diff options
Diffstat (limited to 'lib/stdlib/doc/src/gen_fsm.xml')
| -rw-r--r-- | lib/stdlib/doc/src/gen_fsm.xml | 1095 |
1 files changed, 170 insertions, 925 deletions
diff --git a/lib/stdlib/doc/src/gen_fsm.xml b/lib/stdlib/doc/src/gen_fsm.xml index de06987d38..7187630b43 100644 --- a/lib/stdlib/doc/src/gen_fsm.xml +++ b/lib/stdlib/doc/src/gen_fsm.xml @@ -4,14 +4,14 @@ <erlref> <header> <copyright> - <year>1996</year><year>2016</year> + <year>1996-2017</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> 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 @@ -29,931 +29,176 @@ <rev></rev> </header> <module>gen_fsm</module> - <modulesummary>Generic finite state machine behavior.</modulesummary> - <description> - <note> - <p> - There is a new behaviour - <seealso marker="gen_statem"><c>gen_statem</c></seealso> - that is intended to replace <c>gen_fsm</c> for new code. - <c>gen_fsm</c> will not be removed for the foreseeable future - to keep old state machine implementations running. - </p> - </note> - <p>This behavior module provides a finite state machine. - A generic finite state machine process (<c>gen_fsm</c>) implemented - using this module has a standard set of interface functions - and includes functionality for tracing and error reporting. It - also fits into an OTP supervision tree. For more information, see - <seealso marker="doc/design_principles:fsm">OTP Design Principles</seealso>. - </p> - - <p>A <c>gen_fsm</c> process assumes all specific parts to be located in a - callback module exporting a predefined set of functions. The relationship - between the behavior functions and the callback functions is as - follows:</p> - - <pre> -gen_fsm module Callback module --------------- --------------- -gen_fsm:start -gen_fsm:start_link -----> Module:init/1 - -gen_fsm:stop -----> Module:terminate/3 - -gen_fsm:send_event -----> Module:StateName/2 - -gen_fsm:send_all_state_event -----> Module:handle_event/3 - -gen_fsm:sync_send_event -----> Module:StateName/3 - -gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4 - -- -----> Module:handle_info/3 - -- -----> Module:terminate/3 + <modulesummary>Deprecated and replaced by gen_statem </modulesummary> -- -----> Module:code_change/4</pre> - - <p>If a callback function fails or returns a bad value, the <c>gen_fsm</c> - process terminates.</p> - - <p>A <c>gen_fsm</c> process handles system messages as described in - <seealso marker="sys"><c>sys(3)</c></seealso>. The <c>sys</c> module - can be used for debugging a <c>gen_fsm</c> process.</p> - - <p>Notice that a <c>gen_fsm</c> process does not trap exit signals - automatically, this must be explicitly initiated in the callback - module.</p> - - <p>Unless otherwise stated, all functions in this module fail if - the specified <c>gen_fsm</c> process does not exist or if bad arguments - are specified.</p> - - <p>The <c>gen_fsm</c> process can go into hibernation - (see <seealso marker="erts:erlang#hibernate/3"> - <c>erlang:hibernate/3</c></seealso>) if a callback function - specifies <c>'hibernate'</c> instead of a time-out value. This - can be useful if the server is expected to be idle for a long - time. However, use this feature with care, as hibernation - implies at least two garbage collections (when hibernating and - shortly after waking up) and is not something you want to do - between each call to a busy state machine.</p> + <description> + <p> Deprecated and replaced by <seealso marker="gen_statem"><c>gen_statem</c></seealso> </p> </description> - - <funcs> - <func> - <name>cancel_timer(Ref) -> RemainingTime | false</name> - <fsummary>Cancel an internal timer in a generic FSM.</fsummary> - <type> - <v>Ref = reference()</v> - <v>RemainingTime = integer()</v> - </type> - <desc> - <p>Cancels an internal timer referred by <c>Ref</c> in the - <c>gen_fsm</c> process that calls this function.</p> - <p><c>Ref</c> is a reference returned from - <seealso marker="#send_event_after/2"> - <c>send_event_after/2</c></seealso> or - <seealso marker="#start_timer/2"><c>start_timer/2</c></seealso>.</p> - <p>If the timer has already timed out, but the event not yet - been delivered, it is cancelled as if it had <em>not</em> - timed out, so there is no false timer event after - returning from this function.</p> - <p>Returns the remaining time in milliseconds until the timer would - have expired if <c>Ref</c> referred to an active timer, otherwise - <c>false</c>.</p> - </desc> - </func> - - <func> - <name>enter_loop(Module, Options, StateName, StateData)</name> - <name>enter_loop(Module, Options, StateName, StateData, FsmName)</name> - <name>enter_loop(Module, Options, StateName, StateData, Timeout)</name> - <name>enter_loop(Module, Options, StateName, StateData, FsmName, Timeout)</name> - <fsummary>Enter the <c>gen_fsm</c> receive loop.</fsummary> - <type> - <v>Module = atom()</v> - <v>Options = [Option]</v> - <v> Option = {debug,Dbgs}</v> - <v> Dbgs = [Dbg]</v> - <v> Dbg = trace | log | statistics</v> - <v> | {log_to_file,FileName} | {install,{Func,FuncState}}</v> - <v>StateName = atom()</v> - <v>StateData = term()</v> - <v>FsmName = {local,Name} | {global,GlobalName}</v> - <v> | {via,Module,ViaName}</v> - <v> Name = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Timeout = int() | infinity</v> - </type> - <desc> - <p>Makes an existing process into a <c>gen_fsm</c> process. - Does not return, - instead the calling process enters the <c>gen_fsm</c> receive - loop and becomes a <c>gen_fsm</c> process. The process <em>must</em> - have been started using one of the start functions in - <seealso marker="proc_lib"><c>proc_lib(3)</c></seealso>. The user is - responsible for any initialization of the process, including - registering a name for it.