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use super::plumbing::*;
use super::ParallelIterator;
use std::iter::{self, Sum};
use std::marker::PhantomData;
pub(super) fn sum<PI, S>(pi: PI) -> S
where
PI: ParallelIterator,
S: Send + Sum<PI::Item> + Sum,
{
pi.drive_unindexed(SumConsumer::new())
}
fn add<T: Sum>(left: T, right: T) -> T {
iter::once(left).chain(iter::once(right)).sum()
}
struct SumConsumer<S: Send> {
_marker: PhantomData<*const S>,
}
unsafe impl<S: Send> Send for SumConsumer<S> {}
impl<S: Send> SumConsumer<S> {
fn new() -> SumConsumer<S> {
SumConsumer {
_marker: PhantomData,
}
}
}
impl<S, T> Consumer<T> for SumConsumer<S>
where
S: Send + Sum<T> + Sum,
{
type Folder = SumFolder<S>;
type Reducer = Self;
type Result = S;
fn split_at(self, _index: usize) -> (Self, Self, Self) {
(SumConsumer::new(), SumConsumer::new(), SumConsumer::new())
}
fn into_folder(self) -> Self::Folder {
SumFolder {
sum: iter::empty::<T>().sum(),
}
}
fn full(&self) -> bool {
false
}
}
impl<S, T> UnindexedConsumer<T> for SumConsumer<S>
where
S: Send + Sum<T> + Sum,
{
fn split_off_left(&self) -> Self {
SumConsumer::new()
}
fn to_reducer(&self) -> Self::Reducer {
SumConsumer::new()
}
}
impl<S> Reducer<S> for SumConsumer<S>
where
S: Send + Sum,
{
fn reduce(self, left: S, right: S) -> S {
add(left, right)
}
}
struct SumFolder<S> {
sum: S,
}
impl<S, T> Folder<T> for SumFolder<S>
where
S: Sum<T> + Sum,
{
type Result = S;
fn consume(self, item: T) -> Self {
SumFolder {
sum: add(self.sum, iter::once(item).sum()),
}
}
fn consume_iter<I>(self, iter: I) -> Self
where
I: IntoIterator<Item = T>,
{
SumFolder {
sum: add(self.sum, iter.into_iter().sum()),
}
}
fn complete(self) -> S {
self.sum
}
fn full(&self) -> bool {
false
}
}