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use super::plumbing::*;
use super::*;
/// `Flatten` turns each element to a parallel iterator, then flattens these iterators
/// together. This struct is created by the [`flatten()`] method on [`ParallelIterator`].
///
/// [`flatten()`]: trait.ParallelIterator.html#method.flatten
/// [`ParallelIterator`]: trait.ParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug, Clone)]
pub struct Flatten<I: ParallelIterator> {
base: I,
}
impl<I> Flatten<I>
where
I: ParallelIterator,
I::Item: IntoParallelIterator,
{
/// Creates a new `Flatten` iterator.
pub(super) fn new(base: I) -> Self {
Flatten { base }
}
}
impl<I> ParallelIterator for Flatten<I>
where
I: ParallelIterator,
I::Item: IntoParallelIterator,
{
type Item = <I::Item as IntoParallelIterator>::Item;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let consumer = FlattenConsumer::new(consumer);
self.base.drive_unindexed(consumer)
}
}
/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation
struct FlattenConsumer<C> {
base: C,
}
impl<C> FlattenConsumer<C> {
fn new(base: C) -> Self {
FlattenConsumer { base }
}
}
impl<T, C> Consumer<T> for FlattenConsumer<C>
where
C: UnindexedConsumer<T::Item>,
T: IntoParallelIterator,
{
type Folder = FlattenFolder<C, C::Result>;
type Reducer = C::Reducer;
type Result = C::Result;
fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
let (left, right, reducer) = self.base.split_at(index);
(
FlattenConsumer::new(left),
FlattenConsumer::new(right),
reducer,
)
}
fn into_folder(self) -> Self::Folder {
FlattenFolder {
base: self.base,
previous: None,
}
}
fn full(&self) -> bool {
self.base.full()
}
}
impl<T, C> UnindexedConsumer<T> for FlattenConsumer<C>
where
C: UnindexedConsumer<T::Item>,
T: IntoParallelIterator,
{
fn split_off_left(&self) -> Self {
FlattenConsumer::new(self.base.split_off_left())
}
fn to_reducer(&self) -> Self::Reducer {
self.base.to_reducer()
}
}
struct FlattenFolder<C, R> {
base: C,
previous: Option<R>,
}
impl<T, C> Folder<T> for FlattenFolder<C, C::Result>
where
C: UnindexedConsumer<T::Item>,
T: IntoParallelIterator,
{
type Result = C::Result;
fn consume(self, item: T) -> Self {
let par_iter = item.into_par_iter();
let consumer = self.base.split_off_left();
let result = par_iter.drive_unindexed(consumer);
let previous = match self.previous {
None => Some(result),
Some(previous) => {
let reducer = self.base.to_reducer();
Some(reducer.reduce(previous, result))
}
};
FlattenFolder {
base: self.base,
previous,
}
}
fn complete(self) -> Self::Result {
match self.previous {
Some(previous) => previous,
None => self.base.into_folder().complete(),
}
}
fn full(&self) -> bool {
self.base.full()
}
}