1 files changed, 327 insertions, 0 deletions
diff --git a/src/iter/update.rs b/src/iter/update.rs
new file mode 100644
index 0000000..373a4d7
--- /dev/null
+++ b/src/iter/update.rs
@@ -0,0 +1,327 @@
+use super::plumbing::*;
+use super::*;
+
+use std::fmt::{self, Debug};
+
+/// `Update` is an iterator that mutates the elements of an
+/// underlying iterator before they are yielded.
+///
+/// This struct is created by the [`update()`] method on [`ParallelIterator`]
+///
+/// [`update()`]: trait.ParallelIterator.html#method.update
+/// [`ParallelIterator`]: trait.ParallelIterator.html
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Clone)]
+pub struct Update<I: ParallelIterator, F> {
+    base: I,
+    update_op: F,
+}
+
+impl<I: ParallelIterator + Debug, F> Debug for Update<I, F> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Update").field("base", &self.base).finish()
+    }
+}
+
+impl<I, F> Update<I, F>
+where
+    I: ParallelIterator,
+{
+    /// Creates a new `Update` iterator.
+    pub(super) fn new(base: I, update_op: F) -> Self {
+        Update { base, update_op }
+    }
+}
+
+impl<I, F> ParallelIterator for Update<I, F>
+where
+    I: ParallelIterator,
+    F: Fn(&mut I::Item) + Send + Sync,
+{
+    type Item = I::Item;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        let consumer1 = UpdateConsumer::new(consumer, &self.update_op);
+        self.base.drive_unindexed(consumer1)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        self.base.opt_len()
+    }
+}
+
+impl<I, F> IndexedParallelIterator for Update<I, F>
+where
+    I: IndexedParallelIterator,
+    F: Fn(&mut I::Item) + Send + Sync,
+{
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        let consumer1 = UpdateConsumer::new(consumer, &self.update_op);
+        self.base.drive(consumer1)
+    }
+
+    fn len(&self) -> usize {
+        self.base.len()
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        return self.base.with_producer(Callback {
+            callback,
+            update_op: self.update_op,
+        });
+
+        struct Callback<CB, F> {
+            callback: CB,
+            update_op: F,
+        }
+
+        impl<T, F, CB> ProducerCallback<T> for Callback<CB, F>
+        where
+            CB: ProducerCallback<T>,
+            F: Fn(&mut T) + Send + Sync,
+        {
+            type Output = CB::Output;
+
+            fn callback<P>(self, base: P) -> CB::Output
+            where
+                P: Producer<Item = T>,
+            {
+                let producer = UpdateProducer {
+                    base,
+                    update_op: &self.update_op,
+                };
+                self.callback.callback(producer)
+            }
+        }
+    }
+}
+
+/// ////////////////////////////////////////////////////////////////////////
+
+struct UpdateProducer<'f, P, F> {
+    base: P,
+    update_op: &'f F,
+}
+
+impl<'f, P, F> Producer for UpdateProducer<'f, P, F>
+where
+    P: Producer,
+    F: Fn(&mut P::Item) + Send + Sync,
+{
+    type Item = P::Item;
+    type IntoIter = UpdateSeq<P::IntoIter, &'f F>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        UpdateSeq {
+            base: self.base.into_iter(),
+            update_op: self.update_op,
+        }
+    }
+
+    fn min_len(&self) -> usize {
+        self.base.min_len()
+    }
+    fn max_len(&self) -> usize {
+        self.base.max_len()
+    }
+
+    fn split_at(self, index: usize) -> (Self, Self) {
+        let (left, right) = self.base.split_at(index);
+        (
+            UpdateProducer {
+                base: left,
+                update_op: self.update_op,
+            },
+            UpdateProducer {
+                base: right,
+                update_op: self.update_op,
+            },
+        )
+    }
+
+    fn fold_with<G>(self, folder: G) -> G
+    where
