winsup/cygwin/poll.cc

   1 /* poll.cc. Implements poll(2) via usage of select(2) call.
   2
   3    This file is part of Cygwin.
   4
   5    This software is a copyrighted work licensed under the terms of the
   6    Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
   7    details. */
   8
   9 #define FD_SETSIZE 16384                // lots of fds
  10 #include "winsup.h"
  11 #include <sys/poll.h>
  12 #include <sys/param.h>
  13 #include <stdlib.h>
  14 #define USE_SYS_TYPES_FD_SET
  15 #include "cygerrno.h"
  16 #include "path.h"
  17 #include "fhandler.h"
  18 #include "dtable.h"
  19 #include "cygheap.h"
  20 #include "pinfo.h"
  21 #include "sigproc.h"
  22 #include "select.h"
  23
  24 extern "C" int
  25 poll (struct pollfd *fds, nfds_t nfds, int timeout)
  26 {
  27   int max_fd = 0;
  28   int invalid_fds = 0;
  29   fd_set *read_fds, *write_fds, *except_fds;
  30   struct timeval tv = { timeout / 1000, (timeout % 1000) * 1000 };
  31
  32   for (unsigned int i = 0; i < nfds; ++i)
  33     if (fds[i].fd > max_fd)
  34       max_fd = fds[i].fd;
  35
  36   size_t fds_size = howmany (max_fd + 1, NFDBITS) * sizeof (fd_mask);
  37
  38   read_fds = (fd_set *) alloca (fds_size);
  39   write_fds = (fd_set *) alloca (fds_size);
  40   except_fds = (fd_set *) alloca (fds_size);
  41
  42   if (!read_fds || !write_fds || !except_fds)
  43     {
  44       set_errno (EINVAL);       /* According to SUSv3. */
  45       return -1;
  46     }
  47
  48   memset (read_fds, 0, fds_size);
  49   memset (write_fds, 0, fds_size);
  50   memset (except_fds, 0, fds_size);
  51
  52   for (unsigned int i = 0; i < nfds; ++i)
  53     {
  54       fds[i].revents = 0;
  55       if (!cygheap->fdtab.not_open (fds[i].fd))
  56         {
  57           if (fds[i].events & POLLIN)
  58             FD_SET(fds[i].fd, read_fds);
  59           if (fds[i].events & POLLOUT)
  60             FD_SET(fds[i].fd, write_fds);
  61           if (fds[i].events & POLLPRI)
  62             FD_SET(fds[i].fd, except_fds);
  63         }
  64       else if (fds[i].fd >= 0)
  65         {
  66           ++invalid_fds;
  67           fds[i].revents = POLLNVAL;
  68         }
  69     }
  70
  71   /* Invalid fds? */
  72   if (invalid_fds > 0)
  73     {
  74       /* Only invalid fds?  Return. */
  75       if ((nfds_t) invalid_fds == nfds)
  76         return invalid_fds;
  77       /* POSIX doesn't explicitely define this behaviour, but on Linux,
  78          the timeout is set to 0 if an error occurs, and POLLNVAL is one
  79          of these errors.  So, for Linux-compatibility's sake... */
  80       tv.tv_sec = tv.tv_usec = 0;
  81     }
  82
  83   int ret = cygwin_select (max_fd + 1, read_fds, write_fds, except_fds,
  84                            timeout < 0 ? NULL : &tv);
  85   /* timeout, signal, whatever?  Return.  If invalid fds exist, return with
  86      their number. */
  87   if (ret <= 0)
  88     return invalid_fds ?: ret;
  89
  90   /* Set revents fields and count fds with non-zero revents fields for
  91      return value. */
  92   ret = 0;
  93   for (unsigned int i = 0; i < nfds; ++i)
  94     {
  95       if (fds[i].fd >= 0 && fds[i].revents != POLLNVAL)
  96         {
  97           fhandler_socket_wsock *sock;
  98
  99           /* Check if the descriptor has been closed, or if shutdown for the
 100              read side has been called on a socket. */
 101           if (cygheap->fdtab.not_open (fds[i].fd)
 102               || ((sock = cygheap->fdtab[fds[i].fd]->is_wsock_socket ())
 103                   && sock->saw_shutdown_read ()))
 104             fds[i].revents = POLLHUP;
 105           else
 106             {
 107               if ((fds[i].events & POLLIN) && FD_ISSET(fds[i].fd, read_fds))
 108                 /* This should be sufficient for sockets, too.  Using
 109                    MSG_PEEK, as before, can be considered dangerous at
 110                    best.  Quote from W. Richard Stevens: "The presence
 111                    of an error can be considered either normal data or
 112                    an error (POLLERR).  In either case, a subsequent read
 113                    will return -1 with errno set to the appropriate value."
 114                    So it looks like there's actually no good reason to
 115                    return POLLERR. */
 116                 fds[i].revents |= POLLIN;
 117               /* Handle failed connect.  A failed connect implicitly sets
 118                  POLLOUT, if requested, but it doesn't set POLLIN. */
 119               if ((fds[i].events & POLLIN)
 120                   && (sock = cygheap->fdtab[fds[i].fd]->is_wsock_socket ())
 121                   && sock->connect_state () == connect_failed)
 122                 fds[i].revents |= (POLLIN | POLLERR);
 123               else
 124                 {
 125                   if ((fds[i].events & POLLOUT)
 126                       && FD_ISSET(fds[i].fd, write_fds))
 127                     fds[i].revents |= POLLOUT;
 128                   if ((fds[i].events & POLLPRI)
 129                       && FD_ISSET(fds[i].fd, except_fds))
 130                     fds[i].revents |= POLLPRI;
 131                 }
 132             }
 133           if (fds[i].revents)
 134             ++ret;
 135         }
 136     }
 137   /* Number of fds with event includes the invalid fds. */
 138   return ret + invalid_fds;
 139 }
 140
 141 extern "C" int
 142 ppoll (struct pollfd *fds, nfds_t nfds, const struct timespec *timeout_ts,
 143        const sigset_t *sigmask)
 144 {
 145   int timeout;
 146   sigset_t oldset = _my_tls.sigmask;
 147
 148   __try
 149     {
 150       timeout = (timeout_ts == NULL)
 151                 ? -1
 152                 : (timeout_ts->tv_sec * 1000 + timeout_ts->tv_nsec / 1000000);
 153       if (sigmask)
 154         set_signal_mask (_my_tls.sigmask, *sigmask);
 155       int ret = poll (fds, nfds, timeout);
 156       if (sigmask)
 157         set_signal_mask (_my_tls.sigmask, oldset);
 158       return ret;
 159     }
 160   __except (EFAULT) {}
 161   __endtry
 162   return -1;
 163 }