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sd-bus: add APIs to query the current read and write queue size

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This commit is contained in:
Lennart Poettering 2018-02-13 18:27:05 +01:00
parent 033c836647
commit 2770da027a
4 changed files with 156 additions and 0 deletions
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1
man/rules/meson.build
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@ -186,6 +186,7 @@ manpages = [
['SD_BUS_ERROR_END', 'SD_BUS_ERROR_MAP', 'sd_bus_error_map'],
''],
['sd_bus_get_fd', '3', [], ''],
['sd_bus_get_n_queued_read', '3', ['sd_bus_get_n_queued_write'], ''],
['sd_bus_is_open', '3', ['sd_bus_is_ready'], ''],
['sd_bus_message_append', '3', ['sd_bus_message_appendv'], ''],
['sd_bus_message_append_array',

129
man/sd_bus_get_n_queued_read.xml Normal file
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@ -0,0 +1,129 @@
<?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">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2018 Lennart Poettering
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_get_n_queued_read">
<refentryinfo>
<title>sd_bus_get_fd</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_get_n_queued_read</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_get_n_queued_read</refname>
<refname>sd_bus_get_n_queued_write</refname>
<refpurpose>Get the number of pending bus messages in the read and write queues of a bus connection object</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_get_n_queued_read</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>uint64_t *<parameter>ret</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_get_n_queued_write</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>uint64_t *<parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<function>sd_bus_get_n_queued_read()</function> may be used to query the number of bus messages in the read queue
of a bus connection object. The read queue contains all messages read from the transport medium (e.g. network
socket) but not yet processed locally. The function expects two arguments: the bus object to query the number of
queued messages of, and a pointer to a 64bit counter variable to write the current queue size to. Use
<function>sd_bus_process()</function> in order to process queued messages, i.e. to reduce the size of the read
queue (as well as, in fact, the write queue, see below) when it is non-zero.
</para>
<para>
Similar, <function>sd_bus_get_n_queued_write()</function> may be used to query the number of currently pending
bus messages in the write queue of a bus connection object. The write queue contains all messages enqueued into
the connection with a call such as <function>sd_bus_send()</function> but not yet written to the transport
medium. The expected arguments are similar to the ones of <function>sd_bus_get_n_queued_read()</function>. Here
too, use <function>sd_bus_process()</function> to reduce the size of the write queue. Alternatively, use
<function>sd_bus_flush()</function> to synchronously write out any pending bus messages until the write queue is
empty.
</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
error code.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus connection has been created in a different process.</para></listitem>
</varlistentry>
</variablelist>
</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_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>

6
src/libsystemd/libsystemd.sym
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@ -549,3 +549,9 @@ global:
sd_event_source_get_io_fd_own;
sd_event_source_set_io_fd_own;
} LIBSYSTEMD_236;
LIBSYSTEMD_238 {
global:
sd_bus_get_n_queued_read;
sd_bus_get_n_queued_write;
} LIBSYSTEMD_237;

20
src/libsystemd/sd-bus/sd-bus.c
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@ -4091,3 +4091,23 @@ _public_ int sd_bus_get_sender(sd_bus *bus, const char **ret) {
*ret = bus->patch_sender;
return 0;
}
_public_ int sd_bus_get_n_queued_read(sd_bus *bus, uint64_t *ret) {
assert_return(bus, -EINVAL);
assert_return(bus = bus_resolve(bus), -ENOPKG);
assert_return(!bus_pid_changed(bus), -ECHILD);
assert_return(ret, -EINVAL);
*ret = bus->rqueue_size;
return 0;
}
_public_ int sd_bus_get_n_queued_write(sd_bus *bus, uint64_t *ret) {
assert_return(bus, -EINVAL);
assert_return(bus = bus_resolve(bus), -ENOPKG);
assert_return(!bus_pid_changed(bus), -ECHILD);
assert_return(ret, -EINVAL);
*ret = bus->wqueue_size;
return 0;
}