使用 dbus-cpp 列出 WPA 请求者网络属性

Question

当尝试列出网络属性时 - https://w1.fi/wpa_supplicant/devel/dbus.html#dbus_network 使用 dbus-cpp 我收到一些关于 core::dbus::types::Variant

缺少 operator== 的错误

/usr/include/core/dbus/impl/object.h:185:17:   required from ‘std::shared_ptr<core::dbus::Property<PropertyDescription> > core::dbus::Object::get_property() [with PropertyDescription = fi::w1::wpa_supplicant1::Network::Properties::Propertiez]’ /home/martin/ClionProjects/ang-wifi-controller/src/wpasupplicantclient.cpp:149:118:   required from here /usr/include/c++/6/bits/stl_pair.h:364:51: error: no match for ‘operator==’ (operand types are ‘const core::dbus::types::Variant’ and ‘const core::dbus::types::Variant’)
 { return __x.first == __y.first && __x.second == __y.second; }

我的代码基于 dbus-cpp 示例和 http://quaintous.com/2015/08/30/cpp11-dbus/，但它们仅提供有限的帮助。表示属性属性的代码如下：

namespace fi {
namespace w1 {
struct wpa_supplicant1 {
struct Network {
    struct Properties {
        struct Propertiez {
            inline static std::string name() { return "Properties"; };
            typedef Network Interface;
            typedef std::map<std::string, core::dbus::types::Variant> ValueType;
            static const bool readable = true;
            static const bool writable = true;
        };
    };
};

.cpp 中的违规行是 networkProxy->get_property<fi::w1::wpa_supplicant1::Network::Properties::Propertiez>();

我发现这个问题已经在 https://answers.launchpad.net/ubuntu/+source/dbus-cpp/+question/593271 上被问过了，但是没有人提供任何建议。浏览 apt-cache rdepends libdbus-cpp5 列出的包的代码也没有结果。我尝试弄乱 ValueType 但这一切都导致了运行时错误，因为预期结果可能确实是地图。老实说，这对我来说似乎是库中的一个错误，但由于这一定是一个明显的用例，我试图找出我在使用库时的错误。那我做错了什么？

编辑：由于我没有收到任何回复，所以我包含了最少的样本。

#include <core/dbus/bus.h>
#include <core/dbus/object.h>
#include <core/dbus/property.h>
#include <core/dbus/service.h>
#include <core/dbus/result.h>
#include <core/dbus/asio/executor.h>
#include <core/dbus/interfaces/properties.h>
#include <core/dbus/types/stl/string.h>
#include <core/dbus/types/stl/tuple.h>
#include <core/dbus/types/stl/vector.h>
#include <core/dbus/types/struct.h>
#include <core/dbus/types/variant.h>

using namespace std::chrono_literals;
using DBusDict = std::map<std::string, core::dbus::types::Variant>;

namespace fi {
namespace w1 {
struct wpa_supplicant1
{
    struct GetInterface {
        typedef wpa_supplicant1 Interface;
        static const std::string &name()
        {
            static const std::string s("GetInterface");
            return s;
        }
        inline static const std::chrono::milliseconds default_timeout() { return 1s; }
    };
    struct Iface
    {
        struct AddNetwork {
            typedef Iface Interface;
            static const std::string &name()
            {
                static const std::string s("AddNetwork");
                return s;
            }
            inline static const std::chrono::milliseconds default_timeout() { return 1s; }
        };
        struct Properties
        {
            struct Networks
            {
                inline static std::string name()
                { return "Networks"; };
                typedef Iface Interface;
                typedef std::vector<core::dbus::types::ObjectPath> ValueType;
                static const bool readable = true;
                static const bool writable = false;
            };
        };
    };
    struct Network
    {
        struct Properties
        {
            struct Propertiez
            {
                inline static std::string name()
                { return "Properties"; };
                typedef Network Interface;
                typedef DBusDict ValueType;
                static const bool readable = true;
                static const bool writable = true;
            };
        };
    };
};
};
};

namespace core {
namespace dbus {
namespace traits {
template <> struct Service<fi::w1::wpa_supplicant1> {
    inline static const std::string &interface_name()
    {
        static const std::string s("fi.w1.wpa_supplicant1");
        return s;
    }
};

template <> struct Service<fi::w1::wpa_supplicant1::Iface> {
    inline static const std::string &interface_name()
    {
        static const std::string s("fi.w1.wpa_supplicant1.Interface");
        return s;
    }
};
template <> struct Service<fi::w1::wpa_supplicant1::Network> {
    inline static const std::string &interface_name()
    {
        static const std::string s("fi.w1.wpa_supplicant1.Network");
        return s;
    }
};
}
}
}

int main()
{
    //bus
    auto systemBus = std::make_shared<core::dbus::Bus>(core::dbus::WellKnownBus::system);
    systemBus->install_executor(core::dbus::asio::make_executor(systemBus));
    auto busThread = std::thread(std::bind(&core::dbus::Bus::run, systemBus));

