%% %% %CopyrightBegin% %% %% Copyright Ericsson AB 2016. 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(gen_statem). %% API -export( [start/3,start/4,start_link/3,start_link/4, stop/1,stop/3, cast/2,call/2,call/3, enter_loop/4,enter_loop/5,enter_loop/6, reply/1,reply/2]). %% gen callbacks -export( [init_it/6]). %% sys callbacks -export( [system_continue/3, system_terminate/4, system_code_change/4, system_get_state/1, system_replace_state/2, format_status/2]). %% Internal callbacks -export( [wakeup_from_hibernate/3]). %% Type exports for templates -export_type( [event_type/0, callback_mode/0, state_function_result/0, handle_event_result/0, action/0]). %% Fix problem for doc build -export_type([transition_option/0]). %%%========================================================================== %%% Interface functions. %%%========================================================================== -type from() :: {To :: pid(), Tag :: term()}. % Reply-to specifier for call -type state() :: state_name() | % For StateName/3 callback functios term(). % For handle_event/4 callback function -type state_name() :: atom(). -type data() :: term(). -type event_type() :: {'call',From :: from()} | 'cast' | 'info' | 'timeout' | 'internal'. -type callback_mode() :: 'state_functions' | 'handle_event_function'. -type transition_option() :: postpone() | hibernate() | event_timeout(). -type postpone() :: %% If 'true' postpone the current event %% and retry it when the state changes (=/=) boolean(). -type hibernate() :: %% If 'true' hibernate the server instead of going into receive boolean(). -type event_timeout() :: %% Generate a ('timeout', EventContent, ...) event after Time %% unless some other event is delivered Time :: timeout(). -type action() :: %% During a state change: %% * NextState and NewData are set. %% * All action()s are executed in order of apperance. %% * Postponing the current event is performed %% iff 'postpone' is 'true'. %% * A state timer is started iff 'timeout' is set. %% * Pending events are handled or if there are %% no pending events the server goes into receive %% or hibernate (iff 'hibernate' is 'true') %% %% These action()s are executed in order of appearence %% in the containing list. The ones that set options %% will override any previous so the last of each kind wins. %% 'postpone' | % Set the postpone option {'postpone', Postpone :: postpone()} | %% 'hibernate' | % Set the hibernate option {'hibernate', Hibernate :: hibernate()} | %% (Timeout :: event_timeout()) | % {timeout,Timeout} {'timeout', % Set the event timeout option Time :: event_timeout(), EventContent :: term()} | %% reply_action() | %% %% All 'next_event' events are kept in a list and then %% inserted at state changes so the first in the %% action() list is the first to be delivered. {'next_event', % Insert event as the next to handle EventType :: event_type(), EventContent :: term()}. -type reply_action() :: {'reply', % Reply to a caller From :: from(), Reply :: term()}. -type state_function_result() :: {'next_state', % {next_state,NextStateName,NewData,[]} NextStateName :: state_name(), NewData :: data()} | {'next_state', % State transition, maybe to the same state NextStateName :: state_name(), NewData :: data(), Actions :: [action()] | action()} | common_state_callback_result(). -type handle_event_result() :: {'next_state', % {next_state,NextState,NewData,[]} NextState :: state(), NewData :: data()} | {'next_state', % State transition, maybe to the same state NextState :: state(), NewData :: data(), Actions :: [action()] | action()} | common_state_callback_result(). -type common_state_callback_result() :: 'stop' | % {stop,normal} {'stop', % Stop the server Reason :: term()} | {'stop', % Stop the server Reason :: term(), NewData :: data()} | {'stop_and_reply', % Reply then stop the server Reason :: term(), Replies :: [reply_action()] | reply_action()} | {'stop_and_reply', % Reply then stop the server Reason :: term(), Replies :: [reply_action()] | reply_action(), NewData :: data()} | {'keep_state', % {keep_state,NewData,[]} NewData :: data()} | {'keep_state', % Keep state, change data NewData :: data(), Actions :: [action()] | action()} | 'keep_state_and_data' | % {keep_state_and_data,[]} {'keep_state_and_data', % Keep state and data -> only actions Actions :: [action()] | action()}. %% The state machine init function. It is called only once and %% the server is not running until this function has returned %% an {ok, ...