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use num_traits::{NumOps, One, Zero};
use std::convert::From;
use std::mem::size_of;
use std::num::Wrapping;
use std::ops::Shr;
use std::ops::{BitAnd, BitOr, BitOrAssign, BitXor, Neg, Not};
#[derive(Copy, Clone)]
pub struct ConstantBool<T: NumOps + Copy>(pub T);
macro_rules! constantbool_from_impl {
($($t:ty)*) => ($(
impl From<bool> for ConstantBool<$t> {
fn from(b: bool) -> ConstantBool<$t> {
ConstantBool(b as $t)
}
}
)*)
}
constantbool_from_impl! { u32 u64 }
impl<T: NumOps + Copy + BitXor<Output = T> + One> Not for ConstantBool<T> {
type Output = Self;
#[inline]
fn not(self) -> ConstantBool<T> {
ConstantBool(self.0 ^ <T>::one())
}
}
impl<T: NumOps + Copy + Zero> Default for ConstantBool<T> {
#[inline]
fn default() -> ConstantBool<T> {
ConstantBool(<T>::zero())
}
}
impl<T: NumOps + Copy + BitAnd<Output = T>> BitAnd for ConstantBool<T> {
type Output = Self;
#[inline]
fn bitand(self, rhs: Self) -> Self {
ConstantBool(self.0 & rhs.0)
}
}
impl<T: NumOps + Copy + BitOr<Output = T>> BitOr for ConstantBool<T> {
type Output = Self;
#[inline]
fn bitor(self, rhs: Self) -> Self {
ConstantBool(self.0 | rhs.0)
}
}
impl<T: NumOps + Copy + BitXor<Output = T>> BitXor for ConstantBool<T> {
type Output = Self;
#[inline]
fn bitxor(self, rhs: Self) -> Self {
ConstantBool(self.0 ^ rhs.0)
}
}
impl<T: NumOps + Copy + BitOr<Output = T>> BitOrAssign for ConstantBool<T> {
#[inline]
fn bitor_assign(&mut self, rhs: Self) {
*self = *self | rhs;
}
}
impl<T> ConstantBool<T>
where
Wrapping<T>: Neg<Output = Wrapping<T>> + BitOr<Output = Wrapping<T>>,
T: NumOps
+ Copy
+ BitAnd<Output = T>
+ BitXor<Output = T>
+ BitOr<Output = T>
+ Shr<usize, Output = T>
+ One
+ Zero
+ PartialEq,
{
#[inline]
pub fn mux(self, x: T, y: T) -> T {
y ^ (Wrapping(self.0).neg().0 & (x ^ y))
}
#[inline]
pub fn is_zero(i: T) -> Self {
let q = Wrapping(i);
let shift_amount = size_of::<T>() * 8 - 1;
ConstantBool((q | q.neg()).0 >> shift_amount).not()
}
#[inline]
pub fn not_zero(i: T) -> Self {
ConstantBool(Self::is_zero(i).0 ^ <T>::one())
}
#[inline]
pub fn new_true() -> Self {
ConstantBool(<T>::one())
}
#[inline]
pub fn new_false() -> Self {
ConstantBool(<T>::zero())
}
}