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191 lines
8.1 KiB
XML
191 lines
8.1 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_bus_path_encode">
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<refentryinfo>
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<title>sd_bus_path_encode</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>A monkey with a typewriter</contrib>
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<firstname>Zbigniew</firstname>
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<surname>Jędrzejewski-Szmek</surname>
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<email>zbyszek@in.waw.pl</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_path_encode</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_path_encode</refname>
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<refname>sd_bus_path_encode_many</refname>
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<refname>sd_bus_path_decode</refname>
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<refname>sd_bus_path_decode_many</refname>
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<refpurpose>Convert an external identifier into an object path and back</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_path_encode</function></funcdef>
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<paramdef>const char *<parameter>prefix</parameter></paramdef>
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<paramdef>const char *<parameter>external_id</parameter></paramdef>
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<paramdef>char **<parameter>ret_path</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_path_encode_many</function></funcdef>
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<paramdef>char **<parameter>out</parameter></paramdef>
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<paramdef>const char *<parameter>path_template</parameter></paramdef>
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<paramdef>…</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_path_decode</function></funcdef>
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<paramdef>const char *<parameter>path</parameter></paramdef>
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<paramdef>const char *<parameter>prefix</parameter></paramdef>
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<paramdef>char **<parameter>ret_external_id</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_path_decode_many</function></funcdef>
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<paramdef>const char *<parameter>path</parameter></paramdef>
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<paramdef>const char *<parameter>path_template</parameter></paramdef>
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<paramdef>…</paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_bus_path_encode()</function> and
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<function>sd_bus_path_decode()</function> convert external
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identifier strings into object paths and back. These functions are
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useful to map application-specific string identifiers of any kind
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into bus object paths in a simple, reversible and safe way.</para>
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<para><function>sd_bus_path_encode()</function> takes a bus path
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prefix and an external identifier string as arguments, plus a
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place to store the returned bus path string. The bus path prefix
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must be a valid bus path, starting with a slash
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<literal>/</literal>, and not ending in one. The external
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identifier string may be in any format, may be the empty string,
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and has no restrictions on the charset — however, it must
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always be <constant>NUL</constant>-terminated. The returned string
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will be the concatenation of the bus path prefix plus an escaped
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version of the external identifier string. This operation may be
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reversed with <function>sd_bus_decode()</function>. It is
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recommended to only use external identifiers that generally
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require little escaping to be turned into valid bus path
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identifiers (for example, by sticking to a 7-bit ASCII character
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set), in order to ensure the resulting bus path is still short and
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easily processed.</para>
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<para><function>sd_bus_path_decode()</function> reverses the
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operation of <function>sd_bus_path_encode()</function> and thus
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regenerates an external identifier string from a bus path. It
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takes a bus path and a prefix string, plus a place to store the
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returned external identifier string. If the bus path does not
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start with the specified prefix, 0 is returned and the returned
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string is set to <constant>NULL</constant>. Otherwise, the
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string following the prefix is unescaped and returned in the
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external identifier string.</para>
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<para>The escaping used will replace all characters which are
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invalid in a bus object path by <literal>_</literal>, followed by a
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hexadecimal value. As a special case, the empty string will be
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replaced by a lone <literal>_</literal>.</para>
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<para><function>sd_bus_path_encode_many()</function> works like
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its counterpart <function>sd_bus_path_encode()</function>, but
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takes a path template as argument and encodes multiple labels
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according to its embedded directives. For each
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<literal>%</literal> character found in the template, the caller
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must provide a string via varargs, which will be encoded and
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embedded at the position of the <literal>%</literal> character.
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Any other character in the template is copied verbatim into the
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encoded path.</para>
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<para><function>sd_bus_path_decode_many()</function> does the
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reverse of <function>sd_bus_path_encode_many()</function>. It
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decodes the passed object path according to the given
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path template. For each <literal>%</literal> character in the
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template, the caller must provide an output storage
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(<literal>char **</literal>) via varargs. The decoded label
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will be stored there. Each <literal>%</literal> character will
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only match the current label. It will never match across labels.
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Furthermore, only a single directive is allowed per label.
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If <literal>NULL</literal> is passed as output storage, the
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label is verified but not returned to the caller.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_bus_path_encode()</function>
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returns positive or 0, and a valid bus path in the return
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argument. On success, <function>sd_bus_path_decode()</function>
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returns a positive value if the prefixed matched, or 0 if it
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did not. If the prefix matched, the external identifier is returned
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in the return parameter. If it did not match, NULL is returned in
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the return parameter. On failure, a negative errno-style error
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number is returned by either function. The returned strings must
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be
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<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>'d
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by the caller.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para><function>sd_bus_path_encode()</function> and
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<function>sd_bus_path_decode()</function> are available as a
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shared library, which can be compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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