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
63
64
65
66
67
68
69
70
71


/// Helper to implement generic alignment operator.
pub trait AlignTo {
	type TAlign;
	/// Aligns the given value to a multiple of the align value.
	///
	/// Debug asserts that align is a power of two, otherwise calculates an incorrect result.
	fn align_to(self, align: Self::TAlign) -> Self;
	/// Checks if the given value is aligned to a multiple of the align value.
	///
	/// Debug asserts that align is a power of two, otherwise calculates an incorrect result.
	fn aligned_to(self, align: Self::TAlign) -> bool;
}

macro_rules! impl_align_to {
	($ty:ty) => {
		impl AlignTo for $ty {
			type TAlign = $ty;
			#[inline(always)]
			fn align_to(self, align: $ty) -> $ty {
				debug_assert!(align.is_power_of_two(), "align ({:#x}) is not a power of two", align);
				let mask = align - 1;
				self.wrapping_add(mask) & !mask
			}
			#[inline(always)]
			fn aligned_to(self, align: $ty) -> bool {
				debug_assert!(align.is_power_of_two(), "align ({:#x}) is not a power of two", align);
				let mask = align - 1;
				self & mask == 0
			}
		}
	};
}
impl_align_to!(u8);
impl_align_to!(u16);
impl_align_to!(u32);
impl_align_to!(u64);
impl_align_to!(u128);
impl_align_to!(usize);

impl<T> AlignTo for *const T {
	type TAlign = usize;
	#[inline(always)]
	fn align_to(self, align: usize) -> *const T {
		(self as usize).align_to(align) as *const T
	}
	#[inline(always)]
	fn aligned_to(self, align: usize) -> bool {
		(self as usize).aligned_to(align)
	}
}

impl<T> AlignTo for *mut T {
	type TAlign = usize;
	#[inline(always)]
	fn align_to(self, align: usize) -> *mut T {
		(self as usize).align_to(align) as *mut T
	}
	#[inline(always)]
	fn aligned_to(self, align: usize) -> bool {
		(self as usize).aligned_to(align)
	}
}

#[test]
fn test_align_to() {
	assert_eq!(0, 0_u32.align_to(256_u32));
	assert_eq!(0, (!0_u32).align_to(256_u32));
	assert_eq!(128, 65_u32.align_to(64_u32));
	assert_eq!(64, 64_u32.align_to(64_u32));
}