io/sys/poll.h

   1 /* Compatibility definitions for System V `poll' interface.
   2    Copyright (C) 1994, 1996 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #ifndef _SYS_POLL_H
  21 #define _SYS_POLL_H
  22
  23 #include <sys/cdefs.h>
  24
  25 /* Data structure describing a polling request.  */
  26 struct pollfd
  27   {
  28     int fd;                     /* File descriptor to poll.  */
  29     short int events;           /* Types of events poller cares about.  */
  30     short int revents;          /* Types of events that actually occurred.  */
  31   };
  32
  33 /* Event types that can be polled for.  These bits may be set in `events'
  34    to indicate the interesting event types; they will appear in `revents'
  35    to indicate the status of the file descriptor.  */
  36 #define POLLIN          01              /* There is data to read.  */
  37 #define POLLPRI         02              /* There is urgent data to read.  */
  38 #define POLLOUT         04              /* Writing now will not block.  */
  39
  40 /* Some aliases.  */
  41 #define POLLWRNORM      POLLOUT
  42
  43 /* Event types always implicitly polled for.  These bits need not be set in
  44    `events', but they will appear in `revents' to indicate the status of
  45    the file descriptor.  */
  46 #define POLLERR         010             /* Error condition.  */
  47 #define POLLHUP         020             /* Hung up.  */
  48 #define POLLNVAL        040             /* Invalid polling request.  */
  49
  50 /* Canonical number of polling requests to read in at a time in poll.  */
  51 #define NPOLLFILE       30
  52
  53
  54 __BEGIN_DECLS
  55
  56 /* Poll the file descriptors described by the NFDS structures starting at
  57    FDS.  If TIMEOUT is nonzero and not -1, allow TIMEOUT milliseconds for
  58    an event to occur; if TIMEOUT is -1, block until an event occurs.
  59    Returns the number of file descriptors with events, zero if timed out,
  60    or -1 for errors.  */
  61
  62 extern int poll __P ((struct pollfd *__fds, unsigned long int __nfds,
  63                       int __timeout));
  64
  65 __END_DECLS
  66
  67 #endif  /* sys/poll.h */