compat/poll.c

   1 /*****************************************************************************
   2  * poll.c: poll() emulation
   3  *****************************************************************************
   4  * Copyright © 2007-2012 Rémi Denis-Courmont
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  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 Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <errno.h>
  28
  29 #ifndef _WIN32
  30 # include <sys/time.h>
  31 # include <sys/select.h>
  32 # include <fcntl.h>
  33
  34 int (poll) (struct pollfd *fds, unsigned nfds, int timeout)
  35 {
  36     fd_set rdset[1], wrset[1], exset[1];
  37     struct timeval tv = { 0, 0 };
  38     int val = -1;
  39
  40     FD_ZERO (rdset);
  41     FD_ZERO (wrset);
  42     FD_ZERO (exset);
  43     for (unsigned i = 0; i < nfds; i++)
  44     {
  45         int fd = fds[i].fd;
  46         if (val < fd)
  47             val = fd;
  48
  49         /* With POSIX, FD_SET & FD_ISSET are not defined if fd is negative or
  50          * bigger or equal than FD_SETSIZE. That is one of the reasons why VLC
  51          * uses poll() rather than select(). Most POSIX systems implement
  52          * fd_set has a bit field with no sanity checks. This is especially bad
  53          * on systems (such as BSD) that have no process open files limit by
  54          * default, such that it is quite feasible to get fd >= FD_SETSIZE.
  55          * The next instructions will result in a buffer overflow if run on
  56          * a POSIX system, and the later FD_ISSET would perform an undefined
  57          * memory read. */
  58         if ((unsigned)fd >= FD_SETSIZE)
  59         {
  60             errno = EINVAL;
  61             return -1;
  62         }
  63         if (fds[i].events & POLLRDNORM)
  64             FD_SET (fd, rdset);
  65         if (fds[i].events & POLLWRNORM)
  66             FD_SET (fd, wrset);
  67         if (fds[i].events & POLLPRI)
  68             FD_SET (fd, exset);
  69     }
  70
  71     if (timeout >= 0)
  72     {
  73         div_t d = div (timeout, 1000);
  74         tv.tv_sec = d.quot;
  75         tv.tv_usec = d.rem * 1000;
  76     }
  77
  78     val = select (val + 1, rdset, wrset, exset,
  79                   (timeout >= 0) ? &tv : NULL);
  80     if (val == -1)
  81     {
  82         if (errno != EBADF)
  83             return -1;
  84
  85         val = 0;
  86
  87         for (unsigned i = 0; i < nfds; i++)
  88             if (fcntl (fds[i].fd, F_GETFD) == -1)
  89             {
  90                 fds[i].revents = POLLNVAL;
  91                 val++;
  92             }
  93             else
  94                 fds[i].revents = 0;
  95
  96         return val ? val : -1;
  97     }
  98
  99     for (unsigned i = 0; i < nfds; i++)
 100     {
 101         int fd = fds[i].fd;
 102         fds[i].revents = (FD_ISSET (fd, rdset) ? POLLRDNORM : 0)
 103                        | (FD_ISSET (fd, wrset) ? POLLWRNORM : 0)
 104                        | (FD_ISSET (fd, exset) ? POLLPRI : 0);
 105     }
 106     return val;
 107 }
 108 #else
 109 # include <windows.h>
 110 # include <winsock2.h>
 111
 112 static int poll_compat(struct pollfd *fds, unsigned nfds, int timeout)
 113 {
 114     DWORD to = (timeout >= 0) ? (DWORD)timeout : INFINITE;
 115
 116     if (nfds == 0)
 117     {    /* WSAWaitForMultipleEvents() does not allow zero events */
 118         if (SleepEx(to, TRUE))
 119         {
 120             errno = EINTR;
 121             return -1;
 122         }
 123         return 0;
 124     }
 125
 126     WSAEVENT *evts = malloc(nfds * sizeof (WSAEVENT));
 127     if (evts == NULL)
 128         return -1; /* ENOMEM */
 129
 130     DWORD ret = WSA_WAIT_FAILED;
 131     for (unsigned i = 0; i < nfds; i++)
 132     {
 133         SOCKET fd = fds[i].fd;
 134         long mask = FD_CLOSE;
 135         fd_set rdset, wrset, exset;
 136
 137         FD_ZERO(&rdset);
 138         FD_ZERO(&wrset);
 139         FD_ZERO(&exset);
 140         FD_SET(fd, &exset);
 141
 142         if (fds[i].events & POLLRDNORM)
 143         {
 144             mask |= FD_READ | FD_ACCEPT;
 145             FD_SET(fd, &rdset);
 146         }
 147         if (fds[i].events & POLLWRNORM)
 148         {
 149             mask |= FD_WRITE | FD_CONNECT;
 150             FD_SET(fd, &wrset);
 151         }
 152         if (fds[i].events & POLLPRI)
 153             mask |= FD_OOB;
 154
 155         fds[i].revents = 0;
 156
 157         evts[i] = WSACreateEvent();
 158         if (evts[i] == WSA_INVALID_EVENT)
 159         {
 160             while (i > 0)
 161                 WSACloseEvent(evts[--i]);
 162             free(evts);
 163             errno = ENOMEM;
 164             return -1;
 165         }
 166
 167         if (WSAEventSelect(fds[i].fd, evts[i], mask)
 168          && WSAGetLastError() == WSAENOTSOCK)
 169             fds[i].revents |= POLLNVAL;
 170
 171         struct timeval tv = { 0, 0 };
 172         /* By its horrible design, WSAEnumNetworkEvents() only enumerates
 173          * events that were not already signaled (i.e. it is edge-triggered).
