 | \& // do not ever call adns_afterpoll |
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1773 | .Ve |
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1774 | .PP |
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1775 | Method 4: Do not use a prepare or check watcher because the module you |
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1776 | want to embed is too inflexible to support it. Instead, youc na override |
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1777 | their poll function. The drawback with this solution is that the main |
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1778 | loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does |
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1779 | this. |
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1780 | .PP |
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1781 | .Vb 4 |
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1782 | \& static gint |
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1783 | \& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
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1784 | \& { |
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1785 | \& int got_events = 0; |
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1786 | .Ve |
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1787 | .PP |
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1788 | .Vb 2 |
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1789 | \& for (n = 0; n < nfds; ++n) |
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1790 | \& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
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1791 | .Ve |
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1792 | .PP |
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1793 | .Vb 2 |
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1794 | \& if (timeout >= 0) |
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1795 | \& // create/start timer |
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1796 | .Ve |
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1797 | .PP |
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1798 | .Vb 2 |
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1799 | \& // poll |
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1800 | \& ev_loop (EV_A_ 0); |
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1801 | .Ve |
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1802 | .PP |
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1803 | .Vb 3 |
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1804 | \& // stop timer again |
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1805 | \& if (timeout >= 0) |
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1806 | \& ev_timer_stop (EV_A_ &to); |
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1807 | .Ve |
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1808 | .PP |
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1809 | .Vb 3 |
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1810 | \& // stop io watchers again - their callbacks should have set |
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1811 | \& for (n = 0; n < nfds; ++n) |
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1812 | \& ev_io_stop (EV_A_ iow [n]); |
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1813 | .Ve |
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1814 | .PP |
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1815 | .Vb 2 |
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1816 | \& return got_events; |
1720 | \& } |
1817 | \& } |
1721 | .Ve |
1818 | .Ve |
1722 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
1819 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
1723 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
1820 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
1724 | .IX Subsection "ev_embed - when one backend isn't enough..." |
1821 | .IX Subsection "ev_embed - when one backend isn't enough..." |