%%
%% %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) ->
?UNEXPECTED([Req, From]),
{reply, nok, State}.
%%% ----------------------------------------------------------
%%% # handle_cast(Request, State)
%%% ----------------------------------------------------------
handle_cast(Msg, State)->
?UNEXPECTED([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) ->
?UNEXPECTED([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).
