1 files changed, 85 insertions, 0 deletions
diff --git a/src/iter/interleave_shortest.rs b/src/iter/interleave_shortest.rs
new file mode 100644
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--- /dev/null
+++ b/src/iter/interleave_shortest.rs
@@ -0,0 +1,85 @@
+use super::plumbing::*;
+use super::*;
+
+/// `InterleaveShortest` is an iterator that works similarly to
+/// `Interleave`, but this version stops returning elements once one
+/// of the iterators run out.
+///
+/// This struct is created by the [`interleave_shortest()`] method on
+/// [`IndexedParallelIterator`].
+///
+/// [`interleave_shortest()`]: trait.IndexedParallelIterator.html#method.interleave_shortest
+/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Debug, Clone)]
+pub struct InterleaveShortest<I, J>
+where
+    I: IndexedParallelIterator,
+    J: IndexedParallelIterator<Item = I::Item>,
+{
+    interleave: Interleave<Take<I>, Take<J>>,
+}
+
+impl<I, J> InterleaveShortest<I, J>
+where
+    I: IndexedParallelIterator,
+    J: IndexedParallelIterator<Item = I::Item>,
+{
+    /// Creates a new `InterleaveShortest` iterator
+    pub(super) fn new(i: I, j: J) -> Self {
+        InterleaveShortest {
+            interleave: if i.len() <= j.len() {
+                // take equal lengths from both iterators
+                let n = i.len();
+                i.take(n).interleave(j.take(n))
+            } else {
+                // take one extra item from the first iterator
+                let n = j.len();
+                i.take(n + 1).interleave(j.take(n))
+            },
+        }
+    }
+}
+
+impl<I, J> ParallelIterator for InterleaveShortest<I, J>
+where
+    I: IndexedParallelIterator,
+    J: IndexedParallelIterator<Item = I::Item>,
+{
+    type Item = I::Item;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<I::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        Some(self.len())
+    }
+}
+
+impl<I, J> IndexedParallelIterator for InterleaveShortest<I, J>
+where
+    I: IndexedParallelIterator,
+    J: IndexedParallelIterator<Item = I::Item>,
+{
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn len(&self) -> usize {
+        self.interleave.len()
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        self.interleave.with_producer(callback)
+    }
+}