%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2010. 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(gen_fsm).
%%%-----------------------------------------------------------------
%%%
%%% This state machine is somewhat more pure than state_lib. It is
%%% still based on State dispatching (one function per state), but
%%% allows a function handle_event to take care of events in all states.
%%% It's not that pure anymore :( We also allow synchronized event sending.
%%%
%%% If the Parent process terminates the Module:terminate/2
%%% function is called.
%%%
%%% The user module should export:
%%%
%%% init(Args)
%%% ==> {ok, StateName, StateData}
%%% {ok, StateName, StateData, Timeout}
%%% ignore
%%% {stop, Reason}
%%%
%%% StateName(Msg, StateData)
%%%
%%% ==> {next_state, NewStateName, NewStateData}
%%% {next_state, NewStateName, NewStateData, Timeout}
%%% {stop, Reason, NewStateData}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% StateName(Msg, From, StateData)
%%%
%%% ==> {next_state, NewStateName, NewStateData}
%%% {next_state, NewStateName, NewStateData, Timeout}
%%% {reply, Reply, NewStateName, NewStateData}
%%% {reply, Reply, NewStateName, NewStateData, Timeout}
%%% {stop, Reason, NewStateData}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% handle_event(Msg, StateName, StateData)
%%%
%%% ==> {next_state, NewStateName, NewStateData}
%%% {next_state, NewStateName, NewStateData, Timeout}
%%% {stop, Reason, Reply, NewStateData}
%%% {stop, Reason, NewStateData}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% handle_sync_event(Msg, From, StateName, StateData)
%%%
%%% ==> {next_state, NewStateName, NewStateData}
%%% {next_state, NewStateName, NewStateData, Timeout}
%%% {reply, Reply, NewStateName, NewStateData}
%%% {reply, Reply, NewStateName, NewStateData, Timeout}
%%% {stop, Reason, Reply, NewStateData}
%%% {stop, Reason, NewStateData}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% handle_info(Info, StateName) (e.g. {'EXIT', P, R}, {nodedown, N}, ...
%%%
%%% ==> {next_state, NewStateName, NewStateData}
%%% {next_state, NewStateName, NewStateData, Timeout}
%%% {stop, Reason, NewStateData}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% terminate(Reason, StateName, StateData) Let the user module clean up
%%% always called when server terminates
%%%
%%% ==> the return value is ignored
%%%
%%%
%%% The work flow (of the fsm) can be described as follows:
%%%
%%% User module fsm
%%% ----------- -------
%%% start -----> start
%%% init <----- .
%%%
%%% loop
%%% StateName <----- .
%%%
%%% handle_event <----- .
%%%
%%% handle__sunc_event <----- .
%%%
%%% handle_info <----- .
%%%
%%% terminate <----- .
%%%
%%%
%%% ---------------------------------------------------
-export([start/3, start/4,
start_link/3, start_link/4,
send_event/2, sync_send_event/2, sync_send_event/3,
send_all_state_event/2,
sync_send_all_state_event/2, sync_send_all_state_event/3,
reply/2,
start_timer/2,send_event_after/2,cancel_timer/1,
enter_loop/4, enter_loop/5, enter_loop/6, wake_hib/6]).
-export([behaviour_info/1]).
%% Internal exports
-export([init_it/6,
system_continue/3,
system_terminate/4,
system_code_change/4,
format_status/2]).
-import(error_logger, [format/2]).
%%% ---------------------------------------------------
%%% Interface functions.
%%% ---------------------------------------------------
-spec behaviour_info(atom()) -> 'undefined' | [{atom(), arity()}].
behaviour_info(callbacks) ->
[{init,1},{handle_event,3},{handle_sync_event,4},{handle_info,3},
{terminate,3},{code_change,4}];
behaviour_info(_Other) ->
undefined.
%%% ---------------------------------------------------
%%% Starts a generic state machine.
