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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:41:41 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:41:41 +0000 |
commit | 10ee2acdd26a7f1298c6f6d6b7af9b469fe29b87 (patch) | |
tree | bdffd5d80c26cf4a7a518281a204be1ace85b4c1 /vendor/crypto-bigint/src/uint/div.rs | |
parent | Releasing progress-linux version 1.70.0+dfsg1-9~progress7.99u1. (diff) | |
download | rustc-10ee2acdd26a7f1298c6f6d6b7af9b469fe29b87.tar.xz rustc-10ee2acdd26a7f1298c6f6d6b7af9b469fe29b87.zip |
Merging upstream version 1.70.0+dfsg2.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/crypto-bigint/src/uint/div.rs')
-rw-r--r-- | vendor/crypto-bigint/src/uint/div.rs | 496 |
1 files changed, 496 insertions, 0 deletions
diff --git a/vendor/crypto-bigint/src/uint/div.rs b/vendor/crypto-bigint/src/uint/div.rs new file mode 100644 index 000000000..f7d9d6bf3 --- /dev/null +++ b/vendor/crypto-bigint/src/uint/div.rs @@ -0,0 +1,496 @@ +//! [`UInt`] division operations. + +use super::UInt; +use crate::limb::Word; +use crate::{Integer, Limb, NonZero, Wrapping}; +use core::ops::{Div, DivAssign, Rem, RemAssign}; +use subtle::{Choice, CtOption}; + +impl<const LIMBS: usize> UInt<LIMBS> { + /// Computes `self` / `rhs`, returns the quotient (q), remainder (r) + /// and 1 for is_some or 0 for is_none. The results can be wrapped in [`CtOption`]. + /// NOTE: Use only if you need to access const fn. Otherwise use `div_rem` because + /// the value for is_some needs to be checked before using `q` and `r`. + /// + /// This is variable only with respect to `rhs`. + /// + /// When used with a fixed `rhs`, this function is constant-time with respect + /// to `self`. + pub(crate) const fn ct_div_rem(&self, rhs: &Self) -> (Self, Self, u8) { + let mb = rhs.bits_vartime(); + let mut bd = (LIMBS * Limb::BIT_SIZE) - mb; + let mut rem = *self; + let mut quo = Self::ZERO; + let mut c = rhs.shl_vartime(bd); + + loop { + let (mut r, borrow) = rem.sbb(&c, Limb::ZERO); + rem = Self::ct_select(r, rem, borrow.0); + r = quo.bitor(&Self::ONE); + quo = Self::ct_select(r, quo, borrow.0); + if bd == 0 { + break; + } + bd -= 1; + c = c.shr_vartime(1); + quo = quo.shl_vartime(1); + } + + let is_some = Limb(mb as Word).is_nonzero(); + quo = Self::ct_select(Self::ZERO, quo, is_some); + (quo, rem, (is_some & 1) as u8) + } + + /// Computes `self` % `rhs`, returns the remainder and + /// and 1 for is_some or 0 for is_none. The results can be wrapped in [`CtOption`]. + /// NOTE: Use only if you need to access const fn. Otherwise use `reduce` + /// This is variable only with respect to `rhs`. + /// + /// When used with a fixed `rhs`, this function is constant-time with respect + /// to `self`. + pub(crate) const fn ct_reduce(&self, rhs: &Self) -> (Self, u8) { + let mb = rhs.bits_vartime(); + let mut bd = (LIMBS * Limb::BIT_SIZE) - mb; + let mut rem = *self; + let mut c = rhs.shl_vartime(bd); + + loop { + let (r, borrow) = rem.sbb(&c, Limb::ZERO); + rem = Self::ct_select(r, rem, borrow.0); + if bd == 0 { + break; + } + bd -= 1; + c = c.shr_vartime(1); + } + + let is_some = Limb(mb as Word).is_nonzero(); + (rem, (is_some & 1) as u8) + } + + /// Computes `self` % 2^k. Faster than reduce since its a power of 2. + /// Limited to 2^16-1 since UInt doesn't support higher. + pub const fn reduce2k(&self, k: usize) -> Self { + let highest = (LIMBS - 1) as u32; + let index = k as u32 / (Limb::BIT_SIZE as u32); + let res = Limb::ct_cmp(Limb::from_u32(index), Limb::from_u32(highest)) - 1; + let le = Limb::is_nonzero(Limb(res as Word)); + let word = Limb::ct_select(Limb::from_u32(highest), Limb::from_u32(index), le).0 as usize; + + let base = k % Limb::BIT_SIZE; + let mask = (1 << base) - 1; + let mut out = *self; + + let outmask = Limb(out.limbs[word].0 & mask); + + out.limbs[word] = Limb::ct_select(out.limbs[word], outmask, le); + + let mut i = word + 1; + while i < LIMBS { + out.limbs[i] = Limb::ZERO; + i += 1; + } + + out + } + + /// Computes self / rhs, returns the quotient, remainder + /// if rhs != 0 + pub fn div_rem(&self, rhs: &Self) -> CtOption<(Self, Self)> { + let (q, r, c) = self.ct_div_rem(rhs); + CtOption::new((q, r), Choice::from(c)) + } + + /// Computes self % rhs, returns the remainder + /// if rhs != 0 + pub fn reduce(&self, rhs: &Self) -> CtOption<Self> { + let (r, c) = self.ct_reduce(rhs); + CtOption::new(r, Choice::from(c)) + } + + /// Wrapped division is just normal division i.e. `self` / `rhs` + /// 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_div(&self, rhs: &Self) -> Self { + let (q, _, c) = self.ct_div_rem(rhs); + assert!(c == 1, "divide by zero"); + q + } + + /// Perform checked division, returning a [`CtOption`] which `is_some` + /// only if the rhs != 0 + pub fn checked_div(&self, rhs: &Self) -> CtOption<Self> { + let (q, _, c) = self.ct_div_rem(rhs); + CtOption::new(q, Choice::from(c)) + } + + /// Wrapped (modular) remainder calculation is just `self` % `rhs`. + /// 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_rem(&self, rhs: &Self) -> Self { + let (r, c) = self.ct_reduce(rhs); + assert!(c == 1, "modulo zero"); + r + } + + /// Perform checked reduction, returning a [`CtOption`] which `is_some` + /// only if the rhs != 0 + pub fn checked_rem(&self, rhs: &Self) -> CtOption<Self> { + let (r, c) = self.ct_reduce(rhs); + CtOption::new(r, Choice::from(c)) + } +} + +impl<const LIMBS: usize> Div<&NonZero<UInt<LIMBS>>> for &UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn div(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + *self / *rhs + } +} + +impl<const LIMBS: usize> Div<&NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn div(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + self / *rhs + } +} + +impl<const LIMBS: usize> Div<NonZero<UInt<LIMBS>>> for &UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn div(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + *self / rhs + } +} + +impl<const LIMBS: usize> Div<NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn div(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + let (q, _, _) = self.ct_div_rem(&rhs); + q + } +} + +impl<const LIMBS: usize> DivAssign<&NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + fn div_assign(&mut self, rhs: &NonZero<UInt<LIMBS>>) { + let (q, _, _) = self.ct_div_rem(rhs); + *self = q + } +} + +impl<const LIMBS: usize> DivAssign<NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + fn div_assign(&mut self, rhs: NonZero<UInt<LIMBS>>) { + *self /= &rhs; + } +} + +impl<const LIMBS: usize> Div<NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn div(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + Wrapping(self.0.wrapping_div(rhs.as_ref())) + } +} + +impl<const LIMBS: usize> Div<NonZero<UInt<LIMBS>>> for &Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn div(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + *self / rhs + } +} + +impl<const LIMBS: usize> Div<&NonZero<UInt<LIMBS>>> for &Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn div(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + *self / *rhs + } +} + +impl<const LIMBS: usize> Div<&NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn div(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + self / *rhs + } +} + +impl<const LIMBS: usize> DivAssign<&NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + fn div_assign(&mut self, rhs: &NonZero<UInt<LIMBS>>) { + *self = Wrapping(self.0.wrapping_div(rhs.as_ref())) + } +} + +impl<const LIMBS: usize> DivAssign<NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + fn div_assign(&mut self, rhs: NonZero<UInt<LIMBS>>) { + *self /= &rhs; + } +} + +impl<const LIMBS: usize> Rem<&NonZero<UInt<LIMBS>>> for &UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn rem(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + *self % *rhs + } +} + +impl<const LIMBS: usize> Rem<&NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn rem(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + self % *rhs + } +} + +impl<const LIMBS: usize> Rem<NonZero<UInt<LIMBS>>> for &UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn rem(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + *self % rhs + } +} + +impl<const LIMBS: usize> Rem<NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + type Output = UInt<LIMBS>; + + fn rem(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + let (r, _) = self.ct_reduce(&rhs); + r + } +} + +impl<const LIMBS: usize> RemAssign<&NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + fn rem_assign(&mut self, rhs: &NonZero<UInt<LIMBS>>) { + let (r, _) = self.ct_reduce(rhs); + *self = r + } +} + +impl<const LIMBS: usize> RemAssign<NonZero<UInt<LIMBS>>> for UInt<LIMBS> +where + UInt<LIMBS>: Integer, +{ + fn rem_assign(&mut self, rhs: NonZero<UInt<LIMBS>>) { + *self %= &rhs; + } +} + +impl<const LIMBS: usize> Rem<NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn rem(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + Wrapping(self.0.wrapping_rem(rhs.as_ref())) + } +} + +impl<const LIMBS: usize> Rem<NonZero<UInt<LIMBS>>> for &Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn rem(self, rhs: NonZero<UInt<LIMBS>>) -> Self::Output { + *self % rhs + } +} + +impl<const LIMBS: usize> Rem<&NonZero<UInt<LIMBS>>> for &Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn rem(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + *self % *rhs + } +} + +impl<const LIMBS: usize> Rem<&NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + type Output = Wrapping<UInt<LIMBS>>; + + fn rem(self, rhs: &NonZero<UInt<LIMBS>>) -> Self::Output { + self % *rhs + } +} + +impl<const LIMBS: usize> RemAssign<NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + fn rem_assign(&mut self, rhs: NonZero<UInt<LIMBS>>) { + *self %= &rhs; + } +} + +impl<const LIMBS: usize> RemAssign<&NonZero<UInt<LIMBS>>> for Wrapping<UInt<LIMBS>> { + fn rem_assign(&mut self, rhs: &NonZero<UInt<LIMBS>>) { + *self = Wrapping(self.0.wrapping_rem(rhs.as_ref())) + } +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::{limb::HI_BIT, Limb, U256}; + + #[cfg(feature = "rand")] + use { + crate::{CheckedMul, Random}, + rand_chacha::ChaChaRng, + rand_core::RngCore, + rand_core::SeedableRng, + }; + + #[test] + fn div_word() { + for (n, d, e, ee) in &[ + (200u64, 2u64, 100u64, 0), + (100u64, 25u64, 4u64, 0), + (100u64, 10u64, 10u64, 0), + (1024u64, 8u64, 128u64, 0), + (27u64, 13u64, 2u64, 1u64), + (26u64, 13u64, 2u64, 0u64), + (14u64, 13u64, 1u64, 1u64), + (13u64, 13u64, 1u64, 0u64), + (12u64, 13u64, 0u64, 12u64), + (1u64, 13u64, 0u64, 1u64), + ] { + let lhs = U256::from(*n); + let rhs = U256::from(*d); + let (q, r, is_some) = lhs.ct_div_rem(&rhs); + assert_eq!(is_some, 1); + assert_eq!(U256::from(*e), q); + assert_eq!(U256::from(*ee), r); + } + } + + #[cfg(feature = "rand")] + #[test] + fn div() { + let mut rng = ChaChaRng::from_seed([7u8; 32]); + for _ in 0..25 { + let num = U256::random(&mut rng).shr_vartime(128); + let den = U256::random(&mut rng).shr_vartime(128); + let n = num.checked_mul(&den); + if n.is_some().unwrap_u8() == 1 { + let (q, _, is_some) = n.unwrap().ct_div_rem(&den); + assert_eq!(is_some, 1); + assert_eq!(q, num); + } + } + } + + #[test] + fn div_max() { + let mut a = U256::ZERO; + let mut b = U256::ZERO; + b.limbs[b.limbs.len() - 1] = Limb(Word::MAX); + let q = a.wrapping_div(&b); + assert_eq!(q, UInt::ZERO); + a.limbs[a.limbs.len() - 1] = Limb(1 << (HI_BIT - 7)); + b.limbs[b.limbs.len() - 1] = Limb(0x82 << (HI_BIT - 7)); + let q = a.wrapping_div(&b); + assert_eq!(q, UInt::ZERO); + } + + #[test] + fn div_zero() { + let (q, r, is_some) = U256::ONE.ct_div_rem(&U256::ZERO); + assert_eq!(is_some, 0); + assert_eq!(q, U256::ZERO); + assert_eq!(r, U256::ONE); + } + + #[test] + fn div_one() { + let (q, r, is_some) = U256::from(10u8).ct_div_rem(&U256::ONE); + assert_eq!(is_some, 1); + assert_eq!(q, U256::from(10u8)); + assert_eq!(r, U256::ZERO); + } + + #[test] + fn reduce_one() { + let (r, is_some) = U256::from(10u8).ct_reduce(&U256::ONE); + assert_eq!(is_some, 1); + assert_eq!(r, U256::ZERO); + } + + #[test] + fn reduce_zero() { + let u = U256::from(10u8); + let (r, is_some) = u.ct_reduce(&U256::ZERO); + assert_eq!(is_some, 0); + assert_eq!(r, u); + } + + #[test] + fn reduce_tests() { + let (r, is_some) = U256::from(10u8).ct_reduce(&U256::from(2u8)); + assert_eq!(is_some, 1); + assert_eq!(r, U256::ZERO); + let (r, is_some) = U256::from(10u8).ct_reduce(&U256::from(3u8)); + assert_eq!(is_some, 1); + assert_eq!(r, U256::ONE); + let (r, is_some) = U256::from(10u8).ct_reduce(&U256::from(7u8)); + assert_eq!(is_some, 1); + assert_eq!(r, U256::from(3u8)); + } + + #[test] + fn reduce_max() { + let mut a = U256::ZERO; + let mut b = U256::ZERO; + b.limbs[b.limbs.len() - 1] = Limb(Word::MAX); + let r = a.wrapping_rem(&b); + assert_eq!(r, UInt::ZERO); + a.limbs[a.limbs.len() - 1] = Limb(1 << (HI_BIT - 7)); + b.limbs[b.limbs.len() - 1] = Limb(0x82 << (HI_BIT - 7)); + let r = a.wrapping_rem(&b); + assert_eq!(r, a); + } + + #[cfg(feature = "rand")] + #[test] + fn reduce2krand() { + let mut rng = ChaChaRng::from_seed([7u8; 32]); + for _ in 0..25 { + let num = U256::random(&mut rng); + let k = (rng.next_u32() % 256) as usize; + let den = U256::ONE.shl_vartime(k); + + let a = num.reduce2k(k); + let e = num.wrapping_rem(&den); + assert_eq!(a, e); + } + } +} |