} tuple. Thereafter the state callbacks are called %% for all events to this server. -callback init(Args :: term()) -> {ok, state(), data()} | {ok, state(), data(), [action()] | action()} | 'ignore' | {'stop', Reason :: term()}. %% This callback shall return the callback mode of the callback module. %% %% It is called once after init/0 and code_change/4 but before %% the first state callback StateName/3 or handle_event/4. -callback callback_mode() -> callback_mode(). %% Example state callback for StateName = 'state_name' %% when callback_mode() =:= state_functions. %% %% In this mode all states has to be of type state_name() i.e atom(). %% %% Note that the only callbacks that have arity 3 are these %% StateName/3 callbacks and terminate/3, so the state name %% 'terminate' is unusable in this mode. -callback state_name( event_type(), EventContent :: term(), Data :: data()) -> state_function_result(). %% %% State callback for all states %% when callback_mode() =:= handle_event_function. -callback handle_event( event_type(), EventContent :: term(), State :: state(), % Current state Data :: data()) -> handle_event_result(). %% Clean up before the server terminates. -callback terminate( Reason :: 'normal' | 'shutdown' | {'shutdown', term()} | term(), State :: state(), Data :: data()) -> any(). %% Note that the new code can expect to get an OldState from %% the old code version not only in code_change/4 but in the first %% state callback function called thereafter -callback code_change( OldVsn :: term() | {'down', term()}, OldState :: state(), OldData :: data(), Extra :: term()) -> {ok, NewState :: state(), NewData :: data()} | (Reason :: term()). %% Format the callback module state in some sensible that is %% often condensed way. For StatusOption =:= 'normal' the perferred %% return term is [{data,[{"State",FormattedState}]}], and for %% StatusOption =:= 'terminate' it is just FormattedState. -callback format_status( StatusOption, [ [{Key :: term(), Value :: term()}] | state() | data()]) -> Status :: term() when StatusOption :: 'normal' | 'terminate'. -optional_callbacks( [init/1, % One may use enter_loop/5,6,7 instead format_status/2, % Has got a default implementation %% state_name/3, % Example for callback_mode() =:= state_functions: %% there has to be a StateName/3 callback function %% for every StateName in your state machine but the state name %% 'state_name' does of course not have to be used. %% handle_event/4 % For callback_mode() =:= handle_event_function ]). %% Type validation functions callback_mode(CallbackMode) -> case CallbackMode of state_functions -> true; handle_event_function -> true; _ -> false end. %% from({Pid,_}) when is_pid(Pid) -> true; from(_) -> false. %% event_type({call,From}) -> from(From); event_type(Type) -> case Type of cast -> true; info -> true; timeout -> true; internal -> true; _ -> false end. -define( STACKTRACE(), try throw(ok) catch _ -> erlang:get_stacktrace() end). %%%========================================================================== %%% API -type server_name() :: {'global', GlobalName :: term()} | {'via', RegMod :: module(), Name :: term()} | {'local', atom()}. -type server_ref() :: pid() | (LocalName :: atom()) | {Name :: atom(), Node :: atom()} | {'global', GlobalName :: term()} | {'via', RegMod :: module(), ViaName :: term()}. -type debug_opt() :: {'debug', Dbgs :: ['trace' | 'log' | 'statistics' | 'debug' | {'logfile', string()}]}. -type start_opt() :: debug_opt() | {'timeout', Time :: timeout()} | {'spawn_opt', [proc_lib:spawn_option()]}. -type start_ret() :: {'ok', pid()} | 'ignore' | {'error', term()}. %% Start a state machine -spec start( Module :: module(), Args :: term(), Opts :: [start_opt()]) -> start_ret(). start(Module, Args, Opts) -> gen:start(?MODULE, nolink, Module, Args, Opts). %% -spec start( ServerName :: server_name(), Module :: module(), Args :: term(), Opts :: [start_opt()]) -> start_ret(). start(ServerName, Module, Args, Opts) -> gen:start(?MODULE, nolink, ServerName, Module, Args, Opts). %% Start and link to a state machine -spec start_link( Module :: module(), Args :: term(), Opts :: [start_opt()]) -> start_ret(). start_link(Module, Args, Opts) -> gen:start(?MODULE, link, Module, Args, Opts). %% -spec start_link( ServerName :: server_name(), Module :: module(), Args :: term(), Opts :: [start_opt()]) -> start_ret(). start_link(ServerName, Module, Args, Opts) -> gen:start(?MODULE, link, ServerName, Module, Args, Opts). %% Stop a state machine -spec stop(ServerRef :: server_ref()) -> ok. stop(ServerRef) -> gen:stop(ServerRef). %% -spec stop( ServerRef :: server_ref(), Reason :: term(), Timeout :: timeout()) -> ok. stop(ServerRef, Reason, Timeout) -> gen:stop(ServerRef, Reason, Timeout). %% Send an event to a state machine that arrives with type 'event' -spec cast(ServerRef :: server_ref(), Msg :: term()) -> ok. cast({global,Name}, Msg) -> try global:send(Name, wrap_cast(Msg)) of _ -> ok catch _:_ -> ok end; cast({via,RegMod,Name}, Msg) -> try RegMod:send(Name, wrap_cast(Msg)) of _ -> ok catch _:_ -> ok end; cast({Name,Node} = ServerRef, Msg) when is_atom(Name), is_atom(Node) -> send(ServerRef, wrap_cast(Msg)); cast(ServerRef, Msg) when is_atom(ServerRef) -> send(ServerRef, wrap_cast(Msg)); cast(ServerRef, Msg) when is_pid(ServerRef) -> send(ServerRef, wrap_cast(Msg)). %% Call a state machine (synchronous; a reply is expected) that %% arrives with type {call,From} -spec call(ServerRef :: server_ref(), Request :: term()) -> Reply :: term(). call(ServerRef, Request) -> call(ServerRef, Request, infinity). %% -spec call( ServerRef :: server_ref(), Request :: term(), Timeout :: timeout()) -> Reply :: term(). call(ServerRef, Request, infinity) -> try gen:call(ServerRef, '$gen_call', Request, infinity) of {ok,Reply} -> Reply catch Class:Reason -> erlang:raise( Class, {Reason,{?MODULE,call,[ServerRef,Request,infinity]}}, erlang:get_stacktrace()) end; call(ServerRef, Request, Timeout) -> %% Call server through proxy process to dodge any late reply Ref = make_ref(), Self = self(), Pid = spawn( fun () -> Self ! try gen:call( ServerRef, '$gen_call', Request, Timeout) of Result -> {Ref,Result} catch Class:Reason -> {Ref,Class,Reason,erlang:get_stacktrace()} end end), Mref = monitor(process, Pid), receive {Ref,Result} -> demonitor(Mref, [flush]), case Result of {ok,Reply} -> Reply end; {Ref,Class,Reason,Stacktrace} -> demonitor(Mref, [flush]), erlang:raise( Class, {Reason,{?MODULE,call,[ServerRef,Request,Timeout]}}, Stacktrace); {'DOWN',Mref,_,_,Reason} -> %% There is a theoretical possibility that the %% proxy process gets killed between try--of and ! %% so this clause is in case of that exit(Reason) end. %% Reply from a state machine callback to whom awaits in call/2 -spec reply([reply_action()] | reply_action()) -> ok. reply({reply,From,Reply}) -> reply(From, Reply); reply(Replies) when is_list(Replies) -> replies(Replies). %% -spec reply(From :: from(), Reply :: term()) -> ok. reply({To,Tag}, Reply) when is_pid(To) -> Msg = {Tag,Reply}, try To ! Msg of _ -> ok catch _:_ -> ok end. %% Instead of starting the state machine through start/3,4 %% or start_link/3,4 turn the current process presumably %% started by proc_lib into a state machine using %% the same arguments as you would have returned from init/1 -spec enter_loop( Module :: module(), Opts :: [debug_opt()], State :: state(), Data :: data()) -> no_return(). enter_loop(Module, Opts, State, Data) -> enter_loop(Module, Opts, State, Data, self()). %% -spec enter_loop( Module :: module(), Opts :: [debug_opt()], State :: state(), Data :: data(), Server_or_Actions :: server_name() | pid() | [action()]) -> no_return(). enter_loop(Module, Opts, State, Data, Server_or_Actions) -> if is_list(Server_or_Actions) -> enter_loop(Module, Opts, State, Data, self(), Server_or_Actions); true -> enter_loop(Module, Opts, State, Data, Server_or_Actions, []) end. %% -spec enter_loop( Module :: module(), Opts :: [debug_opt()], State :: state(), Data :: data(), Server :: server_name() | pid(), Actions :: [action()] | action()) -> no_return(). enter_loop(Module, Opts, State, Data, Server, Actions) -> is_atom(Module) orelse