dbus双方向通信例cコード

ネット上の大部分は一方向転送の例しかなく、双方向通信はbusname、interface、pathなどの付与に少しこだわっている.そうしないと、初期化に失敗したり、送受信できなかったりしやすい.ソースコードは以下の通りである.

#include 
#include 
#include 
#include 
#include 
#include 

struct DBus
{
    char m_receiverBusName[64];
    char m_receiverPath[32];
    char m_receiverInterFace[32];
    char m_receiverMethod[16];
    char m_sendBusName[64];
};

DBusConnection * DbusInit(const char *name, DBusError *perr)
{
    int ret;
    DBusError &err = *perr;
    DBusConnection *connection;

    pid_t pid;
    pid = getpid();

    dbus_error_init(&err);
    //    session D-Bus   
    connection = dbus_bus_get(DBUS_BUS_SESSION, &err);
    if (!connection)
    {
        if (dbus_error_is_set(&err))
            printf("Connection Error %s
", err.message);
        else
            printf("%s %d err
", __func__, __LINE__);
        return NULL;
    }

    //      
    printf("init PID = %d, name = %s
", pid, name);
    ret = dbus_bus_request_name(connection, name,
                            DBUS_NAME_FLAG_REPLACE_EXISTING, &err);
    if (ret != DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER)
    {
        if (dbus_error_is_set(&err))
            printf("Name Error %s
", err.message);
        else
            printf("%s %d err
", __func__, __LINE__);
        return NULL;
    }

    //      disconnect            (_exit())
    dbus_connection_set_exit_on_disconnect(connection, false);

    return connection;
}

void ReplyMethodCall(DBusMessage *msg, DBusConnection *conn)
{
    DBusMessageIter msg_arg;
    // msg     ，            
    if (!dbus_message_iter_init(msg, &msg_arg))
    {
        printf("Message has NO Argument
");
        return;
    }

    do
    {
        int ret = dbus_message_iter_get_arg_type(&msg_arg);
        if (DBUS_TYPE_STRING == ret)
        {
            char *pdata;
            dbus_message_iter_get_basic(&msg_arg, &pdata);
            printf("get Method Argument STRING: %s
", pdata);
        }
        else
        {
            printf("Argument Type ERROR
");
        }

    } while (dbus_message_iter_next(&msg_arg));

    dbus_connection_flush(conn);
}

/*   D-Bus  ，              */
//void DbusReceive(DBusConnection *connection)
void * ReceiveThread(void *arg)
{
    struct DBus *dbus = (struct DBus *)arg;
    DBusError err;
    DBusConnection *connection = DbusInit(dbus->m_receiverBusName, &err);
    if (connection == NULL)
    {
        dbus_error_free(&err);
        return NULL;
    }

    printf("ReceiveThread %s, %s, %s, %s
", dbus->m_receiverBusName, dbus->m_receiverPath, dbus->m_receiverInterFace, dbus->m_receiverMethod);

    DBusMessage *msg;

    while (1)
    {
        dbus_connection_read_write(connection, 0);

        msg = dbus_connection_pop_message(connection);
        if (msg == NULL)
        {
            sleep(1);
            continue;
        }

        const char *path = dbus_message_get_path(msg);
        if (path == NULL || strcmp(path, dbus->m_receiverPath))
        {
            printf("Wrong PATH: %s !=%s
", (path==NULL ? "" : path), dbus->m_receiverPath);
            dbus_message_unref(msg);
            continue;
        }

        printf("Get a Message
");
        if (dbus_message_is_method_call(msg, dbus->m_receiverInterFace, dbus->m_receiverMethod))
        {
            printf("Someone Call My Method
");
            ReplyMethodCall(msg, connection);
        }
        else
        {
            printf("NOT a Signal OR a Method
");
        }

        dbus_message_unref(msg);
    }

    dbus_error_free(&err);
}

static void DbusSend(struct DBus *dbus, DBusConnection *connection, const void *value)
{
    printf("DbusSend %s, %s, %s, %s
", dbus->m_receiverBusName, dbus->m_receiverPath, dbus->m_receiverInterFace, dbus->m_receiverMethod);
    //       ，    method call  。
    //Constructs a new message to invoke a method on a remote object.
    DBusMessage *msg = dbus_message_new_method_call(
        dbus->m_receiverBusName, dbus->m_receiverPath,
        dbus->m_receiverInterFace, dbus->m_receiverMethod);
    if (msg == NULL)
    {
        printf("Message NULL");
        return;
    }

    DBusMessageIter arg;
    dbus_message_iter_init_append(msg, &arg);
    if (!dbus_message_iter_append_basic(&arg, DBUS_TYPE_STRING, &value))
    {
        printf("Out of Memory!");
        dbus_message_unref(msg);
        return;
    }

