объявление свойств и методов для пути D-Bus (declare properties and methods for a D-Bus path)
Примеры (Examples)
Example 1. Create a simple listener on the bus
#include <errno.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <systemd/sd-bus.h>
#define _cleanup_(f) __attribute__((cleanup(f)))
typedef struct object {
char *name;
uint32_t number;
} object;
static int method(sd_bus_message *m, void *userdata, sd_bus_error *error) {
printf("Got called with userdata=%p\n", userdata);
return 1;
}
static const sd_bus_vtable vtable[] = {
SD_BUS_VTABLE_START(0),
SD_BUS_METHOD(
"Method1", "s", "s", method, 0),
SD_BUS_METHOD_WITH_NAMES_OFFSET(
"Method2",
"so", SD_BUS_PARAM(string) SD_BUS_PARAM(path),
"s", SD_BUS_PARAM(returnstring),
method, offsetof(object, number),
SD_BUS_VTABLE_DEPRECATED),
SD_BUS_METHOD_WITH_ARGS_OFFSET(
"Method3",
SD_BUS_ARGS("s", string, "o", path),
SD_BUS_RESULT("s", returnstring),
method, offsetof(object, number),
SD_BUS_VTABLE_UNPRIVILEGED),
SD_BUS_METHOD_WITH_ARGS(
"Method4",
SD_BUS_NO_ARGS,
SD_BUS_NO_RESULT,
method,
SD_BUS_VTABLE_UNPRIVILEGED),
SD_BUS_SIGNAL(
"Signal1",
"so",
0),
SD_BUS_SIGNAL_WITH_NAMES(
"Signal2",
"so", SD_BUS_PARAM(string) SD_BUS_PARAM(path),
0),
SD_BUS_SIGNAL_WITH_ARGS(
"Signal3",
SD_BUS_ARGS("s", string, "o", path),
0),
SD_BUS_WRITABLE_PROPERTY(
"AutomaticStringProperty", "s", NULL, NULL,
offsetof(object, name),
SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_WRITABLE_PROPERTY(
"AutomaticIntegerProperty", "u", NULL, NULL,
offsetof(object, number),
SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION),
SD_BUS_VTABLE_END
};
#define check(x) ({ \
int r = x; \
errno = r < 0 ? -r : 0; \
printf(#x ": %m\n"); \
if (r < 0) \
return EXIT_FAILURE; \
})
int main(int argc, char **argv) {
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
sd_bus_default(&bus);
object object = { .number = 666 };
check((object.name = strdup("name")) != NULL);
check(sd_bus_add_object_vtable(bus, NULL, "/object",
"org.freedesktop.systemd.VtableExample",
vtable,
&object));
for (;;) {
check(sd_bus_wait(bus, UINT64_MAX));
check(sd_bus_process(bus, NULL));
}
free(object.name);
return 0;
}
This creates a simple client on the bus (the user bus, when run
as normal user). We may use the D-Bus
org.freedesktop.DBus.Introspectable.Introspect call to acquire
the XML description of the interface:
<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
"http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
<node>
<interface name="org.freedesktop.DBus.Peer">
<method name="Ping"/>
<method name="GetMachineId">
<arg type="s" name="machine_uuid" direction="out"/>
</method>
</interface>
<interface name="org.freedesktop.DBus.Introspectable">
<method name="Introspect">
<arg name="data" type="s" direction="out"/>
</method>
</interface>
<interface name="org.freedesktop.DBus.Properties">
<method name="Get">
<arg name="interface" direction="in" type="s"/>
<arg name="property" direction="in" type="s"/>
<arg name="value" direction="out" type="v"/>
</method>
<method name="GetAll">
<arg name="interface" direction="in" type="s"/>
<arg name="properties" direction="out" type="a{sv}"/>
</method>
<method name="Set">
<arg name="interface" direction="in" type="s"/>
<arg name="property" direction="in" type="s"/>
<arg name="value" direction="in" type="v"/>
</method>
<signal name="PropertiesChanged">
<arg type="s" name="interface"/>
<arg type="a{sv}" name="changed_properties"/>
<arg type="as" name="invalidated_properties"/>
</signal>
</interface>
<interface name="org.freedesktop.systemd.VtableExample">
<method name="Method1">
<arg type="s" direction="in"/>
<arg type="s" direction="out"/>
</method>
<method name="Method2">
<arg type="s" name="string" direction="in"/>
<arg type="o" name="path" direction="in"/>
<arg type="s" name="returnstring" direction="out"/>
<annotation name="org.freedesktop.DBus.Deprecated" value="true"/>
</method>
<property name="AutomaticStringProperty" type="s" access="readwrite">
</property>
<property name="AutomaticIntegerProperty" type="u" access="readwrite">
<annotation name="org.freedesktop.DBus.Property.EmitsChangedSignal" value="invalidates"/>
</property>
</interface>
</node>
