num_traits/ops/
wrapping.rs

1use core::num::Wrapping;
2use core::ops::{Add, Mul, Shl, Shr, Sub};
3
4macro_rules! wrapping_impl {
5    ($trait_name:ident, $method:ident, $t:ty) => {
6        impl $trait_name for $t {
7            #[inline]
8            fn $method(&self, v: &Self) -> Self {
9                <$t>::$method(*self, *v)
10            }
11        }
12    };
13    ($trait_name:ident, $method:ident, $t:ty, $rhs:ty) => {
14        impl $trait_name<$rhs> for $t {
15            #[inline]
16            fn $method(&self, v: &$rhs) -> Self {
17                <$t>::$method(*self, *v)
18            }
19        }
20    };
21}
22
23/// Performs addition that wraps around on overflow.
24pub trait WrappingAdd: Sized + Add<Self, Output = Self> {
25    /// Wrapping (modular) addition. Computes `self + other`, wrapping around at the boundary of
26    /// the type.
27    fn wrapping_add(&self, v: &Self) -> Self;
28}
29
30wrapping_impl!(WrappingAdd, wrapping_add, u8);
31wrapping_impl!(WrappingAdd, wrapping_add, u16);
32wrapping_impl!(WrappingAdd, wrapping_add, u32);
33wrapping_impl!(WrappingAdd, wrapping_add, u64);
34wrapping_impl!(WrappingAdd, wrapping_add, usize);
35#[cfg(has_i128)]
36wrapping_impl!(WrappingAdd, wrapping_add, u128);
37
38wrapping_impl!(WrappingAdd, wrapping_add, i8);
39wrapping_impl!(WrappingAdd, wrapping_add, i16);
40wrapping_impl!(WrappingAdd, wrapping_add, i32);
41wrapping_impl!(WrappingAdd, wrapping_add, i64);
42wrapping_impl!(WrappingAdd, wrapping_add, isize);
43#[cfg(has_i128)]
44wrapping_impl!(WrappingAdd, wrapping_add, i128);
45
46/// Performs subtraction that wraps around on overflow.
47pub trait WrappingSub: Sized + Sub<Self, Output = Self> {
48    /// Wrapping (modular) subtraction. Computes `self - other`, wrapping around at the boundary
49    /// of the type.
50    fn wrapping_sub(&self, v: &Self) -> Self;
51}
52
53wrapping_impl!(WrappingSub, wrapping_sub, u8);
54wrapping_impl!(WrappingSub, wrapping_sub, u16);
55wrapping_impl!(WrappingSub, wrapping_sub, u32);
56wrapping_impl!(WrappingSub, wrapping_sub, u64);
57wrapping_impl!(WrappingSub, wrapping_sub, usize);
58#[cfg(has_i128)]
59wrapping_impl!(WrappingSub, wrapping_sub, u128);
60
61wrapping_impl!(WrappingSub, wrapping_sub, i8);
62wrapping_impl!(WrappingSub, wrapping_sub, i16);
63wrapping_impl!(WrappingSub, wrapping_sub, i32);
64wrapping_impl!(WrappingSub, wrapping_sub, i64);
65wrapping_impl!(WrappingSub, wrapping_sub, isize);
66#[cfg(has_i128)]
67wrapping_impl!(WrappingSub, wrapping_sub, i128);
68
69/// Performs multiplication that wraps around on overflow.
70pub trait WrappingMul: Sized + Mul<Self, Output = Self> {
71    /// Wrapping (modular) multiplication. Computes `self * other`, wrapping around at the boundary
72    /// of the type.
73    fn wrapping_mul(&self, v: &Self) -> Self;
74}
75
76wrapping_impl!(WrappingMul, wrapping_mul, u8);
77wrapping_impl!(WrappingMul, wrapping_mul, u16);
78wrapping_impl!(WrappingMul, wrapping_mul, u32);
79wrapping_impl!(WrappingMul, wrapping_mul, u64);
80wrapping_impl!(WrappingMul, wrapping_mul, usize);
81#[cfg(has_i128)]
82wrapping_impl!(WrappingMul, wrapping_mul, u128);
83
84wrapping_impl!(WrappingMul, wrapping_mul, i8);
85wrapping_impl!(WrappingMul, wrapping_mul, i16);
86wrapping_impl!(WrappingMul, wrapping_mul, i32);
87wrapping_impl!(WrappingMul, wrapping_mul, i64);
88wrapping_impl!(WrappingMul, wrapping_mul, isize);
89#[cfg(has_i128)]
90wrapping_impl!(WrappingMul, wrapping_mul, i128);
91
92macro_rules! wrapping_shift_impl {
93    ($trait_name:ident, $method:ident, $t:ty) => {
94        impl $trait_name for $t {
95            #[inline]
96            fn $method(&self, rhs: u32) -> $t {
97                <$t>::$method(*self, rhs)
98            }
99        }
100    };
101}
102
103/// Performs a left shift that does not panic.