error({atom,Module}), Parent = gen:get_parent(), enter(Module, Opts, State, Data, Server, Actions, Parent). %%--------------------------------------------------------------------------- %% API helpers wrap_cast(Event) -> {'$gen_cast',Event}. replies([{reply,From,Reply}|Replies]) -> reply(From, Reply), replies(Replies); replies([]) -> ok. %% Might actually not send the message in case of caught exception send(Proc, Msg) -> try erlang:send(Proc, Msg, [noconnect]) of noconnect -> _ = spawn(erlang, send, [Proc,Msg]), ok; ok -> ok catch _:_ -> ok end. %% Here the init_it/6 and enter_loop/5,6,7 functions converge enter(Module, Opts, State, Data, Server, Actions, Parent) -> %% The values should already have been type checked Name = gen:get_proc_name(Server), Debug = gen:debug_options(Name, Opts), P = Events = [], Event = {internal,initial_state}, %% We enforce {postpone,false} to ensure that %% our fake Event gets discarded, thought it might get logged NewActions = if is_list(Actions) -> Actions ++ [{postpone,false}]; true -> [Actions,{postpone,false}] end, S = #{ callback_mode => undefined, module => Module, name => Name, %% All fields below will be replaced according to the arguments to %% loop_event_actions/10 when it finally loops back to loop/3 state => State, data => Data, postponed => P, hibernate => false, timer => undefined}, NewDebug = sys_debug(Debug, S, State, {enter,Event,State}), loop_event_actions( Parent, NewDebug, S, Events, State, Data, P, Event, State, NewActions). %%%========================================================================== %%% gen callbacks init_it(Starter, self, ServerRef, Module, Args, Opts) -> init_it(Starter, self(), ServerRef, Module, Args, Opts); init_it(Starter, Parent, ServerRef, Module, Args, Opts) -> try Module:init(Args) of Result -> init_result(Starter, Parent, ServerRef, Module, Result, Opts) catch Result -> init_result(Starter, Parent, ServerRef, Module, Result, Opts); Class:Reason -> Stacktrace = erlang:get_stacktrace(), Name = gen:get_proc_name(ServerRef), gen:unregister_name(ServerRef), proc_lib:init_ack(Starter, {error,Reason}), error_info( Class, Reason, Stacktrace, #{name => Name, callback_mode => undefined}, [], [], undefined), erlang:raise(Class, Reason, Stacktrace) end. %%--------------------------------------------------------------------------- %% gen callbacks helpers init_result(Starter, Parent, ServerRef, Module, Result, Opts) -> case Result of {ok,State,Data} -> proc_lib:init_ack(Starter, {ok,self()}), enter(Module, Opts, State, Data, ServerRef, [], Parent); {ok,State,Data,Actions} -> proc_lib:init_ack(Starter, {ok,self()}), enter(Module, Opts, State, Data, ServerRef, Actions, Parent); {stop,Reason} -> gen:unregister_name(ServerRef), proc_lib:init_ack(Starter, {error,Reason}), exit(Reason); ignore -> gen:unregister_name(ServerRef), proc_lib:init_ack(Starter, ignore), exit(normal); _ -> Name = gen:get_proc_name(ServerRef), gen:unregister_name(ServerRef), Error = {bad_return_from_init,Result}, proc_lib:init_ack(Starter, {error,Error}), error_info( error, Error, ?STACKTRACE(), #{name => Name, callback_mode => undefined}, [], [], undefined), exit(Error) end. %%%========================================================================== %%% sys callbacks system_continue(Parent, Debug, S) -> loop(Parent, Debug, S). system_terminate( Reason, _Parent, Debug, #{state := State, data := Data, postponed := P} = S) -> terminate( exit, Reason, ?STACKTRACE(), Debug, S, [], State, Data, P). system_code_change( #{module := Module, state := State, data := Data} = S, _Mod, OldVsn, Extra) -> case try Module:code_change(OldVsn, State, Data, Extra) catch Result -> Result end of {ok,NewState,NewData} -> {ok, S#{callback_mode := undefined, state := NewState, data := NewData}}; {ok,_} = Error -> error({case_clause,Error}); Error -> Error end. system_get_state(#{state := State, data := Data}) -> {ok,{State,Data}}. system_replace_state( StateFun, #{state := State, data := Data} = S) -> {NewState,NewData} = Result = StateFun({State,Data}), {ok,Result,S#{state := NewState, data := NewData}}. format_status( Opt, [PDict,SysState,Parent,Debug, #{name := Name, postponed := P, state := State, data := Data} = S]) -> Header = gen:format_status_header("Status for state machine", Name), Log = sys:get_debug(log, Debug, []), [{header,Header}, {data, [{"Status",SysState}, {"Parent",Parent}, {"Logged Events",Log}, {"Postponed",P}]} | case format_status(Opt, PDict, S, State, Data) of L when is_list(L) -> L; T -> [T] 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,Event}, {Name,_}) -> io:format( Dev, "*DBG* ~p receive ~s~n", [Name,event_string(Event)]); print_event(Dev, {out,Reply,{To,_Tag}}, {Name,_}) -> io:format( Dev, "*DBG* ~p send ~p to ~p~n", [Name,Reply,To]); print_event(Dev, {Tag,Event,NextState}, {Name,State}) -> StateString = case NextState of State -> io_lib:format("~p", [State]); _ -> io_lib:format("~p => ~p", [State,NextState]) end, io:format( Dev, "*DBG* ~p ~w ~s in state ~s~n", [Name,Tag,event_string(Event),StateString]). event_string(Event) -> case Event of {{call,{Pid,_Tag}},Request} -> io_lib:format("call ~p from ~w", [Request,Pid]); {EventType,EventContent} -> io_lib:format("~w ~p", [EventType,EventContent]) end. sys_debug(Debug, #{name := Name}, State, Entry) -> case Debug of [] -> Debug; _ -> sys:handle_debug( Debug, fun print_event/3, {Name,State}, Entry) end. %%%========================================================================== %%% Internal callbacks wakeup_from_hibernate(Parent, Debug, S) -> %% It is a new message that woke us up so we have to receive it now loop_receive(Parent, Debug, S). %%%========================================================================== %%% State Machine engine implementation of proc_lib/gen server %% Server loop, consists of all loop* functions %% and detours through sys:handle_system_message/7 and proc_lib:hibernate/3 %% Entry point for system_continue/3 loop(Parent, Debug, #{hibernate := Hibernate} = S) -> case Hibernate of true -> %% Does not return but restarts process at %% wakeup_from_hibernate/3 that jumps to loop_receive/3 proc_lib:hibernate( ?MODULE, wakeup_from_hibernate, [Parent,Debug,S]), error( {should_not_have_arrived_here_but_instead_in, {wakeup_from_hibernate,3}}); false -> loop_receive(Parent, Debug, S) end. %% Entry point for wakeup_from_hibernate/3 loop_receive(Parent, Debug, #{timer := Timer} = S) -> receive Msg -> case Msg of {system,Pid,Req} -> #{hibernate := Hibernate} = S, %% Does not return but tail recursively calls %% system_continue/3 that jumps to loop/3 sys:handle_system_msg( Req, Pid, Parent, ?MODULE, Debug, S, Hibernate); {'EXIT',Parent,Reason} = EXIT -> #{state := State, data := Data, postponed := P} = S, %% EXIT is not a 2-tuple and therefore %% not an event and has no event_type(), %% but this will stand out in the crash report... terminate( exit, Reason, ?STACKTRACE(), Debug, S, [EXIT], State, Data, P); {timeout,Timer,Content} when Timer =/= undefined -> loop_receive_result( Parent, Debug, S, {timeout,Content}); _ -> %% Cancel Timer if running case Timer of undefined -> ok; _ -> case erlang:cancel_timer(Timer) of TimeLeft when is_integer(TimeLeft) -> ok; false -> receive {timeout,Timer,_} -> ok after 0 -> ok end end end, Event = case Msg of {'$gen_call',From,Request} -> {{call,From},Request}; {'$gen_cast',E} -> {cast,E}; _ -> {info,Msg} end, loop_receive_result(Parent, Debug, S, Event) end end. loop_receive_result( Parent, Debug, #{state := State, data := Data, postponed := P} = S, Event) -> %% The engine state map S is now dismantled %% and will not be restored until we return to loop/3. %% %% The fields 'callback_mode', 'module', and 'name' are still valid. %% The fields 'state', 'data', and 'postponed' are held in arguments. %% The fields 'timer' and 'hibernate' will be recalculated. %% NewDebug = sys_debug(Debug, S, State, {in,Event}), %% Here the queue of not yet handled events is created Events = [], Hibernate = false, loop_event( Parent, NewDebug, S, Events, State, Data, P, Event, Hibernate). %% Process the event queue, or if it is empty %% loop back to loop/3 to receive a new event loop_events( Parent, Debug, S, [Event|Events], State, Data, P, Hibernate, _Timeout) -> %% %% If there was a state timer requested we just ignore that %% since we have events to handle which cancels the timer