Is it possible to call function with DBUS on the same machine
Marcus Nascimento
marcus.cps at gmail.com
Fri May 6 16:11:21 PDT 2011
Hi Peter,
Just to put everyone up.
Here ir the log of our conversation. We forgot to use reply to all.
I'll try to put this in working code tomorrow...
I cant make a promisse here because it is not that small. But I will try.
You may use a something like this (pseudo alike code):
// Method 1 parameters structure
typedef struct {
int methd1param1;
gchar method1param2[20];
} method1_st;
// Method 2 parameters structure
typedef struct {
int method2param1;
int method2param2;
int method2param3;
} method2_st;
// other methods declaration
// Method call structure
typedef struct {
int methodId,
union params {
method1_st method1params;
method2_st method2params;
// other methods parameters.
} method_call;
Then, you fill a method_call structure with the Id of the method you want to
call.
And them you can fill the parameters of this method inside the union.
Then you have to serialize that method_call into an array of bytes to send
it to the other side.
In the other side, you do the oposite.
Note that the union gives you guarantee on the size of the method call.
So you don't have to read the first field (method id) to know how many bytes
you need to read after to get all the parameters.
I know this is a waste of bandwidth/memory, but it makes your code much
simpler. Tradeoffs are there everytime.
You may face some trouble with threads and SIG_PIPE when you use sockets. If
you decide to go this way, I can give you some hints.
I know iIt is cumbersome, but it was the best option to me. Maybe not for
you.
I did something like this, but I used a much more complex structure based on
C++ and polimorphism to automate the serialization and deserialization work.
It is working very smooth. I'm sorry not to provide you the real code. I did
it in my work and I cant open that to you.
There are a lot of options to do serialization. I went to a "do it yourself"
approach, but you may use some of the available libs around.
If I remember well, there is a library called FUSION that does that.
There is a Google library that does that.
I'm not really the best person to talk about serialization. Maybe you can
ask some general forum on that.
Regards.
Marcus
- Hide quoted text -
On Fri, May 6, 2011 at 7:12 PM, Peter Penzov <peter.penzov at gmail.com> wrote:
> Hi,
> I know that there is IPC solution but as far as I know it can only be
> used to send simple message to other daemon. I don't have idea how I can
> call a remote function using Unix Domain Socket (AF_UNIX) to call a
> function.
>
> Any idea?
>
> Regards
> Peter
>
>
>
> On Sat, May 7, 2011 at 1:08 AM, Marcus Nascimento <marcus.cps at gmail.com>
> wrote:
>
>> Hi,
>>
>> In fact, yes! There is. You can use more general IPC systems like Sockets,
>> Pipes, Shared Memory and so on.
>> I like Sockets very much. In fact, DBus itself is based in unix sockets.
>>
>> You have to choose deppending on your needs. What do you want to do? Maybe
>> I can help you.
>>
>> I had some trouble recently with Dbus because its C implementation (dbus
>> glib porting) imposes the use of a GMainLoop for signal support. That wasn't
>> possible because I was working on a library to be linked into a very large
>> gamma of embedded systems. So I chose Sockets and implemented a full custom
>> solution for my needs.
>>
>> Marcus.
>>
>> On Fri, May 6, 2011 at 7:01 PM, Peter Penzov <peter.penzov at gmail.com>
>> wrote:
>>
>>> Hi,
>>> I found alternatives to DBUS but it seens that they are outdated:
>>>
>>> Orbit(Corba) - is seems that it's not developed since 2004
>>>
>>> SunRPC - it's too not maintained
>>>
>>> Linux Doors - it's not maintained
>>>
>>> There is internal RPC in Linux that I may use
>>> http://www.cs.cf.ac.uk/Dave/C/node33.html
>>>
>>> Is there another way to call a remote function?
>>>
>>> Regards
>>>
>>> Peter
>>>
>>
On Fri, May 6, 2011 at 7:49 PM, Peter Penzov <peter.penzov at gmail.com> wrote:
> Hi,
> Can you implement this in a working code. Sorry but I'm not C expert. I
> started to learn C from several weeks.
> This is a very valuable for me, I'm sure many people will use it too.
>
> Regards
> Peter
>
>
> On Sat, May 7, 2011 at 1:33 AM, Marcus Nascimento <marcus.cps at gmail.com>wrote:
>
>> You may use a something like this (pseudo alike code):
>>
>> // Method 1 parameters structure
>> typedef struct {
>> int methd1param1;
>> gchar method1param2[20];
>> } method1_st;
>>
>> // Method 2 parameters structure
>> typedef struct {
>> int method2param1;
>> int method2param2;
>> int method2param3;
>> } method2_st;
>>
>> // other methods declaration
>>
>> // Method call structure
>> typedef struct {
>> int methodId,
>> union params {
>> method1_st method1params;
>> method2_st method2params;
>> // other methods parameters.
>> } method_call;
>>
>> Then, you fill a method_call structure with the Id of the method you want
>> to call.