%%% start(Mod, Args, Options)
%%% start(Name, Mod, Args, Options)
%%% start_link(Mod, Args, Options)
%%% start_link(Name, Mod, Args, Options) where:
%%% Name ::= {local, atom()} | {global, atom()}
%%% Mod ::= atom(), callback module implementing the 'real' fsm
%%% Args ::= term(), init arguments (to Mod:init/1)
%%% Options ::= [{debug, [Flag]}]
%%% Flag ::= trace | log | {logfile, File} | statistics | debug
%%% (debug == log && statistics)
%%% Returns: {ok, Pid} |
%%% {error, {already_started, Pid}} |
%%% {error, Reason}
%%% ---------------------------------------------------
start(Mod, Args, Options) ->
gen:start(?MODULE, nolink, Mod, Args, Options).
start(Name, Mod, Args, Options) ->
gen:start(?MODULE, nolink, Name, Mod, Args, Options).
start_link(Mod, Args, Options) ->
gen:start(?MODULE, link, Mod, Args, Options).
start_link(Name, Mod, Args, Options) ->
gen:start(?MODULE, link, Name, Mod, Args, Options).
send_event({global, Name}, Event) ->
catch global:send(Name, {'$gen_event', Event}),
ok;
send_event(Name, Event) ->
Name ! {'$gen_event', Event},
ok.
sync_send_event(Name, Event) ->
case catch gen:call(Name, '$gen_sync_event', Event) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, sync_send_event, [Name, Event]}})
end.
sync_send_event(Name, Event, Timeout) ->
case catch gen:call(Name, '$gen_sync_event', Event, Timeout) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, sync_send_event, [Name, Event, Timeout]}})
end.
send_all_state_event({global, Name}, Event) ->
catch global:send(Name, {'$gen_all_state_event', Event}),
ok;
send_all_state_event(Name, Event) ->
Name ! {'$gen_all_state_event', Event},
ok.
sync_send_all_state_event(Name, Event) ->
case catch gen:call(Name, '$gen_sync_all_state_event', Event) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, sync_send_all_state_event, [Name, Event]}})
end.
sync_send_all_state_event(Name, Event, Timeout) ->
case catch gen:call(Name, '$gen_sync_all_state_event', Event, Timeout) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, sync_send_all_state_event,
[Name, Event, Timeout]}})
end.
%% Designed to be only callable within one of the callbacks
%% hence using the self() of this instance of the process.
%% This is to ensure that timers don't go astray in global
%% e.g. when straddling a failover, or turn up in a restarted
%% instance of the process.
%% Returns Ref, sends event {timeout,Ref,Msg} after Time
%% to the (then) current state.
start_timer(Time, Msg) ->
erlang:start_timer(Time, self(), {'$gen_timer', Msg}).
%% Returns Ref, sends Event after Time to the (then) current state.
send_event_after(Time, Event) ->
erlang:start_timer(Time, self(), {'$gen_event', Event}).
%% Returns the remaing time for the timer if Ref referred to
%% an active timer/send_event_after, false otherwise.
cancel_timer(Ref) ->
case erlang:cancel_timer(Ref) of
false ->
receive {timeout, Ref, _} -> 0
after 0 -> false
end;
RemainingTime ->
RemainingTime
end.
%% enter_loop/4,5,6
%% Makes an existing process into a gen_fsm.
%% The calling process will enter the gen_fsm receive loop and become a
%% gen_fsm process.
%% The process *must* have been started using one of the start functions
%% in proc_lib, see proc_lib(3).
