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%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
-module(sys_sp2).
-export([start_link/1]).
-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]]).
alloc() ->
?MODULE ! {self(), alloc},
receive
{?MODULE, Res} ->
Res
end.
free(Ch) ->
?MODULE ! {free, Ch},
ok.
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)
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) ->
{_Allocated=[], _Free=lists:seq(1,NumCh)}.
alloc({_, []}) ->
{error, "no channels available"};
alloc({Allocated, [H|T]}) ->
{H, {[H|Allocated], T}}.
free(Ch, {Alloc, Free}=Channels) ->
case lists:member(Ch, Alloc) of
true ->
{lists:delete(Ch, Alloc), [Ch|Free]};
false ->
Channels
end.
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