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| author | Erlang/OTP <[email protected]> | 2009-11-20 14:54:40 +0000 |
|---|---|---|
| committer | Erlang/OTP <[email protected]> | 2009-11-20 14:54:40 +0000 |
| commit | 84adefa331c4159d432d22840663c38f155cd4c1 (patch) | |
| tree | bff9a9c66adda4df2106dfd0e5c053ab182a12bd /lib/stdlib/doc/src/gen_fsm.xml | |
| download | otp-84adefa331c4159d432d22840663c38f155cd4c1.tar.gz otp-84adefa331c4159d432d22840663c38f155cd4c1.tar.bz2 otp-84adefa331c4159d432d22840663c38f155cd4c1.zip | |
The R13B03 release.OTP_R13B03
Diffstat (limited to 'lib/stdlib/doc/src/gen_fsm.xml')
| -rw-r--r-- | lib/stdlib/doc/src/gen_fsm.xml | 743 |
1 files changed, 743 insertions, 0 deletions
diff --git a/lib/stdlib/doc/src/gen_fsm.xml b/lib/stdlib/doc/src/gen_fsm.xml new file mode 100644 index 0000000000..f5d8b9bb48 --- /dev/null +++ b/lib/stdlib/doc/src/gen_fsm.xml @@ -0,0 +1,743 @@ +<?xml version="1.0" encoding="latin1" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <header> + <copyright> + <year>1996</year><year>2009</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + </legalnotice> + + <title>gen_fsm</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> + </header> + <module>gen_fsm</module> + <modulesummary>Generic Finite State Machine Behaviour</modulesummary> + <description> + <p>A behaviour module for implementing a finite state machine. + A generic finite state machine process (gen_fsm) implemented + using this module will have a standard set of interface functions + and include functionality for tracing and error reporting. It will + also fit into an OTP supervision tree. Refer to + <seealso marker="doc/design_principles:fsm">OTP Design Principles</seealso> for more information.</p> + <p>A gen_fsm assumes all specific parts to be located in a callback + module exporting a pre-defined set of functions. The relationship + between the behaviour functions and the callback functions can be + illustrated as follows:</p> + <pre> +gen_fsm module Callback module +-------------- --------------- +gen_fsm:start_link -----> Module:init/1 + +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 + +- -----> Module:code_change/4</pre> + <p>If a callback function fails or returns a bad value, the gen_fsm + will terminate.</p> + <p>A gen_fsm handles system messages as documented in + <seealso marker="sys">sys(3)</seealso>. The <c>sys</c> module + can be used for debugging a gen_fsm.</p> + <p>Note that a gen_fsm 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 gen_fsm does not exist or if bad arguments are + given.</p> + <p>The gen_fsm process can go into hibernation + (see <seealso marker="erts:erlang#erlang:hibernate/3">erlang(3)</seealso>) if a callback + function specifies <c>'hibernate'</c> instead of a timeout value. This + might be useful if the server is expected to be idle for a long + time. However this feature should be used with care as hibernation + implies at least two garbage collections (when hibernating and + shortly after waking up) and is not something you'd want to do + between each call to a busy state machine.</p> + + </description> + <funcs> + <func> + <name>start_link(Module, Args, Options) -> Result</name> + <name>start_link(FsmName, Module, Args, Options) -> Result</name> + <fsummary>Create a gen_fsm process in a supervision tree.</fsummary> + <type> + <v>FsmName = {local,Name} | {global,GlobalName}</v> + <v> Name = atom()</v> + <v> GlobalName = 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 gen_fsm process as part of a supervision tree. + The function should be called, directly or indirectly, by + the supervisor. It will, among other things, ensure that + the gen_fsm is linked to the supervisor.</p> + <p>The gen_fsm process calls <c>Module:init/1</c> to + initialize. To ensure a synchronized start-up procedure, + <c>start_link/3,4</c> does not return until + <c>Module:init/1</c> has returned.</p> + <p>If <c>FsmName={local,Name}</c>, the gen_fsm is registered + locally as <c>Name</c> using <c>register/2</c>. + If <c>FsmName={global,GlobalName}</c>, the gen_fsm is + registered globally as <c>GlobalName</c> using + <c>global:register_name/2</c>. If no name is provided, + the gen_fsm is not registered.