Update upstream source from tag 'upstream/1.52.1+dfsg1'

[rustc.git] / vendor / itertools-0.8.2 / src / put_back_n_impl.rs

diff --git a/vendor/itertools-0.8.2/src/put_back_n_impl.rs b/vendor/itertools-0.8.2/src/put_back_n_impl.rs
new file mode 100644 (file)
index 0000000..cc08320
--- /dev/null
+++ b/vendor/itertools-0.8.2/src/put_back_n_impl.rs
@@ -0,0 +1,63 @@
+use 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<I::Item> {
+        if self.top.is_empty() {
+            self.iter.next()
+        } else {
+            self.top.pop()
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        size_hint::add_scalar(self.iter.size_hint(), self.top.len())
+    }
+}
+