%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2013. 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%
%%
-module(sys_sp2).
-export([start_link/1, stop/0]).
-export([alloc/0, free/1]).
-export([init/1]).
-export([system_continue/3, system_terminate/4,
write_debug/3]).
%% Implements the ch4 example from the Design Principles doc. Same as
%% sys_sp1 except this module does not export system_get_state/1 or
%% system_replace_state/2
start_link(NumCh) ->
proc_lib:start_link(?MODULE, init, [[self(),NumCh]]).
stop() ->
?MODULE ! stop,
ok.
alloc() ->
?MODULE ! {self(), alloc},
receive
{?MODULE, Res} ->
Res
end.
free(Ch) ->
?MODULE ! {free, Ch},
ok.
%% can't use 2-tuple for state here as we do in sys_sp1, since the 2-tuple
%% is not compatible with the backward compatibility handling for
%% sys:get_state in sys.erl
-record(state, {alloc,free}).
init([Parent,NumCh]) ->
register(?MODULE, self()),
Chs = channels(NumCh),
Deb = sys:debug_options([]),
proc_lib:init_ack(Parent, {ok, self()}),
loop(Chs, Parent, Deb).
loop(Chs, Parent, Deb) ->
receive
{From, alloc} ->
Deb2 = sys:handle_debug(Deb, fun write_debug/3,
?MODULE, {in, alloc, From}),
{Ch, Chs2} = alloc(Chs),
From ! {?MODULE, Ch},
Deb3 = sys:handle_debug(Deb2, fun write_debug/3,
?MODULE, {out, {?MODULE, Ch}, From}),
loop(Chs2, Parent, Deb3);
{free, Ch} ->
Deb2 = sys:handle_debug(Deb, fun write_debug/3,
?MODULE, {in, {free, Ch}}),
Chs2 = free(Ch, Chs),
loop(Chs2, Parent, Deb2);
{system, From, Request} ->
sys:handle_system_msg(Request, From, Parent,
?MODULE, Deb, Chs);
stop ->
sys:handle_debug(Deb, fun write_debug/3,
?MODULE, {in, stop}),
ok
end.
system_continue(Parent, Deb, Chs) ->
loop(Chs, Parent, Deb).
system_terminate(Reason, _Parent, _Deb, _Chs) ->
exit(Reason).
write_debug(Dev, Event, Name) ->
io:format(Dev, "~p event = ~p~n", [Name, Event]).
channels(NumCh) ->
#state{alloc=[], free=lists:seq(1,NumCh)}.
alloc(#state{free=[]}=Channels) ->
{{error, "no channels available"}, Channels};
alloc(#state{alloc=Allocated, free=[H|T]}) ->
{H, #state{alloc=[H|Allocated], free=T}}.
free(Ch, #state{alloc=Alloc, free=Free}=Channels) ->
case lists:member(Ch, Alloc) of
true ->
#state{alloc=lists:delete(Ch, Alloc), free=[Ch|Free]};
false ->
Channels
end.