</p> + <p><c>Module</c> is the name of the callback module.</p> + <p><c>Args</c> is an arbitrary term which is passed as + the argument to <c>Module:init/1</c>.</p> + <p>If the option <c>{timeout,Time}</c> is present, the gen_fsm + is allowed to spend <c>Time</c> milliseconds initializing + or it will be terminated and the start function will return + <c>{error,timeout}</c>.</p> + <p>If the option <c>{debug,Dbgs}</c> is present, + the corresponding <c>sys</c> function will be called for each + item in <c>Dbgs</c>. See + <seealso marker="sys">sys(3)</seealso>.</p> + <p>If the option <c>{spawn_opt,SOpts}</c> is present, + <c>SOpts</c> will be passed as option list to + the <c>spawn_opt</c> BIF which is used to spawn the gen_fsm + process. See + <seealso marker="erts:erlang#spawn_opt/2">erlang(3)</seealso>.</p> + <note> + <p>Using the spawn option <c>monitor</c> is currently not + allowed, but will cause the function to fail with reason + <c>badarg</c>.</p> + </note> + <p>If the gen_fsm is successfully created and initialized + the function returns <c>{ok,Pid}</c>, where <c>Pid</c> is + the pid of the gen_fsm. If there already exists a process with + the specified <c>FsmName</c>, 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(Module, Args, Options) -> Result</name> + <name>start(FsmName, Module, Args, Options) -> Result</name> + <fsummary>Create a stand-alone gen_fsm process.</fsummary> + <type> + <v>FsmName = {local,Name} | {global,GlobalName}</v> + <v> Name = atom()</v> + <v> GlobalName = 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 stand-alone gen_fsm process, i.e. a gen_fsm which + is not part of a supervision tree and thus has no supervisor.</p> + <p>See <seealso marker="#start_link/3">start_link/3,4</seealso> + for a description of arguments and return values.</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} | pid()</v> + <v> Name = Node = atom()</v> + <v> GlobalName = term()</v> + <v>Event = term()</v> + </type> + <desc> + <p>Sends an event asynchronously to the gen_fsm <c>FsmRef</c> + and returns <c>ok</c> immediately. The gen_fsm will call + <c>Module:StateName/2</c> to handle the event, where + <c>StateName</c> is the name of the current state of + the gen_fsm.</p> + <p><c>FsmRef</c> can be:</p> + <list type="bulleted"> + <item>the pid,</item> + <item><c>Name</c>, if the gen_fsm is locally registered,</item> + <item><c>{Name,Node}</c>, if the gen_fsm is locally + registered at another node, or</item> + <item><c>{global,GlobalName}</c>, if the gen_fsm is globally + registered.</item> + </list> + <p><c>Event</c> is an arbitrary term which is passed as one of + the arguments to <c>Module:StateName/2</c>.</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} | pid()</v> + <v> Name = Node = atom()</v> + <v> GlobalName = term()</v> + <v>Event = term()</v> + </type> + <desc> + <p>Sends an event asynchronously to the gen_fsm <c>FsmRef</c> + and returns <c>ok</c> immediately. The gen_fsm will call + <c>Module:handle_event/3</c> to handle the event.</p> + <p>See <seealso marker="#send_event/2">send_event/2</seealso> + for a description of the arguments.</p> + <p>The difference between <c>send_event</c> and + <c>send_all_state_event</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>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} | pid()</v> + <v> Name = Node = atom()</v> + <v> GlobalName = term()</v> + <v>Event = term()</v> + <v>Timeout = int()>0 | infinity</v> + <v>Reply = term()</v> + </type> + <desc> + <p>Sends an event to the gen_fsm <c>FsmRef</c> and waits until a + reply arrives or a timeout occurs. The gen_fsm will call + <c>Module:StateName/3</c> to handle the event, where + <c>StateName</c> is the name of the current state of + the gen_fsm.</p> + <p>See <seealso marker="#send_event/2">send_event/2</seealso> + for a description of <c>FsmRef</c> and <c>Event</c>.</p> + <p><c>Timeout</c> is an integer greater than zero which + specifies how many milliseconds to wait for a reply, or + the atom <c>infinity</c> to wait indefinitely. Default value + is 5000. If no reply is received within the specified time, + the function call fails.