/rust/registry/src/index.crates.io-1949cf8c6b5b557f/num-bigint-0.5.1/src/biguint/addition.rs

Source
use super::{BigUint, IntDigits};

use crate::big_digit::{self, BigDigit};
use crate::UsizePromotion;

use core::iter::Sum;
use core::ops::{Add, AddAssign};
use num_traits::CheckedAdd;

#[cfg(target_arch = "x86_64")]
use core::arch::x86_64 as arch;

#[cfg(target_arch = "x86")]
use core::arch::x86 as arch;

// Add with carry:
#[cfg(target_arch = "x86_64")]
cfg_64!(
    #[inline]
    #[allow(unused_unsafe)] // TODO(MSRV 1.93): the intrinsic became safe
    fn adc(carry: u8, a: u64, b: u64, out: &mut u64) -> u8 {
        // SAFETY: There are absolutely no safety concerns with calling `_addcarry_u64`.
        // It's just unsafe for API consistency with other intrinsics.
        unsafe { arch::_addcarry_u64(carry, a, b, out) }
    }
);

#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
cfg_32!(
    #[inline]
    #[allow(unused_unsafe)] // TODO(MSRV 1.93): the intrinsic became safe
    fn adc(carry: u8, a: u32, b: u32, out: &mut u32) -> u8 {
        // SAFETY: There are absolutely no safety concerns with calling `_addcarry_u32`.
        // It's just unsafe for API consistency with other intrinsics.
        unsafe { arch::_addcarry_u32(carry, a, b, out) }
    }
);

// fallback for environments where we don't have an addcarry intrinsic
// (copied from the standard library's `carrying_add`)
#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
#[inline]
fn adc(carry: u8, lhs: BigDigit, rhs: BigDigit, out: &mut BigDigit) -> u8 {
    let (a, b) = lhs.overflowing_add(rhs);
    let (c, d) = a.overflowing_add(carry as BigDigit);
    *out = c;
    u8::from(b || d)
}

/// Two argument addition of raw slices, `a += b`, returning the carry.
///
/// This is used when the data `Vec` might need to resize to push a non-zero carry, so we perform
/// the addition first hoping that it will fit.
///
/// The caller _must_ ensure that `a` is at least as long as `b`.
#[inline]
pub(super) fn __add2(a: &mut [BigDigit], b: &[BigDigit]) -> BigDigit {
    debug_assert!(a.len() >= b.len());

    let mut carry = 0;
    let (a_lo, a_hi) = a.split_at_mut(b.len());

    for (a, b) in a_lo.iter_mut().zip(b) {
        carry = adc(carry, *a, *b, a);
    }

    if carry != 0 {
        for a in a_hi {
            carry = adc(carry, *a, 0, a);
            if carry == 0 {
                break;
            }
        }
    }

    carry as BigDigit
}

/// Two argument addition of raw slices:
/// a += b
///
/// The caller _must_ ensure that a is big enough to store the result - typically this means
/// resizing a to max(a.len(), b.len()) + 1, to fit a possible carry.
pub(super) fn add2(a: &mut [BigDigit], b: &[BigDigit]) {
    let carry = __add2(a, b);

    debug_assert!(carry == 0);
}

forward_all_binop_to_val_ref_commutative!(impl Add for BigUint, add);
forward_val_assign!(impl AddAssign for BigUint, add_assign);

impl Add<&BigUint> for BigUint {
    type Output = BigUint;

    fn add(mut self, other: &BigUint) -> BigUint {
        self += other;
        self
    }
}
impl AddAssign<&BigUint> for BigUint {
    #[inline]
    fn add_assign(&mut self, other: &BigUint) {
        let self_len = self.data.len();
        let mut other = &*other.data;
        if self_len < other.len() {
            let (low, high) = other.split_at(self_len);
            self.data.extend_from_slice(high);
            other = low;
        }
        let carry = __add2(&mut self.data, other);
        if carry != 0 {
            self.data.push(carry);
        }
    }
}

promote_unsigned_scalars!(impl Add for BigUint, add);
promote_unsigned_scalars_assign!(impl AddAssign for BigUint, add_assign);
forward_all_scalar_binop_to_val_val_commutative!(impl Add<u32> for BigUint, add);
forward_all_scalar_binop_to_val_val_commutative!(impl Add<u64> for BigUint, add);
forward_all_scalar_binop_to_val_val_commutative!(impl Add<u128> for BigUint, add);

impl Add<u32> for BigUint {
    type Output = BigUint;

