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diff --git a/man/sd_bus_error.xml b/man/sd_bus_error.xml new file mode 100644 index 0000000..b2f62f2 --- /dev/null +++ b/man/sd_bus_error.xml @@ -0,0 +1,408 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="sd_bus_error" xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd_bus_error</title> + <productname>systemd</productname> + </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_setfv</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_move</refname> + <refname>sd_bus_error_is_set</refname> + <refname>sd_bus_error_has_name</refname> + <refname>sd_bus_error_has_names_sentinel</refname> + <refname>sd_bus_error_has_names</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_setfv</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>va_list <parameter>ap</parameter></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 <parameter>ap</parameter></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_move</function></funcdef> + <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef> + <paramdef>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> + + <funcprototype> + <funcdef>int <function>sd_bus_error_has_names_sentinel</function></funcdef> + <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> + <paramdef>...</paramdef> + </funcprototype> + + <para> + #define sd_bus_error_has_names(e, ...) sd_bus_error_has_names_sentinel(e, ..., NULL) + </para> + </funcsynopsis> + + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para>The <structname>sd_bus_error</structname> structure carries information about a D-Bus error + condition, or lack thereof. The functions described below may be used to set and query fields in this + structure. + <itemizedlist> + <listitem><para>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="https://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.</para></listitem> + + <listitem><para>The <structfield>message</structfield> field usually contains a human-readable string + describing the details, but might be <constant>NULL</constant>.</para></listitem> + </itemizedlist> + An unset <structname>sd_bus_error</structname> structure should have both fields initialized to + <constant>NULL</constant>, and signifies lack of an error, i.e. success. Assign + <constant>SD_BUS_ERROR_NULL</constant> to the structure in order to initialize both fields to + <constant>NULL</constant>. 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 + contents again when they are not required anymore (see above). Do not use this call on error structures + that have already been set. 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_set()</function> will return an <varname>errno</varname>-like value (see + <citerefentry + project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>) + determined from the specified error name <parameter>name</parameter>. If <parameter>name</parameter> is + <constant>NULL</constant>, it is assumed that no error occurred, and <constant>0</constant> is returned. + If <parameter>name</parameter> is nonnull, a negative value is always returned. If + <parameter>e</parameter> is <constant>NULL</constant>, no error structure is initialized, but + <parameter>name</parameter> is still converted into an <varname>errno</varname>-style value.</para> + + <para>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>. + </para> + + <para><function>sd_bus_error_set()</function> is designed to be conveniently used in a + <function>return</function> statement. If <parameter>message</parameter> is <constant>NULL</constant>, 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 will be set instead and + <constant>-ENOMEM</constant> returned. </para> + + <para><function>sd_bus_error_setf()</function> and <function>sd_bus_error_setfv()</function> are similar + to <function>sd_bus_error_set()</function>, but take a <citerefentry + project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> format + string and corresponding arguments to generate the <structfield>message</structfield> field. + <function>sd_bus_error_setf()</function> uses variadic arguments, and + <function>sd_bus_error_setfv()</function> accepts the arguments as a + <citerefentry + project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry> + parameter list.</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> may, 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 immediately return <constant>0</constant> if the + specified error parameter <parameter>error</parameter> is <constant>0</constant>. Otherwise, it 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 and the absolute value is + used implicitly. If the specified error <parameter>error</parameter> is non-zero, 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 <constant>-ENOMEM</constant> is returned.</para> + + <para><function>sd_bus_error_set_errnof()</function> and <function>sd_bus_error_set_errnof()</function> + are similar to <function>sd_bus_error_set_errno()</function>, but in addition to + <parameter>error</parameter>, take 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. + <function>sd_bus_error_set_errnof()</function> uses variadic arguments, and + <function>sd_bus_error_set_errnofv()</function> accepts the arguments as a + <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>, + <constant>0</constant> will be returned.