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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 ),*; $init_value:expr) => ({
const __ARRAY_SIZE__: usize = $crate::concat_arrays_size!($($array),*);
let mut wrapper = $crate::internals::ArrayConcatWrapper { data: [$init_value; __ARRAY_SIZE__], _marker: core::marker::PhantomData };
#[allow(non_snake_case)]
#[derive(Clone, Copy)]
struct ArrayConcatDecomposed<T: Copy> {
$($array: [T; $array.len()],)*
_marker: core::marker::PhantomData<Self>,
}
union ArrayConcatComposed<T: Copy> {
full: [T; __ARRAY_SIZE__],
decomposed: ArrayConcatDecomposed<T>,
}
let mut composed = ArrayConcatComposed { full: wrapper.data };
$(composed.decomposed.$array = $array;)*
["Size mismatch"][!$crate::internals::__compare_sizes__(wrapper._marker, unsafe { composed.decomposed._marker }) as usize];
wrapper.data = unsafe { composed.full };
wrapper.data
});
}
#[doc(hidden)]
pub mod internals {
pub struct ArrayConcatWrapper<T: Copy, const N: usize> {
pub data: [T; N],
pub _marker: core::marker::PhantomData<[T; N]>,
}
pub const fn __compare_sizes__<A, C>(_: core::marker::PhantomData<A>, _: core::marker::PhantomData<C>) -> bool {
core::mem::size_of::<A>() == core::mem::size_of::<C>()
}
}
#[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; u32::MIN);
const D: [u32; concat_arrays_size!(A, B)] = concat_arrays!(A, B; u32::MIN);
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; u32::MIN);
const E: [u32; concat_arrays_size!(A, C)] = concat_arrays!(A, C; u32::MIN);
assert_eq!([1, 2, 3, 4, 5], E);
assert_eq!([1, 2, 3, 4, 5], e);
}
}