1 files changed, 331 insertions, 0 deletions
diff --git a/third_party/rust/itertools/src/tuple_impl.rs b/third_party/rust/itertools/src/tuple_impl.rs
new file mode 100644
index 0000000000..06b5c13cb3
--- /dev/null
+++ b/third_party/rust/itertools/src/tuple_impl.rs
@@ -0,0 +1,331 @@
+//! Some iterator that produces tuples
+
+use std::iter::Fuse;
+use std::iter::FusedIterator;
+use std::iter::Take;
+use std::iter::Cycle;
+use std::marker::PhantomData;
+
+// `HomogeneousTuple` is a public facade for `TupleCollect`, allowing
+// tuple-related methods to be used by clients in generic contexts, while
+// hiding the implementation details of `TupleCollect`.
+// See https://github.com/rust-itertools/itertools/issues/387
+
+/// Implemented for homogeneous tuples of size up to 12.
+pub trait HomogeneousTuple
+    : TupleCollect
+{}
+
+impl<T: TupleCollect> HomogeneousTuple for T {}
+
+/// An iterator over a incomplete tuple.
+///
+/// See [`.tuples()`](crate::Itertools::tuples) and
+/// [`Tuples::into_buffer()`].
+#[derive(Clone, Debug)]
+pub struct TupleBuffer<T>
+    where T: HomogeneousTuple
+{
+    cur: usize,
+    buf: T::Buffer,
+}
+
+impl<T> TupleBuffer<T>
+    where T: HomogeneousTuple
+{
+    fn new(buf: T::Buffer) -> Self {
+        TupleBuffer {
+            cur: 0,
+            buf,
+        }
+    }
+}
+
+impl<T> Iterator for TupleBuffer<T>
+    where T: HomogeneousTuple
+{
+    type Item = T::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let s = self.buf.as_mut();
+        if let Some(ref mut item) = s.get_mut(self.cur) {
+            self.cur += 1;
+            item.take()
+        } else {
+            None
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let buffer = &self.buf.as_ref()[self.cur..];
+        let len = if buffer.is_empty() {
+            0
+        } else {
+            buffer.iter()
+                  .position(|x| x.is_none())
+                  .unwrap_or_else(|| buffer.len())
+        };
+        (len, Some(len))
+    }
+}
+
+impl<T> ExactSizeIterator for TupleBuffer<T>
+    where T: HomogeneousTuple
+{
+}
+
+/// An iterator that groups the items in tuples of a specific size.
+///
+/// See [`.tuples()`](crate::Itertools::tuples) for more information.
+#[derive(Clone, Debug)]
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+pub struct Tuples<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple
+{
+    iter: Fuse<I>,
+    buf: T::Buffer,
+}
+
+/// Create a new tuples iterator.
+pub fn tuples<I, T>(iter: I) -> Tuples<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple
+{
+    Tuples {
+        iter: iter.fuse(),
+        buf: Default::default(),
+    }
+}
+
+impl<I, T> Iterator for Tuples<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        T::collect_from_iter(&mut self.iter, &mut self.buf)
+    }
+}
+
+impl<I, T> Tuples<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple
+{
+    /// Return a buffer with the produced items that was not enough to be grouped in a tuple.
+    ///
+    /// ```
+    /// use itertools::Itertools;
+    ///
+    /// let mut iter = (0..5).tuples();
+    /// assert_eq!(Some((0, 1, 2)), iter.next());
+    /// assert_eq!(None, iter.next());
+    /// itertools::assert_equal(vec![3, 4], iter.into_buffer());
+    /// ```
+    pub fn into_buffer(self) -> TupleBuffer<T> {
+        TupleBuffer::new(self.buf)
+    }
+}
+
+
+/// An iterator over all contiguous windows that produces tuples of a specific size.
+///
+/// See [`.tuple_windows()`](crate::Itertools::tuple_windows) for more
+/// information.
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Clone, Debug)]
+pub struct TupleWindows<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple
+{
+    iter: I,
+    last: Option<T>,
+}
+
+/// Create a new tuple windows iterator.
+pub fn tuple_windows<I, T>(mut iter: I) -> TupleWindows<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple,
+          T::Item: Clone
+{
+    use std::iter::once;
+
+    let mut last = None;
+    if T::num_items() != 1 {
+        // put in a duplicate item in front of the tuple; this simplifies
+        // .next() function.
