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
61
62
#![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 = $crate::concat_arrays_size!($($array),*);
let mut result = [$init_value; __ARRAY_SIZE__];
#[allow(non_snake_case)]
#[derive(Clone, Copy)]
struct Decomposed<T: Copy> {
$($array: [T; $array.len()],)*
}
union Composed<T: Copy> {
full: [T; __ARRAY_SIZE__],
decomposed: Decomposed<T>,
}
let mut c = Composed { full: result };
$(c.decomposed.$array = $array;)*
unsafe {
result = c.full;
}
result
});
}
#[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);
}
}