189 lines
5.9 KiB
Groff
189 lines
5.9 KiB
Groff
'\"
|
|
'\" Copyright (c)1996-2002 by Hartmut Brandt
|
|
'\" All rights reserved.
|
|
'\"
|
|
'\" Author: Hartmut Brandt
|
|
'\"
|
|
'\" Redistribution of this software and documentation and use in source and
|
|
'\" binary forms, with or without modification, are permitted provided that
|
|
'\" the following conditions are met:
|
|
'\"
|
|
'\" 1. Redistributions of source code or documentation must retain the above
|
|
'\" copyright notice, this list of conditions and the following disclaimer.
|
|
'\" 2. Redistributions in binary form must reproduce the above copyright
|
|
'\" notice, this list of conditions and the following disclaimer in the
|
|
'\" documentation and/or other materials provided with the distribution.
|
|
'\"
|
|
'\" THIS SOFTWARE AND DOCUMENTATION IS PROVIDED BY THE AUTHOR
|
|
'\" AND ITS CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
|
|
'\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
|
|
'\" FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
|
|
'\" THE AUTHOR OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
'\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
'\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
|
|
'\" OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
|
|
'\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
|
|
'\" NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
|
|
'\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
'\"
|
|
'\" $Begemot: libbegemot/rpoll.man,v 1.4 2004/09/21 15:59:00 brandt Exp $
|
|
'\"
|
|
.TH rpoll l "21 Oct 1996" "BEGEMOT" "BEGEMOT Library"
|
|
.SH NAME
|
|
rpoll - callback functions for file descriptors and timers
|
|
.SH SYNOPSIS
|
|
.LP
|
|
.B "# include <rpoll.h>"
|
|
.LP
|
|
.BR "typedef void (*poll_f)(int " "fd" ", int " "mask" ", void *" "arg);"
|
|
.br
|
|
.BR "typedef void (*timer_f)(int " "tid" ", void *" "arg);"
|
|
.LP
|
|
.BR "int poll_register(int " "fd" ", poll_f "
|
|
.RB "func" ", void *" "arg" ", int " "mask" ");"
|
|
.LP
|
|
.BR "void poll_unregister(int " "handle" ");"
|
|
.LP
|
|
.BR "int poll_start_timer(u_int " "msecs" ", int " "repeat" ", timer_f " "func,"
|
|
.if n .ti +.5i
|
|
.BR "void *" "arg);"
|
|
.LP
|
|
.BR "void poll_stop_timer(int " "handle" ");"
|
|
.LP
|
|
.BR "void poll_dispatch(int " "wait" ");"
|
|
.SH DESCRIPTION
|
|
Many programs need to read from several file descriptors at the same time.
|
|
Typically in these programs one of
|
|
.BR select (3c)
|
|
or
|
|
.BR poll (2)
|
|
is used.
|
|
These calls are however clumsy to use and the usage of one of these calls is
|
|
probably not portable to other systems - not all systems support both calls.
|
|
.LP
|
|
The
|
|
.BR rpoll (l)
|
|
family of functions is designed to overcome these restrictions.
|
|
They support the well known and understood technique of event driven
|
|
programing and, in addition to
|
|
.BR select (3c)
|
|
and
|
|
.BR poll (2)
|
|
also support timers.
|
|
.LP
|
|
Each event on a file descriptor or each timer event is translated into a call to a user
|
|
defined callback function. These functions need to be registered.
|
|
A file descriptor is registered with
|
|
.BR poll_register .
|
|
.I fd
|
|
is the file descriptor to watch,
|
|
.I mask
|
|
is an event mask.
|
|
It may be any combination of
|
|
.B POLL_IN
|
|
to get informed, when input on the file descriptor is possible,
|
|
.B POLL_OUT
|
|
to get informed, when output is possible or
|
|
.B POLL_EXCEPT
|
|
to get informed, when an exceptional condition occures.
|
|
An example of an exceptional condition is the arrival of urgent data.
|
|
(Note, that an end of file condition is signaled via POLL_IN).
|
|
.I func
|
|
is the user function to be called and
|
|
.I arg
|
|
is a user supplied argument for this function.
|
|
The callback functions is called with the file descriptor, a mask
|
|
describing the actual events (from the set supplied in the registration) and
|
|
the user argument.
|
|
.B poll_register
|
|
returns a handle, which may be used later to de-register the file descriptor.
|
|
A file descriptor may be registered more than once, if the function, the user arguments
|
|
or both differ in the call to
|
|
.BR poll_register .
|
|
If
|
|
.I func
|
|
and
|
|
.I arg
|
|
are the same, then no new registration is done, instead the event mask of the registration
|
|
is changed to reflect the new mask.
|
|
.LP
|
|
A registered file descriptor may be de-registered by calling
|
|
.B poll_unregister
|
|
with the handle returned by
|
|
.BR poll_register .
|
|
.LP
|
|
A timer is created with
|
|
.BR poll_start_timer .
|
|
.I msecs
|
|
is the number of milliseconds, after which the timer event will be generated.
|
|
.I repeat
|
|
selects one-short behavior (if 0) or a repeatable timer (if not 0). A one-short timer
|
|
will automatically unregistered after expiry.
|
|
.I func
|
|
is the user function which will be called with a timer id and the user supplied
|
|
.IR arg .
|
|
.B poll_start_timer
|
|
returnes a timer id, which may be used to cancel the timer with
|
|
.BR poll_stop_timer .
|
|
A one-short timer should be canceled only if it has not yet fired.
|
|
.LP
|
|
.B poll_dispatch
|
|
must be called to actually dispatch events.
|
|
.I wait
|
|
is a flag, which should be 0, if only a poll should be done. In this case, the function returns,
|
|
after polling the registered file descriptors and timers. If
|
|
.I wait
|
|
is not 0,
|
|
.B poll_dispatch
|
|
waits until an event occures. All events are dispatch (i.e. callback functions called) and
|
|
.B poll_dispatch returns.
|
|
.LP
|
|
Typical use is:
|
|
.LP
|
|
.RS
|
|
.nf
|
|
.ft 3
|
|
while(1)
|
|
poll_dispatch(1);
|
|
.ft 1
|
|
.fi
|
|
.RE
|
|
.SH "SEE ALSO"
|
|
.BR poll (2), select (3C)
|
|
.SH "RETURN VALUES"
|
|
.B poll_register
|
|
and
|
|
.B poll_start_timer
|
|
return a handle which may be used to unregister the file descriptor or cancel the timer.
|
|
.LP
|
|
Both functions and
|
|
.B poll_dispatch
|
|
call
|
|
.BR xrealloc (l)
|
|
and can end in
|
|
.BR panic (l).
|
|
.SH "ERRORS"
|
|
System call or memory allocation errors are fatal and are handle by calling
|
|
.BR panic (l).
|
|
The one exception is a return of EINTR from
|
|
.BR select (3c)
|
|
or
|
|
.BR poll (2)
|
|
in
|
|
.BR poll_dispatch .
|
|
In this case
|
|
.B poll_dispatch
|
|
simply returns.
|
|
.SH "BUGS"
|
|
Obscure sequences of
|
|
.B poll_start_timer
|
|
and
|
|
.B poll_stop_timer
|
|
in callback functions may probably break the code.
|
|
.LP
|
|
The semantics of
|
|
.B POLL_EXCEPT
|
|
are not clear.
|
|
.SH AUTHORS
|
|
Hartmut Brandt, harti@freebsd.org
|