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|
//! Integers used for wide operations, larger than `u128`.
#[cfg(test)]
mod tests;
use core::ops;
use super::{DInt, HInt, Int, MinInt};
const U128_LO_MASK: u128 = u64::MAX as u128;
/// A 256-bit unsigned integer represented as two 128-bit native-endian limbs.
#[allow(non_camel_case_types)]
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
pub struct u256 {
pub lo: u128,
pub hi: u128,
}
impl u256 {
#[cfg(any(test, feature = "unstable-public-internals"))]
pub const MAX: Self = Self {
lo: u128::MAX,
hi: u128::MAX,
};
/// Reinterpret as a signed integer
pub fn signed(self) -> i256 {
i256 {
lo: self.lo,
hi: self.hi,
}
}
}
/// A 256-bit signed integer represented as two 128-bit native-endian limbs.
#[allow(non_camel_case_types)]
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
pub struct i256 {
pub lo: u128,
pub hi: u128,
}
impl i256 {
/// Reinterpret as an unsigned integer
#[cfg(any(test, feature = "unstable-public-internals"))]
pub fn unsigned(self) -> u256 {
u256 {
lo: self.lo,
hi: self.hi,
}
}
}
impl MinInt for u256 {
type OtherSign = i256;
type Unsigned = u256;
const SIGNED: bool = false;
const BITS: u32 = 256;
const ZERO: Self = Self { lo: 0, hi: 0 };
const ONE: Self = Self { lo: 1, hi: 0 };
const MIN: Self = Self { lo: 0, hi: 0 };
const MAX: Self = Self {
lo: u128::MAX,
hi: u128::MAX,
};
}
impl MinInt for i256 {
type OtherSign = u256;
type Unsigned = u256;
const SIGNED: bool = false;
const BITS: u32 = 256;
const ZERO: Self = Self { lo: 0, hi: 0 };
const ONE: Self = Self { lo: 1, hi: 0 };
const MIN: Self = Self {
lo: 0,
hi: 1 << 127,
};
const MAX: Self = Self {
lo: u128::MAX,
hi: u128::MAX >> 1,
};
}
macro_rules! impl_common {
($ty:ty) => {
impl ops::BitOr for $ty {
type Output = Self;
fn bitor(mut self, rhs: Self) -> Self::Output {
self.lo |= rhs.lo;
self.hi |= rhs.hi;
self
}
}
impl ops::Not for $ty {
type Output = Self;
fn not(mut self) -> Self::Output {
self.lo = !self.lo;
self.hi = !self.hi;
self
}
}
impl ops::Shl<u32> for $ty {
type Output = Self;
fn shl(self, _rhs: u32) -> Self::Output {
unimplemented!("only used to meet trait bounds")
}
}
};
}
impl_common!(i256);
impl_common!(u256);
impl ops::Add<Self> for u256 {
type Output = Self;
fn add(self, rhs: Self) -> Self::Output {
let (lo, carry) = self.lo.overflowing_add(rhs.lo);
let hi = self.hi.wrapping_add(carry as u128).wrapping_add(rhs.hi);
Self { lo, hi }
}
}
impl ops::Shr<u32> for u256 {
type Output = Self;
fn shr(mut self, rhs: u32) -> Self::Output {
debug_assert!(rhs < Self::BITS, "attempted to shift right with overflow");
if rhs >= Self::BITS {
return Self::ZERO;
}
if rhs == 0 {
return self;
}
if rhs < 128 {
self.lo >>= rhs;
self.lo |= self.hi << (128 - rhs);
} else {
self.lo = self.hi >> (rhs - 128);
}
if rhs < 128 {
self.hi >>= rhs;
} else {
self.hi = 0;
}
self
}
}
impl HInt for u128 {
type D = u256;
fn widen(self) -> Self::D {
u256 { lo: self, hi: 0 }
}
fn zero_widen(self) -> Self::D {
self.widen()
}
fn zero_widen_mul(self, rhs: Self) -> Self::D {
let l0 = self & U128_LO_MASK;
let l1 = rhs & U128_LO_MASK;
let h0 = self >> 64;
let h1 = rhs >> 64;
let p_ll: u128 = l0.overflowing_mul(l1).0;
let p_lh: u128 = l0.overflowing_mul(h1).0;
let p_hl: u128 = h0.overflowing_mul(l1).0;
let p_hh: u128 = h0.overflowing_mul(h1).0;
let s0 = p_hl + (p_ll >> 64);
let s1 = (p_ll & U128_LO_MASK) + (s0 << 64);
let s2 = p_lh + (s1 >> 64);
let lo = (p_ll & U128_LO_MASK) + (s2 << 64);
let hi = p_hh + (s0 >> 64) + (s2 >> 64);
u256 { lo, hi }
}
fn widen_mul(self, rhs: Self) -> Self::D {
self.zero_widen_mul(rhs)
}
fn widen_hi(self) -> Self::D {
self.widen() << <Self as MinInt>::BITS
}
}
impl HInt for i128 {
type D = i256;
fn widen(self) -> Self::D {
let mut ret = self.unsigned().zero_widen().signed();
if self.is_negative() {
ret.hi = u128::MAX;
}
ret
}
fn zero_widen(self) -> Self::D {
self.unsigned().zero_widen().signed()
}
fn zero_widen_mul(self, rhs: Self) -> Self::D {
self.unsigned().zero_widen_mul(rhs.unsigned()).signed()
}
fn widen_mul(self, _rhs: Self) -> Self::D {
unimplemented!("signed i128 widening multiply is not used")
}
fn widen_hi(self) -> Self::D {
self.widen() << <Self as MinInt>::BITS
}
}
impl DInt for u256 {
type H = u128;
fn lo(self) -> Self::H {
self.lo
}
fn hi(self) -> Self::H {
self.hi
}
}
impl DInt for i256 {
type H = i128;
fn lo(self) -> Self::H {
self.lo as i128
}
fn hi(self) -> Self::H {
self.hi as i128
}
}
|
