1 files changed, 109 insertions, 0 deletions
diff --git a/third_party/rust/rayon/src/delegate.rs b/third_party/rust/rayon/src/delegate.rs
new file mode 100644
index 0000000000..2a6e331930
--- /dev/null
+++ b/third_party/rust/rayon/src/delegate.rs
@@ -0,0 +1,109 @@
+//! Macros for delegating newtype iterators to inner types.
+
+// Note: these place `impl` bounds at the end, as token gobbling is the only way
+// I know how to consume an arbitrary list of constraints, with `$($args:tt)*`.
+
+/// Creates a parallel iterator implementation which simply wraps an inner type
+/// and delegates all methods inward.  The actual struct must already be
+/// declared with an `inner` field.
+///
+/// The implementation of `IntoParallelIterator` should be added separately.
+macro_rules! delegate_iterator {
+    ($iter:ty => $item:ty ,
+     impl $( $args:tt )*
+     ) => {
+        impl $( $args )* ParallelIterator for $iter {
+            type Item = $item;
+
+            fn drive_unindexed<C>(self, consumer: C) -> C::Result
+                where C: UnindexedConsumer<Self::Item>
+            {
+                self.inner.drive_unindexed(consumer)
+            }
+
+            fn opt_len(&self) -> Option<usize> {
+                self.inner.opt_len()
+            }
+        }
+    }
+}
+
+/// Creates an indexed parallel iterator implementation which simply wraps an
+/// inner type and delegates all methods inward.  The actual struct must already
+/// be declared with an `inner` field.
+macro_rules! delegate_indexed_iterator {
+    ($iter:ty => $item:ty ,
+     impl $( $args:tt )*
+     ) => {
+        delegate_iterator!{
+            $iter => $item ,
+            impl $( $args )*
+        }
+
+        impl $( $args )* IndexedParallelIterator for $iter {
+            fn drive<C>(self, consumer: C) -> C::Result
+                where C: Consumer<Self::Item>
+            {
+                self.inner.drive(consumer)
+            }
+
+            fn len(&self) -> usize {
+                self.inner.len()
+            }
+
+            fn with_producer<CB>(self, callback: CB) -> CB::Output
+                where CB: ProducerCallback<Self::Item>
+            {
+                self.inner.with_producer(callback)
+            }
+        }
+    }
+}
+
+#[test]
+fn unindexed_example() {
+    use crate::collections::btree_map::IntoIter;
+    use crate::iter::plumbing::*;
+    use crate::prelude::*;
+
+    use std::collections::BTreeMap;
+
+    struct MyIntoIter<T: Ord + Send, U: Send> {
+        inner: IntoIter<T, U>,
+    }
+
+    delegate_iterator! {
+        MyIntoIter<T, U> => (T, U),
+        impl<T: Ord + Send, U: Send>
+    }
+
+    let map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let iter = MyIntoIter {
+        inner: map.into_par_iter(),
+    };
+    let vec: Vec<_> = iter.map(|(k, _)| k).collect();
+    assert_eq!(vec, &[1, 2, 3]);
+}
+
+#[test]
+fn indexed_example() {
+    use crate::iter::plumbing::*;
+    use crate::prelude::*;
+    use crate::vec::IntoIter;
+
+    struct MyIntoIter<T: Send> {
+        inner: IntoIter<T>,
+    }
+
+    delegate_indexed_iterator! {
+        MyIntoIter<T> => T,
+        impl<T: Send>
+    }
+
+    let iter = MyIntoIter {
+        inner: vec![1, 2, 3].into_par_iter(),
+    };
+    let mut vec = vec![];
+    iter.collect_into_vec(&mut vec);
+    assert_eq!(vec, &[1, 2, 3]);
+}