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+%%
+%% %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/5,enter_loop/6,enter_loop/7,
+ 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 state callback function StateName/5
+ term(). % For state callback function handle_event/5
+
+-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 processed 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()) ->
+ {callback_mode(), state(), data()} |
+ {callback_mode(), state(), data(), [action()] | action()} |
+ 'ignore' |
+ {'stop', Reason :: term()}.
+
+%% Example state callback for callback_mode() =:= state_functions
+%% state name 'state_name'.
+%%
+%% In this mode all states has to be type state_name() i.e atom().
+%%
+%% Note that state callbacks and only state callbacks have arity 5
+%% and that is intended.
+-callback state_name(
+ event_type(),
+ EventContent :: term(),
+ Data :: data()) ->
+ state_function_result().
+%%
+%% State callback for callback_mode() =:= handle_event_function.
+%%
+%% Note that state callbacks and only state callbacks have arity 5
+%% and that is intended.
+-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()) ->
+ {NewCallbackMode :: callback_mode(),
+ NewState :: state(),
+ NewData :: data()}.
+
+%% 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/5 callback function for every StateName.
+ %%
+ 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).
+
+-define(
+ TERMINATE(Class, Reason, Debug, S, Q),
+ terminate(
+ begin Class end,
+ begin Reason end,
+ ?STACKTRACE(),
+ begin Debug end,
+ begin S end,
+ begin Q end)).
+
+%%%==========================================================================
+%%% API
+
+-type server_name() ::
+ {'global', GlobalName :: term()}
+ | {'via', RegMod :: module(), Name :: term()}
+ | {'local', atom()}.
+-type server_ref() ::
+ {'global', GlobalName :: term()}
+ | {'via', RegMod :: module(), ViaName :: term()}
+ | (LocalName :: atom())
+ | {Name :: atom(), Node :: atom()}
+ | pid().
+-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()],
+ CallbackMode :: callback_mode(),
+ State :: state(), Data :: data()) ->
+ no_return().
+enter_loop(Module, Opts, CallbackMode, State, Data) ->
+ enter_loop(Module, Opts, CallbackMode, State, Data, self()).
+%%
+-spec enter_loop(
+ Module :: module(), Opts :: [debug_opt()],
+ CallbackMode :: callback_mode(),
+ State :: state(), Data :: data(),
+ Server_or_Actions ::
+ server_name() | pid() | [action()]) ->
+ no_return().
+enter_loop(Module, Opts, CallbackMode, State, Data, Server_or_Actions) ->
+ if
+ is_list(Server_or_Actions) ->
+ enter_loop(
+ Module, Opts, CallbackMode, State, Data,
+ self(), Server_or_Actions);
+ true ->
+ enter_loop(
+ Module, Opts, CallbackMode, State, Data,
+ Server_or_Actions, [])
+ end.
+%%
+-spec enter_loop(
+ Module :: module(), Opts :: [debug_opt()],
+ CallbackMode :: callback_mode(),
+ State :: state(), Data :: data(),
+ Server :: server_name() | pid(),
+ Actions :: [action()] | action()) ->
+ no_return().
+enter_loop(Module, Opts, CallbackMode, State, Data, Server, Actions) ->
+ is_atom(Module) orelse error({atom,Module}),
+ callback_mode(CallbackMode) orelse error({callback_mode,CallbackMode}),
+ Parent = gen:get_parent(),
+ enter(Module, Opts, CallbackMode, 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 init_it/6 and enter_loop/5,6,7 functions converge
+enter(Module, Opts, CallbackMode, 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),
+ PrevState = make_ref(), % Will be discarded by loop_event_actions/9
+ NewActions =
+ if
+ is_list(Actions) ->
+ Actions ++ [{postpone,false}];
+ true ->
+ [Actions,{postpone,false}]
+ end,
+ S = #{
+ callback_mode => CallbackMode,
+ module => Module,
+ name => Name,
+ state => PrevState,
+ data => Data,
+ timer => undefined,
+ postponed => [],
+ hibernate => false},
+ loop_event_actions(
+ Parent, Debug, S, [],
+ {event,undefined}, % Will be discarded thanks to {postpone,false}
+ PrevState, State, Data, 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 ->
+ gen:unregister_name(ServerRef),
+ proc_lib:init_ack(Starter, {error,Reason}),
+ erlang:raise(Class, Reason, erlang:get_stacktrace())
+ end.
