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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

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

  <refentryinfo>
    <title>sd_bus_path_encode</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_path_encode</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_path_encode</refname>
    <refname>sd_bus_path_encode_many</refname>
    <refname>sd_bus_path_decode</refname>
    <refname>sd_bus_path_decode_many</refname>

    <refpurpose>Convert an external identifier into an object path and back</refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>int <function>sd_bus_path_encode</function></funcdef>
        <paramdef>const char *<parameter>prefix</parameter></paramdef>
        <paramdef>const char *<parameter>external_id</parameter></paramdef>
        <paramdef>char **<parameter>ret_path</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_path_encode_many</function></funcdef>
        <paramdef>char **<parameter>out</parameter></paramdef>
        <paramdef>const char *<parameter>path_template</parameter></paramdef>
        <paramdef></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_path_decode</function></funcdef>
        <paramdef>const char *<parameter>path</parameter></paramdef>
        <paramdef>const char *<parameter>prefix</parameter></paramdef>
        <paramdef>char **<parameter>ret_external_id</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_path_decode_many</function></funcdef>
        <paramdef>const char *<parameter>path</parameter></paramdef>
        <paramdef>const char *<parameter>path_template</parameter></paramdef>
        <paramdef></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_path_encode()</function> and
    <function>sd_bus_path_decode()</function> convert external
    identifier strings into object paths and back. These functions are
    useful to map application-specific string identifiers of any kind
    into bus object paths in a simple, reversible and safe way.</para>

    <para><function>sd_bus_path_encode()</function> takes a bus path
    prefix and an external identifier string as arguments, plus a
    place to store the returned bus path string. The bus path prefix
    must be a valid bus path, starting with a slash
    <literal>/</literal>, and not ending in one. The external
    identifier string may be in any format, may be the empty string,
    and has no restrictions on the charset  however, it must
    always be <constant>NUL</constant>-terminated. The returned string
    will be the concatenation of the bus path prefix plus an escaped
    version of the external identifier string. This operation may be
    reversed with <function>sd_bus_path_decode()</function>. It is
    recommended to only use external identifiers that generally
    require little escaping to be turned into valid bus path
    identifiers (for example, by sticking to a 7-bit ASCII character
    set), in order to ensure the resulting bus path is still short and
    easily processed.</para>

    <para><function>sd_bus_path_decode()</function> reverses the
    operation of <function>sd_bus_path_encode()</function> and thus
    regenerates an external identifier string from a bus path. It
    takes a bus path and a prefix string, plus a place to store the
    returned external identifier string. If the bus path does not
    start with the specified prefix, 0 is returned and the returned
    string is set to <constant>NULL</constant>. Otherwise, the
    string following the prefix is unescaped and returned in the
    external identifier string.</para>

    <para>The escaping used will replace all characters which are
    invalid in a bus object path by <literal>_</literal>, followed by a
    hexadecimal value. As a special case, the empty string will be
    replaced by a lone <literal>_</literal>.</para>

    <para><function>sd_bus_path_encode_many()</function> works like
    its counterpart <function>sd_bus_path_encode()</function>, but
    takes a path template as argument and encodes multiple labels
    according to its embedded directives. For each
    <literal>%</literal> character found in the template, the caller
    must provide a string via varargs, which will be encoded and
    embedded at the position of the <literal>%</literal> character.
    Any other character in the template is copied verbatim into the
    encoded path.</para>

    <para><function>sd_bus_path_decode_many()</function> does the
    reverse of <function>sd_bus_path_encode_many()</function>. It
    decodes the passed object path according to the given
    path template. For each <literal>%</literal> character in the
    template, the caller must provide an output storage
    (<literal>char **</literal>) via varargs. The decoded label
    will be stored there. Each <literal>%</literal> character will
    only match the current label. It will never match across labels.
    Furthermore, only a single directive is allowed per label.
    If <constant>NULL</constant> is passed as output storage, the
    label is verified but not returned to the caller.</para>
  </refsect1>

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

    <para>On success, <function>sd_bus_path_encode()</function>
    returns positive or 0, and a valid bus path in the return
    argument. On success, <function>sd_bus_path_decode()</function>
    returns a positive value if the prefixed matched, or 0 if it
    did not. If the prefix matched, the external identifier is returned
    in the return parameter. If it did not match, <constant>NULL</constant> is returned in
    the return parameter. On failure, a negative errno-style error
    number is returned by either function. The returned strings must
    be
    <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>'d
    by the caller.</para>
  </refsect1>

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

  <refsect1>
    <title>History</title>
    <para><function>sd_bus_path_encode()</function> and
    <function>sd_bus_path_decode()</function> were added in version 211.</para>
    <para><function>sd_bus_path_encode_many()</function> and
    <function>sd_bus_path_decode_many()</function> were added in version 227.</para>
  </refsect1>

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

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>