</p> + <p>The return value <c>Reply</c> is defined in the return value + of <c>Module:StateName/3</c>.</p> + <p>The ancient behaviour of sometimes consuming the server + exit message if the server died during the call while + linked to the client has been removed in OTP R12B/Erlang 5.6.</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} | pid()</v> + <v> Name = Node = atom()</v> + <v> GlobalName = term()</v> + <v>Event = term()</v> + <v>Timeout = int()>0 | infinity</v> + <v>Reply = term()</v> + </type> + <desc> + <p>Sends an event to the gen_fsm <c>FsmRef</c> and waits until a + reply arrives or a timeout occurs. The gen_fsm will call + <c>Module:handle_sync_event/4</c> to handle the event.</p> + <p>See <seealso marker="#send_event/2">send_event/2</seealso> + for a description of <c>FsmRef</c> and <c>Event</c>. See + <seealso marker="#sync_send_event/3">sync_send_event/3</seealso> + for a description of <c>Timeout</c> and <c>Reply</c>.</p> + <p>See + <seealso marker="#send_all_state_event/2">send_all_state_event/2</seealso> + for a discussion about the difference between + <c>sync_send_event</c> and <c>sync_send_all_state_event</c>.</p> + </desc> + </func> + <func> + <name>reply(Caller, Reply) -> true</name> + <fsummary>Send a reply to a caller.</fsummary> + <type> + <v>Caller - see below</v> + <v>Reply = term()</v> + </type> + <desc> + <p>This function can be used by a gen_fsm to explicitly send a + reply to a client process that called + <seealso marker="#sync_send_event/2">sync_send_event/2,3</seealso> + or + <seealso marker="#sync_send_all_state_event/2">sync_send_all_state_event/2,3</seealso>, + when the reply cannot be defined in the return value of + <c>Module:State/3</c> or <c>Module:handle_sync_event/4</c>.</p> + <p><c>Caller</c> must be the <c>From</c> argument provided to + the callback function. <c>Reply</c> is an arbitrary term, + which will be 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> + </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 gen_fsm that calls + this function after <c>Time</c> ms. Returns immediately a + reference that can be used to cancel the delayed send using + <seealso marker="#cancel_timer/1">cancel_timer/1</seealso>.</p> + <p>The gen_fsm will call <c>Module:StateName/2</c> to handle + the event, where <c>StateName</c> is the name of the current + state of the gen_fsm at the time the delayed event is + delivered.</p> + <p><c>Event</c> is an arbitrary term which is passed as one of + the arguments to <c>Module:StateName/2</c>.</p> + </desc> + </func> + <func> + <name>start_timer(Time, Msg) -> Ref</name> + <fsummary>Send a timeout 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 timeout event internally in the gen_fsm that calls + this function after <c>Time</c> ms. Returns immediately a + reference that can be used to cancel the timer using + <seealso marker="#cancel_timer/1">cancel_timer/1</seealso>.</p> + <p>The gen_fsm will call <c>Module:StateName/2</c> to handle + the event, where <c>StateName</c> is the name of the current + state of the gen_fsm at the time the timeout message is + delivered.</p> + <p><c>Msg</c> is an arbitrary term which is passed in the + timeout message, <c>{timeout, Ref, Msg}</c>, as one of + the arguments to <c>Module:StateName/2</c>.</p> + </desc> + </func> + <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 + gen_fsm that calls this function.</p> + <p><c>Ref</c> is a reference returned from + <seealso marker="#send_event_after/2">send_event_after/2</seealso> + or + <seealso marker="#start_timer/2">start_timer/2</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 will be no false timer event after + returning from this function.</p> + <p>Returns the remaining time in ms until the timer would + have expired if <c>Ref</c> referred to an active timer, + <c>false</c> otherwise.