poll.h

SIP（Session Initiation Protocol）是由IETF定义

/* Compatibility definitions for System V `poll' interface.
   Copyright (C) 1994, 1996 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#ifndef	_SYS_POLL_H

#define	_SYS_POLL_H	1
/* #include <features.h> */

__BEGIN_DECLS

/* Data structure describing a polling request.  */
struct pollfd
  {
    int fd;			/* File descriptor to poll.  */
    short int events;		/* Types of events poller cares about.  */
    short int revents;		/* Types of events that actually occurred.  */
  };

/* Event types that can be polled for.  These bits may be set in `events'
   to indicate the interesting event types; they will appear in `revents'
   to indicate the status of the file descriptor.  */
#define POLLIN		01              /* There is data to read.  */
#define POLLPRI		02              /* There is urgent data to read.  */
#define POLLOUT		04              /* Writing now will not block.  */

/* Some aliases.  */
#define POLLWRNORM	POLLOUT

/* Event types always implicitly polled for.  These bits need not be set in
   `events', but they will appear in `revents' to indicate the status of
   the file descriptor.  */
#define POLLERR         010             /* Error condition.  */
#define POLLHUP         020             /* Hung up.  */
#define POLLNVAL        040             /* Invalid polling request.  */

/* Canonical number of polling requests to read in at a time in poll.  */
#define NPOLLFILE	30


/* Poll the file descriptors described by the NFDS structures starting at
   FDS.  If TIMEOUT is nonzero and not -1, allow TIMEOUT milliseconds for
   an event to occur; if TIMEOUT is -1, block until an event occurs.
   Returns the number of file descriptors with events, zero if timed out,
   or -1 for errors.  */

extern int poll __P ((struct pollfd *__fds, unsigned long int __nfds,
		      int __timeout));

__END_DECLS

#endif	/* _SYS_POLL_H */