>> And them you can fill the parameters of this method inside the union.
>> Then you have to serialize that method_call into an array of bytes to send
>> it to the other side.
>> In the other side, you do the oposite.
>>
>> Note that the union gives you guarantee on the size of the method call.
>> So you don't have to read the first field (method id) to know how many
>> bytes you need to read after to get all the parameters.
>> I know this is a waste of bandwidth/memory, but it makes your code much
>> simpler. Tradeoffs are there everytime.
>>
>> You may face some trouble with threads and SIG_PIPE when you use sockets.
>> If you decide to go this way, I can give you some hints.
>>
>> I know iIt is cumbersome, but it was the best option to me. Maybe not for
>> you.
>>
>> I did something like this, but I used a much more complex structure based
>> on C++ and polimorphism to automate the serialization and deserialization
>> work.
>> It is working very smooth. I'm sorry not to provide you the real code. I
>> did it in my work and I cant open that to you.
>>
>> There are a lot of options to do serialization. I went to a "do it
>> yourself" approach, but you may use some of the available libs around.
>> If I remember well, there is a library called FUSION that does that.
>> There is a Google library that does that.
>>
>> I'm not really the best person to talk about serialization. Maybe you can
>> ask some general forum on that.
>>
>> Regards.
>> Marcus
>>
>> On Fri, May 6, 2011 at 7:12 PM, Peter Penzov <peter.penzov at gmail.com>wrote:
>>
>>> Hi,
>>> I know that there is IPC solution but as far as I know it can only be
>>> used to send simple message to other daemon. I don't have idea how I can
>>> call a remote function using Unix Domain Socket (AF_UNIX) to call a
>>> function.
>>>
>>> Any idea?
>>>
>>> Regards
>>> Peter
>>>
>>>
>>>
>>> On Sat, May 7, 2011 at 1:08 AM, Marcus Nascimento <marcus.cps at gmail.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> In fact, yes! There is. You can use more general IPC systems like
>>>> Sockets, Pipes, Shared Memory and so on.
>>>> I like Sockets very much. In fact, DBus itself is based in unix sockets.
>>>>
>>>> You have to choose deppending on your needs. What do you want to do?
>>>> Maybe I can help you.
>>>>
>>>> I had some trouble recently with Dbus because its C implementation (dbus
>>>> glib porting) imposes the use of a GMainLoop for signal support. That wasn't
>>>> possible because I was working on a library to be linked into a very large
>>>> gamma of embedded systems. So I chose Sockets and implemented a full custom
>>>> solution for my needs.
>>>>
>>>> Marcus.
>>>>
>>>> On Fri, May 6, 2011 at 7:01 PM, Peter Penzov <peter.penzov at gmail.com>wrote:
>>>>
>>>>> Hi,
>>>>> I found alternatives to DBUS but it seens that they are outdated:
>>>>>
>>>>> Orbit(Corba) - is seems that it's not developed since 2004
>>>>>
>>>>> SunRPC - it's too not maintained
>>>>>
>>>>> Linux Doors - it's not maintained
>>>>>
>>>>> There is internal RPC in Linux that I may use
>>>>> http://www.cs.cf.ac.uk/Dave/C/node33.html
>>>>>
>>>>> Is there another way to call a remote function?
>>>>>
>>>>> Regards
>>>>>
>>>>> Peter
>>>>>
>>>>>
>>>>> On Fri, May 6, 2011 at 11:32 PM, Marcus Nascimento <
>>>>> marcus.cps at gmail.com> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> As far as I know, DBUS can handle only one call at a time for a given
>>>>>> service (daemon).
>>>>>>
>>>>>> I tried to use feedback this way and it failed (A calling "k" and B
>>>>>> calling "s" inside the body of "k").
>>>>>> I know It is possible to use signals while a given call is ongoing.
>>>>>>
>>>>>> I'm not exactly sure about this, anyone more skilled than me may say
>>>>>> the opposite.
>>>>>> Maybe you should go for a Prove of Concept.
>>>>>>
>>>>>> Regards.
>>>>>> Marcus
>>>>>>
>>>>>>
>>>>>> On Fri, May 6, 2011 at 4:47 PM, Peter Penzov <peter.penzov at gmail.com>wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>> Is it possible to call a remote function in another daemon? Here is
>>>>>>> the setup:
>>>>>>> I have two daemons - daemon A with function "s" and daemon B with
>>>>>>> function "k". I need a way function "s" from daemon A to call a
>>>>>>> function "k" from daemon B and pass some arguments. When the request
>>>>>>> is processed function "k" returns the output to function "s". Is this
>>>>>>> possible?
>>>>>>> Regards
>>>>>>> Peter
>>>>>>> _______________________________________________
>>>>>>> dbus mailing list
>>>>>>> dbus at lists.freedesktop.org
>>>>>>> http://lists.freedesktop.org/mailman/listinfo/dbus
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
--
--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=
Marcus Vinícius do Nascimento
Engenharia de Computação - EC03 - UNICAMP
--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=
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