/usr/share/Yap/broadcast.pl is in yap 6.2.2-6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 | /* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: wielemak@science.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2006, University of Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(broadcast,
[ listen/3, % Listener x Templ x Goal
listen/2, % Templ x Goal
unlisten/1, % Listener
unlisten/2, % Listener x Templ
unlisten/3, % Listener x Templ x Goal
listening/3, % Listener x Templ x Goal
broadcast/1, % Templ
broadcast_request/1 % Templ
]).
:- meta_predicate
listen(+, :),
listen(+, +, :),
unlisten(+, +, :).
:- dynamic
listener/4.
/** <module> Event service
Generic broadcasting service. Broadcasts are made using the predicate
broadcast(+Templ). All registered `listeners' will have their goal
called. Success or failure of this is ignored. The listener can not bind
arguments.
This library is particulary useful for disconnecting modules in an
application. Modules can broadcast events such as changes, anticipating
other modules need to react on such changes. For example, settings.pl
broadcasts changes to settings, allowing dependent modules to react on
changes:
==
:- listing(setting(changed(http:workers, New)),
change_workers(New)).
change_workers(New) :-
setting(http:port, Port),
http_workers(Port, New).
==
*/
%% listen(+Listener, +Templ, :Goal) is det.
%% listen(+Templ, :Goal) is det.
%
% Open a channel for listening for events of the given `Templ'.
listen(Listener0, Templ, Goal) :-
canonical_listener(Listener0, Listener),
strip_module(Goal, Module, TheGoal),
assert_listener(Templ, Listener, Module, TheGoal).
listen(Templ, Goal) :-
strip_module(Goal, Module, TheGoal),
assert_listener(Templ, Module, Module, TheGoal).
%% unlisten(+Listener) is det.
%% unlisten(+Listener, +Templ) is det.
%% unlisten(+Listener, +Templ, :Goal) is det.
%
% Destroy a channel. All arguments may be variables, removing the
% all matching listening channals.
unlisten(Listener0) :-
canonical_listener(Listener0, Listener),
retractall(listener(_, Listener, _, _)).
unlisten(Listener0, Templ) :-
canonical_listener(Listener0, Listener),
retractall(listener(Templ, Listener, _, _)).
unlisten(Listener0, Templ, Goal) :-
canonical_listener(Listener0, Listener),
( var(Goal)
-> true
; strip_module(Goal, Module, TheGoal)
),
retract_listener(Templ, Listener, Module, TheGoal).
%% listening(?Listener, ?Templ, ?Goal) is nondet.
%
% returns currently open channels
listening(Listener0, Templ, Module:Goal) :-
canonical_listener(Listener0, Listener),
listener(Templ, Listener, Module, Goal).
%% broadcast(+Templ) is det.
%
% Broadcast given event.
broadcast(Templ) :-
( listener(Templ, _Listener, Module, Goal),
( Module:Goal
-> fail
)
; true
).
%% broadcast_request(+Templ) is nonet.
%
% Broadcast given event till accepted. Succeeds then, fail if no
% listener accepts the call. Bindings made by the listener goal
% are maintained. May be used to make broadcast requests.
broadcast_request(Templ) :-
listener(Templ, _Listener, Module, Goal),
Module:Goal.
% {assert,retract}_listener(+Templ, +Listener, +Module, +Goal)
%
% Implemented as sub-predicate to ensure storage in this module.
% Second registration is ignored. Is this ok? It avoids problems
% using multiple registration of global listen channels.
assert_listener(Templ, Listener, Module, TheGoal) :-
listener(Templ, Listener, Module, TheGoal), !.
assert_listener(Templ, Listener, Module, TheGoal) :-
asserta(listener(Templ, Listener, Module, TheGoal)).
retract_listener(Templ, Listener, Module, TheGoal) :-
retractall(listener(Templ, Listener, Module, TheGoal)).
%% canonical_listener(+Raw, -Canonical)
%
% Entry for later optimization.
canonical_listener(Templ, Templ).
/*******************************
* GOAL EXPANSION *
*******************************/
:- multifile
user:goal_expansion/2.
user:goal_expansion(listen(L,T,G0), listen(L,T,G)) :-
expand_goal(G0, G).
user:goal_expansion(listen(T,G0), listen(T,G)) :-
expand_goal(G0, G).
user:goal_expansion(unlisten(L,T,G0), unlisten(L,T,G)) :-
expand_goal(G0, G).
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