    //        reply handle 。Queues a message to send, as with dbus_connection_send()
    // but also returns a DBusPendingCall used to receive a reply to the message.
    DBusPendingCall *pending;
    if (!dbus_connection_send_with_reply(connection, msg, &pending, -1))
    {
        printf("Out of Memory!");
        dbus_message_unref(msg);
        return;
    }

    if (pending == NULL)
    {
        printf("Pending Call NULL: connection is disconnected ");
        dbus_message_unref(msg);
        return;
    }

    dbus_connection_flush(connection);
    dbus_message_unref(msg);
}

int main(int argc, char *argv[])
{
    if (strncmp(argv[1], "1", 1) == 0)
    {
        struct DBus rdbus;
        strcpy(rdbus.m_receiverBusName, "com.bt.c2s");
        strcpy(rdbus.m_receiverPath, "/com/bt/c2s/object");
        strcpy(rdbus.m_receiverInterFace, "com.bt.c2s.interface");
        strcpy(rdbus.m_receiverMethod,"method");
        strcpy(rdbus.m_sendBusName, "");

        pthread_t thread;
        pthread_create(&thread, NULL, ReceiveThread, &rdbus);

        struct DBus wdbus;
        strcpy(wdbus.m_receiverBusName, "com.bt.s2c");
        strcpy(wdbus.m_receiverPath, "/com/bt/s2c/object");
        strcpy(wdbus.m_receiverInterFace, "com.bt.s2c.interface");
        strcpy(wdbus.m_receiverMethod,"method");
        strcpy(wdbus.m_sendBusName, "com.bt.s2c_send");

        DBusError err;
        DBusConnection *connection = DbusInit(wdbus.m_sendBusName, &err);
        if (connection == NULL)
        {
            printf("%s %d
", __func__, __LINE__);
            dbus_error_free(&err);
            return -1;
        }

        while (1)
        {
            DbusSend(&wdbus, connection, "world");
            sleep(3);
        }
        dbus_error_free(&err);
    }
    else if (strncmp(argv[1], "2", 1) == 0)
    {
        struct DBus rdbus;
        strcpy(rdbus.m_receiverBusName, "com.bt.s2c");
        strcpy(rdbus.m_receiverPath, "/com/bt/s2c/object");
        strcpy(rdbus.m_receiverInterFace, "com.bt.s2c.interface");
        strcpy(rdbus.m_receiverMethod,"method");
        strcpy(rdbus.m_sendBusName, "");

        pthread_t thread;
        pthread_create(&thread, NULL, ReceiveThread, &rdbus);

        struct DBus wdbus;
        strcpy(wdbus.m_receiverBusName, "com.bt.c2s");
        strcpy(wdbus.m_receiverPath, "/com/bt/c2s/object");
        strcpy(wdbus.m_receiverInterFace, "com.bt.c2s.interface");
        strcpy(wdbus.m_receiverMethod,"method");
        strcpy(wdbus.m_sendBusName, "com.bt.c2s_send");

        DBusError err;
        DBusConnection *connection = DbusInit(wdbus.m_sendBusName, &err);
        if (connection == NULL)
        {
            printf("%s %d
", __func__, __LINE__);
            dbus_error_free(&err);
            return -1;
        }

        while (1)
        {
            DbusSend(&wdbus, connection, "hello");
            sleep(3);
        }

        dbus_error_free(&err);
    }

    printf("%s %d
", __func__, __LINE__);

    return 0;
}

コンパイル:g++test.cpp `pkg-config --cflags --libs dbus-1` -lpthread
テストの実行:
一端、一線読み、もう一つのスレッドはwordを送信します.反対側は、一線で読み、別のスレッドはhelloを送信します.
./a.out 1 init PID = 20744, name = com.bt.s2c_send init PID = 20744, name = com.bt.c2s DbusSend com.bt.s2c,/com/bt/s2c/object, com.bt.s2c.interface, method ReceiveThread com.bt.c2s,/com/bt/c2s/object, com.bt.c2s.interface, method Wrong PATH:/org/freedesktop/DBus !=/com/bt/c2s/object Wrong PATH:/org/freedesktop/DBus !=/com/bt/c2s/object Wrong PATH:/org/freedesktop/DBus !=/com/bt/c2s/object Wrong PATH:  !=/com/bt/c2s/object DbusSend com.bt.s2c,/com/bt/s2c/object, com.bt.s2c.interface, method Wrong PATH:  !=/com/bt/c2s/object Get a Message Someone Call My Method get Method Argument STRING: hello DbusSend com.bt.s2c,/com/bt/s2c/object, com.bt.s2c.interface, method Get a Message Someone Call My Method get Method Argument STRING: hello
 
./a.out 2 init PID = 20746, name = com.bt.c2s_send init PID = 20746, name = com.bt.s2c ReceiveThread com.bt.s2c,/com/bt/s2c/object, com.bt.s2c.interface, method DbusSend com.bt.c2s,/com/bt/c2s/object, com.bt.c2s.interface, method Wrong PATH:/org/freedesktop/DBus !=/com/bt/s2c/object Wrong PATH:/org/freedesktop/DBus !=/com/bt/s2c/object Wrong PATH:/org/freedesktop/DBus !=/com/bt/s2c/object DbusSend com.bt.c2s,/com/bt/c2s/object, com.bt.c2s.interface, method Get a Message Someone Call My Method get Method Argument STRING: world DbusSend com.bt.c2s,/com/bt/c2s/object, com.bt.c2s.interface,method Get a Message Someone Call My Method get Method Argument STRING:world作者:かっこよくて外出できない