如何创建Rust回调函数以传递给FFI函数？

Question

这就是C API的外观

bin

void mosquitto_connect_callback_set(struct mosquitto *mosq, void (*on_connect)(struct mosquitto *, void *, int)); 为我生成了这个

rust-bindgen

如何创建一个生锈回调函数以传递给上面 rust 绑定中的pub fn mosquitto_connect_callback_set(mosq: *mut Struct_mosquitto, on_connect: ::std::option::Option<extern "C" fn(arg1: *mut Struct_mosquitto, arg2: *mut ::libc::c_void, arg3: ::libc::c_int) -> ()>) 参数？

Answer 1

  

如何创建生锈回调函数？

您是否阅读了The Rust Programming Language，特别是关于FFI标题为Callbacks from C code to Rust functions的部分？

那里的例子是

extern fn callback(a: i32) {
    println!("I'm called from C with value {0}", a);
}

#[link(name = "extlib")]
extern {
   fn register_callback(cb: extern fn(i32)) -> i32;
   fn trigger_callback();
}

fn main() {
    unsafe {
        register_callback(callback);
        trigger_callback(); // Triggers the callback
    }
}

针对您的具体情况，您已经了解了所需的特定功能类型：

extern "C" fn mycallback(arg1: *mut Struct_mosquitto,
                         arg2: *mut ::libc::c_void,
                         arg3: ::libc::c_int) -> ()
{
    println!("I'm in Rust!");
}

然后像

一样使用它

mosquitto_connect_callback_set(mosq, Some(mycallback));