    //service
    auto wpaService = core::dbus::Service::use_service<fi::w1::wpa_supplicant1>(systemBus);
    auto wpaObjectPath = core::dbus::types::ObjectPath("/fi/w1/wpa_supplicant1");
    auto wpaRootProxy = wpaService->object_for_path(wpaObjectPath);

    //iface
    auto ifacePath = wpaRootProxy->transact_method<fi::w1::wpa_supplicant1::GetInterface,
                                             core::dbus::types::ObjectPath,
                                             std::string>("wlan0"); //change this to your own wireless interface
    auto wpaIfaceProxy = wpaService->object_for_path(ifacePath.value());
    auto networkPaths = wpaIfaceProxy->get_property<fi::w1::wpa_supplicant1::Iface::Properties::Networks>();

    //network
    std::string ssid("network");
    std::string password("password");
    DBusDict args = {
        {"ssid", core::dbus::types::Variant::encode(ssid)},
        {"psk", core::dbus::types::Variant::encode(password)},
    };

    auto networkPath = wpaIfaceProxy->transact_method<fi::w1::wpa_supplicant1::Iface::AddNetwork,
                                                        core::dbus::types::ObjectPath,
                                                        DBusDict>(args);
    auto networkProxy = wpaService->object_for_path(networkPath.value());

    //get properties - uncomment line below to get compiler errors
    //auto netProps = networkProxy->get_property<fi::w1::wpa_supplicant1::Network::Properties::Propertiez>();

    while (true) {
        continue;
    }
}

编译使用：g++ $(pkg-config --cflags dbus-1 dbus-cpp) ./main.cpp $(pkg-config --libs dbus-1 dbus-cpp) -lpthread

Answer 1

正如 fi.w1.wpa_supplicant1.Network.Properties.Properties 的文档所说：

[...] All values are string type, e.g., frequency is "2437", not 2437.

所以尝试定义DBusDict如下：

using DBusDict = std::map<std::string, std::string>;

Answer 2

更新：

dbus-cpp 有一个 org.freedesktop.DBus.Properties.Get 方法的实现。

得到：

auto resultVariant = dbus_object->invoke_method_synchronously
/*Method*/          <dbus::interfaces::Properties::Get, 
/*Output Type*/      dbus::types::Variant, 
/*Input Types*/      std::string, std::string>
                    ("fi.w1.wpa_supplicant1.Network","Properties").value();
auto props = resultVariant.as<std::map<std::string, dbus::types::Variant>>();

遗憾的是，Set 方法虽然也已实现，但似乎不适用于其中包含嵌套变体的任何 ArgumentType。所以：

a{sv} : std::map<std::string, core::dbus::types::Variant>
a{v} : std::vector<core::dbus::types::Variant>

在一个Set方法调用中实际上会导致程序崩溃。（没有测试更多）

旧post:

我运行今天遇到了同样的错误，并找到了至少获取属性值的解决方法。

而不是使用

auto prop = dbus_object->get_property<fi::w1::wpa_supplicant1::Network::Properties::Propertiez>();

尝试

//returns std::map<std::string, core::dbus::types::Variant>>
auto props = dbus_object->get_all_properties<fi::w1::wpa_supplicant1::Network>();

auto prop = props["Properties"];
auto prop_value = prop.as<std::map<std::string, core::dbus::types::Variant>>();

据我了解这个错误，dbus-cpp 使用了 org.freedesktop.DBus.Properties接口[=52=]读取属性。

因此 dbus_object->get_property() 尝试调用 org.freedesktop.DBus.Properties.Get 并且由于缺少 == 运算符实现而无法编译。（我猜它需要转换特定的 ValueType 的东西）

dbus_object->get_all_properties() 调用 org.freedesktop.DBus.Properties.GetAll 不需要特定的 ValueType，因此它可以工作。

当然这只是获取属性的一种解决方法，因为设置属性值与获取它绑定到相同的 shared_pointer。

使用 dbus-cpp 列出 WPA 请求者网络属性

List WPA supplicant network properties using dbus-cpp

c++

dbus

wpa-supplicant