</p> - <p>This function is useful when a more complex initialization - procedure is needed than the <c>gen_fsm</c> behavior provides.</p> - <p><c>Module</c>, <c>Options</c>, and <c>FsmName</c> have - the same meanings as when calling - <seealso marker="#start_link/3"><c>start[_link]/3,4</c></seealso>. - However, if <c>FsmName</c> is specified, the process must have - been registered accordingly <em>before</em> this function is - called.</p> - <p><c>StateName</c>, <c>StateData</c>, and <c>Timeout</c> have - the same meanings as in the return value of - <seealso marker="#Moduleinit"><c>Module:init/1</c></seealso>. - The callback module <c>Module</c> does not need to - export an <c>init/1</c> function.</p> - <p>The function fails if the calling process was not started by a - <c>proc_lib</c> start function, or if it is not registered - according to <c>FsmName</c>.</p> - </desc> - </func> - - <func> - <name>reply(Caller, Reply) -> Result</name> - <fsummary>Send a reply to a caller.</fsummary> - <type> - <v>Caller - see below</v> - <v>Reply = term()</v> - <v>Result = term()</v> - </type> - <desc> - <p>This function can be used by a <c>gen_fsm</c> process to - explicitly send a reply to a client process that called - <seealso marker="#sync_send_event/2"> - <c>sync_send_event/2,3</c></seealso> or - <seealso marker="#sync_send_all_state_event/2"> - <c>sync_send_all_state_event/2,3</c></seealso> - when the reply cannot be defined in the return value of - <seealso marker="#Module:StateName/3"> - <c>Module:StateName/3</c></seealso> or - <seealso marker="#Module:handle_sync_event/4"> - <c>Module:handle_sync_event/4</c></seealso>.</p> - <p><c>Caller</c> must be the <c>From</c> argument provided to - the callback function. <c>Reply</c> is any term - given back to the client as the return value of - <c>sync_send_event/2,3</c> or - <c>sync_send_all_state_event/2,3</c>.</p> - <p>Return value <c>Result</c> is not further defined, and - is always to be ignored.</p> - </desc> - </func> - - <func> - <name>send_all_state_event(FsmRef, Event) -> ok</name> - <fsummary>Send an event asynchronously to a generic FSM.</fsummary> - <type> - <v>FsmRef = Name | {Name,Node} | {global,GlobalName}</v> - <v> | {via,Module,ViaName} | pid()</v> - <v> Name = Node = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Event = term()</v> - </type> - <desc> - <p>Sends an event asynchronously to the <c>FsmRef</c> of the - <c>gen_fsm</c> process and returns <c>ok</c> immediately. - The <c>gen_fsm</c> process calls - <seealso marker="#Module:handle_event/3"> - <c>Module:handle_event/3</c></seealso> to handle the event.</p> - <p>For a description of the arguments, see - <seealso marker="#send_event/2"><c>send_event/2</c></seealso>.</p> - <p>The difference between <c>send_event/2</c> and - <c>send_all_state_event/2</c> is which callback function is - used to handle the event. This function is useful when - sending events that are handled the same way in every state, - as only one <c>handle_event</c> clause is needed to handle - the event instead of one clause in each state name function.</p> - </desc> - </func> - - <func> - <name>send_event(FsmRef, Event) -> ok</name> - <fsummary>Send an event asynchronously to a generic FSM.</fsummary> - <type> - <v>FsmRef = Name | {Name,Node} | {global,GlobalName}</v> - <v> | {via,Module,ViaName} | pid()</v> - <v> Name = Node = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Event = term()</v> - </type> - <desc> - <p>Sends an event asynchronously to the <c>FsmRef</c> of the - <c>gen_fsm</c> process - and returns <c>ok</c> immediately. The <c>gen_fsm</c> process calls - <seealso marker="#Module:StateName/2"> - <c>Module:StateName/2</c></seealso> to handle the event, where - <c>StateName</c> is the name of the current state of - the <c>gen_fsm</c> process.</p> - <p><c>FsmRef</c> can be any of the following:</p> - <list type="bulleted"> - <item>The pid</item> - <item><c>Name</c>, if the <c>gen_fsm</c> process is locally - registered</item> - <item><c>{Name,Node}</c>, if the <c>gen_fsm</c> process is locally - registered at another node</item> - <item><c>{global,GlobalName}</c>, if the <c>gen_fsm</c> process is - globally registered</item> - <item><c>{via,Module,ViaName}</c>, if the <c>gen_fsm</c> process is - registered through an alternative process registry</item> - </list> - <p><c>Event</c> is any term that is passed as one of - the arguments to <c>Module:StateName/2</c>.</p> - </desc> - </func> - - <func> - <name>send_event_after(Time, Event) -> Ref</name> - <fsummary>Send a delayed event internally in a generic FSM.</fsummary> - <type> - <v>Time = integer()</v> - <v>Event = term()</v> - <v>Ref = reference()</v> - </type> - <desc> - <p>Sends a delayed event internally in the <c>gen_fsm</c> process - that calls this function after <c>Time</c> milliseconds. - Returns immediately a - reference that can be used to cancel the delayed send using - <seealso marker="#cancel_timer/1"><c>cancel_timer/1</c></seealso>.</p> - <p>The <c>gen_fsm</c> process calls - <seealso marker="#Module:StateName/2"> - <c>Module:StateName/2</c></seealso> to handle - the event, where <c>StateName</c> is the name of the current - state of the <c>gen_fsm</c> process at the time the delayed event is - delivered.</p> - <p><c>Event</c> is any term that is passed as one of - the arguments to <c>Module:StateName/2</c>.</p> - </desc> - </func> - - <func> - <name>start(Module, Args, Options) -> Result</name> - <name>start(FsmName, Module, Args, Options) -> Result</name> - <fsummary>Create a standalone <c>gen_fsm</c> process.</fsummary> - <type> - <v>FsmName = {local,Name} | {global,GlobalName}</v> - <v> | {via,Module,ViaName}</v> - <v> Name = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Module = atom()</v> - <v>Args = term()</v> - <v>Options = [Option]</v> - <v> Option = {debug,Dbgs} | {timeout,Time} | {spawn_opt,SOpts}</v> - <v> Dbgs = [Dbg]</v> - <v> Dbg = trace | log | statistics</v> - <v> | {log_to_file,FileName} | {install,{Func,FuncState}}</v> - <v> SOpts = [term()]</v> - <v>Result = {ok,Pid} | ignore | {error,Error}</v> - <v> Pid = pid()</v> - <v> Error = {already_started,Pid} | term()</v> - </type> - <desc> - <p>Creates a standalone <c>gen_fsm</c> process, that is, a process that - is not part of a supervision tree and thus has no supervisor.</p> - <p>For a description of arguments and return values, see - <seealso marker="#start_link/3"><c>start_link/3,4</c></seealso>.</p> - </desc> - </func> - - <func> - <name>start_link(Module, Args, Options) -> Result</name> - <name>start_link(FsmName, Module, Args, Options) -> Result</name> - <fsummary>Create a <c>gen_fsm</c> process in a supervision tree. - </fsummary> - <type> - <v>FsmName = {local,Name} | {global,GlobalName}</v> - <v> | {via,Module,ViaName}</v> - <v> Name = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Module = atom()</v> - <v>Args = term()</v> - <v>Options = [Option]</v> - <v> Option = {debug,Dbgs} | {timeout,Time} | {spawn_opt,SOpts}</v> - <v> Dbgs = [Dbg]</v> - <v> Dbg = trace | log | statistics</v> - <v> | {log_to_file,FileName} | {install,{Func,FuncState}}</v> - <v> SOpts = [SOpt]</v> - <v> SOpt - see erlang:spawn_opt/2,3,4,5</v> - <v>Result = {ok,Pid} | ignore | {error,Error}</v> - <v> Pid = pid()</v> - <v> Error = {already_started,Pid} | term()</v> - </type> - <desc> - <p>Creates a <c>gen_fsm</c> process as part of a supervision tree. - The function is to be called, directly or indirectly, by - the supervisor. For example, it ensures that - the <c>gen_fsm</c> process is linked to the supervisor.</p> - <p>The <c>gen_fsm</c> process calls - <seealso marker="#Module:init/1"><c>Module:init/1</c></seealso> to - initialize. To ensure a synchronized startup procedure, - <c>start_link/3,4</c> does not return until - <c>Module:init/1</c> has returned.</p> - <list type="bulleted"> - <item> - <p>If <c>FsmName={local,Name}</c>, the <c>gen_fsm</c> process is - registered locally as <c>Name</c> using <c>register/2</c>.</p> - </item> - <item> - <p>If <c>FsmName={global,GlobalName}</c>, the <c>gen_fsm</c> process - is registered globally as <c>GlobalName</c> using - <seealso marker="kernel:global#register_name/2"> - <c>global:register_name/2</c></seealso>.</p> - </item> - <item> - <p>If <c>FsmName={via,Module,ViaName}</c>, the <c>gen_fsm</c> - process registers with the registry represented by <c>Module</c>. - The <c>Module</c> callback is to export the functions - <c>register_name/2</c>, <c>unregister_name/1</c>, - <c>whereis_name/1</c>, and <c>send/2</c>, which are to behave - like the corresponding functions in - <seealso marker="kernel:global"><c>global</c></seealso>. - Thus, <c>{via,global,GlobalName}</c> is a valid reference.</p> - </item> - </list> - <p>If no name is provided, the <c>gen_fsm</c> process is not - registered.</p> - <p><c>Module</c> is the name of the callback module.</p> - <p><c>Args</c> is any term that is passed as - the argument to <c>Module:init/1</c>.</p> - <p>If option <c>{timeout,Time}</c> is present, the <c>gen_fsm</c> - process is allowed to spend <c>Time</c> milliseconds initializing - or it terminates and the start function returns - <c>{error,timeout}</c>.</p> - <p>If option <c>{debug,Dbgs}</c> is present, the corresponding - <c>sys</c> function is called for each item in <c>Dbgs</c>; see - <seealso marker="sys"><c>sys(3)</c></seealso>.</p> - <p>If option <c>{spawn_opt,SOpts}</c> is present, <c>SOpts</c> is - passed as option list to the <c>spawn_opt</c> BIF that is used to - spawn the <c>gen_fsm</c> process; see - <seealso marker="erts:erlang#spawn_opt/2"> - <c>spawn_opt/2</c></seealso>.</p> - <note> - <p>Using spawn option <c>monitor</c> is not - allowed, it causes the function to fail with reason - <c>badarg</c>.</p> - </note> - <p>If the <c>gen_fsm</c> process is successfully created and - initialized, the function returns <c>{ok,Pid}</c>, where <c>Pid</c> - is the pid of the <c>gen_fsm</c> process. If a process with the - specified <c>FsmName</c> exists already, the function returns - <c>{error,{already_started,Pid}}</c>, where <c>Pid</c> is - the pid of that process.</p> - <p>If <c>Module:init/1</c> fails with <c>Reason</c>, - the function returns <c>{error,Reason}</c>. If - <c>Module:init/1</c> returns <c>{stop,Reason}</c> or - <c>ignore</c>, the process is terminated and the function - returns <c>{error,Reason}</c> or <c>ignore</c>, respectively.</p> - </desc> - </func> - - <func> - <name>start_timer(Time, Msg) -> Ref</name> - <fsummary>Send a time-out event internally in a generic FSM.