104pub trait WrappingShl: Sized + Shl<usize, Output = Self> {
105    /// Panic-free bitwise shift-left; yields `self << mask(rhs)`,
106    /// where `mask` removes any high order bits of `rhs` that would
107    /// cause the shift to exceed the bitwidth of the type.
108    ///
109    /// ```
110    /// use num_traits::WrappingShl;
111    ///
112    /// let x: u16 = 0x0001;
113    ///
114    /// assert_eq!(WrappingShl::wrapping_shl(&x, 0),  0x0001);
115    /// assert_eq!(WrappingShl::wrapping_shl(&x, 1),  0x0002);
116    /// assert_eq!(WrappingShl::wrapping_shl(&x, 15), 0x8000);
117    /// assert_eq!(WrappingShl::wrapping_shl(&x, 16), 0x0001);
118    /// ```
119    fn wrapping_shl(&self, rhs: u32) -> Self;
120}
121
122wrapping_shift_impl!(WrappingShl, wrapping_shl, u8);
123wrapping_shift_impl!(WrappingShl, wrapping_shl, u16);
124wrapping_shift_impl!(WrappingShl, wrapping_shl, u32);
125wrapping_shift_impl!(WrappingShl, wrapping_shl, u64);
126wrapping_shift_impl!(WrappingShl, wrapping_shl, usize);
127#[cfg(has_i128)]
128wrapping_shift_impl!(WrappingShl, wrapping_shl, u128);
129
130wrapping_shift_impl!(WrappingShl, wrapping_shl, i8);
131wrapping_shift_impl!(WrappingShl, wrapping_shl, i16);
132wrapping_shift_impl!(WrappingShl, wrapping_shl, i32);
133wrapping_shift_impl!(WrappingShl, wrapping_shl, i64);
134wrapping_shift_impl!(WrappingShl, wrapping_shl, isize);
135#[cfg(has_i128)]
136wrapping_shift_impl!(WrappingShl, wrapping_shl, i128);
137
138/// Performs a right shift that does not panic.
139pub trait WrappingShr: Sized + Shr<usize, Output = Self> {
140    /// Panic-free bitwise shift-right; yields `self >> mask(rhs)`,
141    /// where `mask` removes any high order bits of `rhs` that would
142    /// cause the shift to exceed the bitwidth of the type.
143    ///
144    /// ```
145    /// use num_traits::WrappingShr;
146    ///
147    /// let x: u16 = 0x8000;
148    ///
149    /// assert_eq!(WrappingShr::wrapping_shr(&x, 0),  0x8000);
150    /// assert_eq!(WrappingShr::wrapping_shr(&x, 1),  0x4000);
151    /// assert_eq!(WrappingShr::wrapping_shr(&x, 15), 0x0001);
152    /// assert_eq!(WrappingShr::wrapping_shr(&x, 16), 0x8000);
153    /// ```
154    fn wrapping_shr(&self, rhs: u32) -> Self;
155}
156
157wrapping_shift_impl!(WrappingShr, wrapping_shr, u8);
158wrapping_shift_impl!(WrappingShr, wrapping_shr, u16);
159wrapping_shift_impl!(WrappingShr, wrapping_shr, u32);
160wrapping_shift_impl!(WrappingShr, wrapping_shr, u64);
161wrapping_shift_impl!(WrappingShr, wrapping_shr, usize);
162#[cfg(has_i128)]
163wrapping_shift_impl!(WrappingShr, wrapping_shr, u128);
164
165wrapping_shift_impl!(WrappingShr, wrapping_shr, i8);
166wrapping_shift_impl!(WrappingShr, wrapping_shr, i16);
167wrapping_shift_impl!(WrappingShr, wrapping_shr, i32);
168wrapping_shift_impl!(WrappingShr, wrapping_shr, i64);
169wrapping_shift_impl!(WrappingShr, wrapping_shr, isize);
170#[cfg(has_i128)]
171wrapping_shift_impl!(WrappingShr, wrapping_shr, i128);
172
173// Well this is a bit funny, but all the more appropriate.
