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    use super::plumbing::*;
    use super::*;
    use std::sync::atomic::{AtomicBool, Ordering};

    /// `WhileSome` is an iterator that yields the `Some` elements of an iterator,
    /// halting as soon as any `None` is produced.
    ///
    /// This struct is created by the [`while_some()`] method on [`ParallelIterator`]
    ///
    /// [`while_some()`]: trait.ParallelIterator.html#method.while_some
    /// [`ParallelIterator`]: trait.ParallelIterator.html
    #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
    #[derive(Debug, Clone)]
    pub struct WhileSome<I: ParallelIterator> {
        base: I,
    }

    impl<I> WhileSome<I>
    where
        I: ParallelIterator,
    {
        /// Create a new `WhileSome` iterator.
        pub(super) fn new(base: I) -> Self {
            WhileSome { base }
        }
    }

    impl<I, T> ParallelIterator for WhileSome<I>
    where
        I: ParallelIterator<Item = Option<T>>,
        T: Send,
    {
        type Item = T;

        fn drive_unindexed<C>(self, consumer: C) -> C::Result
        where
            C: UnindexedConsumer<Self::Item>,
        {
            let full = AtomicBool::new(false);
            let consumer1 = WhileSomeConsumer {
                base: consumer,
                full: &full,
            };
            self.base.drive_unindexed(consumer1)
        }
    }

    /// ////////////////////////////////////////////////////////////////////////
    /// Consumer implementation

    struct WhileSomeConsumer<'f, C> {
        base: C,
        full: &'f AtomicBool,
    }

    impl<'f, T, C> Consumer<Option<T>> for WhileSomeConsumer<'f, C>
    where
        C: Consumer<T>,
        T: Send,
    {
        type Folder = WhileSomeFolder<'f, C::Folder>;
        type Reducer = C::Reducer;
        type Result = C::Result;

        fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
            let (left, right, reducer) = self.base.split_at(index);
            (
                WhileSomeConsumer { base: left, ..self },
                WhileSomeConsumer {
                    base: right,
                    ..self
                },
                reducer,
            )
        }

        fn into_folder(self) -> Self::Folder {
            WhileSomeFolder {
                base: self.base.into_folder(),
                full: self.full,
            }
        }

        fn full(&self) -> bool {
            self.full.load(Ordering::Relaxed) || self.base.full()
        }
    }

    impl<'f, T, C> UnindexedConsumer<Option<T>> for WhileSomeConsumer<'f, C>
    where
        C: UnindexedConsumer<T>,
        T: Send,
    {
        fn split_off_left(&self) -> Self {
            WhileSomeConsumer {
                base: self.base.split_off_left(),
                ..*self
            }
        }

        fn to_reducer(&self) -> Self::Reducer {
            self.base.to_reducer()
        }
    }

    struct WhileSomeFolder<'f, C> {
        base: C,
        full: &'f AtomicBool,
    }

    impl<'f, T, C> Folder<Option<T>> for WhileSomeFolder<'f, C>
    where
        C: Folder<T>,
    {
        type Result = C::Result;

        fn consume(mut self, item: Option<T>) -> Self {
            match item {
                Some(item) => self.base = self.base.consume(item),
                None => self.full.store(true, Ordering::Relaxed),
            }
            self
        }

        fn consume_iter<I>(mut self, iter: I) -> Self
        where
            I: IntoIterator<Item = Option<T>>,
        {
            let full = self.full;
            self.base = self.base.consume_iter(
                iter.into_iter()
                    .take_while(|x| match *x {
                        Some(_) => !full.load(Ordering::Relaxed),
                        None => {
                            full.store(true, Ordering::Relaxed);
                            false
                        }
                    })
                    .map(Option::unwrap),
            );
            self
        }

        fn complete(self) -> C::Result {
            self.base.complete()
        }

        fn full(&self) -> bool {
            self.full.load(Ordering::Relaxed) || self.base.full()
        }
    }

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