%% The user is responsible for any initialization of the process,
%% including registering a name for it.
enter_loop(Mod, Options, StateName, StateData) ->
enter_loop(Mod, Options, StateName, StateData, self(), infinity).
enter_loop(Mod, Options, StateName, StateData, ServerName = {_,_}) ->
enter_loop(Mod, Options, StateName, StateData, ServerName,infinity);
enter_loop(Mod, Options, StateName, StateData, Timeout) ->
enter_loop(Mod, Options, StateName, StateData, self(), Timeout).
enter_loop(Mod, Options, StateName, StateData, ServerName, Timeout) ->
Name = get_proc_name(ServerName),
Parent = get_parent(),
Debug = gen:debug_options(Options),
loop(Parent, Name, StateName, StateData, Mod, Timeout, Debug).
get_proc_name(Pid) when is_pid(Pid) ->
Pid;
get_proc_name({local, Name}) ->
case process_info(self(), registered_name) of
{registered_name, Name} ->
Name;
{registered_name, _Name} ->
exit(process_not_registered);
[] ->
exit(process_not_registered)
end;
get_proc_name({global, Name}) ->
case global:safe_whereis_name(Name) of
undefined ->
exit(process_not_registered_globally);
Pid when Pid =:= self() ->
Name;
_Pid ->
exit(process_not_registered_globally)
end.
get_parent() ->
case get('$ancestors') of
[Parent | _] when is_pid(Parent) ->
Parent;
[Parent | _] when is_atom(Parent) ->
name_to_pid(Parent);
_ ->
exit(process_was_not_started_by_proc_lib)
end.
name_to_pid(Name) ->
case whereis(Name) of
undefined ->
case global:safe_whereis_name(Name) of
undefined ->
exit(could_not_find_registerd_name);
Pid ->
Pid
end;
Pid ->
Pid
end.
%%% ---------------------------------------------------
%%% Initiate the new process.
%%% Register the name using the Rfunc function
%%% Calls the Mod:init/Args function.
%%% Finally an acknowledge is sent to Parent and the main
%%% loop is entered.
%%% ---------------------------------------------------
init_it(Starter, self, Name, Mod, Args, Options) ->
init_it(Starter, self(), Name, Mod, Args, Options);
init_it(Starter, Parent, Name0, Mod, Args, Options) ->
Name = name(Name0),
Debug = gen:debug_options(Options),
case catch Mod:init(Args) of
{ok, StateName, StateData} ->
proc_lib:init_ack(Starter, {ok, self()}),
loop(Parent, Name, StateName, StateData, Mod, infinity, Debug);
{ok, StateName, StateData, Timeout} ->
proc_lib:init_ack(Starter, {ok, self()}),
loop(Parent, Name, StateName, StateData, Mod, Timeout, Debug);
{stop, Reason} ->
proc_lib:init_ack(Starter, {error, Reason}),
exit(Reason);
ignore ->
proc_lib:init_ack(Starter, ignore),
exit(normal);
{'EXIT', Reason} ->
proc_lib:init_ack(Starter, {error, Reason}),
exit(Reason);
Else ->
Error = {bad_return_value, Else},
proc_lib:init_ack(Starter, {error, Error}),
exit(Error)
end.
name({local,Name}) -> Name;
name({global,Name}) -> Name;
name(Pid) when is_pid(Pid) -> Pid.
%%-----------------------------------------------------------------
%% The MAIN loop
%%-----------------------------------------------------------------
loop(Parent, Name, StateName, StateData, Mod, hibernate, Debug) ->
proc_lib:hibernate(?MODULE,wake_hib,
[Parent, Name, StateName, StateData, Mod,
Debug]);
loop(Parent, Name, StateName, StateData, Mod, Time, Debug) ->
Msg = receive
Input ->
Input
after Time ->
{'$gen_event', timeout}
end,
decode_msg(Msg,Parent, Name, StateName, StateData, Mod, Time, Debug, false).
wake_hib(Parent, Name, StateName, StateData, Mod, Debug) ->
Msg = receive
Input ->
Input
end,
decode_msg(Msg, Parent, Name, StateName, StateData, Mod, hibernate, Debug, true).
