int-conv 0.1.4

Explicit integer conversions
Documentation 
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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188

//! Zero extension

// Imports
use crate::Signed;
use core::mem;

/// Zero extend
///
/// This trait serves to extend integers with `0`s,
/// including signed ones.
pub trait ZeroExtend<T>: Sized {
	/// Zero extends this type
	fn zero_extend(self) -> T;
}

/// Zero extending to the same type simply returns it
impl<T> ZeroExtend<T> for T {
	#[inline]
	fn zero_extend(self) -> Self {
		self
	}
}

/// Macro to help implement [`ZeroExtend`]
///
/// Note: Regardless if `GAT`s are available, a `impl ZeroExtend<&'b U> for &'a T` isn't
///       possible, as it would require memory available for `U` at `T`, which we don't
///       know from just receiving a reference to `T`.
macro_rules! impl_zero_extend {
	($T:ty => $( $U:ty ),+ $(,)?) => {
		$(
			// Make sure `U` is bigger or equal to `T` so we don't truncate the integer
			// Note: It is guaranteed that signed and unsigned variants have the same size
			::static_assertions::const_assert!(mem::size_of::<$U>() >= mem::size_of::<$T>());

			impl ZeroExtend<$U> for $T
			{
				#[inline]
				#[allow(clippy::as_conversions)]
				fn zero_extend(self) -> $U {
					// Casting between signedness is a no-op.
					// Casting from a smaller to larger unsigned integer will zero-extend.
					self
						as <$T as Signed>::Unsigned
						as <$U as Signed>::Unsigned
						as $U
				}
			}

			// TODO: Replace with generic version once specialization is stable
			impl<'a> ZeroExtend<$U> for &'a $T
			where
				$T: ZeroExtend<$U>
			{
				#[inline]
				fn zero_extend(self) -> $U {
					<$T as ZeroExtend<$U>>::zero_extend(*self)
				}
			}
		)+
	};
}

// Unsigned
impl_zero_extend! { u8   => u16, u32, u64, u128 }
impl_zero_extend! { u16  =>      u32, u64, u128 }
impl_zero_extend! { u32  =>           u64, u128 }
impl_zero_extend! { u64  =>                u128 }

// Signed
impl_zero_extend! { i8   => i16, i32, i64, i128 }
impl_zero_extend! { i16  =>      i32, i64, i128 }
impl_zero_extend! { i32  =>           i64, i128 }
impl_zero_extend! { i64  =>                i128 }

/// Helper trait for [`ZeroExtend`] to be used with turbofish syntax
pub trait ZeroExtended: Sized {
	/// Zero extends this type
	#[inline]
	fn zero_extended<T>(self) -> T
	where
		Self: ZeroExtend<T>,
	{
		self.zero_extend()
	}
}
impl<T> ZeroExtended for T {}

// Check that all `ZeroExtend` impls exist
static_assertions::assert_impl_all! { i8   : ZeroExtend<i8>, ZeroExtend<i16>, ZeroExtend<i32>, ZeroExtend<i64>, ZeroExtend<i128> }
static_assertions::assert_impl_all! { i16  :                 ZeroExtend<i16>, ZeroExtend<i32>, ZeroExtend<i64>, ZeroExtend<i128> }
static_assertions::assert_impl_all! { i32  :                                  ZeroExtend<i32>, ZeroExtend<i64>, ZeroExtend<i128> }
static_assertions::assert_impl_all! { i64  :                                                   ZeroExtend<i64>, ZeroExtend<i128> }
static_assertions::assert_impl_all! { i128 :                                                                    ZeroExtend<i128> }
static_assertions::assert_impl_all! { u8   : ZeroExtend<u8>, ZeroExtend<u16>, ZeroExtend<u32>, ZeroExtend<u64>, ZeroExtend<u128> }
static_assertions::assert_impl_all! { u16  :                 ZeroExtend<u16>, ZeroExtend<u32>, ZeroExtend<u64>, ZeroExtend<u128> }
static_assertions::assert_impl_all! { u32  :                                  ZeroExtend<u32>, ZeroExtend<u64>, ZeroExtend<u128> }
static_assertions::assert_impl_all! { u64  :                                                   ZeroExtend<u64>, ZeroExtend<u128> }
static_assertions::assert_impl_all! { u128 :                                                                    ZeroExtend<u128> }

#[cfg(test)]
mod tests {
	// Imports
	use super::*;