    #[inline]
    fn add(mut self, other: u32) -> BigUint {
        self += other;
        self
    }
}

impl AddAssign<u32> for BigUint {
    #[inline]
    fn add_assign(&mut self, other: u32) {
        if other != 0 {
            if self.data.is_empty() {
                self.data.push(other as BigDigit);
            } else {
                let carry = __add2(&mut self.data, &[other as BigDigit]);
                if carry != 0 {
                    self.data.push(carry);
                }
            }
        }
    }
}

impl Add<u64> for BigUint {
    type Output = BigUint;

    #[inline]
    fn add(mut self, other: u64) -> BigUint {
        self += other;
        self
    }
}

impl AddAssign<u64> for BigUint {
    cfg_digit!(
        #[inline]
        fn add_assign(&mut self, other: u64) {
            let (hi, lo) = big_digit::from_doublebigdigit(other);
            if hi == 0 {
                *self += lo;
            } else {
                while self.data.len() < 2 {
                    self.data.push(0);
                }

                let carry = __add2(&mut self.data, &[lo, hi]);
                if carry != 0 {
                    self.data.push(carry);
                }
            }
        }

        #[inline]
        fn add_assign(&mut self, other: u64) {
            if other != 0 {
                if self.data.is_empty() {
                    self.data.push(other as BigDigit);
                } else {
                    let carry = __add2(&mut self.data, &[other as BigDigit]);
                    if carry != 0 {
                        self.data.push(carry);
                    }
                }
            }
        }
    );
}

impl Add<u128> for BigUint {
    type Output = BigUint;

    #[inline]
    fn add(mut self, other: u128) -> BigUint {
        self += other;
        self
    }
}

impl AddAssign<u128> for BigUint {
    cfg_digit!(
        #[inline]
        fn add_assign(&mut self, other: u128) {
            if other <= u128::from(u64::MAX) {
                *self += other as u64
            } else {
                let (a, b, c, d) = super::u32_from_u128(other);
                let carry = if a > 0 {
                    while self.data.len() < 4 {
                        self.data.push(0);
                    }
                    __add2(&mut self.data, &[d, c, b, a])
                } else {
                    debug_assert!(b > 0);
                    while self.data.len() < 3 {
                        self.data.push(0);
                    }
                    __add2(&mut self.data, &[d, c, b])
                };

                if carry != 0 {
                    self.data.push(carry);
                }
            }
        }

        #[inline]
        fn add_assign(&mut self, other: u128) {
            let (hi, lo) = big_digit::from_doublebigdigit(other);
            if hi == 0 {
                *self += lo;
            } else {
                while self.data.len() < 2 {
                    self.data.push(0);
                }

                let carry = __add2(&mut self.data, &[lo, hi]);
                if carry != 0 {
                    self.data.push(carry);
                }
            }
        }
    );
}

impl CheckedAdd for BigUint {
    #[inline]
    fn checked_add(&self, v: &BigUint) -> Option<BigUint> {
        Some(self.add(v))
    }
}

impl_sum_iter_type!(BigUint);

