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<refentry id="sd_bus_path_encode">

<refentryinfo>

<title>sd_bus_path_encode</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>A monkey with a typewriter</contrib>

<firstname>Zbigniew</firstname>

<surname>Jędrzejewski-Szmek</surname>

<email>zbyszek@in.waw.pl</email>

</author>

</authorgroup>

</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_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 such directive is allowed per label.

If <literal>NULL</literal> 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, NULL 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>

<refsect1>

<title>Notes</title>

<para><function>sd_bus_path_encode()</function> and

<function>sd_bus_path_decode()</function> are available as a

shared library, which can be compiled and linked to with the

<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>

file.</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>