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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+%%
+%% The module implements a simple term -> pid registry.
+%%
+
+-module(diameter_reg).
+-compile({no_auto_import, [monitor/2]}).
+
+-behaviour(gen_server).
+
+-export([add/1,
+ add_new/1,
+ del/1,
+ repl/2,
+ match/1]).
+
+-export([start_link/0]).
+
+%% gen_server callbacks
+-export([init/1,
+ terminate/2,
+ handle_call/3,
+ handle_cast/2,
+ handle_info/2,
+ code_change/3]).
+
+%% test
+-export([pids/0,
+ terms/0]).
+
+%% debug
+-export([state/0,
+ uptime/0]).
+
+-include("diameter_internal.hrl").
+
+-define(SERVER, ?MODULE).
+-define(TABLE, ?MODULE).
+
+%% Table entry used to keep from starting more than one monitor on the
+%% same process. This isn't a problem but there's no point in starting
+%% multiple monitors if we can avoid it. Note that we can't have a 2-tuple
+%% keyed on Pid since a registered term can be anything. Want the entry
+%% keyed on Pid so that lookup is fast.
+-define(MONITOR(Pid, MRef), {Pid, monitor, MRef}).
+
+%% Table entry containing the Term -> Pid mapping.
+-define(MAPPING(Term, Pid), {Term, Pid}).
+
+-record(state, {id = now()}).
+
+%%% ----------------------------------------------------------
+%%% # add(T)
+%%%
+%%% Input: Term = term()
+%%%
+%%% Output: true
+%%%
+%%% Description: Associate the specified term with self(). The list of pids
+%%% having this or other assocations can be retrieved using
+%%% match/1.
+%%%
+%%% An association is removed when the calling process dies
+%%% or as a result of calling del/1. Adding the same term
+%%% more than once is equivalent to adding it exactly once.
+%%%
+%%% Note that since match/1 takes a pattern as argument,
+%%% specifying a term that contains match variables is
+%%% probably not a good idea
+%%% ----------------------------------------------------------
+
+-spec add(any())
+ -> true.
+
+add(T) ->
+ call({add, fun ets:insert/2, T, self()}).
+
+%%% ----------------------------------------------------------
+%%% # add_new(T)
+%%%
+%%% Input: T = term()
+%%%
+%%% Output: true | false
+%%%
+%%% Description: Like add/1 but only one process is allowed to have the
+%%% the association, false being returned if an association
+%%% already exists.
+%%% ----------------------------------------------------------
+
+-spec add_new(any())
+ -> boolean().
+
+add_new(T) ->
+ call({add, fun insert_new/2, T, self()}).
+
+%%% ----------------------------------------------------------
+%%% # repl(T, NewT)
+%%%
+%%% Input: T, NewT = term()
+%%%
+%%% Output: true | false
+%%%
+%%% Description: Like add/1 but only replace an existing association on T,
+%%% false being returned if it doesn't exist.
+%%% ----------------------------------------------------------
+
+-spec repl(any(), any())
+ -> boolean().
+
+repl(T, U) ->
+ call({repl, T, U, self()}).
+
+%%% ----------------------------------------------------------
+%%% # del(Term)
+%%%
+%%% Input: Term = term()
+%%%
+%%% Output: true
+%%%
+%%% Description: Remove any existing association of Term with self().
+%%% ----------------------------------------------------------
+
+-spec del(any())
+ -> true.
+
+del(T) ->
+ call({del, T, self()}).
+
+%%% ----------------------------------------------------------
+%%% # match(Pat)
+%%%
+%%% Input: Pat = pattern in the sense of ets:match_object/2.
+%%%
+%%% Output: list of {Term, Pid}
+%%%
+%%% Description: Return the list of associations whose Term, as specified
+%%% to add/1 or add_new/1, matches the specified pattern.
+%%%
+%%% Note that there's no guarantee that the returned processes
+%%% are still alive. (Although one that isn't will soon have
+%%% its associations removed.)
+%%% ----------------------------------------------------------
+
+-spec match(tuple())
+ -> [{term(), pid()}].
+
+match(Pat) ->
+ ets:match_object(?TABLE, ?MAPPING(Pat, '_')).
+
+%% ---------------------------------------------------------
+%% EXPORTED INTERNAL FUNCTIONS
+%% ---------------------------------------------------------
+
+start_link() ->
+ ServerName = {local, ?SERVER},
+ Options = [{spawn_opt, diameter_lib:spawn_opts(server, [])}],
+ gen_server:start_link(ServerName, ?MODULE, [], Options).
+
+state() ->
+ call(state).
+
+uptime() ->
+ call(uptime).
+
+%% pids/0
+%%
+%% Output: list of {Pid, [Term, ...]}
+
+pids() ->
+ to_list(fun swap/1).
