这就是C API的外观
void mosquitto_connect_callback_set(struct mosquitto *mosq, void (*on_connect)(struct mosquitto *, void *, int));
rust-bindgen为我生成了这个
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,
) -> (),
>,
)
如何创建一个Rust回调函数来传递给上述Rust绑定中的on_connect参数？
The Rust Programming Languagefirst edition有一个关于 foreign 金融机构的章节，标题是Callbacks from C code to Rust functions.
这里有一个例子
extern "C" fn callback(a: i32) {
println!("I'm called from C with value {0}", a);
}
#[link(name = "extlib")]
extern "C" {
fn register_callback(cb: extern "C" fn(i32)) -> i32;
fn trigger_callback();
}
fn main() {
unsafe {
register_callback(callback);
trigger_callback(); // Triggers the callback
}
}
对于您的具体情况，您已经知道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!");
}
然后像这样使用它
mosquitto_connect_callback_set(mosq, Some(mycallback));