<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2013</year><year>2016</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
      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.
    
    </legalnotice>

    <title>snmpa_mib_data</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
    <file>snmpa_mib_data.xml</file>
  </header>

  <module>snmpa_mib_data</module>
  <modulesummary>Behaviour module for the SNMP agent mib-server 
  data module.</modulesummary>
  <description>
    <p>This module defines the behaviour of the SNMP agent mib-server 
    data module. A <c>snmpa_mib_data</c> compliant module 
    must export the following functions: </p>
    <list type="bulleted">
      <item>
	<seealso marker="#new">new/1</seealso>
      </item>
      <item>
	<seealso marker="#close">close/1</seealso>
      </item>
      <item>
	<seealso marker="#sync">sync/1</seealso>
      </item>
      <item>
	<seealso marker="#load_mib">load_mib/4</seealso>
      </item>
      <item>
	<seealso marker="#unload_mib">unload_mib/4</seealso>
      </item>
      <item>
	<seealso marker="#lookup">lookup/2</seealso>
      </item>
      <item>
	<seealso marker="#next">next/3</seealso>
      </item>
      <item>
	<seealso marker="#register_subagent">register_subagent/3</seealso>
      </item>
      <item>
	<seealso marker="#unregister_subagent">unregister_subagent/2</seealso>
      </item>
      <item>
	<seealso marker="#which_mib">which_mib/2</seealso>
      </item>
      <item>
	<seealso marker="#which_mibs">which_mibs/1</seealso>
      </item>
      <item>
	<seealso marker="#whereis_mib">whereis_mib/2</seealso>
      </item>
      <item>
	<seealso marker="#dump">dump/2</seealso>
      </item>
      <item>
	<seealso marker="#info">info/1</seealso>
      </item>
      <item>
	<seealso marker="#backup">backup/2</seealso>
      </item>
      <item>
	<seealso marker="#code_change">code_change/4</seealso>
      </item>
    </list>

    <p>The semantics of them and their exact signatures are 
    explained below. </p>

    <p>Note that the data extracted from the imported (loaded) 
    mibs are stored partly by the mib-server and partly by the 
    symbolic-store server. See the default mib-server data 
    module, <c>snmpa_mib_data_tttn</c> for details. </p>

  </description>

  <section>
    <title>CALLBACK FUNCTIONS</title>
    <p>The following functions must be exported from a 
    <c>mib-server</c> data callback module: </p>

    <marker id="new"></marker>
  </section>

  <funcs>
    <func>
      <name>Module:new(Storage) -> State</name>
      <fsummary>Create new (mib-server) data instance</fsummary>
      <type>
        <v>Storage = mib_storage()</v>
        <v>State = term()</v>
      </type>
      <desc>
        <p>Create a new mib-server data instance. </p>

        <marker id="close"></marker>
      </desc>
    </func>

    <func>
      <name>Module:close(State) -> void()</name>
      <fsummary>Close the mib-server data instance</fsummary>
      <type>
        <v>State = term()</v>
      </type>
      <desc>
        <p>Close the mib-storage.</p>

        <marker id="sync"></marker>
      </desc>
    </func>

    <func>
      <name>Module:sync(State) -> void()</name>
      <fsummary>Synchronize to disc</fsummary>
      <type>
        <v>State = term()</v>
      </type>
      <desc>
        <p>Synchronize (write to disc, if possible) the mib-server data. 
	This depends on the <c>mib_storage</c> option, and will only have 
	an effect if the mib-storage option has an actual disc component 
	(such as dets, or ets with a file). </p>

        <marker id="load_mib"></marker>
      </desc>
    </func>

    <func>
      <name>Module:load_mib(State, Filename, MeOverride, TeOverride) -> {ok, NewState} | {error, Reason}</name>
      <fsummary>Load a mib into the mib-server</fsummary>
      <type>
        <v>State = NewState = term()</v>
        <v>Filename = filename()</v>
        <v>MeOverride = boolean()</v>
        <v>TeOverride = boolean()</v>
        <v>Reason = already_loaded | term()</v>
      </type>
      <desc>
        <p>Load the mib specified by the <c>Filename</c> argument 
	into the mib-server. 
	The <c>MeOverride</c> and <c>TeOverride</c> arguments 
	specifies how the mib-server shall handle duplicate mib- and trap-
	entries. </p>

        <marker id="unload_mib"></marker>
      </desc>
    </func>

    <func>
      <name>Module:unload_mib(State, Filename) -> {ok, NewState} | {error, Reason}</name>
      <fsummary>Unload mib from the mib-server</fsummary>
      <type>
        <v>State = NewState = term()</v>
        <v>Filename = filename()</v>
        <v>Reason = not_loaded | term()</v>
      </type>
      <desc>
        <p>Unload the mib specified by the <c>Filename</c> argument 
	from the mib-server. </p>

        <marker id="lookup"></marker>
      </desc>
    </func>

    <func>
      <name>Module:lookup(State, Oid) -> Reply</name>
      <fsummary>Find the mib-entry corresponding to the Oid</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = {variable, ME} | {table_column, ME, TEOid} | {subagent, SAPid, SAOid} | {false, Reason}</v>
        <v>Oid = TEOid = SAOid = oid()</v>
        <v>SAPid = pid()</v>
        <v>ME = me()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Find the mib-entry corresponding to the <c>Oid</c>. 
	If it is a variable, the <c>Oid</c> must be 
	&lt;Oid for var&gt;.0 
	and if it is a table, <c>Oid</c> must be 
	&lt;table&gt;.&lt;entry&gt;.&lt;col&gt;.&lt;any&gt;.</p>