</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 gen_fsm 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> Name = atom()</v> + <v> GlobalName = term()</v> + <v>Timeout = int() | infinity</v> + </type> + <desc> + <p>Makes an existing process into a gen_fsm. Does not return, + instead the calling process will enter the gen_fsm receive + loop and become a gen_fsm process. The process <em>must</em> + have been started using one of the start functions in + <c>proc_lib</c>, see + <seealso marker="proc_lib">proc_lib(3)</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 gen_fsm behaviour 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">start[_link]/3,4</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">Module:init/1</seealso>. + Also, the callback module <c>Module</c> does not need to + export an <c>init/1</c> function.</p> + <p>Failure: 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> + </funcs> + + <section> + <title>CALLBACK FUNCTIONS</title> + <p>The following functions should be exported from a <c>gen_fsm</c> + callback module.</p> + <p>In the description, the expression <em>state name</em> is used to + denote a state of the state machine. <em>state data</em> is used + to denote the internal state of the Erlang process which + implements the state machine.</p> + <p></p> + </section> + <funcs> + <func> + <name>Module:init(Args) -> Result</name> + <fsummary>Initialize process and internal state name and state data.</fsummary> + <type> + <v>Args = term()</v> + <v>Return = {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 gen_fsm is started using + <seealso marker="#start/3">gen_fsm:start/3,4</seealso> or + <seealso marker="#start_link/3">gen_fsm:start_link/3,4</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 should 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 gen_fsm.</p> + <p>If an integer timeout value is provided, a timeout will occur + unless an event or a message is received within <c>Timeout</c> + milliseconds. A timeout is represented by the atom + <c>timeout</c> and should be handled by + the <c>Module:StateName/2</c> 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 timeout value, the process will go + into hibernation when waiting for the next message to arrive (by calling + <seealso marker="proc_lib#hibernate/3">proc_lib:hibernate/3</seealso>).</p> + <p>If something goes wrong during the initialization + the function should return <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 should be one instance of this function for each + possible state name. Whenever a gen_fsm receives an event + sent using + <seealso marker="#send_event/2">gen_fsm:send_event/2</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 timeout occurs.</p> + <p><c>Event</c> is either the atom <c>timeout</c>, if a timeout + 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 gen_fsm.</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 gen_fsm will continue executing with the current state + name set to <c>NextStateName</c> and with the possibly + updated state data <c>NewStateData</c>. See + <c>Module:init/1</c> for a description of <c>Timeout</c> and <c>hibernate</c>.</p> + <p>If the function returns <c>{stop,Reason,NewStateData}</c>, + the gen_fsm will call + <c>Module:terminate(Reason,NewStateData)</c> and terminate.</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 gen_fsm receives an event sent using + <seealso marker="#send_all_state_event/2">gen_fsm:send_all_state_event/2</seealso>, + this function is called to handle the event.</p> + <p><c>StateName</c> is the current state name of the gen_fsm.</p> + <p>See <c>Module:StateName/2</c> for a description of the other + arguments and possible return values.</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 should be one instance of this function for each + possible state name. Whenever a gen_fsm receives an event + sent using + <seealso marker="#sync_send_event/2">gen_fsm:sync_send_event/2,3</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</c>.</p> + <p><c>From</c> is a tuple <c>{Pid,Tag}</c> where <c>Pid</c> is + the pid of the process which 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 gen_fsm.</p> + <p>If the function returns + <c>{reply,Reply,NextStateName,NewStateData}</c>, + <c>{reply,Reply,NextStateName,NewStateData,Timeout}</c> or + <c>{reply,Reply,NextStateName,NewStateData,hibernate}</c>, + <c>Reply</c> will be given back to <c>From</c> as the return + value of <c>sync_send_event/2,3</c>. The gen_fsm then + continues executing with the current state name set to + <c>NextStateName</c> and with the possibly updated state data + <c>NewStateData</c>. See <c>Module:init/1</c> for a + description of <c>Timeout</c> and <c>hibernate</c>.