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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_bus_path_encode" xmlns:xi="">
<refpurpose>Convert an external identifier into an object path and back</refpurpose>
<funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
<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>
<funcdef>int <function>sd_bus_path_encode_many</function></funcdef>
<paramdef>char **<parameter>out</parameter></paramdef>
<paramdef>const char *<parameter>path_template</parameter></paramdef>
<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>
<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>
<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>
<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
<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>'d
by the caller.</para>
<xi:include href="libsystemd-pkgconfig.xml" />
<title>See Also</title>
<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>