Coverage Report

Created: 2026-08-13 07:14

Line	Count	Source
1		use super::{BigUint, IntDigits};
2
3		use crate::big_digit::{self, BigDigit};
4		use crate::UsizePromotion;
5
6		use core::iter::Sum;
7		use core::ops::{Add, AddAssign};
8		use num_traits::CheckedAdd;
9
10		#[cfg(target_arch = "x86_64")]
11		use core::arch::x86_64 as arch;
12
13		#[cfg(target_arch = "x86")]
14		use core::arch::x86 as arch;
15
16		// Add with carry:
17		#[cfg(target_arch = "x86_64")]
18		cfg_64!(
19		#[inline]
20		#[allow(unused_unsafe)] // TODO(MSRV 1.93): the intrinsic became safe
21	991k	fn adc(carry: u8, a: u64, b: u64, out: &mut u64) -> u8 {
22		// SAFETY: There are absolutely no safety concerns with calling `_addcarry_u64`.
23		// It's just unsafe for API consistency with other intrinsics.
24	991k	unsafe { arch::_addcarry_u64(carry, a, b, out) }
25	991k	}
26		);
27
28		#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
29		cfg_32!(
30		#[inline]
31		#[allow(unused_unsafe)] // TODO(MSRV 1.93): the intrinsic became safe
32		fn adc(carry: u8, a: u32, b: u32, out: &mut u32) -> u8 {
33		// SAFETY: There are absolutely no safety concerns with calling `_addcarry_u32`.
34		// It's just unsafe for API consistency with other intrinsics.
35		unsafe { arch::_addcarry_u32(carry, a, b, out) }
36		}
37		);
38
39		// fallback for environments where we don't have an addcarry intrinsic
40		// (copied from the standard library's `carrying_add`)
41		#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
42		#[inline]
43		fn adc(carry: u8, lhs: BigDigit, rhs: BigDigit, out: &mut BigDigit) -> u8 {
44		let (a, b) = lhs.overflowing_add(rhs);
45		let (c, d) = a.overflowing_add(carry as BigDigit);
46		*out = c;
47		u8::from(b \|\| d)
48		}
49
50		/// Two argument addition of raw slices, `a += b`, returning the carry.
51		///
52		/// This is used when the data `Vec` might need to resize to push a non-zero carry, so we perform
53		/// the addition first hoping that it will fit.
54		///
55		/// The caller _must_ ensure that `a` is at least as long as `b`.
56		#[inline]
57	984k	pub(super) fn __add2(a: &mut [BigDigit], b: &[BigDigit]) -> BigDigit {
58	984k	debug_assert!(a.len() >= b.len());
59
60	984k	let mut carry = 0;
61	984k	let (a_lo, a_hi) = a.split_at_mut(b.len());
62
63	984k	for (a, b) in a_lo.iter_mut().zip(b) {
64	984k	carry = adc(carry, a, b, a);
65	984k	}
66
67	984k	if carry != 0 {
68	6.59k	for a in a_hi {
69	6.59k	carry = adc(carry, *a, 0, a);
70	6.59k	if carry == 0 {
71	6.32k	break;
72	271	}
73		}
74	978k	}
75
76	984k	carry as BigDigit
77	984k	}
78
79		/// Two argument addition of raw slices:
80		/// a += b
81		///
82		/// The caller _must_ ensure that a is big enough to store the result - typically this means
83		/// resizing a to max(a.len(), b.len()) + 1, to fit a possible carry.
84	984k	pub(super) fn add2(a: &mut [BigDigit], b: &[BigDigit]) {
85	984k	let carry = __add2(a, b);
86
87	984k	debug_assert!(carry == 0);
88	984k	}
89
90		forward_all_binop_to_val_ref_commutative!(impl Add for BigUint, add);
91		forward_val_assign!(impl AddAssign for BigUint, add_assign);
92
93		impl Add<&BigUint> for BigUint {
94		type Output = BigUint;
95
96	0	fn add(mut self, other: &BigUint) -> BigUint {
97	0	self += other;
98	0	self
99	0	}
100		}
101		impl AddAssign<&BigUint> for BigUint {
102		#[inline]
103	0	fn add_assign(&mut self, other: &BigUint) {
104	0	let self_len = self.data.len();
105	0	let mut other = &*other.data;
106	0	if self_len < other.len() {
