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#![no_std]
#[macro_export]
macro_rules! concat_arrays_size {
($( $array:tt ),*) => {{
0 $(+ $array.len())*
}};
}
#[macro_export]
macro_rules! concat_arrays {
($( $array:tt ),*) => ({
const __ARRAY_SIZE__: usize = $crate::concat_arrays_size!($($array),*);
#[allow(dead_code, non_snake_case)]
struct ArrayConcatDecomposed<T> {
$($array: [T; $array.len()],)*
}
union ArrayConcatComposed<T, const N: usize> {
full: core::mem::ManuallyDrop<[T; N]>,
decomposed: core::mem::ManuallyDrop<ArrayConcatDecomposed<T>>,
}
impl<T, const N: usize> ArrayConcatComposed<T, N> {
const fn compare_sizes(&self) -> bool {
core::mem::size_of::<[T; N]>() == core::mem::size_of::<Self>()
}
}
let composed = ArrayConcatComposed { decomposed: core::mem::ManuallyDrop::new(ArrayConcatDecomposed { $($array,)* })};
["Size mismatch"][!composed.compare_sizes() as usize];
core::mem::ManuallyDrop::into_inner(unsafe { composed.full })
});
}
#[allow(dead_code)]
#[cfg(test)]
mod tests {
use super::*;
const A: [u32; 3] = [1, 2, 3];
const B: [u32; 3] = [4, 5, 6];
const C: [u32; 2] = [4, 5];
#[test]
fn test_simple_concat() {
let d = concat_arrays!(A, B);
const D: [u32; concat_arrays_size!(A, B)] = concat_arrays!(A, B);
assert_eq!([1, 2, 3, 4, 5, 6], D);
assert_eq!([1, 2, 3, 4, 5, 6], d);
}
#[test]
fn test_different_sizes() {
let e = concat_arrays!(A, C);
const E: [u32; concat_arrays_size!(A, C)] = concat_arrays!(A, C);
assert_eq!([1, 2, 3, 4, 5], E);
assert_eq!([1, 2, 3, 4, 5], e);
}
}