1 /*****************************************************************************
2 * poll.c: I/O event multiplexing
3 *****************************************************************************
4 * Copyright © 2007 Rémi Denis-Courmont
7 * Author: Rémi Denis-Courmont
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
22 *****************************************************************************/
28 #include <vlc_common.h>
33 int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
35 (void)fds; (void)nfds; (void)timeout;
38 #else /* !HAVE_POLL */
41 #include <vlc_network.h>
43 int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
45 fd_set rdset, wrset, exset;
46 struct timeval tv = { 0, 0 };
52 for (unsigned i = 0; i < nfds; i++)
58 /* With POSIX, FD_SET & FD_ISSET are not defined if fd is negative or
59 * bigger or equal than FD_SETSIZE. That is one of the reasons why VLC
60 * uses poll() rather than select(). Most POSIX systems implement
61 * fd_set has a bit field with no sanity checks. This is especially bad
62 * on systems (such as BSD) that have no process open files limit by
63 * default, such that it is quite feasible to get fd >= FD_SETSIZE.
64 * The next instructions will result in a buffer overflow if run on
65 * a POSIX system, and the later FD_ISSET will do undefined memory
68 * With Winsock, fd_set is a table of integers. This is awfully slow.
69 * However, FD_SET and FD_ISSET silently and safely discard
70 * overflows. If it happens we will loose socket events. Note that
71 * most (if not all) Winsock SOCKET handles are actually bigger than
72 * FD_SETSIZE in terms of absolute value - they are not POSIX file
73 * descriptors. From Vista, there is a much nicer WSAPoll(), but Mingw
74 * is yet to support it.
76 * With BeOS, the situation is unknown (FIXME: document).
78 if (fds[i].events & POLLIN)
80 if (fds[i].events & POLLOUT)
82 if (fds[i].events & POLLPRI)
88 div_t d = div (timeout, 1000);
90 tv.tv_usec = d.rem * 1000;
93 val = select (val + 1, &rdset, &wrset, &exset,
94 (timeout >= 0) ? &tv : NULL);
98 for (unsigned i = 0; i < nfds; i++)
101 fds[i].revents = (FD_ISSET (fd, &rdset) ? POLLIN : 0)
102 | (FD_ISSET (fd, &wrset) ? POLLOUT : 0)
103 | (FD_ISSET (fd, &exset) ? POLLPRI : 0);
107 #endif /* !HAVE_POLL */