hamlib-developer

[Hamlib-developer] backend lib loading strategy.

[Frank S. <vk...@ix...>]

Hi,

In between the Olympic events I had some thoughts
on loading strategies, and share them below.

After browsing man page for dl_open etc... :-)

Reference Example.

<snip>
       Load the math library, and print the cosine of 2.0:
              #include <dlfcn.h>
 
              int main(int argc, char **argv) {
                  void *handle = dlopen ("/lib/libm.so", RTLD_LAZY);
                  double (*cosine)(double) = dlsym(handle, "cos");
                  printf ("%f\n", (*cosine)(2.0));
                  dlclose(handle);
              }
 <snip>

1. frontend should load appropriate backend lib
   at say, rig_init or similar.

2. multiple instances of same RIG type should not 
   cause multiple dl_open requests ??

3. Must have way of resolving symbol names for
   dlsym(handle, "symbol_name"); stuff.

  eg: for things like ..
  void *handle = dlopen ("libft747.so", RTLD_LAZY);
  int (*cmd_set_vfo)(vfo_t vfo)= dlsym(handle, "rig_set_vfo");
   (*cmd_set_vfo)(RIg_MAIN_VFO)

etc..	

4. A whole lot more to come, but you see the idea.

5. GNU libtool ??

6. Lots of other stuff to follow...

/Frank
        
-- 
Frank Singleton				VK3FCS

Email: victor kilo three foxtrot charlie sierra at ix dot netcom dot com

Re: [Hamlib-developer] backend lib loading strategy.

[Stephane F. <f4...@fr...>]

Frank Singleton wrote:
> 
> 1. frontend should load appropriate backend lib
>    at say, rig_init or similar.

	nope, rig_init is already in use. init_rig isn't ;-)
> 
> 2. multiple instances of same RIG type should not 
>    cause multiple dl_open requests ??
> 
	sure not. Actually, the backend won't be loaded
  by rig type, but by backend lib!
  using something like rig_load_backend("ft847");
  which would load libhamlib-ft847.so and register it.

> 3. Must have way of resolving symbol names for
>    dlsym(handle, "symbol_name"); stuff.
> 
    We need to call dlsym() only once, ie. when the frontend
    resolves the init_rig symbol. Then, the init_rig function
    will register the capabilities in the frontend rig list.
    And that's it! Thanks to the cool API design.

> 4. A whole lot more to come, but you see the idea.
> 
	Well, very much. The registering and rig_load_backend()
  are coded, and are working fine! There's only a couple of
  lines to add in a backend to support it!
  I haven't commited this code yet, just to let you some time
  to catch up with the last commit. I will do on monday.

> 5. GNU libtool ??
> 
	done already with autoconf/automake stuff

> 6. Lots of other stuff to follow...
> 
	yup, sure!

-- 
Stephane Fillod					F4CFE