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

//! [`UInt`] bitwise and operations.

use super::UInt;
use crate::{Limb, Wrapping};
use core::ops::{BitAnd, BitAndAssign};
use subtle::{Choice, CtOption};

impl<const LIMBS: usize> UInt<LIMBS> {
    /// Computes bitwise `a & b`.
    #[inline(always)]
    pub const fn bitand(&self, rhs: &Self) -> Self {
        let mut limbs = [Limb::ZERO; LIMBS];
        let mut i = 0;

        while i < LIMBS {
            limbs[i] = self.limbs[i].bitand(rhs.limbs[i]);
            i += 1;
        }

        Self { limbs }
    }

    /// Perform wrapping bitwise `AND`.
    ///
    /// There's no way wrapping could ever happen.
    /// This function exists so that all operations are accounted for in the wrapping operations
    pub const fn wrapping_and(&self, rhs: &Self) -> Self {
        self.bitand(rhs)
    }

    /// Perform checked bitwise `AND`, returning a [`CtOption`] which `is_some` always
    pub fn checked_and(&self, rhs: &Self) -> CtOption<Self> {
        let result = self.bitand(rhs);
        CtOption::new(result, Choice::from(1))
    }
}

impl<const LIMBS: usize> BitAnd for UInt<LIMBS> {
    type Output = Self;

    fn bitand(self, rhs: Self) -> UInt<LIMBS> {
        self.bitand(&rhs)
    }
}

impl<const LIMBS: usize> BitAnd<&UInt<LIMBS>> for UInt<LIMBS> {
    type Output = UInt<LIMBS>;

    fn bitand(self, rhs: &UInt<LIMBS>) -> UInt<LIMBS> {
        (&self).bitand(rhs)
    }
}

impl<const LIMBS: usize> BitAnd<UInt<LIMBS>> for &UInt<LIMBS> {
    type Output = UInt<LIMBS>;

    fn bitand(self, rhs: UInt<LIMBS>) -> UInt<LIMBS> {
        self.bitand(&rhs)
    }
}

impl<const LIMBS: usize> BitAnd<&UInt<LIMBS>> for &UInt<LIMBS> {
    type Output = UInt<LIMBS>;

    fn bitand(self, rhs: &UInt<LIMBS>) -> UInt<LIMBS> {
        self.bitand(rhs)
    }
}

impl<const LIMBS: usize> BitAndAssign for UInt<LIMBS> {
    #[allow(clippy::assign_op_pattern)]
    fn bitand_assign(&mut self, other: Self) {
        *self = *self & other;
    }
}

impl<const LIMBS: usize> BitAndAssign<&UInt<LIMBS>> for UInt<LIMBS> {
    #[allow(clippy::assign_op_pattern)]
    fn bitand_assign(&mut self, other: &Self) {
        *self = *self & other;
    }
}

impl<const LIMBS: usize> BitAnd for Wrapping<UInt<LIMBS>> {
    type Output = Self;

    fn bitand(self, rhs: Self) -> Wrapping<UInt<LIMBS>> {
        Wrapping(self.0.bitand(&rhs.0))
    }
}

impl<const LIMBS: usize> BitAnd<&Wrapping<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> {
    type Output = Wrapping<UInt<LIMBS>>;

    fn bitand(self, rhs: &Wrapping<UInt<LIMBS>>) -> Wrapping<UInt<LIMBS>> {
        Wrapping(self.0.bitand(&rhs.0))
    }
}

impl<const LIMBS: usize> BitAnd<Wrapping<UInt<LIMBS>>> for &Wrapping<UInt<LIMBS>> {
    type Output = Wrapping<UInt<LIMBS>>;

    fn bitand(self, rhs: Wrapping<UInt<LIMBS>>) -> Wrapping<UInt<LIMBS>> {
        Wrapping(self.0.bitand(&rhs.0))
    }
}

impl<const LIMBS: usize> BitAnd<&Wrapping<UInt<LIMBS>>> for &Wrapping<UInt<LIMBS>> {
    type Output = Wrapping<UInt<LIMBS>>;

    fn bitand(self, rhs: &Wrapping<UInt<LIMBS>>) -> Wrapping<UInt<LIMBS>> {
        Wrapping(self.0.bitand(&rhs.0))
    }
}

impl<const LIMBS: usize> BitAndAssign for Wrapping<UInt<LIMBS>> {
    #[allow(clippy::assign_op_pattern)]
    fn bitand_assign(&mut self, other: Self) {
        *self = *self & other;
    }
}

impl<const LIMBS: usize> BitAndAssign<&Wrapping<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> {
    #[allow(clippy::assign_op_pattern)]
    fn bitand_assign(&mut self, other: &Self) {
        *self = *self & other;
    }
}

#[cfg(test)]
mod tests {
    use crate::U128;

    #[test]
    fn checked_and_ok() {
        let result = U128::ZERO.checked_and(&U128::ONE);
        assert_eq!(result.unwrap(), U128::ZERO);
    }

    #[test]
    fn overlapping_and_ok() {
        let result = U128::MAX.wrapping_and(&U128::ONE);
        assert_eq!(result, U128::ONE);
    }
}