1<?xml version='1.0'?>
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
5
6<refentry id="sd_bus_path_encode" xmlns:xi="http://www.w3.org/2001/XInclude">
7
8  <refentryinfo>
9    <title>sd_bus_path_encode</title>
10    <productname>systemd</productname>
11  </refentryinfo>
12
13  <refmeta>
14    <refentrytitle>sd_bus_path_encode</refentrytitle>
15    <manvolnum>3</manvolnum>
16  </refmeta>
17
18  <refnamediv>
19    <refname>sd_bus_path_encode</refname>
20    <refname>sd_bus_path_encode_many</refname>
21    <refname>sd_bus_path_decode</refname>
22    <refname>sd_bus_path_decode_many</refname>
23
24    <refpurpose>Convert an external identifier into an object path and back</refpurpose>
25  </refnamediv>
26
27  <refsynopsisdiv>
28    <funcsynopsis>
29      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
30
31      <funcprototype>
32        <funcdef>int <function>sd_bus_path_encode</function></funcdef>
33        <paramdef>const char *<parameter>prefix</parameter></paramdef>
34        <paramdef>const char *<parameter>external_id</parameter></paramdef>
35        <paramdef>char **<parameter>ret_path</parameter></paramdef>
36      </funcprototype>
37
38      <funcprototype>
39        <funcdef>int <function>sd_bus_path_encode_many</function></funcdef>
40        <paramdef>char **<parameter>out</parameter></paramdef>
41        <paramdef>const char *<parameter>path_template</parameter></paramdef>
42        <paramdef>…</paramdef>
43      </funcprototype>
44
45      <funcprototype>
46        <funcdef>int <function>sd_bus_path_decode</function></funcdef>
47        <paramdef>const char *<parameter>path</parameter></paramdef>
48        <paramdef>const char *<parameter>prefix</parameter></paramdef>
49        <paramdef>char **<parameter>ret_external_id</parameter></paramdef>
50      </funcprototype>
51
52      <funcprototype>
53        <funcdef>int <function>sd_bus_path_decode_many</function></funcdef>
54        <paramdef>const char *<parameter>path</parameter></paramdef>
55        <paramdef>const char *<parameter>path_template</parameter></paramdef>
56        <paramdef>…</paramdef>
57      </funcprototype>
58    </funcsynopsis>
59  </refsynopsisdiv>
60
61  <refsect1>
62    <title>Description</title>
63
64    <para><function>sd_bus_path_encode()</function> and
65    <function>sd_bus_path_decode()</function> convert external
66    identifier strings into object paths and back. These functions are
67    useful to map application-specific string identifiers of any kind
68    into bus object paths in a simple, reversible and safe way.</para>
69
70    <para><function>sd_bus_path_encode()</function> takes a bus path
71    prefix and an external identifier string as arguments, plus a
72    place to store the returned bus path string. The bus path prefix
73    must be a valid bus path, starting with a slash
74    <literal>/</literal>, and not ending in one. The external
75    identifier string may be in any format, may be the empty string,
76    and has no restrictions on the charset — however, it must
77    always be <constant>NUL</constant>-terminated. The returned string
78    will be the concatenation of the bus path prefix plus an escaped
79    version of the external identifier string. This operation may be
80    reversed with <function>sd_bus_path_decode()</function>. It is
81    recommended to only use external identifiers that generally
82    require little escaping to be turned into valid bus path
83    identifiers (for example, by sticking to a 7-bit ASCII character
84    set), in order to ensure the resulting bus path is still short and
85    easily processed.</para>
86
87    <para><function>sd_bus_path_decode()</function> reverses the
88    operation of <function>sd_bus_path_encode()</function> and thus
89    regenerates an external identifier string from a bus path. It
90    takes a bus path and a prefix string, plus a place to store the
91    returned external identifier string. If the bus path does not
92    start with the specified prefix, 0 is returned and the returned
93    string is set to <constant>NULL</constant>. Otherwise, the
94    string following the prefix is unescaped and returned in the
95    external identifier string.</para>
96
97    <para>The escaping used will replace all characters which are
98    invalid in a bus object path by <literal>_</literal>, followed by a
99    hexadecimal value. As a special case, the empty string will be
100    replaced by a lone <literal>_</literal>.</para>
101
102    <para><function>sd_bus_path_encode_many()</function> works like
103    its counterpart <function>sd_bus_path_encode()</function>, but
104    takes a path template as argument and encodes multiple labels
105    according to its embedded directives. For each
106    <literal>%</literal> character found in the template, the caller
107    must provide a string via varargs, which will be encoded and
108    embedded at the position of the <literal>%</literal> character.
109    Any other character in the template is copied verbatim into the
110    encoded path.</para>
111
112    <para><function>sd_bus_path_decode_many()</function> does the
113    reverse of <function>sd_bus_path_encode_many()</function>. It
114    decodes the passed object path according to the given
115    path template. For each <literal>%</literal> character in the
116    template, the caller must provide an output storage
117    (<literal>char **</literal>) via varargs. The decoded label
118    will be stored there. Each <literal>%</literal> character will
119    only match the current label. It will never match across labels.
120    Furthermore, only a single directive is allowed per label.
121    If <constant>NULL</constant> is passed as output storage, the
122    label is verified but not returned to the caller.</para>
123  </refsect1>
124
125  <refsect1>
126    <title>Return Value</title>
127
128    <para>On success, <function>sd_bus_path_encode()</function>
129    returns positive or 0, and a valid bus path in the return
130    argument. On success, <function>sd_bus_path_decode()</function>
131    returns a positive value if the prefixed matched, or 0 if it
132    did not. If the prefix matched, the external identifier is returned
133    in the return parameter. If it did not match, <constant>NULL</constant> is returned in
134    the return parameter. On failure, a negative errno-style error
135    number is returned by either function. The returned strings must
136    be
137    <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>'d
138    by the caller.</para>
139  </refsect1>
140
141  <xi:include href="libsystemd-pkgconfig.xml" />
142
143  <refsect1>
144    <title>See Also</title>
145
146    <para>
147      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
148      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
149      <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
150    </para>
151  </refsect1>
152
153</refentry>
154