decode_msg(Msg,Parent, Name, StateName, StateData, Mod, Time, Debug, Hib) ->
case Msg of
{system, From, Req} ->
sys:handle_system_msg(Req, From, Parent, ?MODULE, Debug,
[Name, StateName, StateData, Mod, Time], Hib);
{'EXIT', Parent, Reason} ->
terminate(Reason, Name, Msg, Mod, StateName, StateData, Debug);
_Msg when Debug =:= [] ->
handle_msg(Msg, Parent, Name, StateName, StateData, Mod, Time);
_Msg ->
Debug1 = sys:handle_debug(Debug, fun print_event/3,
{Name, StateName}, {in, Msg}),
handle_msg(Msg, Parent, Name, StateName, StateData,
Mod, Time, Debug1)
end.
%%-----------------------------------------------------------------
%% Callback functions for system messages handling.
%%-----------------------------------------------------------------
system_continue(Parent, Debug, [Name, StateName, StateData, Mod, Time]) ->
loop(Parent, Name, StateName, StateData, Mod, Time, Debug).
-spec system_terminate(term(), _, _, [term(),...]) -> no_return().
system_terminate(Reason, _Parent, Debug,
[Name, StateName, StateData, Mod, _Time]) ->
terminate(Reason, Name, [], Mod, StateName, StateData, Debug).
system_code_change([Name, StateName, StateData, Mod, Time],
_Module, OldVsn, Extra) ->
case catch Mod:code_change(OldVsn, StateName, StateData, Extra) of
{ok, NewStateName, NewStateData} ->
{ok, [Name, NewStateName, NewStateData, Mod, Time]};
Else -> Else
end.
%%-----------------------------------------------------------------
%% Format debug messages. Print them as the call-back module sees
%% them, not as the real erlang messages. Use trace for that.
%%-----------------------------------------------------------------
print_event(Dev, {in, Msg}, {Name, StateName}) ->
case Msg of
{'$gen_event', Event} ->
io:format(Dev, "*DBG* ~p got event ~p in state ~w~n",
[Name, Event, StateName]);
{'$gen_all_state_event', Event} ->
io:format(Dev,
"*DBG* ~p got all_state_event ~p in state ~w~n",
[Name, Event, StateName]);
{timeout, Ref, {'$gen_timer', Message}} ->
io:format(Dev,
"*DBG* ~p got timer ~p in state ~w~n",
[Name, {timeout, Ref, Message}, StateName]);
{timeout, _Ref, {'$gen_event', Event}} ->
io:format(Dev,
"*DBG* ~p got timer ~p in state ~w~n",
[Name, Event, StateName]);
_ ->
io:format(Dev, "*DBG* ~p got ~p in state ~w~n",
[Name, Msg, StateName])
end;
print_event(Dev, {out, Msg, To, StateName}, Name) ->
io:format(Dev, "*DBG* ~p sent ~p to ~w~n"
" and switched to state ~w~n",
[Name, Msg, To, StateName]);
print_event(Dev, return, {Name, StateName}) ->
io:format(Dev, "*DBG* ~p switched to state ~w~n",
[Name, StateName]).
handle_msg(Msg, Parent, Name, StateName, StateData, Mod, _Time) -> %No debug here
From = from(Msg),
case catch dispatch(Msg, Mod, StateName, StateData) of
{next_state, NStateName, NStateData} ->
loop(Parent, Name, NStateName, NStateData, Mod, infinity, []);
{next_state, NStateName, NStateData, Time1} ->
loop(Parent, Name, NStateName, NStateData, Mod, Time1, []);
{reply, Reply, NStateName, NStateData} when From =/= undefined ->
reply(From, Reply),
loop(Parent, Name, NStateName, NStateData, Mod, infinity, []);
{reply, Reply, NStateName, NStateData, Time1} when From =/= undefined ->
reply(From, Reply),
loop(Parent, Name, NStateName, NStateData, Mod, Time1, []);
{stop, Reason, NStateData} ->
terminate(Reason, Name, Msg, Mod, StateName, NStateData, []);
{stop, Reason, Reply, NStateData} when From =/= undefined ->
{'EXIT', R} = (catch terminate(Reason, Name, Msg, Mod,
StateName, NStateData, [])),
reply(From, Reply),
exit(R);
{'EXIT', What} ->
terminate(What, Name, Msg, Mod, StateName, StateData, []);
Reply ->
terminate({bad_return_value, Reply},
Name, Msg, Mod, StateName, StateData, [])
end.
