Ptr-to-member as callback in a c-function

[rammel]

Hi,

I'm using a c-library in my c++ project.
Therefore I've to call this c-function:
int rm_init(int id, char* ip, unsigned short port, int timeout,
callaback_fnc);

the signatures of the callback function is:
void callback_fnc(int, int, int, char*)

I want to use a class member as the callback-function and the call
shall be done in the ctor of the same class:

struct C
{
void cb(int id, int cmd, int len, char* data);

C()
{

}
};

[rammel]

Sorry I pressed enter to fast and forget the question:

how would I call rm_init() from C() and give the member funtions
(C::cb()) instead a c-funtion to it?
I guess I need some bind or mem_fun magic, but Im not shure about ist.

Thank you in advance!

[John Harrison]

rammel wrote:

Sorry I pressed enter to fast and forget the question:

how would I call rm_init() from C() and give the member funtions
(C::cb()) instead a c-funtion to it?
I guess I need some bind or mem_fun magic, but Im not shure about ist.

Thank you in advance!

Simple answer, you can't.

You must provide a global function for your callback. Your global
function can then call C::cb() if that is what you want to do. The C
library appears to have been badly designed so that this is not easy.

john

[=?ISO-8859-1?Q?Erik_Wikstr=F6m?=]

On 2007-06-26 08:37, John Harrison wrote:

rammel wrote:

>Sorry I pressed enter to fast and forget the question:

how would I call rm_init() from C() and give the member funtions
(C::cb()) instead a c-funtion to it?
I guess I need some bind or mem_fun magic, but Im not shure about ist.

Thank you in advance!

Simple answer, you can't.

You must provide a global function for your callback. Your global
function can then call C::cb() if that is what you want to do. The C
library appears to have been badly designed so that this is not easy.

Actually it does not have anything to do with the C library, but rather
the difference between a function-pointer and an member-function-
pointer. If you want to call a member-function through a pointer you
must have a way to tell for which object you want to call the member-
function.

--
Erik Wikström

[John Harrison]

Erik Wikström wrote:

On 2007-06-26 08:37, John Harrison wrote:

>rammel wrote:

>>Sorry I pressed enter to fast and forget the question:

how would I call rm_init() from C() and give the member funtions
(C::cb()) instead a c-funtion to it?
I guess I need some bind or mem_fun magic, but Im not shure about ist.

Thank you in advance!

Simple answer, you can't.

You must provide a global function for your callback. Your global
function can then call C::cb() if that is what you want to do. The C
library appears to have been badly designed so that this is not easy.

Actually it does not have anything to do with the C library, but rather
the difference between a function-pointer and an member-function-
pointer. If you want to call a member-function through a pointer you
must have a way to tell for which object you want to call the member-
function.

Sorry, I meant the C library that the OP is using. The API for that
library appears badly designed.

john