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use crate::number::{
CheckedAddAssign, CheckedSubAssign, SaturatingAddAssign, SaturatingSubAssign, UpcastFrom,
};
use core::{cmp::Ordering, convert::TryFrom, marker::PhantomData, ops};
#[derive(Clone, Copy, Debug, Default, Hash)]
pub struct Counter<T, Behavior = ()>(T, PhantomData<Behavior>);
#[derive(Clone, Copy, Debug, Default, Hash)]
pub struct Saturating;
impl<T, Behavior> Counter<T, Behavior> {
#[inline]
pub const fn new(value: T) -> Self {
Self(value, PhantomData)
}
#[inline]
pub fn try_add<V>(&mut self, value: V) -> Result<(), T::Error>
where
T: TryFrom<V>,
Self: ops::AddAssign<T>,
{
let value = T::try_from(value)?;
*self += value;
Ok(())
}
#[inline]
pub fn try_sub<V>(&mut self, value: V) -> Result<(), T::Error>
where
T: TryFrom<V>,
Self: ops::SubAssign<T>,
{
let value = T::try_from(value)?;
*self -= value;
Ok(())
}
}
macro_rules! assign_trait {
(
$op:ident,
$method:ident,
$saturating_trait:ident,
$saturating_method:ident,
$checked_trait:ident,
$checked:ident
) => {
impl<T, R> ops::$op<R> for Counter<T, ()>
where
T: $saturating_trait<R> + $checked_trait<R> + ops::$op + UpcastFrom<R>,
{
#[inline]
fn $method(&mut self, rhs: R) {
if cfg!(feature = "checked-counters") {
(self.0).$checked(rhs).expect("counter overflow");
} else if cfg!(debug_assertions) {
(self.0).$method(T::upcast_from(rhs));
} else {
(self.0).$saturating_method(rhs);
}
}
}
impl<T, R> ops::$op<R> for Counter<T, Saturating>
where
T: $saturating_trait<R>,
{
#[inline]
fn $method(&mut self, rhs: R) {
(self.0).$saturating_method(rhs);
}
}
};
}
assign_trait!(
AddAssign,
add_assign,
SaturatingAddAssign,
saturating_add_assign,
CheckedAddAssign,
checked_add_assign
);
assign_trait!(
SubAssign,
sub_assign,
SaturatingSubAssign,
saturating_sub_assign,
CheckedSubAssign,
checked_sub_assign
);
impl<T, B> UpcastFrom<Counter<T, B>> for T {
#[inline]
fn upcast_from(value: Counter<T, B>) -> Self {
value.0
}
}
impl<T, B> UpcastFrom<&Counter<T, B>> for T
where
T: for<'a> UpcastFrom<&'a T>,
{
#[inline]
fn upcast_from(value: &Counter<T, B>) -> Self {
T::upcast_from(&value.0)
}
}
impl<T, B> ops::Deref for Counter<T, B> {
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<T, B, R> PartialEq<R> for Counter<T, B>
where
Self: PartialOrd<R>,
{
#[inline]
fn eq(&self, other: &R) -> bool {
self.partial_cmp(other) == Some(Ordering::Equal)
}
}
impl<T, B> PartialOrd<T> for Counter<T, B>
where
T: PartialOrd<T>,
{
#[inline]
fn partial_cmp(&self, other: &T) -> Option<Ordering> {
self.0.partial_cmp(other)
}
}
impl<T, B> PartialOrd for Counter<T, B>
where
T: PartialOrd<T>,
{
#[inline]
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
self.0.partial_cmp(&other.0)
}
}
impl<T, B> Eq for Counter<T, B> where Self: Ord {}
impl<T, B> Ord for Counter<T, B>
where
T: Ord,
{
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
self.0.cmp(&other.0)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn automatic_upcast() {
let mut a: Counter<u32> = Counter::new(0);
a += 1u8;
a += 2u16;
a += 3u32;
assert_eq!(a, Counter::new(6));
assert_eq!(a, 6u32);
}
#[test]
fn saturating() {
let mut a: Counter<u8, Saturating> = Counter::new(0);
a += 250;
a += 250;
a += 123;
assert_eq!(a, Counter::new(255));
}
}