handle_msg(Msg, Parent, Name, StateName, StateData, Mod, _Time, Debug) ->
From = from(Msg),
case catch dispatch(Msg, Mod, StateName, StateData) of
{next_state, NStateName, NStateData} ->
Debug1 = sys:handle_debug(Debug, fun print_event/3,
{Name, NStateName}, return),
loop(Parent, Name, NStateName, NStateData, Mod, infinity, Debug1);
{next_state, NStateName, NStateData, Time1} ->
Debug1 = sys:handle_debug(Debug, fun print_event/3,
{Name, NStateName}, return),
loop(Parent, Name, NStateName, NStateData, Mod, Time1, Debug1);
{reply, Reply, NStateName, NStateData} when From =/= undefined ->
Debug1 = reply(Name, From, Reply, Debug, NStateName),
loop(Parent, Name, NStateName, NStateData, Mod, infinity, Debug1);
{reply, Reply, NStateName, NStateData, Time1} when From =/= undefined ->
Debug1 = reply(Name, From, Reply, Debug, NStateName),
loop(Parent, Name, NStateName, NStateData, Mod, Time1, Debug1);
{stop, Reason, NStateData} ->
terminate(Reason, Name, Msg, Mod, StateName, NStateData, Debug);
{stop, Reason, Reply, NStateData} when From =/= undefined ->
{'EXIT', R} = (catch terminate(Reason, Name, Msg, Mod,
StateName, NStateData, Debug)),
reply(Name, From, Reply, Debug, StateName),
exit(R);
{'EXIT', What} ->
terminate(What, Name, Msg, Mod, StateName, StateData, Debug);
Reply ->
terminate({bad_return_value, Reply},
Name, Msg, Mod, StateName, StateData, Debug)
end.
dispatch({'$gen_event', Event}, Mod, StateName, StateData) ->
Mod:StateName(Event, StateData);
dispatch({'$gen_all_state_event', Event}, Mod, StateName, StateData) ->
Mod:handle_event(Event, StateName, StateData);
dispatch({'$gen_sync_event', From, Event}, Mod, StateName, StateData) ->
Mod:StateName(Event, From, StateData);
dispatch({'$gen_sync_all_state_event', From, Event},
Mod, StateName, StateData) ->
Mod:handle_sync_event(Event, From, StateName, StateData);
dispatch({timeout, Ref, {'$gen_timer', Msg}}, Mod, StateName, StateData) ->
Mod:StateName({timeout, Ref, Msg}, StateData);
dispatch({timeout, _Ref, {'$gen_event', Event}}, Mod, StateName, StateData) ->
Mod:StateName(Event, StateData);
dispatch(Info, Mod, StateName, StateData) ->
Mod:handle_info(Info, StateName, StateData).
from({'$gen_sync_event', From, _Event}) -> From;
from({'$gen_sync_all_state_event', From, _Event}) -> From;
from(_) -> undefined.
%% Send a reply to the client.
reply({To, Tag}, Reply) ->
catch To ! {Tag, Reply}.
reply(Name, {To, Tag}, Reply, Debug, StateName) ->
reply({To, Tag}, Reply),
sys:handle_debug(Debug, fun print_event/3, Name,
{out, Reply, To, StateName}).
%%% ---------------------------------------------------
%%% Terminate the server.