 174          * WSAPoll() would be better in this respect, but worse in others.
 175          * So use WSAEnumNetworkEvents() after manually checking for pending
 176          * events. */
 177         if (select(0, &rdset, &wrset, &exset, &tv) > 0)
 178         {
 179             if (FD_ISSET(fd, &rdset))
 180                 fds[i].revents |= fds[i].events & POLLRDNORM;
 181             if (FD_ISSET(fd, &wrset))
 182                 fds[i].revents |= fds[i].events & POLLWRNORM;
 183             if (FD_ISSET(fd, &exset))
 184                 /* To add pain to injury, POLLERR and POLLPRI cannot be
 185                  * distinguished here. */
 186                 fds[i].revents |= POLLERR | (fds[i].events & POLLPRI);
 187         }
 188
 189         if (fds[i].revents != 0 && ret == WSA_WAIT_FAILED)
 190             ret = WSA_WAIT_EVENT_0 + i;
 191     }
 192
 193     if (ret == WSA_WAIT_FAILED)
 194         ret = WSAWaitForMultipleEvents(nfds, evts, FALSE, to, TRUE);
 195
 196     unsigned count = 0;
 197     for (unsigned i = 0; i < nfds; i++)
 198     {
 199         WSANETWORKEVENTS ne;
 200
 201         if (WSAEnumNetworkEvents(fds[i].fd, evts[i], &ne))
 202             memset(&ne, 0, sizeof (ne));
 203         WSAEventSelect(fds[i].fd, evts[i], 0);
 204         WSACloseEvent(evts[i]);
 205
 206         if (ne.lNetworkEvents & FD_CONNECT)
 207         {
 208             fds[i].revents |= POLLWRNORM;
 209             if (ne.iErrorCode[FD_CONNECT_BIT] != 0)
 210                 fds[i].revents |= POLLERR;
 211         }
 212         if (ne.lNetworkEvents & FD_CLOSE)
 213         {
 214             fds[i].revents |= (fds[i].events & POLLRDNORM) | POLLHUP;
 215             if (ne.iErrorCode[FD_CLOSE_BIT] != 0)
 216                 fds[i].revents |= POLLERR;
 217         }
 218         if (ne.lNetworkEvents & FD_ACCEPT)
 219         {
 220             fds[i].revents |= POLLRDNORM;
 221             if (ne.iErrorCode[FD_ACCEPT_BIT] != 0)
 222                 fds[i].revents |= POLLERR;
 223         }
 224         if (ne.lNetworkEvents & FD_OOB)
 225         {
 226             fds[i].revents |= POLLPRI;
 227             if (ne.iErrorCode[FD_OOB_BIT] != 0)
 228                 fds[i].revents |= POLLERR;
 229         }
 230         if (ne.lNetworkEvents & FD_READ)
 231         {
 232             fds[i].revents |= POLLRDNORM;
 233             if (ne.iErrorCode[FD_READ_BIT] != 0)
 234                 fds[i].revents |= POLLERR;
 235         }
 236         if (ne.lNetworkEvents & FD_WRITE)
 237         {
 238             fds[i].revents |= POLLWRNORM;
 239             if (ne.iErrorCode[FD_WRITE_BIT] != 0)
 240                 fds[i].revents |= POLLERR;
 241         }
 242         count += fds[i].revents != 0;
 243     }
 244
 245     free(evts);
 246
 247     if (count == 0 && ret == WSA_WAIT_IO_COMPLETION)
 248     {
 249         errno = EINTR;
 250         return -1;
 251     }
 252     return count;
 253 }
 254
 255 int poll(struct pollfd *fds, unsigned nfds, int timeout)
 256 {
 257     if (timeout == -1)
 258     {
 259         /* HACK: In some cases, we lose some events because events are
 260          * destroyed and recreated only when we need to poll. In order to work
 261          * arround this issue, we try to call the poll compat function every
 262          * 100ms (in case of infinite timeout). */
 263         int ret;
 264         while ((ret = poll_compat(fds, nfds, 100)) == 0);
 265         return ret;
 266     }
 267     else
 268         return poll_compat(fds, nfds, timeout);
 269 }
 270
 271 #endif