</fsummary> - <type> - <v>Time = integer()</v> - <v>Msg = term()</v> - <v>Ref = reference()</v> - </type> - <desc> - <p>Sends a time-out event internally in the <c>gen_fsm</c> - process that calls this function after <c>Time</c> milliseconds. - Returns immediately a - reference that can be used to cancel the timer using - <seealso marker="#cancel_timer/1"><c>cancel_timer/1</c></seealso>.</p> - <p>The <c>gen_fsm</c> process calls - <seealso marker="#Module:StateName/2"> - <c>Module:StateName/2</c></seealso> to handle - the event, where <c>StateName</c> is the name of the current - state of the <c>gen_fsm</c> process at the time the time-out - message is delivered.</p> - <p><c>Msg</c> is any term that is passed in the - time-out message, <c>{timeout, Ref, Msg}</c>, as one of - the arguments to <c>Module:StateName/2</c>.</p> - </desc> - </func> - - <func> - <name>stop(FsmRef) -> ok</name> - <name>stop(FsmRef, Reason, Timeout) -> ok</name> - <fsummary>Synchronously stop a generic FSM.</fsummary> - <type> - <v>FsmRef = Name | {Name,Node} | {global,GlobalName}</v> - <v> | {via,Module,ViaName} | pid()</v> - <v> Node = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Reason = term()</v> - <v>Timeout = int()>0 | infinity</v> - </type> - <desc> - <p>Orders a generic finite state machine to exit with the specified - <c>Reason</c> and waits for it to terminate. The <c>gen_fsm</c> - process calls <seealso marker="#Module:terminate/3"> - <c>Module:terminate/3</c></seealso> before exiting.</p> - <p>The function returns <c>ok</c> if the generic finite state machine - terminates with the expected reason. Any other reason than - <c>normal</c>, <c>shutdown</c>, or <c>{shutdown,Term}</c> causes an - error report to be issued using - <seealso marker="kernel:error_logger#format/2"> - <c>error_logger:format/2</c></seealso>. - The default <c>Reason</c> is <c>normal</c>.</p> - <p><c>Timeout</c> is an integer greater than zero that - specifies how many milliseconds to wait for the generic FSM - to terminate, or the atom <c>infinity</c> to wait - indefinitely. The default value is <c>infinity</c>. If the - generic finite state machine has not terminated within the specified - time, a <c>timeout</c> exception is raised.</p> - <p>If the process does not exist, a <c>noproc</c> exception - is raised.</p> - </desc> - </func> - - <func> - <name>sync_send_all_state_event(FsmRef, Event) -> Reply</name> - <name>sync_send_all_state_event(FsmRef, Event, Timeout) -> Reply</name> - <fsummary>Send an event synchronously to a generic FSM.</fsummary> - <type> - <v>FsmRef = Name | {Name,Node} | {global,GlobalName}</v> - <v> | {via,Module,ViaName} | pid()</v> - <v> Name = Node = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Event = term()</v> - <v>Timeout = int()>0 | infinity</v> - <v>Reply = term()</v> - </type> - <desc> - <p>Sends an event to the <c>FsmRef</c> of the <c>gen_fsm</c> - process and waits until a reply arrives or a time-out occurs. - The <c>gen_fsm</c> process calls - <seealso marker="#Module:handle_sync_event/4"> - <c>Module:handle_sync_event/4</c></seealso> to handle the event.</p> - <p>For a description of <c>FsmRef</c> and <c>Event</c>, see - <seealso marker="#send_event/2">send_event/2</seealso>. - For a description of <c>Timeout</c> and <c>Reply</c>, see - <seealso marker="#sync_send_event/3"> - <c>sync_send_event/3</c></seealso>.</p> - <p>For a discussion about the difference between - <c>sync_send_event</c> and <c>sync_send_all_state_event</c>, see - <seealso marker="#send_all_state_event/2"> - <c>send_all_state_event/2</c></seealso>.</p> - </desc> - </func> - - <func> - <name>sync_send_event(FsmRef, Event) -> Reply</name> - <name>sync_send_event(FsmRef, Event, Timeout) -> Reply</name> - <fsummary>Send an event synchronously to a generic FSM.</fsummary> - <type> - <v>FsmRef = Name | {Name,Node} | {global,GlobalName}</v> - <v> | {via,Module,ViaName} | pid()</v> - <v> Name = Node = atom()</v> - <v> GlobalName = ViaName = term()</v> - <v>Event = term()</v> - <v>Timeout = int()>0 | infinity</v> - <v>Reply = term()</v> - </type> - <desc> - <p>Sends an event to the <c>FsmRef</c> of the <c>gen_fsm</c> - process and waits until a reply arrives or a time-out occurs. - <c>The gen_fsm</c> process calls - <seealso marker="#Module:StateName/3"> - <c>Module:StateName/3</c></seealso> to handle the event, where - <c>StateName</c> is the name of the current state of - the <c>gen_fsm</c> process.</p> - <p>For a description of <c>FsmRef</c> and <c>Event</c>, see - <seealso marker="#send_event/2"><c>send_event/2</c></seealso>.</p> - <p><c>Timeout</c> is an integer greater than zero that - specifies how many milliseconds to wait for a reply, or - the atom <c>infinity</c> to wait indefinitely. Defaults - to 5000. If no reply is received within the specified time, - the function call fails.</p> - <p>Return value <c>Reply</c> is defined in the return value - of <c>Module:StateName/3</c>.</p> - <note> - <p>The ancient behavior of sometimes consuming the server - exit message if the server died during the call while - linked to the client was removed in Erlang 5.6/OTP R12B.</p> - </note> - </desc> - </func> - </funcs> - - <section> - <title>Callback Functions</title> - <p>The following functions are to be exported from a <c>gen_fsm</c> - callback module.