loop_event( Parent, Debug, S, Events, State, Data, P, Event, Hibernate); loop_events( Parent, Debug, S, [], State, Data, P, Hibernate, Timeout) -> case Timeout of {timeout,0,EventContent} -> %% Immediate timeout - simulate it %% so we do not get the timeout message %% after any received event loop_event( Parent, Debug, S, [], State, Data, P, {timeout,EventContent}, Hibernate); {timeout,Time,EventContent} -> %% Actually start a timer Timer = erlang:start_timer(Time, self(), EventContent), loop_events_done( Parent, Debug, S, Timer, State, Data, P, Hibernate); undefined -> %% No state timeout has been requested Timer = undefined, loop_events_done( Parent, Debug, S, Timer, State, Data, P, Hibernate) end. %% loop_events_done(Parent, Debug, S, Timer, State, Data, P, Hibernate) -> NewS = S#{ state := State, data := Data, postponed := P, hibernate := Hibernate, timer := Timer}, loop(Parent, Debug, NewS). loop_event( Parent, Debug, #{callback_mode := CallbackMode, module := Module} = S, Events, State, Data, P, {Type,Content} = Event, Hibernate) -> %% %% If Hibernate is true here it can only be %% because it was set from an event action %% and we did not go into hibernation since there %% were events in queue, so we do what the user %% might depend on i.e collect garbage which %% would have happened if we actually hibernated %% and immediately was awakened Hibernate andalso garbage_collect(), %% try case CallbackMode of undefined -> Module:callback_mode(); state_functions -> erlang:apply(Module, State, [Type,Content,Data]); handle_event_function -> Module:handle_event(Type, Content, State, Data) end of Result when CallbackMode =:= undefined -> loop_event_callback_mode( Parent, Debug, S, Events, State, Data, P, Event, Result); Result -> loop_event_result( Parent, Debug, S, Events, State, Data, P, Event, Result) catch Result when CallbackMode =:= undefined -> loop_event_callback_mode( Parent, Debug, S, Events, State, Data, P, Event, Result); Result -> loop_event_result( Parent, Debug, S, Events, State, Data, P, Event, Result); error:badarg -> case erlang:get_stacktrace() of [{erlang,apply, [Module,State,[Type,Content,Data]=Args], _} |Stacktrace] when CallbackMode =:= state_functions -> %% We get here e.g if apply fails %% due to State not being an atom terminate( error, {undef_state_function,{Module,State,Args}}, Stacktrace, Debug, S, [Event|Events], State, Data, P); Stacktrace -> terminate( error, badarg, Stacktrace, Debug, S, [Event|Events], State, Data, P) end; error:undef -> %% Process undef to check for the simple mistake %% of calling a nonexistent state function %% to make the undef more precise case erlang:get_stacktrace() of [{Module,callback_mode,[]=Args,_} |Stacktrace] when CallbackMode =:= undefined -> terminate( error, {undef_callback,{Module,callback_mode,Args}}, Stacktrace, Debug, S, [Event|Events], State, Data, P); [{Module,State,[Type,Content,Data]=Args,_} |Stacktrace] when CallbackMode =:= state_functions -> terminate( error, {undef_state_function,{Module,State,Args}}, Stacktrace, Debug, S, [Event|Events], State, Data, P); [{Module,handle_event,[Type,Content,State,Data]=Args,_} |Stacktrace] when CallbackMode =:= handle_event_function -> terminate( error, {undef_state_function,{Module,handle_event,Args}}, Stacktrace, Debug, S, [Event|Events], State, Data, P); Stacktrace -> terminate( error, undef, Stacktrace, Debug, S, [Event|Events], State, Data, P) end; Class:Reason -> Stacktrace = erlang:get_stacktrace(), terminate( Class, Reason, Stacktrace, Debug, S, [Event|Events], State, Data, P) end. %% Interpret callback_mode() result loop_event_callback_mode( Parent, Debug, S, Events, State, Data, P, Event, CallbackMode) -> case callback_mode(CallbackMode) of true -> Hibernate = false, % We have already GC:ed recently loop_event( Parent, Debug, S#{callback_mode := CallbackMode}, Events, State, Data, P, Event, Hibernate); false -> terminate( error, {bad_return_from_callback_mode,CallbackMode}, ?STACKTRACE(), Debug, S, [Event|Events], State, Data, P) end. %% Interpret all callback return variants loop_event_result( Parent, Debug, S, Events, State, Data, P, Event, Result) -> case Result of stop -> terminate( exit, normal, ?STACKTRACE(), Debug, S, [Event|Events], State, Data, P); {stop,Reason} -> terminate( exit, Reason, ?STACKTRACE(), Debug, S, [Event|Events], State, Data, P); {stop,Reason,NewData} -> terminate( exit, Reason, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P); {stop_and_reply,Reason,Replies} -> Q = [Event|Events], reply_then_terminate( exit, Reason, ?STACKTRACE(), Debug, S, Q, State, Data, P, Replies); {stop_and_reply,Reason,Replies,NewData} -> Q = [Event|Events], reply_then_terminate( exit, Reason, ?STACKTRACE(), Debug, S, Q, State, NewData, P, Replies); {next_state,NextState,NewData} -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, []); {next_state,NextState,NewData,Actions} -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions); {keep_state,NewData} -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, State, []); {keep_state,NewData,Actions} -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, State, Actions); keep_state_and_data -> loop_event_actions( Parent, Debug, S, Events, State, Data, P, Event, State, []); {keep_state_and_data,Actions} -> loop_event_actions( Parent, Debug, S, Events, State, Data, P, Event, State, Actions); _ -> terminate( error, {bad_return_from_state_function,Result}, ?STACKTRACE(), Debug, S, [Event|Events], State, Data, P) end. loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions) -> Postpone = false, % Shall we postpone this event; boolean() Hibernate = false, Timeout = undefined, NextEvents = [], loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, if is_list(Actions) -> Actions; true -> [Actions] end, Postpone, Hibernate, Timeout, NextEvents). %% %% Process all actions loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, [Action|Actions], Postpone, Hibernate, Timeout, NextEvents) -> case Action of %% Actual actions {reply,From,Reply} -> case from(From) of true -> NewDebug = do_reply(Debug, S, State, From, Reply), loop_event_actions( Parent, NewDebug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, Hibernate, Timeout, NextEvents); false -> terminate( error, {bad_action_from_state_function,Action}, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P) end; {next_event,Type,Content} -> case event_type(Type) of true -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, Hibernate, Timeout, [{Type,Content}|NextEvents]); false -> terminate( error, {bad_action_from_state_function,Action}, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P) end; %% Actions that set options {postpone,NewPostpone} when is_boolean(NewPostpone) -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, NewPostpone, Hibernate, Timeout, NextEvents); {postpone,_} -> terminate( error, {bad_action_from_state_function,Action}, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P); postpone -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, true, Hibernate, Timeout, NextEvents); {hibernate,NewHibernate} when is_boolean(NewHibernate) -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, NewHibernate, Timeout, NextEvents); {hibernate,_} -> terminate( error, {bad_action_from_state_function,Action}, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P); hibernate -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, true, Timeout, NextEvents); {timeout,infinity,_} -> % Clear timer - it will never trigger loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, Hibernate, undefined, NextEvents); {timeout,Time,_} = NewTimeout when is_integer(Time), Time >= 0 -> loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, Hibernate, NewTimeout, NextEvents); {timeout,_,_} -> terminate( error, {bad_action_from_state_function,Action}, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P); infinity -> % Clear timer - it will never trigger loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, Hibernate, undefined, NextEvents); Time when is_integer(Time), Time >= 0 -> NewTimeout = {timeout,Time,Time}, loop_event_actions( Parent, Debug, S, Events, State, NewData, P, Event, NextState, Actions, Postpone, Hibernate, NewTimeout, NextEvents); _ -> terminate( error, {bad_action_from_state_function,Action}, ?STACKTRACE(), Debug, S, [Event|Events], State, NewData, P) end; %% %% End of actions list