man: update and extend the various sd_bus_message_append_*() man pages
Some calls changed their signature since the man pages were written. Also extend on a number of details.
This commit is contained in:
Lennart Poettering
@@ -49,7 +49,8 @@
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<refname>sd_bus_message_append_array_iovec</refname>
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<refname>sd_bus_message_append_array_space</refname>
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<refpurpose>Attach an array of items to a message</refpurpose>
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<refpurpose>Appaned an array of fields to a D-Bus
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message</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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@@ -69,6 +70,8 @@
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>int <parameter>memfd</parameter></paramdef>
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<paramdef>uint64_t <parameter>offset</parameter></paramdef>
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<paramdef>uint64_t <parameter>size</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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@@ -83,7 +86,7 @@
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<funcdef>int sd_bus_message_append_array_space</funcdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>size_t <parameter>size</parameter></paramdef>
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<paramdef>char void **<parameter>ptr</parameter></paramdef>
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<paramdef>void **<parameter>ptr</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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@@ -91,18 +94,19 @@
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<refsect1>
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<title>Description</title>
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<para>The <function>sd_bus_message_append_array</function> functionc
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appends items to message <parameter>m</parameter> as the single
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array. A container will be opened, items appended, and the
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container closed. Parameter <parameter>type</parameter> determines
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how pointer <parameter>p</parameter> is interpreted.
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<para>The <function>sd_bus_message_append_array()</function>
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function appends an array to a D-Bus message
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<parameter>m</parameter>. A container will be opened, the array
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contents appended, and the container closed. The parameter
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<parameter>type</parameter> determines how the pointer
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<parameter>p</parameter> is interpreted.
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<parameter>type</parameter> must be one of the "trivial" types
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<literal>y</literal>, <literal>n</literal>, <literal>q</literal>,
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<literal>i</literal>, <literal>u</literal>, <literal>x</literal>,
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<literal>t</literal>, <literal>d</literal> (but not
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<literal>b</literal>), as defined by the
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<ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic Types</ulink>
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section of the D-Bus specification, and listed in
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<literal>b</literal>), as defined by the <ulink
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url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic
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Types</ulink> section of the D-Bus specification, and listed in
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<citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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Pointer <parameter>p</parameter> must point to an array of size
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<parameter>size</parameter> bytes containing items of the
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@@ -110,50 +114,68 @@
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multiple of the size of the type <parameter>type</parameter>. As a
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special case, <parameter>p</parameter> may be
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<constant>NULL</constant>, if <parameter>size</parameter> is 0.
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</para>
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The memory pointed to by <parameter>p</parameter> is copied into
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the memory area containing the message and stays in possession of
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the caller. The caller may hence freely change the data after this
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call without affecting the message the array was appended
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to.</para>
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<para>The memory pointed at by <parameter>p</parameter> is copied
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into the memory area containing the message and may be changed
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after this call.</para>
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<para>The <function>sd_bus_message_append_array_memfd()</function>
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function appends an array of a trivial type to message
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<parameter>m</parameter>, similar to
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<function>sd_bus_message_append_array()</function>. The contents
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of the memory file descriptor <parameter>memfd</parameter>
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starting at the specified offset and and of the specified size is
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used as the contents of the array. The offset and size must be a
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multiple of the size of the type
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<parameter>type</parameter>. However, as a special exception, if
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the offset is specified as zero and the size specified as
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UINT64_MAX the full memory file descriptor contents is used. The
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memory file descriptor is sealed by this call if it hasn't been
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sealed yet, and cannot be modified a after this call. See
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<citerefentry
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project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details about memory file descriptors. Appending arrays with
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memory file descriptors enables efficient zero-copy data transfer,
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as the memory file descriptor may be passed as-is to the
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destination, without copying the memory in it to the destination
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process. Not all protocol transports support passing memory file
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descriptors between participants, in which case this call will
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automatically fall back to copying. Also, as memory file
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descriptor passing is inefficient for smaller amounts of data
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copying might still be enforced even where memory file descriptor
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passing is supported.</para>
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<para>The
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<function>sd_bus_message_append_array_memfd</function> function appends
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items to message <parameter>m</parameter>, similarly to
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<function>sd_bus_message_append_array</function>. Contents of the
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memory file descriptor <parameter>memfd</parameter> are used as
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the contents of the array. Their size must be a multiple of the
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size of the type <parameter>type</parameter>.</para>
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<para>The descriptor specified with <parameter>memfd</parameter>
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will be sealed and cannot be modified after this call.</para>
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<para>The
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<function>sd_bus_message_append_array_iovec</function> function appends
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items to message <parameter>m</parameter>, similarly to
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<function>sd_bus_message_append_array</function>. Contents of the
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iovec <parameter>iov</parameter> are used as the contents of the
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array. The total size of <parameter>iov</parameter> payload (the
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sum of <structfield>iov_len</structfield> fields) must be a multiple
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of the size of the type <parameter>type</parameter>.</para>
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<para>The <parameter>iov</parameter> argument must point to
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<parameter>n</parameter> <structname>struct iovec</structname>
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structures. Each structure may have the
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<structname>iov_base</structname> field set, in which case the
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memory pointed to will be copied into the message, or unset, in
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which case a block of zeros of length
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<para>The <function>sd_bus_message_append_array_iovec()</function>
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function appends an array of a trivial type to the message
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<parameter>m</parameter>, similar to
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<function>sd_bus_message_append_array()</function>. Contents of
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the IO vector array <parameter>iov</parameter> are used as the
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contents of the array. The total size of
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<parameter>iov</parameter> payload (the sum of
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<structfield>iov_len</structfield> fields) must be a multiple of
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the size of the type <parameter>type</parameter>. The
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<parameter>iov</parameter> argument must point to
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<parameter>n</parameter> IO vector structures. Each structure may
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have the <structname>iov_base</structname> field set, in which
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case the memory pointed to will be copied into the message, or
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unset (set to zero), in which case a block of zeros of length
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<structname>iov_len</structname> bytes will be inserted. The
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memory pointed at by <parameter>iov</parameter> may be changed
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after this call.</para>
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<para>The
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<function>sd_bus_message_append_array_space</function> function appends
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space for an array of items to message <parameter>m</parameter>.
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It behaves the same as
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<function>sd_bus_message_append_array</function>, but instead
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of copying items to the message, it returns a pointer to the
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destination area to the caller in pointer <parameter>p</parameter>.
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</para>
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<para>The <function>sd_bus_message_append_array_space()</function>
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function appends space for an array of a trivial type to message
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<parameter>m</parameter>. It behaves the same as
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<function>sd_bus_message_append_array()</function>, but instead of
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copying items to the message, it returns a pointer to the
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destination area to the caller in pointer
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<parameter>p</parameter>. The caller should subsequently write the
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array contents to this memory. Modifications of the memory
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pointed to should only occur until the next operation on the bus
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message is invoked, most imporantly the memory should not be
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altered anymore when another field has been added to the message
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or the message has been sealed.</para>
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</refsect1>
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<refsect1>
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@@ -183,6 +205,7 @@
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
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<ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink>
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</para>
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</refsect1>
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