simple_ref_fn/
ref_fn.rs

1use crate::static_ref_function::StaticRefFunction;
2use core::marker::PhantomData;
3use core::ptr::NonNull;
4
5unsafe fn call_fn<'a, F, D, T>(data: NonNull<()>, arg: T) -> F::Output
6where
7    F: StaticRefFunction<'a, D, T> + ?Sized,
8    D: 'a,
9{
10    F::call(unsafe { data.cast().as_ref() }, arg)
11}
12
13/// A simple function wrapper that behaves like a [`&dyn Fn(T) -> R`](`Fn`) type, but does not require a virtual table.
14pub struct RefFn<'a, T, R> {
15    data: NonNull<()>,
16    call_fn: unsafe fn(NonNull<()>, T) -> R,
17    _phantom: PhantomData<&'a ()>,
18}
19
20impl<'a, T, R> RefFn<'a, T, R> {
21    /// Create a [`RefFn`] object by binding [`F::call`](`StaticRefFunction::call`) function with `data`.
22    pub fn new<F, D>(data: &'a D) -> Self
23    where
24        F: StaticRefFunction<'a, D, T, Output = R> + ?Sized,
25    {
26        Self {
27            data: NonNull::from(data).cast(),
28            call_fn: call_fn::<'a, F, D, T>,
29            _phantom: PhantomData,
30        }
31    }
32
33    /// Create a [`RefFn`] object from a function reference.
34    pub fn from_fn<F>(f: &'a F) -> Self
35    where
36        F: Fn(T) -> R,
37    {
38        Self::new::<F, F>(f)
39    }
40
41    /// Call the wrapped function.
42    pub fn call(&self, arg: T) -> R {
43        unsafe { (self.call_fn)(self.data, arg) }
44    }
45}
46
47impl<T, R> Clone for RefFn<'_, T, R> {
48    fn clone(&self) -> Self {
49        *self
50    }
51}
52
53impl<T, R> Copy for RefFn<'_, T, R> {}
54
55impl<'a, F, T, R> From<&'a F> for RefFn<'a, T, R>
56where
57    F: Fn(T) -> R,
58{
59    fn from(value: &'a F) -> Self {
60        Self::from_fn(value)
61    }
62}
63
64#[cfg(test)]
65mod tests {
66    use super::RefFn;
67    use crate::static_ref_function::StaticRefFunction;
68
69    static_assertions::assert_impl_all!(RefFn<'static, (), ()>: Clone, Copy, From<&'static fn(())>);
70    static_assertions::assert_not_impl_any!(RefFn<'static, (), ()>: Send, Sync);
71
72    #[test]
73    fn test_ref_fn_new() {
74        struct F;
75
76        impl StaticRefFunction<'_, u32, u32> for F {
77            type Output = u32;
78
79            fn call(data: &u32, arg: u32) -> Self::Output {
80                data + arg
81            }
82        }
83
84        let data = 2;
85        let f: RefFn<u32, u32> = F::bind(&data);
86
87        assert_eq!(f.call(3), 5);
88        assert_eq!(f.call(5), 7);
89        assert_eq!(f.call(7), 9);
90    }
91
92    #[test]
93    fn test_ref_fn_from() {
94        let data = 2_u32;
95        let closure = |arg: u32| data + arg;
96        let f: RefFn<u32, u32> = RefFn::from(&closure);
97
98        assert_eq!(f.call(3), 5);
99        assert_eq!(f.call(5), 7);
100        assert_eq!(f.call(7), 9);
101    }
102}
simple_ref_fn/ref_fn.rs

simple_ref_fn/
ref_fn.rs