+        if let Some(item) = iter.next() {
+            let iter = once(item.clone()).chain(once(item)).chain(&mut iter);
+            last = T::collect_from_iter_no_buf(iter);
+        }
+    }
+
+    TupleWindows {
+        iter,
+        last,
+    }
+}
+
+impl<I, T> Iterator for TupleWindows<I, T>
+    where I: Iterator<Item = T::Item>,
+          T: HomogeneousTuple + Clone,
+          T::Item: Clone
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if T::num_items() == 1 {
+            return T::collect_from_iter_no_buf(&mut self.iter)
+        }
+        if let Some(ref mut last) = self.last {
+            if let Some(new) = self.iter.next() {
+                last.left_shift_push(new);
+                return Some(last.clone());
+            }
+        }
+        None
+    }
+}
+
+impl<I, T> FusedIterator for TupleWindows<I, T>
+    where I: FusedIterator<Item = T::Item>,
+          T: HomogeneousTuple + Clone,
+          T::Item: Clone
+{}
+
+/// An iterator over all windows,wrapping back to the first elements when the
+/// window would otherwise exceed the length of the iterator, producing tuples
+/// of a specific size.
+///
+/// See [`.circular_tuple_windows()`](crate::Itertools::circular_tuple_windows) for more
+/// information.
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Debug)]
+pub struct CircularTupleWindows<I, T: Clone>
+    where I: Iterator<Item = T::Item> + Clone,
+          T: TupleCollect + Clone
+{
+    iter: Take<TupleWindows<Cycle<I>, T>>,
+    phantom_data: PhantomData<T>
+}
+
+pub fn circular_tuple_windows<I, T>(iter: I) -> CircularTupleWindows<I, T>
+    where I: Iterator<Item = T::Item> + Clone + ExactSizeIterator,
+          T: TupleCollect + Clone,
+          T::Item: Clone
+{
+    let len = iter.len();
+    let iter = tuple_windows(iter.cycle()).take(len);
+
+    CircularTupleWindows {
+        iter,
+        phantom_data: PhantomData{}
+    }
+}
+
+impl<I, T> Iterator for CircularTupleWindows<I, T>
+    where I: Iterator<Item = T::Item> + Clone,
+          T: TupleCollect + Clone,
+          T::Item: Clone
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+}
+
+pub trait TupleCollect: Sized {
+    type Item;
+    type Buffer: Default + AsRef<[Option<Self::Item>]> + AsMut<[Option<Self::Item>]>;
+
+    fn collect_from_iter<I>(iter: I, buf: &mut Self::Buffer) -> Option<Self>
+        where I: IntoIterator<Item = Self::Item>;
+
+    fn collect_from_iter_no_buf<I>(iter: I) -> Option<Self>
+        where I: IntoIterator<Item = Self::Item>;
+
+    fn num_items() -> usize;
+
+    fn left_shift_push(&mut self, item: Self::Item);
+}
+
+macro_rules! count_ident{
+    () => {0};
+    ($i0:ident, $($i:ident,)*) => {1 + count_ident!($($i,)*)};
+}
+macro_rules! rev_for_each_ident{
+    ($m:ident, ) => {};
+    ($m:ident, $i0:ident, $($i:ident,)*) => {
+        rev_for_each_ident!($m, $($i,)*);
+        $m!($i0);
+    };
+}
+
+macro_rules! impl_tuple_collect {
+    ($dummy:ident,) => {}; // stop
+    ($dummy:ident, $($Y:ident,)*) => (
+        impl_tuple_collect!($($Y,)*);
+        impl<A> TupleCollect for ($(ignore_ident!($Y, A),)*) {
+            type Item = A;
+            type Buffer = [Option<A>; count_ident!($($Y,)*) - 1];
+
+            #[allow(unused_assignments, unused_mut)]
+            fn collect_from_iter<I>(iter: I, buf: &mut Self::Buffer) -> Option<Self>
+                where I: IntoIterator<Item = A>
+            {
+                let mut iter = iter.into_iter();
+                $(
+                    let mut $Y = None;
+                )*
+
+                loop {
+                    $(
+                        $Y = iter.next();
+                        if $Y.is_none() {
+                            break
+                        }
+                    )*
+                    return Some(($($Y.unwrap()),*,))
+                }
+
+                let mut i = 0;
+                let mut s = buf.as_mut();
+                $(
+                    if i < s.len() {
+                        s[i] = $Y;
+                        i += 1;
+                    }
+                )*
+                return None;
+            }
+
+            fn collect_from_iter_no_buf<I>(iter: I) -> Option<Self>
+                where I: IntoIterator<Item = A>
+            {
+                let mut iter = iter.into_iter();
+
+                Some(($(
+                    { let $Y = iter.next()?; $Y },
+                )*))
+            }
+
+            fn num_items() -> usize {
+                count_ident!($($Y,)*)
+            }
+
+            fn left_shift_push(&mut self, mut item: A) {
+                use std::mem::replace;
+
+                let &mut ($(ref mut $Y),*,) = self;
+                macro_rules! replace_item{($i:ident) => {
+                    item = replace($i, item);
+                }}
+                rev_for_each_ident!(replace_item, $($Y,)*);
+                drop(item);
+            }
+        }
+    )
+}
+impl_tuple_collect!(dummy, a, b, c, d, e, f, g, h, i, j, k, l,);