+        G: Folder<Self::Item>,
+    {
+        let folder1 = UpdateFolder {
+            base: folder,
+            update_op: self.update_op,
+        };
+        self.base.fold_with(folder1).base
+    }
+}
+
+/// ////////////////////////////////////////////////////////////////////////
+/// Consumer implementation
+
+struct UpdateConsumer<'f, C, F> {
+    base: C,
+    update_op: &'f F,
+}
+
+impl<'f, C, F> UpdateConsumer<'f, C, F> {
+    fn new(base: C, update_op: &'f F) -> Self {
+        UpdateConsumer { base, update_op }
+    }
+}
+
+impl<'f, T, C, F> Consumer<T> for UpdateConsumer<'f, C, F>
+where
+    C: Consumer<T>,
+    F: Fn(&mut T) + Send + Sync,
+{
+    type Folder = UpdateFolder<'f, C::Folder, F>;
+    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);
+        (
+            UpdateConsumer::new(left, self.update_op),
+            UpdateConsumer::new(right, self.update_op),
+            reducer,
+        )
+    }
+
+    fn into_folder(self) -> Self::Folder {
+        UpdateFolder {
+            base: self.base.into_folder(),
+            update_op: self.update_op,
+        }
+    }
+
+    fn full(&self) -> bool {
+        self.base.full()
+    }
+}
+
+impl<'f, T, C, F> UnindexedConsumer<T> for UpdateConsumer<'f, C, F>
+where
+    C: UnindexedConsumer<T>,
+    F: Fn(&mut T) + Send + Sync,
+{
+    fn split_off_left(&self) -> Self {
+        UpdateConsumer::new(self.base.split_off_left(), &self.update_op)
+    }
+
+    fn to_reducer(&self) -> Self::Reducer {
+        self.base.to_reducer()
+    }
+}
+
+struct UpdateFolder<'f, C, F> {
+    base: C,
+    update_op: &'f F,
+}
+
+fn apply<T>(update_op: impl Fn(&mut T)) -> impl Fn(T) -> T {
+    move |mut item| {
+        update_op(&mut item);
+        item
+    }
+}
+
+impl<'f, T, C, F> Folder<T> for UpdateFolder<'f, C, F>
+where
+    C: Folder<T>,
+    F: Fn(&mut T),
+{
+    type Result = C::Result;
+
+    fn consume(self, mut item: T) -> Self {
+        (self.update_op)(&mut item);
+
+        UpdateFolder {
+            base: self.base.consume(item),
+            update_op: self.update_op,
+        }
+    }
+
+    fn consume_iter<I>(mut self, iter: I) -> Self
+    where
+        I: IntoIterator<Item = T>,
+    {
+        let update_op = self.update_op;
+        self.base = self
+            .base
+            .consume_iter(iter.into_iter().map(apply(update_op)));
+        self
+    }
+
+    fn complete(self) -> C::Result {
+        self.base.complete()
+    }
+
+    fn full(&self) -> bool {
+        self.base.full()
+    }
+}
+
+/// Standard Update adaptor, based on `itertools::adaptors::Update`
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Debug, Clone)]
+struct UpdateSeq<I, F> {
+    base: I,
+    update_op: F,
+}
+
+impl<I, F> Iterator for UpdateSeq<I, F>
+where
+    I: Iterator,
+    F: Fn(&mut I::Item),
+{
+    type Item = I::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut v = self.base.next()?;
+        (self.update_op)(&mut v);
+        Some(v)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.base.size_hint()
+    }
+
+    fn fold<Acc, G>(self, init: Acc, g: G) -> Acc
+    where
+        G: FnMut(Acc, Self::Item) -> Acc,
+    {
+        self.base.map(apply(self.update_op)).fold(init, g)
+    }
+
+    // if possible, re-use inner iterator specializations in collect
+    fn collect<C>(self) -> C
+    where
+        C: ::std::iter::FromIterator<Self::Item>,
+    {
+        self.base.map(apply(self.update_op)).collect()
+    }
+}
+
+impl<I, F> ExactSizeIterator for UpdateSeq<I, F>
+where
+    I: ExactSizeIterator,
+    F: Fn(&mut I::Item),
+{
+}
+
+impl<I, F> DoubleEndedIterator for UpdateSeq<I, F>
+where
+    I: DoubleEndedIterator,
+    F: Fn(&mut I::Item),
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        let mut v = self.base.next_back()?;
+        (self.update_op)(&mut v);
+        Some(v)
+    }
+}