+
+%%---------------------------------------------------------------------------
+%% gen callbacks helpers
+
+init_result(Starter, Parent, ServerRef, Module, Result, Opts) ->
+ case Result of
+ {CallbackMode,State,Data} ->
+ case callback_mode(CallbackMode) of
+ true ->
+ proc_lib:init_ack(Starter, {ok,self()}),
+ enter(
+ Module, Opts, CallbackMode, State, Data,
+ ServerRef, [], Parent);
+ false ->
+ Error = {callback_mode,CallbackMode},
+ proc_lib:init_ack(Starter, {error,Error}),
+ exit(Error)
+ end;
+ {CallbackMode,State,Data,Actions} ->
+ case callback_mode(CallbackMode) of
+ true ->
+ proc_lib:init_ack(Starter, {ok,self()}),
+ enter(
+ Module, Opts, CallbackMode, State, Data,
+ ServerRef, Actions, Parent);
+ false ->
+ Error = {callback_mode,CallbackMode},
+ proc_lib:init_ack(Starter, {error,Error}),
+ exit(Error)
+ end;
+ {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);
+ _ ->
+ Error = {bad_return_value,Result},
+ proc_lib:init_ack(Starter, {error,Error}),
+ exit(Error)
+ end.
+
+%%%==========================================================================
+%%% sys callbacks
+
+system_continue(Parent, Debug, S) ->
+ loop(Parent, Debug, S).
+
+system_terminate(Reason, _Parent, Debug, S) ->
+ ?TERMINATE(exit, Reason, Debug, S, []).
+
+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
+ {NewCallbackMode,NewState,NewData} ->
+ callback_mode(NewCallbackMode) orelse
+ error({callback_mode,NewCallbackMode}),
+ {ok,S#{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} = 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) 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 := Name}) ->
+ io:format(
+ Dev, "*DBG* ~p received ~s~n",
+ [Name,event_string(Event)]);
+print_event(Dev, {out,Reply,{To,_Tag}}, #{name := Name}) ->
+ io:format(
+ Dev, "*DBG* ~p sent ~p to ~p~n",
+ [Name,Reply,To]);
+print_event(Dev, {Tag,Event,NewState}, #{name := Name, state := State}) ->
+ StateString =
+ case NewState of
+ State ->
+ io_lib:format("~p", [State]);
+ _ ->
+ io_lib:format("~p => ~p", [State,NewState])
+ 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]);
+ {Tag,Content} ->
+ io_lib:format("~w ~p", [Tag,Content])
+ end.
+
+sys_debug(Debug, S, Entry) ->
+ case Debug of
+ [] ->
+ Debug;
+ _ ->
+ sys:handle_debug(Debug, fun print_event/3, S, 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 some detours through sys and proc_lib
+
+%% 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 ->
+ %% 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, Debug, S, [EXIT]);
+ {timeout,Timer,Content} when Timer =/= undefined ->
+ loop_event(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_event(Parent, Debug, S, Event)
+ end
+ end.
+
+loop_event(Parent, Debug, S, Event) ->
+ %% The timer field and the hibernate flag in S
+ %% are now invalid and ignored until we get back to loop/3
+ NewDebug = sys_debug(Debug, S, {in,Event}),
+ %% Here the queue of not yet processed events is created
+ loop_events(Parent, NewDebug, S, [Event], false).
