1 files changed, 61 insertions, 0 deletions
diff --git a/vendor/itertools/src/put_back_n_impl.rs b/vendor/itertools/src/put_back_n_impl.rs
new file mode 100644
index 000000000..60ea8e649
--- /dev/null
+++ b/vendor/itertools/src/put_back_n_impl.rs
@@ -0,0 +1,61 @@
+use alloc::vec::Vec;
+
+use crate::size_hint;
+
+/// An iterator adaptor that allows putting multiple
+/// items in front of the iterator.
+///
+/// Iterator element type is `I::Item`.
+#[derive(Debug, Clone)]
+pub struct PutBackN<I: Iterator> {
+    top: Vec<I::Item>,
+    iter: I,
+}
+
+/// Create an iterator where you can put back multiple values to the front
+/// of the iteration.
+///
+/// Iterator element type is `I::Item`.
+pub fn put_back_n<I>(iterable: I) -> PutBackN<I::IntoIter>
+    where I: IntoIterator
+{
+    PutBackN {
+        top: Vec::new(),
+        iter: iterable.into_iter(),
+    }
+}
+
+impl<I: Iterator> PutBackN<I> {
+    /// Puts x in front of the iterator.
+    /// The values are yielded in order of the most recently put back
+    /// values first.
+    ///
+    /// ```rust
+    /// use itertools::put_back_n;
+    ///
+    /// let mut it = put_back_n(1..5);
+    /// it.next();
+    /// it.put_back(1);
+    /// it.put_back(0);
+    ///
+    /// assert!(itertools::equal(it, 0..5));
+    /// ```
+    #[inline]
+    pub fn put_back(&mut self, x: I::Item) {
+        self.top.push(x);
+    }
+}
+
+impl<I: Iterator> Iterator for PutBackN<I> {
+    type Item = I::Item;
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.top.pop().or_else(|| self.iter.next())
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        size_hint::add_scalar(self.iter.size_hint(), self.top.len())
+    }
+}
+