174impl<T: WrappingAdd> WrappingAdd for Wrapping<T>
175where
176    Wrapping<T>: Add<Output = Wrapping<T>>,
177{
178    fn wrapping_add(&self, v: &Self) -> Self {
179        Wrapping(self.0.wrapping_add(&v.0))
180    }
181}
182impl<T: WrappingSub> WrappingSub for Wrapping<T>
183where
184    Wrapping<T>: Sub<Output = Wrapping<T>>,
185{
186    fn wrapping_sub(&self, v: &Self) -> Self {
187        Wrapping(self.0.wrapping_sub(&v.0))
188    }
189}
190impl<T: WrappingMul> WrappingMul for Wrapping<T>
191where
192    Wrapping<T>: Mul<Output = Wrapping<T>>,
193{
194    fn wrapping_mul(&self, v: &Self) -> Self {
195        Wrapping(self.0.wrapping_mul(&v.0))
196    }
197}
198impl<T: WrappingShl> WrappingShl for Wrapping<T>
199where
200    Wrapping<T>: Shl<usize, Output = Wrapping<T>>,
201{
202    fn wrapping_shl(&self, rhs: u32) -> Self {
203        Wrapping(self.0.wrapping_shl(rhs))
204    }
205}
206impl<T: WrappingShr> WrappingShr for Wrapping<T>
207where
208    Wrapping<T>: Shr<usize, Output = Wrapping<T>>,
209{
210    fn wrapping_shr(&self, rhs: u32) -> Self {
211        Wrapping(self.0.wrapping_shr(rhs))
212    }
213}
214
215#[test]
216fn test_wrapping_traits() {
217    fn wrapping_add<T: WrappingAdd>(a: T, b: T) -> T {
218        a.wrapping_add(&b)
219    }
220    fn wrapping_sub<T: WrappingSub>(a: T, b: T) -> T {
221        a.wrapping_sub(&b)
222    }
223    fn wrapping_mul<T: WrappingMul>(a: T, b: T) -> T {
224        a.wrapping_mul(&b)
225    }
226    fn wrapping_shl<T: WrappingShl>(a: T, b: u32) -> T {
227        a.wrapping_shl(b)
228    }
229    fn wrapping_shr<T: WrappingShr>(a: T, b: u32) -> T {
230        a.wrapping_shr(b)
231    }
232    assert_eq!(wrapping_add(255, 1), 0u8);
233    assert_eq!(wrapping_sub(0, 1), 255u8);
234    assert_eq!(wrapping_mul(255, 2), 254u8);
235    assert_eq!(wrapping_shl(255, 8), 255u8);
236    assert_eq!(wrapping_shr(255, 8), 255u8);
237    assert_eq!(wrapping_add(255, 1), (Wrapping(255u8) + Wrapping(1u8)).0);
238    assert_eq!(wrapping_sub(0, 1), (Wrapping(0u8) - Wrapping(1u8)).0);
239    assert_eq!(wrapping_mul(255, 2), (Wrapping(255u8) * Wrapping(2u8)).0);
240    assert_eq!(wrapping_shl(255, 8), (Wrapping(255u8) << 8).0);
241    assert_eq!(wrapping_shr(255, 8), (Wrapping(255u8) >> 8).0);
242}
243
244#[test]
245fn wrapping_is_wrappingadd() {
246    fn require_wrappingadd<T: WrappingAdd>(_: &T) {}
247    require_wrappingadd(&Wrapping(42));
248}
249
250#[test]
251fn wrapping_is_wrappingsub() {
252    fn require_wrappingsub<T: WrappingSub>(_: &T) {}
253    require_wrappingsub(&Wrapping(42));
254}
255
256#[test]
257fn wrapping_is_wrappingmul() {
258    fn require_wrappingmul<T: WrappingMul>(_: &T) {}
259    require_wrappingmul(&Wrapping(42));
260}
261
262#[test]
263fn wrapping_is_wrappingshl() {
264    fn require_wrappingshl<T: WrappingShl>(_: &T) {}
265    require_wrappingshl(&Wrapping(42));
266}
267
268#[test]
269fn wrapping_is_wrappingshr() {
270    fn require_wrappingshr<T: WrappingShr>(_: &T) {}
271    require_wrappingshr(&Wrapping(42));
272}