+
+%% Process first the event queue, or if it is empty
+%% loop back to receive a new event
+loop_events(Parent, Debug, S, [], _Hibernate) ->
+ loop(Parent, Debug, S);
+loop_events(
+ Parent, Debug,
+ #{callback_mode := CallbackMode,
+ module := Module,
+ state := State,
+ data := Data} = S,
+ [{Type,Content} = Event|Events] = Q,
+ Hibernate) ->
+ %% If the Hibernate flag 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
+ state_functions ->
+ Module:State(Type, Content, Data);
+ handle_event_function ->
+ Module:handle_event(Type, Content, State, Data)
+ end of
+ Result ->
+ loop_event_result(
+ Parent, Debug, S, Events, Event, Result)
+ catch
+ Result ->
+ loop_event_result(
+ Parent, Debug, S, Events, Event, Result);
+ error:badarg when CallbackMode =:= state_functions ->
+ case erlang:get_stacktrace() of
+ [{erlang,apply,[Module,State,_],_}|Stacktrace] ->
+ Args = [Type,Content,Data],
+ terminate(
+ error,
+ {undef_state_function,{Module,State,Args}},
+ Stacktrace,
+ Debug, S, Q);
+ Stacktrace ->
+ terminate(error, badarg, Stacktrace, Debug, S, Q)
+ end;
+ error:undef ->
+ %% Process an undef to check for the simple mistake
+ %% of calling a nonexistent state function
+ case erlang:get_stacktrace() of
+ [{Module,State,
+ [Type,Content,Data]=Args,
+ _}
+ |Stacktrace]
+ when CallbackMode =:= state_functions ->
+ terminate(
+ error,
+ {undef_state_function,{Module,State,Args}},
+ Stacktrace,
+ Debug, S, Q);
+ [{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, Q);
+ Stacktrace ->
+ terminate(error, undef, Stacktrace, Debug, S, Q)
+ end;
+ Class:Reason ->
+ Stacktrace = erlang:get_stacktrace(),
+ terminate(Class, Reason, Stacktrace, Debug, S, Q)
+ end.
+
+%% Interpret all callback return variants
+loop_event_result(
+ Parent, Debug,
+ #{state := State, data := Data} = S,
+ Events, Event, Result) ->
+ %% From now until we loop back to the loop_events/4
+ %% the state and data fields in S are old
+ case Result of
+ stop ->
+ ?TERMINATE(exit, normal, Debug, S, [Event|Events]);
+ {stop,Reason} ->
+ ?TERMINATE(exit, Reason, Debug, S, [Event|Events]);
+ {stop,Reason,NewData} ->
+ NewS = S#{data := NewData},
+ Q = [Event|Events],
+ ?TERMINATE(exit, Reason, Debug, NewS, Q);
+ {stop_and_reply,Reason,Replies} ->
+ Q = [Event|Events],
+ [Class,NewReason,Stacktrace,NewDebug] =
+ reply_then_terminate(
+ exit, Reason, ?STACKTRACE(), Debug, S, Q, Replies),
+ %% Since we got back here Replies was bad
+ terminate(Class, NewReason, Stacktrace, NewDebug, S, Q);
+ {stop_and_reply,Reason,Replies,NewData} ->
+ NewS = S#{data := NewData},
+ Q = [Event|Events],
+ [Class,NewReason,Stacktrace,NewDebug] =
+ reply_then_terminate(
+ exit, Reason, ?STACKTRACE(), Debug, NewS, Q, Replies),
+ %% Since we got back here Replies was bad
+ terminate(Class, NewReason, Stacktrace, NewDebug, NewS, Q);
+ {next_state,NextState,NewData} ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, []);
+ {next_state,NextState,NewData,Actions} ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions);
+ {keep_state,NewData} ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, State, NewData, []);
+ {keep_state,NewData,Actions} ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, State, NewData, Actions);
+ keep_state_and_data ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, State, Data, []);
+ {keep_state_and_data,Actions} ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, State, Data, Actions);
+ _ ->
+ ?TERMINATE(
+ error, {bad_return_value,Result}, Debug, S, [Event|Events])
+ end.
