systemd/man/sd_bus_add_node_enumerator.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="sd_bus_add_node_enumerator"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_bus_add_node_enumerator</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_add_node_enumerator</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_add_node_enumerator</refname>

    <refpurpose>Add a node enumerator for a D-Bus object path prefix</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>typedef int (*<function>sd_bus_node_enumerator_t</function>)</funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
        <paramdef>const char *<parameter>prefix</parameter></paramdef>
        <paramdef>void *<parameter>userdata</parameter></paramdef>
        <paramdef>char ***<parameter>ret_nodes</parameter></paramdef>
        <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_add_node_enumerator</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
        <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
        <paramdef>const char *<parameter>path</parameter></paramdef>
        <paramdef>sd_bus_node_enumerator_t <parameter>callback</parameter></paramdef>
        <paramdef>void *<parameter>userdata</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_add_node_enumerator()</function> adds a D-Bus node enumerator for the
    given path prefix. The given callback is called to enumerate all the available objects with
    the given path prefix when required (e.g. when
    <constant>org.freedesktop.DBus.Introspectable.Introspect</constant> or
    <constant>org.freedesktop.DBus.ObjectManager.GetManagedObjects</constant> are called on a
    D-Bus service managed by sd-bus).</para>

    <para><parameter>callback</parameter> is called with the path and userdata pointer registered
    with <function>sd_bus_add_node_enumerator()</function>. When called, it should store all the
    child object paths of the given path prefix in <parameter>ret_nodes</parameter> with a NULL
    terminator item. The callback should return a non-negative value on success.
    If an error occurs, it can either return a
    negative integer, set <parameter>ret_error</parameter> to a non-empty error or do both. Any
    errors returned by the callback are encoded as D-Bus errors and sent back to the caller. Errors
    in <parameter>ret_error</parameter> take priority over negative return values.</para>

    <para>Note that a node enumerator callback will only ever be called for a single  path prefix
    and hence, for normal operation, <parameter>prefix</parameter> can be ignored. Also, a node
    enumerator is only used to enumerate the available child objects under a given prefix. To
    install a handler for a set of dynamic child objects, use
    <citerefentry><refentrytitle>sd_bus_add_fallback_vtable</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    </para>

    <para>When <function>sd_bus_add_node_enumerator()</function> succeeds, a slot is created
    internally. If the output parameter <replaceable>slot</replaceable> is <constant>NULL</constant>,
    a "floating" slot object is created, see
    <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    Otherwise, a pointer to the slot object is returned. In that case, the reference to the slot
    object should be dropped when the node enumerator is not needed anymore, see
    <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    </para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, <function>sd_bus_add_node_enumerator()</function> returns a non-negative
    integer. On failure, it returns a negative errno-style error code.</para>

    <refsect2>
      <title>Errors</title>

      <para>Returned errors may indicate the following problems:</para>

      <variablelist>
        <varlistentry>
          <term><constant>-EINVAL</constant></term>

          <listitem><para>One of the required parameters is <constant>NULL</constant> or
          <parameter>path</parameter> is not a valid object path.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOPKG</constant></term>

          <listitem><para>The bus cannot be resolved.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ECHILD</constant></term>

          <listitem><para>The bus was created in a different process, library or module instance.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOMEM</constant></term>

          <listitem><para>Memory allocation failed.</para></listitem>
        </varlistentry>
      </variablelist>
    </refsect2>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <refsect1>
    <title>History</title>
    <para><function>sd_bus_node_enumerator_t()</function> and
    <function>sd_bus_add_node_enumerator()</function> were added in version 221.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd_bus_add_fallback_vtable</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
    </simplelist></para>
  </refsect1>
</refentry>