        <marker id="next"></marker>
      </desc>
    </func>

    <func>
      <name>Module:next(State, Oid, MibView) -> Reply</name>
      <fsummary>Finds the lexicographically next oid</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = false | endOfTable | {subagent, SAPid, SAOid} | {variable, ME, VarOid} | {table, TableOid, TableRestOid, ME}</v>
        <v>Oid = SAOid = VarOid = TableOid = TableRestOid = oid()</v>
        <v>SAPid = pid()</v>
        <v>ME = me()</v>
      </type>
      <desc>
        <p>Finds the lexicographically next oid. </p>

        <marker id="register_subagent"></marker>
      </desc>
    </func>

    <func>
      <name>Module:register_subagent(State, Oid, Pid) -> Reply</name>
      <fsummary>Register the subagent</fsummary>
      <type>
        <v>State = NewState = term()</v>
        <v>Reply = {ok, NewState} | {error, Reason}</v>
        <v>Oid = oid()</v>
        <v>Pid = pid()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Register the subagent, process, 
	handling part of the mib-tree. </p>

        <marker id="unregister_subagent"></marker>
      </desc>
    </func>

    <func>
      <name>Module:unregister_subagent(State, PidOrOid) -> Reply</name>
      <fsummary>Unregister the subagent</fsummary>
      <type>
        <v>State = NewState = term()</v>
        <v>Reply = {ok, NewState} | {ok, NewState, Pid} | {error, Reason}</v>
        <v>PidOrOid = pid() | oid()</v>
        <v>Pid = pid()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Unregister the subagent, handling part of the mib-tree, 
	as specified by the <c>oid()</c> or <c>pid()</c> 
	(<c>PidOrOid</c>). </p>
        <p>When unregister the subagent using an <c>oid()</c>, the <c>pid()</c> 
	of the process handling the sub-tree is also returned. </p>

        <marker id="dump"></marker>
      </desc>
    </func>

    <func>
      <name>Module:dump(State, Destination) -> Reply</name>
      <fsummary>Unregister the subagent</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = ok | {error, Reason}</v>
        <v>Destination = io | filename()</v>
        <v>Pid = pid()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Dump the mib-server data to <c>stdio</c> (Destination = <c>io</c>) or
	the specified file. </p>

        <marker id="which_mib"></marker>
      </desc>
    </func>

    <func>
      <name>Module:which_mib(State, Oid) -> Reply</name>
      <fsummary>Retrieve the mib file for an oid()</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = {ok, MibFile} | {error, Reason}</v>
        <v>Oid = oid()</v>
        <v>MibFile = string()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Retrieve the mib-file to which an given <c>oid()</c> belongs. </p>

        <marker id="which_mibs"></marker>
      </desc>
    </func>

    <func>
      <name>Module:which_mibs(State) -> Reply</name>
      <fsummary>Retrieve all loaded mib files</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = [{MibName, Filename}]</v>
        <v>MibName = atom()</v>
        <v>Filename = string()</v>
      </type>
      <desc>
        <p>Retrieve all loaded mib-files. </p>

        <marker id="whereis_mib"></marker>
      </desc>
    </func>

    <func>
      <name>Module:whereis_mib(State, MibName) -> Reply</name>
      <fsummary>Retrieve the mib file for the mib</fsummary>
      <type>
        <v>State = term()</v>
        <v>MibName = atom()</v>
        <v>Reply = {ok, Filename} | {error, Reason}</v>
        <v>Filename = string()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Retrieve the mib file for the mib. </p>

        <marker id="info"></marker>
      </desc>
    </func>

    <func>
      <name>Module:info(State) -> Reply</name>
      <fsummary>Retrieve misc info for the mib data</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = {ok, Filename} | {error, Reason}</v>
        <v>Filename = string()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Retrieve misc info for the mib data. </p>
        <p>This is a utility function used to inspect, for instance, 
	memory usage, in a simple way. </p>

        <marker id="backup"></marker>
      </desc>
    </func>

    <func>
      <name>Module:backup(State, BackupDir) -> Reply</name>
      <fsummary>Perform a backup of the mib-server data</fsummary>
      <type>
        <v>State = term()</v>
        <v>Reply = ok | {error, Reason}</v>
        <v>BackupDir = string()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Perform a backup of the mib-server data. </p>
        <p>Note that its implementation dependant (and also 
	dependent on mib-storage is used) if a backup is possible. </p>

        <marker id="code_change"></marker>
      </desc>
    </func>

    <func>
      <name>Module:code_change(Destination, Vsn, Extra, State) -> NewState</name>
      <fsummary>Perform a code-change</fsummary>
      <type>
        <v>Destination = up | down</v>
        <v>Vsn = term()</v>
        <v>Extra = term()</v>
        <v>State = NewState = term()</v>
      </type>
      <desc>
        <p>Perform a code-change (upgrade or downgrade). </p>
        <p>See 
	<seealso marker="stdlib:gen_server">gen_server</seealso>
	for more info regarding the <c>Vsn</c> and <c>Extra</c> arguments. </p>

      </desc>
    </func>

  </funcs>
  
</erlref>

