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
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
use core::mem;
pub trait Truncate<T>: Sized {
fn truncate(self) -> T;
}
impl<T> Truncate<T> for T {
#[inline]
fn truncate(self) -> T {
self
}
}
macro_rules! impl_truncate {
($T:ty => $($U:ty),* $(,)?) => {
$(
::static_assertions::const_assert!(mem::size_of::<$T>() > mem::size_of::<$U>());
impl Truncate<$U> for $T {
#[inline]
#[allow(clippy::as_conversions)]
fn truncate(self) -> $U {
self as $U
}
}
impl<'a> Truncate<$U> for &'a $T {
#[inline]
fn truncate(self) -> $U {
<$T as Truncate<$U>>::truncate(*self)
}
}
)*
};
}
impl_truncate! { u128 => u64, u32, u16, u8 }
impl_truncate! { u64 => u32, u16, u8 }
impl_truncate! { u32 => u16, u8 }
impl_truncate! { u16 => u8 }
impl_truncate! { i128 => i64, i32, i16, i8 }
impl_truncate! { i64 => i32, i16, i8 }
impl_truncate! { i32 => i16, i8 }
impl_truncate! { i16 => i8 }
pub trait Truncated {
#[inline]
fn truncated<T>(self) -> T
where
Self: Truncate<T>,
{
self.truncate()
}
}
impl<T> Truncated for T {}
static_assertions::assert_impl_all! { i128 : Truncate<i128>, Truncate<i64>, Truncate<i32>, Truncate<i16>, Truncate<i8> }
static_assertions::assert_impl_all! { i64 : Truncate<i64>, Truncate<i32>, Truncate<i16>, Truncate<i8> }
static_assertions::assert_impl_all! { i32 : Truncate<i32>, Truncate<i16>, Truncate<i8> }
static_assertions::assert_impl_all! { i16 : Truncate<i16>, Truncate<i8> }
static_assertions::assert_impl_all! { i8 : Truncate<i8> }
static_assertions::assert_impl_all! { u128 : Truncate<u128>, Truncate<u64>, Truncate<u32>, Truncate<u16>, Truncate<u8> }
static_assertions::assert_impl_all! { u64 : Truncate<u64>, Truncate<u32>, Truncate<u16>, Truncate<u8> }
static_assertions::assert_impl_all! { u32 : Truncate<u32>, Truncate<u16>, Truncate<u8> }
static_assertions::assert_impl_all! { u16 : Truncate<u16>, Truncate<u8> }
static_assertions::assert_impl_all! { u8 : Truncate<u8> }
#[cfg(test)]
mod tests {
use super::*;
#[test]
#[rustfmt::skip]
fn truncate_unsigned() {
assert_eq!(u128::truncated::<u128>(1), 1);
assert_eq!(u128::truncated::< u64>(1), 1);
assert_eq!(u128::truncated::< u32>(1), 1);
assert_eq!(u128::truncated::< u16>(1), 1);
assert_eq!(u128::truncated::< u8>(1), 1);
assert_eq!( u64::truncated::< u64>(1), 1);
assert_eq!( u64::truncated::< u32>(1), 1);
assert_eq!( u64::truncated::< u16>(1), 1);
assert_eq!( u64::truncated::< u8>(1), 1);
assert_eq!( u32::truncated::< u32>(1), 1);
assert_eq!( u32::truncated::< u16>(1), 1);
assert_eq!( u32::truncated::< u8>(1), 1);
assert_eq!( u16::truncated::< u16>(1), 1);
assert_eq!( u16::truncated::< u8>(1), 1);
assert_eq!( u8::truncated::< u8>(1), 1);
}
#[test]
#[rustfmt::skip]
fn truncate_signed() {
assert_eq!(i128::truncated::<i128>(-1), -1);
assert_eq!(i128::truncated::< i64>(-1), -1);
assert_eq!(i128::truncated::< i32>(-1), -1);
assert_eq!(i128::truncated::< i16>(-1), -1);
assert_eq!(i128::truncated::< i8>(-1), -1);
assert_eq!( i64::truncated::< i64>(-1), -1);
assert_eq!( i64::truncated::< i32>(-1), -1);
assert_eq!( i64::truncated::< i16>(-1), -1);
assert_eq!( i64::truncated::< i8>(-1), -1);
assert_eq!( i32::truncated::< i32>(-1), -1);
assert_eq!( i32::truncated::< i16>(-1), -1);
assert_eq!( i32::truncated::< i8>(-1), -1);
assert_eq!( i16::truncated::< i16>(-1), -1);
assert_eq!( i16::truncated::< i8>(-1), -1);
assert_eq!( i8::truncated::< i8>(-1), -1);
}
}