io/sys/poll.h

   1 /* Compatibility definitions for System V `poll' interface.
   2 Copyright (C) 1994 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
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, 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 /* Event types always implicitly polled for.  These bits need not be set in
  41    `events', but they will appear in `revents' to indicate the status of
  42    the file descriptor.  */
  43 #define POLLERR         010             /* Error condition.  */
  44 #define POLLHUP         020             /* Hung up.  */
  45 #define POLLNVAL        040             /* Invalid polling request.  */
  46
  47 /* Canonical number of polling requests to read in at a time in poll.  */
  48 #define NPOLLFILE       30
  49
  50
  51 __BEGIN_DECLS
  52
  53 /* Poll the file descriptors described by the NFDS structures starting at
  54    FDS.  If TIMEOUT is nonzero and not -1, allow TIMEOUT milliseconds for
  55    an event to occur; if TIMEOUT is -1, block until an event occurs.
  56    Returns the number of file descriptors with events, zero if timed out,
  57    or -1 for errors.  */
  58
  59 extern int poll __P ((struct pollfd *__fds, unsigned long int __nfds,
  60                       int __timeout));
  61
  62 __END_DECLS
  63
  64 #endif  /* sys/poll.h */
  65