%%% ---------------------------------------------------
-spec terminate(term(), _, _, atom(), _, _, _) -> no_return().
terminate(Reason, Name, Msg, Mod, StateName, StateData, Debug) ->
case catch Mod:terminate(Reason, StateName, StateData) of
{'EXIT', R} ->
error_info(R, Name, Msg, StateName, StateData, Debug),
exit(R);
_ ->
case Reason of
normal ->
exit(normal);
shutdown ->
exit(shutdown);
{shutdown,_}=Shutdown ->
exit(Shutdown);
_ ->
FmtStateData =
case erlang:function_exported(Mod, format_status, 2) of
true ->
Args = [get(), StateData],
case catch Mod:format_status(terminate, Args) of
{'EXIT', _} -> StateData;
Else -> Else
end;
_ ->
StateData
end,
error_info(Reason,Name,Msg,StateName,FmtStateData,Debug),
exit(Reason)
end
end.
error_info(Reason, Name, Msg, StateName, StateData, Debug) ->
Reason1 =
case Reason of
{undef,[{M,F,A,L}|MFAs]} ->
case code:is_loaded(M) of
false ->
{'module could not be loaded',[{M,F,A,L}|MFAs]};
_ ->
case erlang:function_exported(M, F, length(A)) of
true ->
Reason;
false ->
{'function not exported',[{M,F,A,L}|MFAs]}
end
end;
_ ->
Reason
end,
Str = "** State machine ~p terminating \n" ++
get_msg_str(Msg) ++
"** When State == ~p~n"
"** Data == ~p~n"
"** Reason for termination = ~n** ~p~n",
format(Str, [Name, get_msg(Msg), StateName, StateData, Reason1]),
sys:print_log(Debug),
ok.
get_msg_str({'$gen_event', _Event}) ->
"** Last event in was ~p~n";
get_msg_str({'$gen_sync_event', _Event}) ->
"** Last sync event in was ~p~n";
get_msg_str({'$gen_all_state_event', _Event}) ->
"** Last event in was ~p (for all states)~n";
get_msg_str({'$gen_sync_all_state_event', _Event}) ->
"** Last sync event in was ~p (for all states)~n";
get_msg_str({timeout, _Ref, {'$gen_timer', _Msg}}) ->
"** Last timer event in was ~p~n";
get_msg_str({timeout, _Ref, {'$gen_event', _Msg}}) ->
"** Last timer event in was ~p~n";
get_msg_str(_Msg) ->
"** Last message in was ~p~n".
get_msg({'$gen_event', Event}) -> Event;
get_msg({'$gen_sync_event', Event}) -> Event;
get_msg({'$gen_all_state_event', Event}) -> Event;
get_msg({'$gen_sync_all_state_event', Event}) -> Event;
get_msg({timeout, Ref, {'$gen_timer', Msg}}) -> {timeout, Ref, Msg};
get_msg({timeout, _Ref, {'$gen_event', Event}}) -> Event;
get_msg(Msg) -> Msg.
%%-----------------------------------------------------------------
%% Status information
%%-----------------------------------------------------------------
format_status(Opt, StatusData) ->
[PDict, SysState, Parent, Debug, [Name, StateName, StateData, Mod, _Time]] =
StatusData,
Header = gen:format_status_header("Status for state machine",
Name),
Log = sys:get_debug(log, Debug, []),
DefaultStatus = [{data, [{"StateData", StateData}]}],
Specfic =
case erlang:function_exported(Mod, format_status, 2) of
true ->
case catch Mod:format_status(Opt,[PDict,StateData]) of
{'EXIT', _} -> DefaultStatus;
StatusList when is_list(StatusList) -> StatusList;
Else -> [Else]
end;
_ ->
DefaultStatus
end,
[{header, Header},
{data, [{"Status", SysState},
{"Parent", Parent},
{"Logged events", Log},
{"StateName", StateName}]} |
Specfic].
