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Merge pull request #15569 from DaanDeMeyer/sd-bus-message-peek-type-docs

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Zbigniew Jędrzejewski-Szmek 2020-04-23 20:11:14 +02:00
commit 927cffd57f
3 changed files with 47 additions and 33 deletions
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5
man/rules/meson.build
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@ -325,7 +325,10 @@ manpages = [
'sd_bus_message_enter_container',
'sd_bus_message_exit_container'],
''],
['sd_bus_message_read', '3', ['sd_bus_message_readv'], ''],
['sd_bus_message_read',
'3',
['sd_bus_message_peek_type', 'sd_bus_message_readv'],
''],
['sd_bus_message_read_array', '3', [], ''],
['sd_bus_message_read_basic', '3', [], ''],
['sd_bus_message_read_strv', '3', [], ''],

1
man/sd-bus.xml
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@ -117,6 +117,7 @@
<citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_open_container</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_peek_type</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_read</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_read_array</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_read_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

74
man/sd_bus_message_read.xml
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@ -19,6 +19,7 @@
<refnamediv>
<refname>sd_bus_message_read</refname>
<refname>sd_bus_message_readv</refname>
<refname>sd_bus_message_peek_type</refname>
<refpurpose>Read a sequence of values from a message</refpurpose>
</refnamediv>
@ -40,38 +41,42 @@
<paramdef>const char *<parameter>types</parameter></paramdef>
<paramdef>va_list <parameter>ap</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_peek_type</function></funcdef>
<paramdef>char *<parameter>type</parameter></paramdef>
<paramdef>const char **<parameter>contents</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_message_read()</function> reads a sequence of fields from
the D-Bus message object <parameter>m</parameter> and advances the read position
in the message. The type string <parameter>types</parameter> describes the types
of items expected in the message and the field arguments that follow. The type
string may be <constant>NULL</constant> or empty, in which case nothing is
read.</para>
<para><function>sd_bus_message_read()</function> reads a sequence of fields from the D-Bus message object
<parameter>m</parameter> and advances the read position in the message. The type string
<parameter>types</parameter> describes the types of items expected in the message and the field arguments
that follow. The type string may be <constant>NULL</constant> or empty, in which case nothing is read.
</para>
<para>The type string is composed of the elements described in
<citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
i.e. basic and container types. It must contain zero or more single "complete
types". The type string is <constant>NUL</constant>-terminated.</para>
i.e. basic and container types. It must contain zero or more single "complete types". The type string is
<constant>NUL</constant>-terminated.</para>
<para>For each type specified in the type string, one or more arguments need to be specified
after the <parameter>types</parameter> parameter, in the same order. The arguments must be
pointers to appropriate types (a pointer to <type>int8_t</type> for a <literal>y</literal> in
the type string, a pointer to <type>int32_t</type> for an <literal>i</literal>, a pointer to
<type>const char*</type> for an <literal>s</literal>, ...) which are set based on the values in
the message. As an exception, in case of array and variant types, the first argument is an
"input" argument that further specifies how the message should be read. See the table below for
a complete list of allowed arguments and their types. Note that, if the basic type is a pointer
(e.g., <type>const char *</type> in the case of a string), the argument is a pointer to a
pointer, and also the pointer value that is written is only borrowed and the contents must be
copied if they are to be used after the end of the messages lifetime.</para>
<para>For each type specified in the type string, one or more arguments need to be specified after the
<parameter>types</parameter> parameter, in the same order. The arguments must be pointers to appropriate
types (a pointer to <type>int8_t</type> for a <literal>y</literal> in the type string, a pointer to
<type>int32_t</type> for an <literal>i</literal>, a pointer to <type>const char*</type> for an
<literal>s</literal>, ...) which are set based on the values in the message. As an exception, in case of
array and variant types, the first argument is an "input" argument that further specifies how the message
should be read. See the table below for a complete list of allowed arguments and their types. Note that,
if the basic type is a pointer (e.g., <type>const char *</type> in the case of a string), the argument is
a pointer to a pointer, and also the pointer value that is written is only borrowed and the contents must
be copied if they are to be used after the end of the messages lifetime.</para>
<para>Each argument may also be <constant>NULL</constant>, in which case the value is read and
ignored.</para>
<para>Each argument may also be <constant>NULL</constant>, in which case the value is read and ignored.
</para>
<table>
<title>Item type specifiers</title>
@ -139,24 +144,29 @@
</tgroup>
</table>
<para>If objects of the specified types are not present at the current position
in the message, an error is returned.
</para>
<para>If objects of the specified types are not present at the current position in the message, an error
is returned.</para>
<para>The <function>sd_bus_message_readv()</function> is equivalent to the
<function>sd_bus_message_read()</function>, except that it is called with a
<literal>va_list</literal> instead of a variable number of arguments. This
function does not call the <function>va_end()</function> macro. Because it
invokes the <function>va_arg()</function> macro, the value of
<parameter>ap</parameter> is undefined after the call.</para>
<function>sd_bus_message_read()</function>, except that it is called with a <literal>va_list</literal>
instead of a variable number of arguments. This function does not call the <function>va_end()</function>
macro. Because it invokes the <function>va_arg()</function> macro, the value of <parameter>ap</parameter>
is undefined after the call.</para>
<para><function>sd_bus_message_peek_type()</function> determines the type of the next element in
<parameter>m</parameter> to be read by <function>sd_bus_message_read()</function> or similar functions.
On success, the type is stored in <parameter>type</parameter>, if it is not <constant>NULL</constant>.
If the type is a container type, the type of its elements is stored in <parameter>contents</parameter>,
if it is not <constant>NULL</constant>. If this function successfully determines the type of the next
element in <parameter>m</parameter>, it returns a positive integer. If there are no more elements to be
read, it returns zero.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, <function>sd_bus_message_read()</function> and
<function>sd_bus_message_readv()</function> return 0 or a positive integer. On failure, they return a
negative errno-style error code.</para>
<para>On success, these functions return a non-negative integer. On failure, they return a negative
errno-style error code.</para>
<xi:include href="sd_bus_message_read_basic.xml" xpointer="errors" />
</refsect1>