</p> - - <p><em>state name</em> denotes a state of the state machine.</p> - - <p><em>state data</em> denotes the internal state of the Erlang process - that implements the state machine.</p> - </section> - - <funcs> - <func> - <name>Module:code_change(OldVsn, StateName, StateData, Extra) -> {ok, NextStateName, NewStateData}</name> - <fsummary>Update the internal state data during upgrade/downgrade. - </fsummary> - <type> - <v>OldVsn = Vsn | {down, Vsn}</v> - <v> Vsn = term()</v> - <v>StateName = NextStateName = atom()</v> - <v>StateData = NewStateData = term()</v> - <v>Extra = term()</v> - </type> - <desc> - <p>This function is called by a <c>gen_fsm</c> process when it is to - update its internal state data during a release upgrade/downgrade, - that is, when instruction <c>{update,Module,Change,...}</c>, - where <c>Change={advanced,Extra}</c>, is given in - the <c>appup</c> file; see section - <seealso marker="doc/design_principles:release_handling#instr"> - Release Handling Instructions</seealso> in OTP Design Principles.</p> - <p>For an upgrade, <c>OldVsn</c> is <c>Vsn</c>, and for a downgrade, - <c>OldVsn</c> is <c>{down,Vsn}</c>. <c>Vsn</c> is defined by the - <c>vsn</c> attribute(s) of the old version of the callback module - <c>Module</c>. If no such attribute is defined, the version is - the checksum of the Beam file.</p> - <p><c>StateName</c> is the current state name and <c>StateData</c> the - internal state data of the <c>gen_fsm</c> process.</p> - <p><c>Extra</c> is passed "as is" from the <c>{advanced,Extra}</c> - part of the update instruction.</p> - <p>The function is to return the new current state name and - updated internal data.</p> - </desc> - </func> - - <func> - <name>Module:format_status(Opt, [PDict, StateData]) -> Status</name> - <fsummary>Optional function for providing a term describing the - current <c>gen_fsm</c> process status.</fsummary> - <type> - <v>Opt = normal | terminate</v> - <v>PDict = [{Key, Value}]</v> - <v>StateData = term()</v> - <v>Status = term()</v> - </type> - <desc> - <note> - <p>This callback is optional, so callback modules need not - export it. The <c>gen_fsm</c> module provides a default - implementation of this function that returns the callback - module state data.</p> - </note> - <p>This function is called by a <c>gen_fsm</c> process in the - following situations:</p> - <list type="bulleted"> - <item>One of <seealso marker="sys#get_status/1"> - <c>sys:get_status/1,2</c></seealso> - is invoked to get the <c>gen_fsm</c> status. <c>Opt</c> is set to - the atom <c>normal</c> for this case.</item> - <item>The <c>gen_fsm</c> process terminates abnormally and logs an - error. <c>Opt</c> is set to the atom <c>terminate</c> for - this case.</item> - </list> - <p>This function is useful for changing the form and - appearance of the <c>gen_fsm</c> status for these cases. A callback - module wishing to change the <c>sys:get_status/1,2</c> - return value as well as how its status appears in - termination error logs, exports an instance - of <c>format_status/2</c> that returns a term describing the - current status of the <c>gen_fsm</c> process.</p> - <p><c>PDict</c> is the current value of the process dictionary of the - <c>gen_fsm</c> process.</p> - <p><c>StateData</c> is the internal state data of the - <c>gen_fsm</c> process.</p> - <p>The function is to return <c>Status</c>, a term that - change the details of the current state and status of - the <c>gen_fsm</c> process. There are no restrictions on the - form <c>Status</c> can take, but for - the <c>sys:get_status/1,2</c> case (when <c>Opt</c> - is <c>normal</c>), the recommended form for - the <c>Status</c> value is <c>[{data, [{"StateData", - Term}]}]</c>, where <c>Term</c> provides relevant details of - the <c>gen_fsm</c> state data. Following this recommendation is not - required, but it makes the callback module status - consistent with the rest of the <c>sys:get_status/1,2</c> - return value.</p> - <p>One use for this function is to return compact alternative - state data representations to avoid that large state terms - are printed in log files.</p> - </desc> - </func> - - <func> - <name>Module:handle_event(Event, StateName, StateData) -> Result</name> - <fsummary>Handle an asynchronous event.</fsummary> - <type> - <v>Event = term()</v> - <v>StateName = atom()</v> - <v>StateData = term()</v> - <v>Result = {next_state,NextStateName,NewStateData}</v> - <v> | {next_state,NextStateName,NewStateData,Timeout}</v> - <v> | {next_state,NextStateName,NewStateData,hibernate}</v> - <v> | {stop,Reason,NewStateData}</v> - <v> NextStateName = atom()</v> - <v> NewStateData = term()</v> - <v> Timeout = int()>0 | infinity</v> - <v> Reason = term()</v> - </type> - <desc> - <p>Whenever a <c>gen_fsm</c> process receives an event sent using - <seealso marker="#send_all_state_event/2"> - <c>send_all_state_event/2</c></seealso>, - this function is called to handle the event.</p> - <p><c>StateName</c> is the current state name of the <c>gen_fsm</c> - process.</p> - <p>For a description of the other arguments and possible return values, - see <seealso marker="#Module:StateName/2"> - <c>Module:StateName/2</c></seealso>.</p> - </desc> - </func> - - <func> - <name>Module:handle_info(Info, StateName, StateData) -> Result</name> - <fsummary>Handle an incoming message.