From: Oliver <fwang2@...>
Date: 2007-07-17T04:20:04+09:00
Subject: C library extension question

hi, folks -

I am working on a ruby extension for a C library, and having
difficulty of figuring out how to deal with this structure and
wrapping it nicely in Ruby. it is a command dispatch structure, where
you supply an array of function pointers:

/* command dispatch structure */
typedef int (*proxy_cmd)(int trans_id, int nargs, char **args);

struct proxy_commands {
        int                      cmd_base;
        int                      cmd_size;
        proxy_cmd *      cmd_funcs;
};
typedef struct proxy_commands   proxy_commands;

/* end of definition */

Then, as a user you can define an array of function pointers like
this:

proxy_cmd cmds[] = {
   func_a,
   func_b,
   func_c,
   ...
};

and fill in the structure:

proxy_commands mytabs = {
    CMD_BASE;
    sizeof(cmds)/sizeof(proxy_cmd),
    cmds
}

An example of API will look like this:
register(&mytabs, .... )

What is the best way of wrapping this in Ruby?

>From end user perspective, I am thinking the interaction like this:

def func_a ( ...)
end

def func_b( ...)
end

mytabs = [func_a, func_b]
register(mytabs)

If you have experience on writing C extensions, I'd appreciate your
input.
TIA

Oliver