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

//! Multiplication operators.

use crate::{
    arch::word::Word,
    buffer::Buffer,
    ibig::IBig,
    memory::MemoryAllocation,
    mul,
    primitive::extend_word,
    sign::Sign::{self, *},
    ubig::{Repr::*, UBig},
};
use core::{
    mem,
    ops::{Mul, MulAssign},
};

impl Mul<UBig> for UBig {
    type Output = UBig;

    fn mul(self, rhs: UBig) -> UBig {
        match (self.into_repr(), rhs.into_repr()) {
            (Small(word0), Small(word1)) => UBig::mul_word(word0, word1),
            (Small(word0), Large(buffer1)) => UBig::mul_large_word(buffer1, word0),
            (Large(buffer0), Small(word1)) => UBig::mul_large_word(buffer0, word1),
            (Large(buffer0), Large(buffer1)) => UBig::mul_large(&buffer0, &buffer1),
        }
    }
}

impl Mul<&UBig> for UBig {
    type Output = UBig;

    fn mul(self, rhs: &UBig) -> UBig {
        match self.into_repr() {
            Small(word0) => match rhs.repr() {
                Small(word1) => UBig::mul_word(word0, *word1),
                Large(buffer1) => UBig::mul_large_word(buffer1.clone(), word0),
            },
            Large(buffer0) => match rhs.repr() {
                Small(word1) => UBig::mul_large_word(buffer0, *word1),
                Large(buffer1) => UBig::mul_large(&buffer0, buffer1),
            },
        }
    }
}

impl Mul<UBig> for &UBig {
    type Output = UBig;

    fn mul(self, rhs: UBig) -> UBig {
        rhs.mul(self)
    }
}

impl Mul<&UBig> for &UBig {
    type Output = UBig;

    fn mul(self, rhs: &UBig) -> UBig {
        match (self.repr(), rhs.repr()) {
            (Small(word0), Small(word1)) => UBig::mul_word(*word0, *word1),
            (Small(word0), Large(buffer1)) => UBig::mul_large_word(buffer1.clone(), *word0),
            (Large(buffer0), Small(word1)) => UBig::mul_large_word(buffer0.clone(), *word1),
            (Large(buffer0), Large(buffer1)) => UBig::mul_large(buffer0, buffer1),
        }
    }
}

impl MulAssign<UBig> for UBig {
    fn mul_assign(&mut self, rhs: UBig) {
        *self = mem::take(self) * rhs;
    }
}

impl MulAssign<&UBig> for UBig {
    fn mul_assign(&mut self, rhs: &UBig) {
        *self = mem::take(self) * rhs;
    }
}

impl Mul<IBig> for IBig {
    type Output = IBig;

    fn mul(self, rhs: IBig) -> IBig {
        let (sign0, mag0) = self.into_sign_magnitude();
        let (sign1, mag1) = rhs.into_sign_magnitude();
        IBig::from_sign_magnitude(sign0 * sign1, mag0 * mag1)
    }
}

impl Mul<&IBig> for IBig {
    type Output = IBig;

    fn mul(self, rhs: &IBig) -> IBig {
        let (sign0, mag0) = self.into_sign_magnitude();
        let (sign1, mag1) = (rhs.sign(), rhs.magnitude());
        IBig::from_sign_magnitude(sign0 * sign1, mag0 * mag1)
    }
}

impl Mul<IBig> for &IBig {
    type Output = IBig;

    fn mul(self, rhs: IBig) -> IBig {
        rhs.mul(self)
    }
}

impl Mul<&IBig> for &IBig {
    type Output = IBig;

    fn mul(self, rhs: &IBig) -> IBig {
        let (sign0, mag0) = (self.sign(), self.magnitude());
        let (sign1, mag1) = (rhs.sign(), rhs.magnitude());
        IBig::from_sign_magnitude(sign0 * sign1, mag0 * mag1)
    }
}

impl MulAssign<IBig> for IBig {
    fn mul_assign(&mut self, rhs: IBig) {
        *self = mem::take(self) * rhs;
    }
}

impl MulAssign<&IBig> for IBig {
    fn mul_assign(&mut self, rhs: &IBig) {
        *self = mem::take(self) * rhs;
    }
}

impl Mul<Sign> for Sign {
    type Output = Sign;

    fn mul(self, rhs: Sign) -> Sign {
        match (self, rhs) {
            (Positive, Positive) => Positive,
            (Positive, Negative) => Negative,
            (Negative, Positive) => Negative,
            (Negative, Negative) => Positive,
        }
    }
}

impl MulAssign<Sign> for Sign {
    fn mul_assign(&mut self, rhs: Sign) {
        *self = *self * rhs;
    }
}

impl UBig {
    /// Multiply two `Word`s.
    fn mul_word(a: Word, b: Word) -> UBig {
        UBig::from(extend_word(a) * extend_word(b))
    }

    /// Multiply a large number by a `Word`.
    fn mul_large_word(mut buffer: Buffer, a: Word) -> UBig {
        match a {
            0 => UBig::from_word(0),
            1 => buffer.into(),
            _ => {
                let carry = mul::mul_word_in_place(&mut buffer, a);
                if carry != 0 {
                    buffer.push_may_reallocate(carry);
                }
                buffer.into()
            }
        }
    }

    /// Multiply two large numbers.
    fn mul_large(lhs: &[Word], rhs: &[Word]) -> UBig {
        debug_assert!(lhs.len() >= 2 && rhs.len() >= 2);

        let res_len = lhs.len() + rhs.len();
        let mut buffer = Buffer::allocate(res_len);
        buffer.push_zeros(res_len);

        let mut allocation = MemoryAllocation::new(mul::memory_requirement_exact(
            res_len,
            lhs.len().min(rhs.len()),
        ));
        let mut memory = allocation.memory();
        let overflow = mul::add_signed_mul(&mut buffer, Positive, lhs, rhs, &mut memory);
        assert!(overflow == 0);
        buffer.into()
    }
}