</fsummary> - <type> - <v>Info = term()</v> - <v>StateName = atom()</v> - <v>StateData = term()</v> - <v>Result = {next_state,NextStateName,NewStateData}</v> - <v> | {next_state,NextStateName,NewStateData,Timeout}</v> - <v> | {next_state,NextStateName,NewStateData,hibernate}</v> - <v> | {stop,Reason,NewStateData}</v> - <v> NextStateName = atom()</v> - <v> NewStateData = term()</v> - <v> Timeout = int()>0 | infinity</v> - <v> Reason = normal | term()</v> - </type> - <desc> - <p>This function is called by a <c>gen_fsm</c> process when it receives - any other message than a synchronous or asynchronous event (or a - system message).</p> - <p><c>Info</c> is the received message.</p> - <p>For a description of the other arguments and possible return values, - see <seealso marker="#Module:StateName/2"> - <c>Module:StateName/2</c></seealso>.</p> - </desc> - </func> - - <func> - <name>Module:handle_sync_event(Event, From, StateName, StateData) -> Result</name> - <fsummary>Handle a synchronous event.</fsummary> - <type> - <v>Event = term()</v> - <v>From = {pid(),Tag}</v> - <v>StateName = atom()</v> - <v>StateData = term()</v> - <v>Result = {reply,Reply,NextStateName,NewStateData}</v> - <v> | {reply,Reply,NextStateName,NewStateData,Timeout}</v> - <v> | {reply,Reply,NextStateName,NewStateData,hibernate}</v> - <v> | {next_state,NextStateName,NewStateData}</v> - <v> | {next_state,NextStateName,NewStateData,Timeout}</v> - <v> | {next_state,NextStateName,NewStateData,hibernate}</v> - <v> | {stop,Reason,Reply,NewStateData} | {stop,Reason,NewStateData}</v> - <v> Reply = term()</v> - <v> NextStateName = atom()</v> - <v> NewStateData = term()</v> - <v> Timeout = int()>0 | infinity</v> - <v> Reason = term()</v> - </type> - <desc> - <p>Whenever a <c>gen_fsm</c> process receives an event sent using - <seealso marker="#sync_send_all_state_event/2"> - <c>sync_send_all_state_event/2,3</c></seealso>, - this function is called to handle the event.</p> - <p><c>StateName</c> is the current state name of the <c>gen_fsm</c> - process.</p> - <p>For a description of the other arguments and possible return values, - see <seealso marker="#Module:StateName/3"> - <c>Module:StateName/3</c></seealso>.</p> - </desc> - </func> - - <func> - <name>Module:init(Args) -> Result</name> - <fsummary>Initialize process and internal state name and state data. - </fsummary> - <type> - <v>Args = term()</v> - <v>Result = {ok,StateName,StateData} | {ok,StateName,StateData,Timeout}</v> - <v> | {ok,StateName,StateData,hibernate}</v> - <v> | {stop,Reason} | ignore</v> - <v> StateName = atom()</v> - <v> StateData = term()</v> - <v> Timeout = int()>0 | infinity</v> - <v> Reason = term()</v> - </type> - <desc> - <marker id="Moduleinit"></marker> - <p>Whenever a <c>gen_fsm</c> process is started using - <seealso marker="#start/3"><c>start/3,4</c></seealso> or - <seealso marker="#start_link/3"><c>start_link/3,4</c></seealso>, - this function is called by the new process to initialize.</p> - <p><c>Args</c> is the <c>Args</c> argument provided to the start - function.</p> - <p>If initialization is successful, the function is to return - <c>{ok,StateName,StateData}</c>, - <c>{ok,StateName,StateData,Timeout}</c>, or - <c>{ok,StateName,StateData,hibernate}</c>, where <c>StateName</c> - is the initial state name and <c>StateData</c> the initial - state data of the <c>gen_fsm</c> process.</p> - <p>If an integer time-out value is provided, a time-out occurs - unless an event or a message is received within <c>Timeout</c> - milliseconds. A time-out is represented by the atom - <c>timeout</c> and is to be handled by the - <seealso marker="#Module:StateName/2"> - <c>Module:StateName/2</c></seealso> callback functions. The atom - <c>infinity</c> can be used to wait indefinitely, this is - the default value.</p> - <p>If <c>hibernate</c> is specified instead of a time-out value, the - process goes into hibernation when waiting for the next message - to arrive (by calling <seealso marker="proc_lib#hibernate/3"> - <c>proc_lib:hibernate/3</c></seealso>).</p> - <p>If the initialization fails, the function returns - <c>{stop,Reason}</c>, where <c>Reason</c> is any term, - or <c>ignore</c>.</p> - </desc> - </func> - - <func> - <name>Module:StateName(Event, StateData) -> Result</name> - <fsummary>Handle an asynchronous event.</fsummary> - <type> - <v>Event = timeout | term()</v> - <v>StateData = term()</v> - <v>Result = {next_state,NextStateName,NewStateData} </v> - <v> | {next_state,NextStateName,NewStateData,Timeout}</v> - <v> | {next_state,NextStateName,NewStateData,hibernate}</v> - <v> | {stop,Reason,NewStateData}</v> - <v> NextStateName = atom()</v> - <v> NewStateData = term()</v> - <v> Timeout = int()>0 | infinity</v> - <v> Reason = term()</v> - </type> - <desc> - <p>There is to be one instance of this function for each - possible state name. Whenever a <c>gen_fsm</c> process receives - an event sent using - <seealso marker="#send_event/2"><c>send_event/2</c></seealso>, - the instance of this function with the same name as - the current state name <c>StateName</c> is called to handle - the event. It is also called if a time-out occurs.</p> - <p><c>Event</c> is either the atom <c>timeout</c>, if a time-out - has occurred, or the <c>Event</c> argument provided to - <c>send_event/2</c>.</p> - <p><c>StateData</c> is the state data of the <c>gen_fsm</c> process.