</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 gen_fsm will continue executing in <c>NextStateName</c> + with <c>NewStateData</c>. Any reply to <c>From</c> must be + given explicitly using + <seealso marker="#reply/2">gen_fsm:reply/2</seealso>.</p> + <p>If the function returns + <c>{stop,Reason,Reply,NewStateData}</c>, <c>Reply</c> will be + given back to <c>From</c>. If the function returns + <c>{stop,Reason,NewStateData}</c>, any reply to <c>From</c> + must be given explicitly using <c>gen_fsm:reply/2</c>. + The gen_fsm will then call + <c>Module:terminate(Reason,NewStateData)</c> and terminate.</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 gen_fsm receives an event sent using + <seealso marker="#sync_send_all_state_event/2">gen_fsm:sync_send_all_state_event/2,3</seealso>, + this function is called to handle the event.</p> + <p><c>StateName</c> is the current state name of the gen_fsm.</p> + <p>See <c>Module:StateName/3</c> for a description of the other + arguments and possible return values.</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 gen_fsm 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>See <c>Module:StateName/2</c> for a description of the other + arguments and possible return values.</p> + </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 gen_fsm when it is about to + terminate. It should be the opposite of <c>Module:init/1</c> + and do any necessary cleaning up. When it returns, the gen_fsm + 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 gen_fsm.</p> + <p><c>Reason</c> depends on why the gen_fsm is terminating. If + it is because another callback function has returned a stop + tuple <c>{stop,..}</c>, <c>Reason</c> will have the value + specified in that tuple. If it is due to a failure, + <c>Reason</c> is the error reason.</p> + <p>If the gen_fsm is part of a supervision tree and is ordered + by its supervisor to terminate, this function will be called + with <c>Reason=shutdown</c> if the following conditions apply:</p> + <list type="bulleted"> + <item>the gen_fsm has been set to trap exit signals, and</item> + <item>the shutdown strategy as defined in the supervisor's + child specification is an integer timeout value, not + <c>brutal_kill</c>.</item> + </list> + <p>Even if the gen_fsm is <em>not</em> part of a supervision tree, + this function will be called if it receives an <c>'EXIT'</c> + message from its parent. <c>Reason</c> will be the same as in + the <c>'EXIT'</c> message.</p> + <p>Otherwise, the gen_fsm will be immediately terminated.</p> + <p>Note that for any other reason than <c>normal</c>, + <c>shutdown</c>, or <c>{shutdown,Term}</c> the gen_fsm is + assumed to terminate due to an error and + an error report is issued using + <seealso marker="kernel:error_logger#format/2">error_logger:format/2</seealso>.</p> + </desc> + </func> + <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 gen_fsm when it should update + its internal state data during a release upgrade/downgrade, + i.e. when the instruction <c>{update,Module,Change,...}</c> + where <c>Change={advanced,Extra}</c> is given in + the <c>appup</c> file. See + <seealso marker="doc/design_principles:release_handling#instr">OTP Design Principles</seealso>.</p> + <p>In the case of an upgrade, <c>OldVsn</c> is <c>Vsn</c>, and + in the case of 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 gen_fsm.</p> + <p><c>Extra</c> is passed as-is from the <c>{advanced,Extra}</c> + part of the update instruction.</p> + <p>The function should return the new current state name and + updated internal data.</p> + </desc> + </func> + </funcs> + + <section> + <title>SEE ALSO</title> + <p><seealso marker="gen_event">gen_event(3)</seealso>, + <seealso marker="gen_server">gen_server(3)</seealso>, + <seealso marker="supervisor">supervisor(3)</seealso>, + <seealso marker="proc_lib">proc_lib(3)</seealso>, + <seealso marker="sys">sys(3)</seealso></p> + </section> +</erlref> + |