如何使用c api sd总线读取dict的dbus数组

Question

我试图用sd总线读取一个类似于｛sv｝的dbus数据结构，但当我使用下面的代码时，我只能读取8个dict中的一个。

#include <stdio.h>
#include <stdlib.h>
#include <systemd/sd-bus.h>
int main ()
{
sd_bus *bus = NULL;
sd_bus_error err = SD_BUS_ERROR_NULL;
sd_bus_message *msg = NULL;
char const *sign;
int signi = 0;
int error;
sd_bus_default_user (&bus);
sd_bus_get_property (bus,
"org.mpris.MediaPlayer2.plasma-browser-integration",
"/org/mpris/MediaPlayer2",
"org.mpris.MediaPlayer2.Player",
"Metadata", &err, &msg, "a{sv}");
sign = sd_bus_message_get_signature (msg, signi);
error = sd_bus_message_enter_container (msg, SD_BUS_TYPE_ARRAY, "{sv}");
while (error =
sd_bus_message_enter_container (msg, SD_BUS_TYPE_DICT_ENTRY,
"sv") > 0) {
const char *key;
sd_bus_message_read_basic (msg, SD_BUS_TYPE_STRING, &key);
sign = sd_bus_message_get_signature (msg, signi);
printf ("returned: %s n", key);
sd_bus_message_exit_container (msg);
}
sd_bus_message_exit_container (msg);
if (err._need_free != 0) {
printf ("%d n", error);
printf ("returned error: %sn", err.message);
}
else {
printf ("%s", sign);
}
sd_bus_error_free (&err);
sd_bus_unref (bus);
return 0;
}

我在hotexamples.com上查找了函数sd_bus_message_enter_container，所有函数似乎都有，而在进入dict的函数周围有不止一个循环，在我看来，这会循环一个，告诉它有所有的值，但这似乎不起作用。我还试着将该循环与进入数组的函数一起使用，但没有起作用。另一种尝试的方法是运行一个循环8次的for循环，之后我试图寻找其他解决方案，但我看不到。我也使用免费桌面网站上的文档(https://www.freedesktop.org/software/systemd/man/sd-bus.html)我有它与gdbus合作，但据我所知，这是贬值的。我不明白这怎么不起作用。

提前感谢您的帮助。

Answer 1

我没有意识到我必须读取每个值，否则它会抛出一个错误，如果你不想，还有一个跳过函数。这是的代码

#include <stdio.h>
#include <stdlib.h>
#include <systemd/sd-bus.h>
#include <stdbool.h>
#include <string.h>
int bus_print_property(const char *name, sd_bus_message *property) {
char type;
const char *contents;
int r;

r = sd_bus_message_peek_type(property, &type, &contents);
if (r < 0)
return r;
switch (type) {
case SD_BUS_TYPE_STRING: {
const char *s;
r = sd_bus_message_read_basic(property, type, &s);
if (r < 0)
return r;
printf("%s=%sn", name, s);
return 1;
}
case SD_BUS_TYPE_BOOLEAN: {
bool b;
r = sd_bus_message_read_basic(property, type, &b);
if (r < 0)
return r;
printf("%sn", name);
return 1;
}
case SD_BUS_TYPE_INT64: {
int64_t i64;
r = sd_bus_message_read_basic(property, type, &i64);
if (r < 0)
return r;
printf("%s=%in", name, (int) i64);
return 1;
}
case SD_BUS_TYPE_INT32: {
int32_t i;
r = sd_bus_message_read_basic(property, type, &i);
if (r < 0)
return r;
printf("%s=%in", name, (int) i);
return 1;
}
case SD_BUS_TYPE_OBJECT_PATH:{
const char *p;
r = sd_bus_message_read_basic(property, type, &p);
if (r < 0)
return r;
printf("%s=%sn", name, p);
return 1;

}
case SD_BUS_TYPE_DOUBLE: {
double d;
r = sd_bus_message_read_basic(property, type, &d);
if (r < 0)
return r;
printf("%s=%gn", name, d);
return 1;
}
case SD_BUS_TYPE_ARRAY:
if (strcmp(contents, "s")==0) {
bool first = true;
const char *str;
r = sd_bus_message_enter_container(property, SD_BUS_TYPE_ARRAY, contents);
if (r < 0)
return r;
while((r = sd_bus_message_read_basic(property, SD_BUS_TYPE_STRING, &str)) > 0) {
if (first)
printf("%s=", name);
printf("%s%s", first ? "" : " ", str);
first = false;
}
if (r < 0)
return r;
if (first )
printf("%s=", name);
if (!first )
puts("");
r = sd_bus_message_exit_container(property);
if (r < 0)
return r;
return 1;
} else {
printf("array unreadable");
return 0;
}
break;
}
return 0;
}
int main()
{
sd_bus* bus = NULL;
sd_bus_error err = SD_BUS_ERROR_NULL;
sd_bus_message *msg = NULL;
int error;

sd_bus_default_user(&bus);
sd_bus_get_property(bus,
"org.mpris.MediaPlayer2.plasma-browser-integration",
"/org/mpris/MediaPlayer2",
"org.mpris.MediaPlayer2.Player",
"Metadata",
&err,&msg,"a{sv}");
error = sd_bus_message_enter_container(msg, SD_BUS_TYPE_ARRAY, "{sv}");
if (error < 0)
return error;
while ((error = sd_bus_message_enter_container(msg, SD_BUS_TYPE_DICT_ENTRY, "sv")) > 0) {
const char *name;
const char *contents;
error = sd_bus_message_read_basic(msg, SD_BUS_TYPE_STRING, &name);
if (error < 0)
return error;

error = sd_bus_message_peek_type(msg, NULL, &contents);
if (error < 0)
return error;
error = sd_bus_message_enter_container(msg, SD_BUS_TYPE_VARIANT, contents);
if (error < 0)
return error;
error = bus_print_property(name, msg);
if (error < 0)
return error;
if (error == 0) {
printf("%s=[unprintable]n", name);
/* skip what we didn't read */
error = sd_bus_message_skip(msg, contents);
if (error < 0)
return error;
}
error = sd_bus_message_exit_container(msg);
if (error < 0)
return error;

error = sd_bus_message_exit_container(msg);
if (error < 0)
return error;
}
if (error < 0)
return error;
error = sd_bus_message_exit_container(msg);
if (error < 0)
return error;

if(err._need_free!=0){
printf("%d n",error);
printf("returned error: %sn",err.message);
}else{

}
sd_bus_error_free(&err);
sd_bus_unref(bus);
return 0;
}