</p> - <p>If the function returns - <c>{next_state,NextStateName,NewStateData}</c>, - <c>{next_state,NextStateName,NewStateData,Timeout}</c>, or - <c>{next_state,NextStateName,NewStateData,hibernate}</c>, the - <c>gen_fsm</c> process continues executing with the current state - name set to <c>NextStateName</c> and with the possibly - updated state data <c>NewStateData</c>. For a description of - <c>Timeout</c> and <c>hibernate</c>, see - <seealso marker="#Module:init/1"><c>Module:init/1</c></seealso>.</p> - <p>If the function returns <c>{stop,Reason,NewStateData}</c>, - the <c>gen_fsm</c> process calls - <c>Module:terminate(Reason,StateName,NewStateData)</c> and - terminates.</p> - </desc> - </func> - - <func> - <name>Module:StateName(Event, From, StateData) -> Result</name> - <fsummary>Handle a synchronous event.</fsummary> - <type> - <v>Event = term()</v> - <v>From = {pid(),Tag}</v> - <v>StateData = term()</v> - <v>Result = {reply,Reply,NextStateName,NewStateData}</v> - <v> | {reply,Reply,NextStateName,NewStateData,Timeout}</v> - <v> | {reply,Reply,NextStateName,NewStateData,hibernate}</v> - <v> | {next_state,NextStateName,NewStateData}</v> - <v> | {next_state,NextStateName,NewStateData,Timeout}</v> - <v> | {next_state,NextStateName,NewStateData,hibernate}</v> - <v> | {stop,Reason,Reply,NewStateData} | {stop,Reason,NewStateData}</v> - <v> Reply = term()</v> - <v> NextStateName = atom()</v> - <v> NewStateData = term()</v> - <v> Timeout = int()>0 | infinity</v> - <v> Reason = normal | term()</v> - </type> - <desc> - <p>There is to be one instance of this function for each - possible state name. Whenever a <c>gen_fsm</c> process receives an - event sent using <seealso marker="#sync_send_event/2"> - <c>sync_send_event/2,3</c></seealso>, - the instance of this function with the same name as - the current state name <c>StateName</c> is called to handle - the event.</p> - <p><c>Event</c> is the <c>Event</c> argument provided to - <c>sync_send_event/2,3</c>.</p> - <p><c>From</c> is a tuple <c>{Pid,Tag}</c> where <c>Pid</c> is - the pid of the process that called <c>sync_send_event/2,3</c> - and <c>Tag</c> is a unique tag.</p> - <p><c>StateData</c> is the state data of the <c>gen_fsm</c> process.</p> - <list type="bulleted"> - <item> - <p>If <c>{reply,Reply,NextStateName,NewStateData}</c>, - <c>{reply,Reply,NextStateName,NewStateData,Timeout}</c>, or - <c>{reply,Reply,NextStateName,NewStateData,hibernate}</c> is - returned, <c>Reply</c> is given back to <c>From</c> as the return - value of <c>sync_send_event/2,3</c>. The <c>gen_fsm</c> process - then continues executing with the current state name set to - <c>NextStateName</c> and with the possibly updated state data - <c>NewStateData</c>. For a description of <c>Timeout</c> and - <c>hibernate</c>, see - <seealso marker="#Module:init/1"> - <c>Module:init/1</c></seealso>.</p> - </item> - <item> - <p>If <c>{next_state,NextStateName,NewStateData}</c>, - <c>{next_state,NextStateName,NewStateData,Timeout}</c>, or - <c>{next_state,NextStateName,NewStateData,hibernate}</c> is - returned, the <c>gen_fsm</c> process continues executing in - <c>NextStateName</c> with <c>NewStateData</c>. - Any reply to <c>From</c> must be specified explicitly using - <seealso marker="#reply/2"><c>reply/2</c></seealso>.</p> - </item> - <item> - <p>If the function returns - <c>{stop,Reason,Reply,NewStateData}</c>, <c>Reply</c> is - given back to <c>From</c>. If the function returns - <c>{stop,Reason,NewStateData}</c>, any reply to <c>From</c> - must be specified explicitly using <c>reply/2</c>. - The <c>gen_fsm</c> process then calls - <c>Module:terminate(Reason,StateName,NewStateData)</c> and - terminates.</p> - </item> - </list> - </desc> - </func> - - <func> - <name>Module:terminate(Reason, StateName, StateData)</name> - <fsummary>Clean up before termination.</fsummary> - <type> - <v>Reason = normal | shutdown | {shutdown,term()} | term()</v> - <v>StateName = atom()</v> - <v>StateData = term()</v> - </type> - <desc> - <p>This function is called by a <c>gen_fsm</c> process when it is about - to terminate. It is to be the opposite of - <seealso marker="#Module:init/1"><c>Module:init/1</c></seealso> - and do any necessary cleaning up. When it returns, the <c>gen_fsm</c> - process terminates with <c>Reason</c>. The return value is ignored. - </p> - <p><c>Reason</c> is a term denoting the stop reason, - <c>StateName</c> is the current state name, and - <c>StateData</c> is the state data of the <c>gen_fsm</c> process.</p> - <p><c>Reason</c> depends on why the <c>gen_fsm</c> process is - terminating. If - it is because another callback function has returned a stop - tuple <c>{stop,..}</c>, <c>Reason</c> has the value - specified in that tuple. If it is because of a failure, - <c>Reason</c> is the error reason.</p> - <p>If the <c>gen_fsm</c> process is part of a supervision tree and is - ordered by its supervisor to terminate, this function is called - with <c>Reason=shutdown</c> if the following conditions apply:</p> - <list type="bulleted"> - <item> - <p>The <c>gen_fsm</c> process has been set to trap exit signals.</p> - </item> - <item> - <p>The shutdown strategy as defined in the child specification of - the supervisor is an integer time-out value, not - <c>brutal_kill</c>.</p> - </item> - </list> - <p>Even if the <c>gen_fsm</c> process is <em>not</em> part of a - supervision tree, - this function is called if it receives an <c>'EXIT'</c> - message from its parent. <c>Reason</c> is the same as in - the <c>'EXIT'</c> message.