+
+loop_event_actions(
+ Parent, Debug, S, Events, Event, State, NextState, NewData, Actions) ->
+ Postpone = false, % Shall we postpone this event, true or false
+ Hibernate = false,
+ Timeout = undefined,
+ NextEvents = [],
+ loop_event_actions(
+ Parent, Debug, S, Events, Event, State, NextState, NewData,
+ if
+ is_list(Actions) ->
+ Actions;
+ true ->
+ [Actions]
+ end,
+ Postpone, Hibernate, Timeout, NextEvents).
+%%
+%% Process all action()s
+loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, [Action|Actions],
+ Postpone, Hibernate, Timeout, NextEvents) ->
+ case Action of
+ %% Actual actions
+ {reply,From,Reply} ->
+ case from(From) of
+ true ->
+ NewDebug = do_reply(Debug, S, From, Reply),
+ loop_event_actions(
+ Parent, NewDebug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, Hibernate, Timeout, NextEvents);
+ false ->
+ ?TERMINATE(
+ error, {bad_action,Action}, Debug, S, [Event|Events])
+ end;
+ {next_event,Type,Content} ->
+ case event_type(Type) of
+ true ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, Hibernate, Timeout,
+ [{Type,Content}|NextEvents]);
+ false ->
+ ?TERMINATE(
+ error, {bad_action,Action}, Debug, S, [Event|Events])
+ end;
+ %% Actions that set options
+ {postpone,NewPostpone} when is_boolean(NewPostpone) ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ NewPostpone, Hibernate, Timeout, NextEvents);
+ {postpone,_} ->
+ ?TERMINATE(
+ error, {bad_action,Action}, Debug, S, [Event|Events]);
+ postpone ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ true, Hibernate, Timeout, NextEvents);
+ {hibernate,NewHibernate} when is_boolean(NewHibernate) ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, NewHibernate, Timeout, NextEvents);
+ {hibernate,_} ->
+ ?TERMINATE(
+ error, {bad_action,Action}, Debug, S, [Event|Events]);
+ hibernate ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, true, Timeout, NextEvents);
+ {timeout,infinity,_} -> % Clear timer - it will never trigger
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, Hibernate, undefined, NextEvents);
+ {timeout,Time,_} = NewTimeout when is_integer(Time), Time >= 0 ->
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, Hibernate, NewTimeout, NextEvents);
+ {timeout,_,_} ->
+ ?TERMINATE(
+ error, {bad_action,Action}, Debug, S, [Event|Events]);
+ infinity -> % Clear timer - it will never trigger
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, Hibernate, undefined, NextEvents);
+ Time when is_integer(Time), Time >= 0 ->
+ NewTimeout = {timeout,Time,Time},
+ loop_event_actions(
+ Parent, Debug, S, Events, Event,
+ State, NextState, NewData, Actions,
+ Postpone, Hibernate, NewTimeout, NextEvents);
+ _ ->
+ ?TERMINATE(
+ error, {bad_action,Action}, Debug, S, [Event|Events])
+ end;
+%%
+%% End of actions list
+loop_event_actions(
+ Parent, Debug, #{postponed := P0} = S, Events, Event,
+ State, NextState, NewData, [],
+ 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
+ Q3 = lists:reverse(NextEvents, Q2),
+ %%
+ NewDebug =
+ sys_debug(
+ Debug, S,
+ case Postpone of
+ true ->
+ {postpone,Event,NextState};
+ false ->
+ {consume,Event,NextState}
+ end),
+ %% Have a peek on the event queue so we can avoid starting
+ %% the state timer unless we have to
+ {Q,Timer} =
+ case Timeout of
+ undefined ->
+ %% No state timeout has been requested
+ {Q3,undefined};
+ {timeout,Time,EventContent} ->
+ %% A state timeout has been requested
+ case Q3 of
+ [] when Time =:= 0 ->
+ %% Immediate timeout - simulate it
+ %% so we do not get the timeout message
+ %% after any received event
+ {[{timeout,EventContent}],undefined};
+ [] ->
+ %% Actually start a timer
+ {Q3,erlang:start_timer(Time, self(), EventContent)};
+ _ ->
+ %% Do not start a timer since any queued
+ %% event cancels the state timer so we pretend
+ %% that the timer has been started and cancelled
+ {Q3,undefined}
+ end
+ end,
+ %% Loop to top of event queue loop; process next event
+ loop_events(
+ Parent, NewDebug,
+ S#{
+ state := NextState,
+ data := NewData,
+ timer := Timer,
+ postponed := P,
+ hibernate := Hibernate},
+ Q, Hibernate).
