1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
//! Callback support infrastructure for C callbacks with Rust closures.
//!
//! This module provides safe abstractions for passing Rust closures to C functions
//! that expect callback function pointers with void* baton parameters.
use std::ffi::c_void;
/// Simple wrapper for passing Rust closures as C callbacks.
///
/// Boxes the closure and provides the pointer as a baton.
pub struct CallbackHandle<F> {
boxed: Box<F>,
}
impl<F> CallbackHandle<F> {
/// Create a new callback handle from a closure
pub fn new(callback: F) -> Self {
CallbackHandle {
boxed: Box::new(callback),
}
}
/// Get the baton pointer to pass to C functions
pub fn baton(&self) -> *mut c_void {
&*self.boxed as *const F as *mut c_void
}
}
// Example of how to create extern "C" trampolines for callbacks:
//
// type CancelFn = dyn FnMut() -> bool;
//
// extern "C" fn cancel_trampoline(baton: *mut c_void) -> i32 {
// if baton.is_null() {
// return 0;
// }
// unsafe {
// let cancel_fn = &mut *(baton as *mut Box<CancelFn>);
// if cancel_fn() { 1 } else { 0 }
// }
// }
//
// The CallbackHandle above can be used to manage the boxed closure lifetime.
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_callback_handle() {
let mut counter = 0;
let callback = move || {
counter += 1;
counter
};
let handle = CallbackHandle::new(callback);
assert!(!handle.baton().is_null());
}
}
|