+
+to_list(Fun) ->
+ ets:foldl(fun(T,A) -> acc(Fun, T, A) end, orddict:new(), ?TABLE).
+
+acc(Fun, ?MAPPING(Term, Pid), Dict) ->
+ append(Fun({Term, Pid}), Dict);
+acc(_, _, Dict) ->
+ Dict.
+
+append({K,V}, Dict) ->
+ orddict:append(K, V, Dict).
+
+id(T) -> T.
+
+%% terms/0
+%%
+%% Output: list of {Term, [Pid, ...]}
+
+terms() ->
+ to_list(fun id/1).
+
+swap({X,Y}) -> {Y,X}.
+
+%%% ----------------------------------------------------------
+%%% # init(Role)
+%%%
+%%% Output: {ok, State}
+%%% ----------------------------------------------------------
+
+init(_) ->
+ ets:new(?TABLE, [bag, named_table]),
+ {ok, #state{}}.
+
+%%% ----------------------------------------------------------
+%%% # handle_call(Request, From, State)
+%%% ----------------------------------------------------------
+
+handle_call({add, Fun, Key, Pid}, _, State) ->
+ B = Fun(?TABLE, {Key, Pid}),
+ monitor(B andalso no_monitor(Pid), Pid),
+ {reply, B, State};
+
+handle_call({del, Key, Pid}, _, State) ->
+ {reply, ets:delete_object(?TABLE, ?MAPPING(Key, Pid)), State};
+
+handle_call({repl, T, U, Pid}, _, State) ->
+ MatchSpec = [{?MAPPING('$1', Pid),
+ [{'=:=', '$1', {const, T}}],
+ ['$_']}],
+ {reply, repl(ets:select(?TABLE, MatchSpec), U, Pid), State};
+
+handle_call(state, _, State) ->
+ {reply, State, State};
+
+handle_call(uptime, _, #state{id = Time} = State) ->
+ {reply, diameter_lib:now_diff(Time), State};
+
+handle_call(_Req, _From, State) ->
+ {reply, nok, State}.
+
+%%% ----------------------------------------------------------
+%%% # handle_cast(Request, State)
+%%% ----------------------------------------------------------
+
+handle_cast(Msg, State)->
+ warning_msg("received unexpected message:~n~w", [Msg]),
+ {noreply, State}.
+
+%%% ----------------------------------------------------------
+%%% # handle_info(Request, State)
+%%% ----------------------------------------------------------
+
+handle_info({'DOWN', MRef, process, Pid, _}, State) ->
+ ets:delete_object(?TABLE, ?MONITOR(Pid, MRef)),
+ ets:match_delete(?TABLE, ?MAPPING('_', Pid)),
+ {noreply, State};
+
+handle_info(Info, State) ->
+ warning_msg("received unknown info:~n~w", [Info]),
+ {noreply, State}.
+
+%%% ----------------------------------------------------------
+%%% # terminate(Reason, State)
+%%% ----------------------------------------------------------
+
+terminate(_Reason, _State)->
+ ok.
+
+%%% ----------------------------------------------------------
+%%% # code_change(OldVsn, State, Extra)
+%%% ----------------------------------------------------------
+
+code_change(_OldVsn, State, _Extra) ->
+ {ok, State}.
+
+%% ---------------------------------------------------------
+%% INTERNAL FUNCTIONS
+%% ---------------------------------------------------------
+
+monitor(true, Pid) ->
+ ets:insert(?TABLE, ?MONITOR(Pid, erlang:monitor(process, Pid)));
+monitor(false, _) ->
+ ok.
+
+%% Do we need a monitor for the specified Pid?
+no_monitor(Pid) ->
+ [] == ets:match_object(?TABLE, ?MONITOR(Pid, '_')).
+
+%% insert_new/2
+
+insert_new(?TABLE, {Key, _} = T) ->
+ flush(ets:lookup(?TABLE, Key)),
+ ets:insert_new(?TABLE, T).
+
+%% Remove any processes that are dead but for which we may not have
+%% received 'DOWN' yet. This is to ensure that add_new can be used
+%% to register a unique name each time a process restarts.
+flush(List) ->
+ lists:foreach(fun({_,P} = T) ->
+ del(erlang:is_process_alive(P), T)
+ end,
+ List).
+
+del(Alive, T) ->
+ Alive orelse ets:delete_object(?TABLE, T).
+
+%% repl/3
+
+repl([?MAPPING(_, Pid) = M], Key, Pid) ->
+ ets:delete_object(?TABLE, M),
+ true = ets:insert(?TABLE, ?MAPPING(Key, Pid));
+repl([], _, _) ->
+ false.
+
+%% call/1
+
+call(Request) ->
+ gen_server:call(?SERVER, Request, infinity).
+
+%% warning_msg/2
+
+warning_msg(F, A) ->
+ ?diameter_warning("~p: " ++ F, [?MODULE | A]).
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