+
+%%---------------------------------------------------------------------------
+%% Server helpers
+
+reply_then_terminate(Class, Reason, Stacktrace, Debug, S, Q, Replies) ->
+ if
+ is_list(Replies) ->
+ do_reply_then_terminate(
+ Class, Reason, Stacktrace, Debug, S, Q, Replies);
+ true ->
+ do_reply_then_terminate(
+ Class, Reason, Stacktrace, Debug, S, Q, [Replies])
+ end.
+%%
+do_reply_then_terminate(Class, Reason, Stacktrace, Debug, S, Q, []) ->
+ terminate(Class, Reason, Stacktrace, Debug, S, Q);
+do_reply_then_terminate(
+ Class, Reason, Stacktrace, Debug, S, Q, [R|Rs]) ->
+ case R of
+ {reply,{_To,_Tag}=From,Reply} ->
+ NewDebug = do_reply(Debug, S, From, Reply),
+ do_reply_then_terminate(
+ Class, Reason, Stacktrace, NewDebug, S, Q, Rs);
+ _ ->
+ [error,{bad_action,R},?STACKTRACE(),Debug]
+ end.
+
+do_reply(Debug, S, From, Reply) ->
+ reply(From, Reply),
+ sys_debug(Debug, S, {out,Reply,From}).
+
+
+terminate(
+ Class, Reason, Stacktrace, Debug,
+ #{module := Module,
+ state := State, data := Data} = S,
+ Q) ->
+ try Module:terminate(Reason, State, Data) of
+ _ -> ok
+ catch
+ _ -> ok;
+ C:R ->
+ ST = erlang:get_stacktrace(),
+ error_info(
+ C, R, ST, Debug, S, Q,
+ format_status(terminate, get(), S)),
+ erlang:raise(C, R, ST)
+ end,
+ case Reason of
+ normal -> ok;
+ shutdown -> ok;
+ {shutdown,_} -> ok;
+ _ ->
+ error_info(
+ Class, Reason, Stacktrace, Debug, S, Q,
+ format_status(terminate, get(), S))
+ end,
+ case Stacktrace of
+ [] ->
+ erlang:Class(Reason);
+ _ ->
+ erlang:raise(Class, Reason, Stacktrace)
+ end.
+
+error_info(
+ Class, Reason, Stacktrace, Debug,
+ #{name := Name, callback_mode := CallbackMode,
+ state := State, postponed := P},
+ Q, 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" ++
+ "** State = ~p~n" ++
+ "** Callback mode = ~p~n" ++
+ "** Queued/Postponed = ~w/~w~n" ++
+ case FixedStacktrace of
+ [] ->
+ "";
+ _ ->
+ "** Stacktrace =~n"
+ "** ~p~n"
+ end,
+ [Name |
+ case Q of
+ [] ->
+ [];
+ [Event|_] ->
+ [Event]
+ end] ++
+ [FmtData,Class,FixedReason,
+ State,CallbackMode,length(Q),length(P)] ++
+ case FixedStacktrace of
+ [] ->
+ [];
+ _ ->
+ [FixedStacktrace]
+ end),
+ sys:print_log(Debug),
+ ok.
+
+
+%% Call Module:format_status/2 or return a default value
+format_status(
+ Opt, PDict,
+ #{module := Module, state := State, data := 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,
+ "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) ->
+ SSD = {State,Data},
+ case Opt of
+ terminate ->
+ SSD;
+ _ ->
+ [{data,[{"State",SSD}]}]
+ end.