</para> + + <para><function>sd_bus_error_copy()</function> will initialize <parameter>dst</parameter> using the + values in <parameter>e</parameter>, if <parameter>e</parameter> has been set with an error value before. + Otherwise, it will return immediately. If the strings in <parameter>e</parameter> were set using + <function>sd_bus_error_set_const()</function>, they will be shared. Otherwise, they will be + copied. Before this call, <parameter>dst</parameter> must be unset, i.e. either freshly initialized with + <constant>NULL</constant> or reset using <function>sd_bus_error_free()</function>.</para> + + <para><function>sd_bus_error_copy()</function> generally returns <constant>0</constant> or a negative + <varname>errno</varname>-like value based on the input parameter <parameter>e</parameter>: + <constant>0</constant> if it was unset and a negative integer if it was set to some error, similarly to + <function>sd_bus_error_set()</function>. It may however also return an error generated internally, for + example <constant>-ENOMEM</constant> if a memory allocation fails.</para> + + <para><function>sd_bus_error_move()</function> is similar to <function>sd_bus_error_copy()</function>, + but will move any error information from <parameter>e</parameter> into <parameter>dst</parameter>, + resetting the former. This function cannot fail, as no new memory is allocated. Note that if + <parameter>e</parameter> is not set, <parameter>dst</parameter> is initialized to + <constant>SD_BUS_ERROR_NULL</constant>. Moreover, if <parameter>dst</parameter> is + <constant>NULL</constant> no operation is executed on it and resources held by <parameter>e</parameter> + are freed and reset. Returns a converted <varname>errno</varname>-like, non-positive error value.</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_has_names_sentinel()</function> is similar to + <function>sd_bus_error_has_name()</function>, but takes multiple names to check against. The list must be + terminated with <constant>NULL</constant>. <function>sd_bus_error_has_names()</function> + is a macro wrapper around <function>sd_bus_error_has_names_sentinel()</function> that adds the + <constant>NULL</constant> sentinel automatically.</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 <constant>NULL</constant>), + 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 <constant>NULL</constant>. The structure may be reused afterwards.</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>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> always return <constant>0</constant> when the specified + error value is <constant>NULL</constant>, and a negative errno-like value corresponding to the + <parameter>name</parameter> parameter otherwise. The functions + <function>sd_bus_error_set_errno()</function>, <function>sd_bus_error_set_errnof()</function> and + <function>sd_bus_error_set_errnofv()</function>, return <constant>0</constant> when the specified error + value is <constant>0</constant>, and a negative errno-like value corresponding to the + <parameter>error</parameter> parameter otherwise. If an error occurs internally, one of the negative + error values listed below will be returned. This allows those functions to be conveniently used in a + <constant>return</constant> statement, see the example below.</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> and <function>sd_bus_error_move()</function> return a + negative error value converted from the source error, and zero if the error has not been set. This + allows those functions to be conveniently used in a <constant>return</constant> statement, see the + example below.</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>, <function>sd_bus_error_has_names()</function>, and + <function>sd_bus_error_has_names_sentinel()</function> return a non-zero value when <parameter>e</parameter> is + non-<constant>NULL</constant> and the <structfield>name</structfield> field is equal to one of the given + names, zero otherwise.</para> + + <refsect2> + <title>Errors</title> + + <para>Return value may indicate the following problems in the invocation of the function itself:</para> + + <variablelist> + <varlistentry> + <term><constant>-EINVAL</constant></term> + + <listitem><para>Error was already set in the <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> + + <para>On success, <function>sd_bus_error_set()</function>, <function>sd_bus_error_setf()</function>, + <function>sd_bus_error_set_const()</function>, <function>sd_bus_error_set_errno()</function>, + <function>sd_bus_error_set_errnof()</function>, <function>sd_bus_error_set_errnofv()</function>, + <function>sd_bus_error_copy()</function>, and <function>sd_bus_error_move()</function> will return a + negative converted <varname>errno</varname>-style value, or <constant>0</constant> if the error + parameter is <constant>NULL</constant> or unset. D-Bus errors are converted to the integral + <varname>errno</varname>-style value, and the mapping mechanism is extensible, see the discussion + above. This effectively means that almost any negative <varname>errno</varname>-style value can be + returned.</para> + </refsect2> + </refsect1> + + <refsect1> + <title>Examples</title> + + <example> + <title>Using the negative return value to propagate an error</title> + + <programlisting><xi:include href="sd_bus_error-example.c" parse="text" /></programlisting> + </example> + </refsect1> + + <xi:include href="libsystemd-pkgconfig.xml" /> + + <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='man-pages'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |