1 /*****************************************************************************
2 * poll.c: poll() emulation for Winsock
3 *****************************************************************************
4 * Copyright © 2007 Rémi Denis-Courmont
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
19 *****************************************************************************/
29 #include <vlc_common.h>
32 /* Too late for #undef FD_SETSIZE to work: fd_set is already defined. */
33 # error Header inclusion order compromised!
36 #include <vlc_network.h>
40 #include <sys/select.h>
41 #define SOCKET unsigned
44 int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
46 size_t setsize = sizeof (fd_set) + nfds * sizeof (SOCKET);
47 fd_set *rdset = malloc (setsize);
48 fd_set *wrset = malloc (setsize);
49 fd_set *exset = malloc (setsize);
50 struct timeval tv = { 0, 0 };
53 if (unlikely(rdset == NULL || wrset == NULL || exset == NULL))
62 /* Winsock FD_SET uses FD_SETSIZE in its expansion */
64 #define FD_SETSIZE (nfds)
73 for (unsigned i = 0; i < nfds; i++)
79 /* With POSIX, FD_SET & FD_ISSET are not defined if fd is negative or
80 * bigger or equal than FD_SETSIZE. That is one of the reasons why VLC
81 * uses poll() rather than select(). Most POSIX systems implement
82 * fd_set has a bit field with no sanity checks. This is especially bad
83 * on systems (such as BSD) that have no process open files limit by
84 * default, such that it is quite feasible to get fd >= FD_SETSIZE.
85 * The next instructions will result in a buffer overflow if run on
86 * a POSIX system, and the later FD_ISSET would perform an undefined
89 * With Winsock, fd_set is a table of integers. This is awfully slow.
90 * However, FD_SET and FD_ISSET silently and safely discard excess
91 * entries. Here, overflow cannot happen anyway: fd_set of adequate
93 * Note that Vista has a much nicer WSAPoll(), but Mingw does not
96 if (fds[i].events & POLLIN)
97 FD_SET ((SOCKET)fd, rdset);
98 if (fds[i].events & POLLOUT)
99 FD_SET ((SOCKET)fd, wrset);
100 if (fds[i].events & POLLPRI)
101 FD_SET ((SOCKET)fd, exset);
104 #ifndef HAVE_ALERTABLE_SELECT
105 # warning FIXME! Fix cancellation and remove this crap.
106 if ((timeout < 0) || (timeout > 50))
115 div_t d = div (timeout, 1000);
117 tv.tv_usec = d.rem * 1000;
120 val = select (val + 1, rdset, wrset, exset,
121 /*(timeout >= 0) ?*/ &tv /*: NULL*/);
123 #ifndef HAVE_ALERTABLE_SELECT
127 timeout -= (timeout > 50) ? 50 : timeout;
136 for (unsigned i = 0; i < nfds; i++)
139 fds[i].revents = (FD_ISSET (fd, rdset) ? POLLIN : 0)
140 | (FD_ISSET (fd, wrset) ? POLLOUT : 0)
141 | (FD_ISSET (fd, exset) ? POLLPRI : 0);