107	0	let (low, high) = other.split_at(self_len);
108	0	self.data.extend_from_slice(high);
109	0	other = low;
110	0	}
111	0	let carry = __add2(&mut self.data, other);
112	0	if carry != 0 {
113	0	self.data.push(carry);
114	0	}
115	0	}
116		}
117
118		promote_unsigned_scalars!(impl Add for BigUint, add);
119		promote_unsigned_scalars_assign!(impl AddAssign for BigUint, add_assign);
120		forward_all_scalar_binop_to_val_val_commutative!(impl Add<u32> for BigUint, add);
121		forward_all_scalar_binop_to_val_val_commutative!(impl Add<u64> for BigUint, add);
122		forward_all_scalar_binop_to_val_val_commutative!(impl Add<u128> for BigUint, add);
123
124		impl Add<u32> for BigUint {
125		type Output = BigUint;
126
127		#[inline]
128	0	fn add(mut self, other: u32) -> BigUint {
129	0	self += other;
130	0	self
131	0	}
132		}
133
134		impl AddAssign<u32> for BigUint {
135		#[inline]
136	0	fn add_assign(&mut self, other: u32) {
137	0	if other != 0 {
138	0	if self.data.is_empty() {
139	0	self.data.push(other as BigDigit);
140	0	} else {
141	0	let carry = __add2(&mut self.data, &[other as BigDigit]);
142	0	if carry != 0 {
143	0	self.data.push(carry);
144	0	}
145		}
146	0	}
147	0	}
148		}
149
150		impl Add<u64> for BigUint {
151		type Output = BigUint;
152
153		#[inline]
154	0	fn add(mut self, other: u64) -> BigUint {
155	0	self += other;
156	0	self
157	0	}
158		}
159
160		impl AddAssign<u64> for BigUint {
161		cfg_digit!(
162		#[inline]
163		fn add_assign(&mut self, other: u64) {
164		let (hi, lo) = big_digit::from_doublebigdigit(other);
165		if hi == 0 {
166		*self += lo;
167		} else {
168		while self.data.len() < 2 {
169		self.data.push(0);
170		}
171
172		let carry = __add2(&mut self.data, &[lo, hi]);
173		if carry != 0 {
174		self.data.push(carry);
175		}
176		}
177		}
178
179		#[inline]
180	0	fn add_assign(&mut self, other: u64) {
181	0	if other != 0 {
182	0	if self.data.is_empty() {
183	0	self.data.push(other as BigDigit);
184	0	} else {
185	0	let carry = __add2(&mut self.data, &[other as BigDigit]);
186	0	if carry != 0 {
187	0	self.data.push(carry);
188	0	}
189		}
190	0	}
191	0	}
192		);
193		}
194
195		impl Add<u128> for BigUint {
196		type Output = BigUint;
197
198		#[inline]
199	0	fn add(mut self, other: u128) -> BigUint {
200	0	self += other;
201	0	self
202	0	}
203		}
204
205		impl AddAssign<u128> for BigUint {
206		cfg_digit!(
207		#[inline]
208		fn add_assign(&mut self, other: u128) {
209		if other <= u128::from(u64::MAX) {
210		*self += other as u64
211		} else {
212		let (a, b, c, d) = super::u32_from_u128(other);
213		let carry = if a > 0 {
214		while self.data.len() < 4 {
215		self.data.push(0);
216		}
217		__add2(&mut self.data, &[d, c, b, a])
218		} else {
219		debug_assert!(b > 0);
220		while self.data.len() < 3 {
221		self.data.push(0);
222		}
223		__add2(&mut self.data, &[d, c, b])
224		};
225
226		if carry != 0 {
227		self.data.push(carry);
228		}
229		}
230		}
231
232		#[inline]
233	0	fn add_assign(&mut self, other: u128) {
234	0	let (hi, lo) = big_digit::from_doublebigdigit(other);
235	0	if hi == 0 {
236	0	*self += lo;
237	0	} else {
238	0	while self.data.len() < 2 {
239	0	self.data.push(0);
240	0	}
241
242	0	let carry = __add2(&mut self.data, &[lo, hi]);
243	0	if carry != 0 {
244	0	self.data.push(carry);
245	0	}
246		}
247	0	}
248		);
249		}
250
251		impl CheckedAdd for BigUint {
252		#[inline]
253	0	fn checked_add(&self, v: &BigUint) -> Option<BigUint> {
254	0	Some(self.add(v))
255	0	}
256		}
257
258		impl_sum_iter_type!(BigUint);