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