loop_event_actions( Parent, Debug, S, Events, State, NewData, P0, Event, NextState, [], Postpone, Hibernate, Timeout, NextEvents) -> %% %% All options have been collected and next_events are buffered. %% Do the actual state transition. %% P1 = % Move current event to postponed if Postpone case Postpone of true -> [Event|P0]; false -> P0 end, {Q2,P} = % Move all postponed events to queue if state change if NextState =:= State -> {Events,P1}; true -> {lists:reverse(P1, Events),[]} end, %% Place next events first in queue Q = lists:reverse(NextEvents, Q2), %% NewDebug = sys_debug( Debug, S, State, case Postpone of true -> {postpone,Event,NextState}; false -> {consume,Event,NextState} end), loop_events( Parent, NewDebug, S, Q, NextState, NewData, P, Hibernate, Timeout). %%--------------------------------------------------------------------------- %% Server helpers reply_then_terminate( Class, Reason, Stacktrace, Debug, S, Q, State, Data, P, Replies) -> if is_list(Replies) -> do_reply_then_terminate( Class, Reason, Stacktrace, Debug, S, Q, State, Data, P, Replies); true -> do_reply_then_terminate( Class, Reason, Stacktrace, Debug, S, Q, State, Data, P, [Replies]) end. %% do_reply_then_terminate( Class, Reason, Stacktrace, Debug, S, Q, State, Data, P, []) -> terminate(Class, Reason, Stacktrace, Debug, S, Q, State, Data, P); do_reply_then_terminate( Class, Reason, Stacktrace, Debug, S, Q, State, Data, P, [R|Rs]) -> case R of {reply,{_To,_Tag}=From,Reply} -> NewDebug = do_reply(Debug, S, State, From, Reply), do_reply_then_terminate( Class, Reason, Stacktrace, NewDebug, S, Q, State, Data, P, Rs); _ -> terminate( error, {bad_reply_action_from_state_function,R}, ?STACKTRACE(), Debug, S, Q, State, Data, P) end. do_reply(Debug, S, State, From, Reply) -> reply(From, Reply), sys_debug(Debug, S, State, {out,Reply,From}). terminate( Class, Reason, Stacktrace, Debug, #{module := Module} = S, Q, State, Data, P) -> try Module:terminate(Reason, State, Data) of _ -> ok catch _ -> ok; C:R -> ST = erlang:get_stacktrace(), error_info( C, R, ST, S, Q, P, format_status(terminate, get(), S, State, Data)), sys:print_log(Debug), erlang:raise(C, R, ST) end, case Reason of normal -> ok; shutdown -> ok; {shutdown,_} -> ok; _ -> error_info( Class, Reason, Stacktrace, S, Q, P, format_status(terminate, get(), S, State, Data)), sys:print_log(Debug) end, case Stacktrace of [] -> erlang:Class(Reason); _ -> erlang:raise(Class, Reason, Stacktrace) end. error_info( Class, Reason, Stacktrace, #{name := Name, callback_mode := CallbackMode}, Q, P, FmtData) -> {FixedReason,FixedStacktrace} = case Stacktrace of [{M,F,Args,_}|ST] when Class =:= error, Reason =:= undef -> case code:is_loaded(M) of false -> {{'module could not be loaded',M},ST}; _ -> Arity = if is_list(Args) -> length(Args); is_integer(Args) -> Args end, case erlang:function_exported(M, F, Arity) of true -> {Reason,Stacktrace}; false -> {{'function not exported',{M,F,Arity}}, ST} end end; _ -> {Reason,Stacktrace} end, error_logger:format( "** State machine ~p terminating~n" ++ case Q of [] -> ""; _ -> "** Last event = ~p~n" end ++ "** When server state = ~p~n" ++ "** Reason for termination = ~w:~p~n" ++ "** Callback mode = ~p~n" ++ case Q of [_,_|_] -> "** Queued = ~p~n"; _ -> "" end ++ case P of [] -> ""; _ -> "** Postponed = ~p~n" end ++ case FixedStacktrace of [] -> ""; _ -> "** Stacktrace =~n** ~p~n" end, [Name | case Q of [] -> []; [Event|_] -> [Event] end] ++ [FmtData,Class,FixedReason, CallbackMode] ++ case Q of [_|[_|_] = Events] -> [Events]; _ -> [] end ++ case P of [] -> []; _ -> [P] end ++ case FixedStacktrace of [] -> []; _ -> [FixedStacktrace] end). %% Call Module:format_status/2 or return a default value format_status(Opt, PDict, #{module := Module}, State, Data) -> case erlang:function_exported(Module, format_status, 2) of true -> try Module:format_status(Opt, [PDict,State,Data]) catch Result -> Result; _:_ -> format_status_default( Opt, State, atom_to_list(Module) ++ ":format_status/2 crashed") end; false -> format_status_default(Opt, State, Data) end. %% The default Module:format_status/2 format_status_default(Opt, State, Data) -> StateData = {State,Data}, case Opt of terminate -> StateData; _ -> [{data,[{"State",StateData}]}] end.