Variyak

This crate provides a macro call_variadic which can be used to construct boilerplate code to call variadic functions using data from a container such as a Vec.

Example:

```rust

![feature(c_variadic)]

use variyak::call_variadic;

fn main() { let data = vec![1, 2]; let arg = 0;

mod test {
    #[no_mangle]
    pub unsafe extern "C" fn my_func(_fixed: u32, mut _args: ...) -> bool {
        true
    }
}

unsafe {
    assert!(call_variadic!(
        test::my_func(arg, ...)   // function to call, `...` is the variadic arguments
        data,                     // container identifier
        n,                        // index identifier
        data[n],                  // argument expression: get `argument` at index `n`
        2,                        // maximum number of arguments to expand
    ));
}

unsafe {
    use test::my_func;
    assert!(call_variadic!(my_func(arg, ...), data, n, data[n], 2));
    assert!(call_variadic!(my_func(arg, ...), data, n, data[n], 2));
    assert!(call_variadic!(my_func(arg, arg, ..., arg), data, n, data[n], 2));
    assert!(call_variadic!(my_func(arg, ..., arg), data, n, data[n], 2));
    assert!(call_variadic!(my_func(arg, 42 + 27, ..., arg, 10usize), data, n, data[n], 2));
};

} ```