1 files changed, 124 insertions, 0 deletions
diff --git a/vendor/itertools/src/with_position.rs b/vendor/itertools/src/with_position.rs
new file mode 100644
index 00000000..2d56bb9b
--- /dev/null
+++ b/vendor/itertools/src/with_position.rs
@@ -0,0 +1,124 @@
+use std::fmt;
+use std::iter::{Fuse, FusedIterator, Peekable};
+
+/// An iterator adaptor that wraps each element in an [`Position`].
+///
+/// Iterator element type is `(Position, I::Item)`.
+///
+/// See [`.with_position()`](crate::Itertools::with_position) for more information.
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+pub struct WithPosition<I>
+where
+    I: Iterator,
+{
+    handled_first: bool,
+    peekable: Peekable<Fuse<I>>,
+}
+
+impl<I> fmt::Debug for WithPosition<I>
+where
+    I: Iterator,
+    Peekable<Fuse<I>>: fmt::Debug,
+{
+    debug_fmt_fields!(WithPosition, handled_first, peekable);
+}
+
+impl<I> Clone for WithPosition<I>
+where
+    I: Clone + Iterator,
+    I::Item: Clone,
+{
+    clone_fields!(handled_first, peekable);
+}
+
+/// Create a new `WithPosition` iterator.
+pub fn with_position<I>(iter: I) -> WithPosition<I>
+where
+    I: Iterator,
+{
+    WithPosition {
+        handled_first: false,
+        peekable: iter.fuse().peekable(),
+    }
+}
+
+/// The first component of the value yielded by `WithPosition`.
+/// Indicates the position of this element in the iterator results.
+///
+/// See [`.with_position()`](crate::Itertools::with_position) for more information.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Position {
+    /// This is the first element.
+    First,
+    /// This is neither the first nor the last element.
+    Middle,
+    /// This is the last element.
+    Last,
+    /// This is the only element.
+    Only,
+}
+
+impl<I: Iterator> Iterator for WithPosition<I> {
+    type Item = (Position, I::Item);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.peekable.next() {
+            Some(item) => {
+                if !self.handled_first {
+                    // Haven't seen the first item yet, and there is one to give.
+                    self.handled_first = true;
+                    // Peek to see if this is also the last item,
+                    // in which case tag it as `Only`.
+                    match self.peekable.peek() {
+                        Some(_) => Some((Position::First, item)),
+                        None => Some((Position::Only, item)),
+                    }
+                } else {
+                    // Have seen the first item, and there's something left.
+                    // Peek to see if this is the last item.
+                    match self.peekable.peek() {
+                        Some(_) => Some((Position::Middle, item)),
+                        None => Some((Position::Last, item)),
+                    }
+                }
+            }
+            // Iterator is finished.
+            None => None,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.peekable.size_hint()
+    }
+
+    fn fold<B, F>(mut self, mut init: B, mut f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        if let Some(mut head) = self.peekable.next() {
+            if !self.handled_first {
+                // The current head is `First` or `Only`,
+                // it depends if there is another item or not.
+                match self.peekable.next() {
+                    Some(second) => {
+                        let first = std::mem::replace(&mut head, second);
+                        init = f(init, (Position::First, first));
+                    }
+                    None => return f(init, (Position::Only, head)),
+                }
+            }
+            // Have seen the first item, and there's something left.
+            init = self.peekable.fold(init, |acc, mut item| {
+                std::mem::swap(&mut head, &mut item);
+                f(acc, (Position::Middle, item))
+            });
+            // The "head" is now the last item.
+            init = f(init, (Position::Last, head));
+        }
+        init
+    }
+}
+
+impl<I> ExactSizeIterator for WithPosition<I> where I: ExactSizeIterator {}
+
+impl<I: Iterator> FusedIterator for WithPosition<I> {}