--- /dev/null
+<?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_error">
+
+ <refentryinfo>
+ <title>sd_bus_error</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_error</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_bus_error</refname>
+ <refname>SD_BUS_ERROR_MAKE_CONST</refname>
+ <refname>SD_BUS_ERROR_NULL</refname>
+ <refname>sd_bus_error_free</refname>
+ <refname>sd_bus_error_set</refname>
+ <refname>sd_bus_error_setf</refname>
+ <refname>sd_bus_error_set_const</refname>
+ <refname>sd_bus_error_set_errno</refname>
+ <refname>sd_bus_error_set_errnof</refname>
+ <refname>sd_bus_error_set_errnofv</refname>
+ <refname>sd_bus_error_get_errno</refname>
+ <refname>sd_bus_error_copy</refname>
+ <refname>sd_bus_error_is_set</refname>
+ <refname>sd_bus_error_has_name</refname>
+
+ <refpurpose>sd-bus error handling</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
+
+ <funcsynopsisinfo>typedef struct {
+ const char *name;
+ const char *message;
+ …
+} sd_bus_error;</funcsynopsisinfo>
+
+ <para>
+ <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant>
+ </para>
+ <para>
+ <constant>SD_BUS_ERROR_NULL</constant>
+ </para>
+
+ <funcprototype>
+ <funcdef>void <function>sd_bus_error_free</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_set</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ <paramdef>const char *<parameter>message</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_setf</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ <paramdef>const char *<parameter>format</parameter></paramdef>
+ <paramdef>…</paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_set_const</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ <paramdef>const char *<parameter>message</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_set_errno</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>int <parameter>error</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>int <parameter>error</parameter></paramdef>
+ <paramdef>const char *<parameter>format</parameter></paramdef>
+ <paramdef>…</paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>int <parameter>error</parameter></paramdef>
+ <paramdef>const char *<parameter>format</parameter></paramdef>
+ <paramdef>va_list ap</paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_get_errno</function></funcdef>
+ <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_copy</function></funcdef>
+ <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef>
+ <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_is_set</function></funcdef>
+ <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_error_has_name</function></funcdef>
+ <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>The <structname>sd_bus_error</structname> structure carries
+ information about a D-Bus error condition. The functions described
+ below may be used to set and query fields in this structure. The
+ <structfield>name</structfield> field contains a short identifier
+ of an error. It should follow the rules for error names described
+ in the D-Bus specification, subsection <ulink
+ url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid
+ Names</ulink>. A number of common, standardized error names are
+ described in
+ <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ but additional domain-specific errors may be defined by
+ applications. The <structfield>message</structfield> field usually
+ contains a human-readable string describing the details, but might
+ be NULL. An unset <structname>sd_bus_error</structname> structure
+ should have both fields initialized to NULL. Set an error
+ structure to <constant>SD_BUS_ERROR_NULL</constant> in order to
+ reset both fields to NULL. When no longer necessary, resources
+ held by the <structname>sd_bus_error</structname>structure should
+ be destroyed with <function>sd_bus_error_free()</function>.</para>
+
+ <para><function>sd_bus_error_set()</function> sets an error
+ structure to the specified name and message strings. The strings
+ will be copied into internal, newly allocated memory. It is
+ essential to free the error structure again when it is not
+ required anymore (see above). The function will return an
+ <varname>errno</varname>-like negative value (see <citerefentry
+ project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
+ determined from the specified error name. Various well-known
+ D-Bus errors are converted to well-known <varname>errno</varname>
+ counterparts, and the other ones to <constant>-EIO</constant>. See
+ <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for a list of well-known error names. Additional error mappings
+ may be defined with
+ <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
+ <parameter>e</parameter> is NULL, no error structure is initialized,
+ but the error is still converted into an
+ <varname>errno</varname>-style error. If
+ <parameter>name</parameter> is <constant>NULL</constant>, it is
+ assumed that no error occurred, and 0 is returned. This means that
+ this function may be conveniently used in a
+ <function>return</function> statement. If
+ <parameter>message</parameter> is NULL, no message is set. This
+ call can fail if no memory may be allocated for the name and
+ message strings, in which case an
+ <constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set
+ instead and -ENOMEM be returned. Do not use this call on error
+ structures that are already initialized. If you intend to reuse an
+ error structure, free the old data stored in it with
+ <function>sd_bus_error_free()</function> first.</para>
+
+ <para><function>sd_bus_error_setf()</function> is similar to
+ <function>sd_bus_error_set()</function>, but takes a <citerefentry
+ project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ format string and corresponding arguments to generate the
+ <structfield>message</structfield> field.</para>
+
+ <para><function>sd_bus_error_set_const()</function> is similar to
+ <function>sd_bus_error_set()</function>, but the string parameters
+ are not copied internally, and must hence remain constant and
+ valid for the lifetime of <parameter>e</parameter>. Use this call
+ to avoid memory allocations when setting error structures. Since
+ this call does not allocate memory, it will not fail with an
+ out-of-memory condition as
+ <function>sd_bus_error_set()</function> can, as described
