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