</p> - <p>Otherwise, the <c>gen_fsm</c> process terminates immediately.</p> - <p>Notice that for any other reason than <c>normal</c>, - <c>shutdown</c>, or <c>{shutdown,Term}</c> the <c>gen_fsm</c> process - is assumed to terminate because of an error and an error report is - issued using <seealso marker="kernel:error_logger#format/2"> - <c>error_logger:format/2</c></seealso>.</p> - </desc> - </func> - </funcs> - <section> - <title>See Also</title> - <p><seealso marker="gen_event"><c>gen_event(3)</c></seealso>, - <seealso marker="gen_server"><c>gen_server(3)</c></seealso>, - <seealso marker="gen_statem"><c>gen_statem(3)</c></seealso>, - <seealso marker="proc_lib"><c>proc_lib(3)</c></seealso>, - <seealso marker="supervisor"><c>supervisor(3)</c></seealso>, - <seealso marker="sys"><c>sys(3)</c></seealso></p> + <marker id="Migration to gen_statem"/> + <title>Migration to gen_statem</title> + + <p>Here follows a simple example of turning a gen_fsm into + a <seealso marker="gen_statem"><c>gen_statem</c></seealso>. The example comes + from the previous Users Guide for <c>gen_fsm</c> </p> + + <code type="erl"> +-module(code_lock). +-define(NAME, code_lock). +%-define(BEFORE_REWRITE, true). + +-ifdef(BEFORE_REWRITE). +-behaviour(gen_fsm). +-else. +-behaviour(gen_statem). +-endif. + +-export([start_link/1, button/1, stop/0]). + +-ifdef(BEFORE_REWRITE). +-export([init/1, locked/2, open/2, handle_sync_event/4, handle_event/3, + handle_info/3, terminate/3, code_change/4]). +-else. +-export([init/1, callback_mode/0, locked/3, open/3, terminate/3, code_change/4]). +%% Add callback__mode/0 +%% Change arity of the state functions +%% Remove handle_info/3 +-endif. + +-ifdef(BEFORE_REWRITE). +start_link(Code) -> + gen_fsm:start_link({local, ?NAME}, ?MODULE, Code, []). +-else. +start_link(Code) -> + gen_statem:start_link({local,?NAME}, ?MODULE, Code, []). +-endif. + +-ifdef(BEFORE_REWRITE). +button(Digit) -> + gen_fsm:send_event(?NAME, {button, Digit}). +-else. +button(Digit) -> + gen_statem:cast(?NAME, {button,Digit}). + %% send_event is asynchronous and becomes a cast +-endif. + +-ifdef(BEFORE_REWRITE). +stop() -> + gen_fsm:sync_send_all_state_event(?NAME, stop). +-else. +stop() -> + gen_statem:call(?NAME, stop). + %% sync_send is synchronous and becomes call + %% all_state is handled by callback code in gen_statem +-endif. + +init(Code) -> + do_lock(), + Data = #{code => Code, remaining => Code}, + {ok, locked, Data}. + +-ifdef(BEFORE_REWRITE). +-else. +callback_mode() -> + state_functions. +%% state_functions mode is the mode most similar to +%% gen_fsm. There is also handle_event mode which is +%% a fairly different concept. +-endif. + +-ifdef(BEFORE_REWRITE). +locked({button, Digit}, Data0) -> + case analyze_lock(Digit, Data0) of + {open = StateName, Data} -> + {next_state, StateName, Data, 10000}; + {StateName, Data} -> + {next_state, StateName, Data} + end. +-else. +locked(cast, {button,Digit}, Data0) -> + case analyze_lock(Digit, Data0) of + {open = StateName, Data} -> + {next_state, StateName, Data, 10000}; + {StateName, Data} -> + {next_state, StateName, Data} + end; +locked({call, From}, Msg, Data) -> + handle_call(From, Msg, Data); +locked({info, Msg}, StateName, Data) -> + handle_info(Msg, StateName, Data). +%% Arity differs +%% All state events are dispatched to handle_call and handle_info help +%% functions. If you want to handle a call or cast event specifically +%% for this state you would add a special clause for it above. +-endif. + +-ifdef(BEFORE_REWRITE). +open(timeout, State) -> + do_lock(), + {next_state, locked, State}; +open({button,_}, Data) -> + {next_state, locked, Data}. +-else. +open(timeout, _, Data) -> + do_lock(), + {next_state, locked, Data}; +open(cast, {button,_}, Data) -> + {next_state, locked, Data}; +open({call, From}, Msg, Data) -> + handle_call(From, Msg, Data); +open(info, Msg, Data) -> + handle_info(Msg, open, Data). +%% Arity differs +%% All state events are dispatched to handle_call and handle_info help +%% functions. If you want to handle a call or cast event specifically +%% for this state you would add a special clause for it above. +-endif. + +-ifdef(BEFORE_REWRITE). +handle_sync_event(stop, _From, _StateName, Data) -> + {stop, normal, ok, Data}. + +handle_event(Event, StateName, Data) -> + {stop, {shutdown, {unexpected, Event, StateName}}, Data}. + +handle_info(Info, StateName, Data) -> + {stop, {shutdown, {unexpected, Info, StateName}}, StateName, Data}. +-else. +-endif. + +terminate(_Reason, State, _Data) -> + State =/= locked andalso do_lock(), + ok. +code_change(_Vsn, State, Data, _Extra) -> + {ok, State, Data}. + +%% Internal functions +-ifdef(BEFORE_REWRITE). +-else. +handle_call(From, stop, Data) -> + {stop_and_reply, normal, {reply, From, ok}, Data}. + +handle_info(Info, StateName, Data) -> + {stop, {shutdown, {unexpected, Info, StateName}}, StateName, Data}. +%% These are internal functions for handling all state events +%% and not behaviour callbacks as in gen_fsm +-endif. + +analyze_lock(Digit, #{code := Code, remaining := Remaining} = Data) -> + case Remaining of + [Digit] -> + do_unlock(), + {open, Data#{remaining := Code}}; + [Digit|Rest] -> % Incomplete + {locked, Data#{remaining := Rest}}; + _Wrong -> + {locked, Data#{remaining := Code}} + end. + +do_lock() -> + io:format("Lock~n", []). +do_unlock() -> + io:format("Unlock~n", []). + </code> </section> </erlref> |