	#[test]
	#[rustfmt::skip]
	fn zero_extend_unsigned() {
		assert_eq!(  u8::zero_extended::<  u8>(1), 1);
		assert_eq!(  u8::zero_extended::< u16>(1), 1);
		assert_eq!(  u8::zero_extended::< u32>(1), 1);
		assert_eq!(  u8::zero_extended::< u64>(1), 1);
		assert_eq!(  u8::zero_extended::<u128>(1), 1);
		assert_eq!( u16::zero_extended::< u16>(1), 1);
		assert_eq!( u16::zero_extended::< u32>(1), 1);
		assert_eq!( u16::zero_extended::< u64>(1), 1);
		assert_eq!( u16::zero_extended::<u128>(1), 1);
		assert_eq!( u32::zero_extended::< u32>(1), 1);
		assert_eq!( u32::zero_extended::< u64>(1), 1);
		assert_eq!( u32::zero_extended::<u128>(1), 1);
		assert_eq!( u64::zero_extended::< u64>(1), 1);
		assert_eq!( u64::zero_extended::<u128>(1), 1);
		assert_eq!(u128::zero_extended::<u128>(1), 1);
	}

	#[test]
	#[rustfmt::skip]
	fn zero_extend_unsigned_big() {
		
		assert_eq!( u8::zero_extended::< u16>( u8::MAX),  u16::from( u8::MAX));
		assert_eq!( u8::zero_extended::< u32>( u8::MAX),  u32::from( u8::MAX));
		assert_eq!( u8::zero_extended::< u64>( u8::MAX),  u64::from( u8::MAX));
		assert_eq!( u8::zero_extended::<u128>( u8::MAX), u128::from( u8::MAX));
		assert_eq!(u16::zero_extended::< u32>(u16::MAX),  u32::from(u16::MAX));
		assert_eq!(u16::zero_extended::< u64>(u16::MAX),  u64::from(u16::MAX));
		assert_eq!(u16::zero_extended::<u128>(u16::MAX), u128::from(u16::MAX));
		assert_eq!(u32::zero_extended::< u64>(u32::MAX),  u64::from(u32::MAX));
		assert_eq!(u32::zero_extended::<u128>(u32::MAX), u128::from(u32::MAX));
		assert_eq!(u64::zero_extended::<u128>(u64::MAX), u128::from(u64::MAX));
		
		assert_eq!(  u8::zero_extended::<  u8>(  u8::MAX),   u8::MAX);
		assert_eq!( u16::zero_extended::< u16>( u16::MAX),  u16::MAX);
		assert_eq!( u32::zero_extended::< u32>( u32::MAX),  u32::MAX);
		assert_eq!( u64::zero_extended::< u64>( u64::MAX),  u64::MAX);
		assert_eq!(u128::zero_extended::<u128>(u128::MAX), u128::MAX);
	}

	#[test]
	#[rustfmt::skip]
	fn zero_extend_signed_positive() {
		assert_eq!(  i8::zero_extended::<  i8>(1), 1);
		assert_eq!(  i8::zero_extended::< i16>(1), 1);
		assert_eq!(  i8::zero_extended::< i32>(1), 1);
		assert_eq!(  i8::zero_extended::< i64>(1), 1);
		assert_eq!(  i8::zero_extended::<i128>(1), 1);
		assert_eq!( i16::zero_extended::< i16>(1), 1);
		assert_eq!( i16::zero_extended::< i32>(1), 1);
		assert_eq!( i16::zero_extended::< i64>(1), 1);
		assert_eq!( i16::zero_extended::<i128>(1), 1);
		assert_eq!( i32::zero_extended::< i32>(1), 1);
		assert_eq!( i32::zero_extended::< i64>(1), 1);
		assert_eq!( i32::zero_extended::<i128>(1), 1);
		assert_eq!( i64::zero_extended::< i64>(1), 1);
		assert_eq!( i64::zero_extended::<i128>(1), 1);
		assert_eq!(i128::zero_extended::<i128>(1), 1);
	}

	#[test]
	#[rustfmt::skip]
	fn zero_extend_signed_negative() {
		assert_eq!( i8::zero_extended::< i16>(-1),  i16::from(u8  ::MAX));
		assert_eq!( i8::zero_extended::< i32>(-1),  i32::from(u8  ::MAX));
		assert_eq!( i8::zero_extended::< i64>(-1),  i64::from(u8  ::MAX));
		assert_eq!( i8::zero_extended::<i128>(-1), i128::from(u8  ::MAX));
		assert_eq!(i16::zero_extended::< i32>(-1),  i32::from(u16 ::MAX));
		assert_eq!(i16::zero_extended::< i64>(-1),  i64::from(u16 ::MAX));
		assert_eq!(i16::zero_extended::<i128>(-1), i128::from(u16 ::MAX));
		assert_eq!(i32::zero_extended::< i64>(-1),  i64::from(u32 ::MAX));
		assert_eq!(i32::zero_extended::<i128>(-1), i128::from(u32 ::MAX));
		assert_eq!(i64::zero_extended::<i128>(-1), i128::from(u64 ::MAX));
		
		assert_eq!(  i8::zero_extended::<  i8>(-1), -1);
		assert_eq!( i16::zero_extended::< i16>(-1), -1);
		assert_eq!( i32::zero_extended::< i32>(-1), -1);
		assert_eq!( i64::zero_extended::< i64>(-1), -1);
		assert_eq!(i128::zero_extended::<i128>(-1), -1);
	}
}