+ above. Alternatively, the
+ <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used
+ to generate a literal, constant bus error structure
+ on-the-fly.</para>
+
+ <para><function>sd_bus_error_set_errno()</function> will set
+ <structfield>name</structfield> from an
+ <varname>errno</varname>-like value that is converted to a D-Bus
+ error. <citerefentry
+ project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ will be used to set <structfield>message</structfield>. Well-known
+ D-Bus error names will be used for <structfield>name</structfield>
+ if applicable, otherwise a name in the
+ <literal>System.Error.</literal> namespace will be generated. The
+ sign of the specified error number is ignored. The absolute value
+ is used implicitly. The call always returns a negative value, for
+ convenient usage in <function>return</function> statements. This
+ call might fail due to lack of memory, in which case an
+ <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead,
+ and -ENOMEM is returned.</para>
+
+ <para><function>sd_bus_error_set_errnof()</function> is similar to
+ <function>sd_bus_error_set_errno()</function>, but in addition to
+ <parameter>error</parameter>, takes a <citerefentry
+ project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ format string and corresponding arguments. The
+ <structfield>message</structfield> field will be generated from
+ <parameter>format</parameter> and the arguments.</para>
+
+ <para><function>sd_bus_error_set_errnofv()</function> is similar to
+ <function>sd_bus_error_set_errnof()</function>, but takes the
+ format string parameters as <citerefentry
+ project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ parameter list.</para>
+
+ <para><function>sd_bus_error_get_errno()</function> converts the
+ <structfield>name</structfield> field of an error structure to an
+ <varname>errno</varname>-like (positive) value using the same
+ rules as <function>sd_bus_error_set()</function>. If
+ <parameter>e</parameter> is <constant>NULL</constant>, 0 will be
+ returned.</para>
+
+ <para><function>sd_bus_error_copy()</function> will initialize
+ <parameter>dst</parameter> using the values in
+ <parameter>e</parameter>. If the strings in
+ <parameter>e</parameter> were set using
+ <function>sd_bus_set_error_const()</function>, they will be shared.
+ Otherwise, they will be copied. Returns a converted
+ <varname>errno</varname>-like, negative error code.</para>
+
+ <para><function>sd_bus_error_is_set()</function> will return a
+ non-zero value if <parameter>e</parameter> is
+ non-<constant>NULL</constant> and an error has been set,
+ <constant>false</constant> otherwise.</para>
+
+ <para><function>sd_bus_error_has_name()</function> will return a
+ non-zero value if <parameter>e</parameter> is
+ non-<constant>NULL</constant> and an error with the same
+ <parameter>name</parameter> has been set,
+ <constant>false</constant> otherwise.</para>
+
+ <para><function>sd_bus_error_free()</function> will destroy
+ resources held by <parameter>e</parameter>. The parameter itself
+ will not be deallocated, and must be <citerefentry
+ project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d
+ by the caller if necessary. The function may also be called safely
+ on unset errors (error structures with both fields set to NULL),
+ in which case it performs no operation. This call will reset the
+ error structure after freeing the data, so that all fields are set
+ to NULL. The structure may be reused afterwards.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>The functions <function>sd_bus_error_set()</function>,
+ <function>sd_bus_error_setf()</function>, and
+ <function>sd_bus_error_set_const()</function>, when successful,
+ return the negative errno value corresponding to the
+ <parameter>name</parameter> parameter. The functions
+ <function>sd_bus_error_set_errno()</function>,
+ <function>sd_bus_error_set_errnof()</function> and
+ <function>sd_bus_error_set_errnofv()</function>, when successful,
+ return the negative value of the <parameter>error</parameter>
+ parameter. If an error occurs, one of the negative error values
+ listed below will be returned.</para>
+
+ <para><function>sd_bus_error_get_errno()</function> returns
+ <constant>false</constant> when <parameter>e</parameter> is
+ <constant>NULL</constant>, and a positive errno value mapped from
+ <parameter>e->name</parameter> otherwise.</para>
+
+ <para><function>sd_bus_error_copy()</function> returns 0 or a
+ positive integer on success, and a negative error value converted
+ from the error name otherwise.</para>
+
+ <para><function>sd_bus_error_is_set()</function> returns a
+ non-zero value when <parameter>e</parameter> and the
+ <structfield>name</structfield> field are
+ non-<constant>NULL</constant>, zero otherwise.</para>
+
+ <para><function>sd_bus_error_has_name()</function> returns a
+ non-zero value when <parameter>e</parameter> is
+ non-<constant>NULL</constant> and the
+ <structfield>name</structfield> field is equal to
+ <parameter>name</parameter>, zero otherwise.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Reference ownership</title>
+ <para><structname>sd_bus_error</structname> is not reference
+ counted. Users should destroy resources held by it by calling
+ <function>sd_bus_error_free()</function>. Usually, error structures
+ are allocated on the stack or passed in as function parameters,
+ but they may also be allocated dynamically, in which case it is
+ the duty of the caller to <citerefentry
+ project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ the memory held by the structure itself after freeing its contents
+ with <function>sd_bus_error_free()</function>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>Error was already set in
+ <structname>sd_bus_error</structname> structure when one the
+ error-setting functions was called.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Memory allocation failed.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para><function>sd_bus_set_error()</function> and other functions
+ described here are available as a shared library, which can be
+ compiled and linked to with the
+ <constant>libelogind</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><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / blobdiff