<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2014 Zbigniew Jędrzejewski-Szmek systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <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 <systemd/sd-bus.h></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 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>