unsigned long int nfds;
nfds_t nfds;
__poll (fds, nfds, timeout)     struct pollfd *fds;     unsigned long int nfds;     int timeout;{  static int max_fd_size;  struct timeval tv;  fd_set *rset, *wset, *xset;  struct pollfd *f;  int ready;  int maxfd = 0;  int bytes;  if (!max_fd_size)    max_fd_size = __getdtablesize ();  bytes = howmany (max_fd_size, __NFDBITS);  rset = alloca (bytes);  wset = alloca (bytes);  xset = alloca (bytes);  /* We can't call FD_ZERO, since FD_ZERO only works with sets     of exactly __FD_SETSIZE size.  */  __bzero (rset, bytes);  __bzero (wset, bytes);  __bzero (xset, bytes);  for (f = fds; f < &fds[nfds]; ++f)    {      f->revents = 0;      if (f->fd >= 0)	{	  if (f->fd >= max_fd_size)	    {	      /* The user provides a file descriptor number which is higher		 than the maximum we got from the `getdtablesize' call.		 Maybe this is ok so enlarge the arrays.  */	      fd_set *nrset, *nwset, *nxset;	      int nbytes;	      max_fd_size = roundup (f->fd, __NFDBITS);	      nbytes = howmany (max_fd_size, __NFDBITS);	      nrset = alloca (nbytes);	      nwset = alloca (nbytes);	      nxset = alloca (nbytes);	      __bzero ((char *) nrset + bytes, nbytes - bytes);	      __bzero ((char *) nwset + bytes, nbytes - bytes);	      __bzero ((char *) nxset + bytes, nbytes - bytes);	      rset = memcpy (nrset, rset, bytes);	      wset = memcpy (nwset, wset, bytes);	      xset = memcpy (nxset, xset, bytes);	      bytes = nbytes;	    }	  if (f->events & POLLIN)	    FD_SET (f->fd, rset);	  if (f->events & POLLOUT)	    FD_SET (f->fd, wset);	  if (f->events & POLLPRI)	    FD_SET (f->fd, xset);	  if (f->fd > maxfd && (f->events & (POLLIN|POLLOUT|POLLPRI)))	    maxfd = f->fd;	}    }  tv.tv_sec = timeout / 1000;  tv.tv_usec = (timeout % 1000) * 1000;  while (1)    {      ready = __select (maxfd + 1, rset, wset, xset,			timeout == -1 ? NULL : &tv);      /* It might be that one or more of the file descriptors is invalid.	 We now try to find and mark them and then try again.  */      if (ready == -1 && errno == EBADF)	{	  fd_set *sngl_rset = alloca (bytes);	  fd_set *sngl_wset = alloca (bytes);	  fd_set *sngl_xset = alloca (bytes);	  struct timeval sngl_tv;	  /* Clear the original set.  */	  __bzero (rset, bytes);	  __bzero (wset, bytes);	  __bzero (xset, bytes);	  /* This means we don't wait for input.  */	  sngl_tv.tv_sec = 0;	  sngl_tv.tv_usec = 0;	  maxfd = -1;	  /* Reset the return value.  */	  ready = 0;	  for (f = fds; f < &fds[nfds]; ++f)	    if (f->fd != -1 && (f->events & (POLLIN|POLLOUT|POLLPRI))		&& (f->revents & POLLNVAL) == 0)	      {		int n;		__bzero (sngl_rset, bytes);		__bzero (sngl_wset, bytes);		__bzero (sngl_xset, bytes);		if (f->events & POLLIN)		  FD_SET (f->fd, sngl_rset);		if (f->events & POLLOUT)		  FD_SET (f->fd, sngl_wset);		if (f->events & POLLPRI)		  FD_SET (f->fd, sngl_xset);		n = __select (f->fd + 1, sngl_rset, sngl_wset, sngl_xset,			      &sngl_tv);		if (n != -1)		  {		    /* This descriptor is ok.  */		    if (f->events & POLLIN)		      FD_SET (f->fd, rset);		    if (f->events & POLLOUT)		      FD_SET (f->fd, wset);		    if (f->events & POLLPRI)		      FD_SET (f->fd, xset);		    if (f->fd > maxfd)		      maxfd = f->fd;		    if (n > 0)		      /* Count it as being available.  */		      ++ready;		  }		else if (errno == EBADF)		  f->revents |= POLLNVAL;	      }	  /* Try again.  */	  continue;	}      break;    }  if (ready > 0)    for (f = fds; f < &fds[nfds]; ++f)      {	if (f->fd >= 0)	  {	    if (FD_ISSET (f->fd, rset))	      f->revents |= POLLIN;	    if (FD_ISSET (f->fd, wset))	      f->revents |= POLLOUT;	    if (FD_ISSET (f->fd, xset))	      f->revents |= POLLPRI;	  }      }  return ready;}