1 files changed, 99 insertions, 0 deletions
diff --git a/vendor/itertools/src/multipeek_impl.rs b/vendor/itertools/src/multipeek_impl.rs
new file mode 100644
index 000000000..5917681fc
--- /dev/null
+++ b/vendor/itertools/src/multipeek_impl.rs
@@ -0,0 +1,99 @@
+use std::iter::Fuse;
+use alloc::collections::VecDeque;
+use crate::size_hint;
+use crate::PeekingNext;
+
+/// See [`multipeek()`] for more information.
+#[derive(Clone, Debug)]
+pub struct MultiPeek<I>
+    where I: Iterator
+{
+    iter: Fuse<I>,
+    buf: VecDeque<I::Item>,
+    index: usize,
+}
+
+/// An iterator adaptor that allows the user to peek at multiple `.next()`
+/// values without advancing the base iterator.
+pub fn multipeek<I>(iterable: I) -> MultiPeek<I::IntoIter>
+    where I: IntoIterator
+{
+    MultiPeek {
+        iter: iterable.into_iter().fuse(),
+        buf: VecDeque::new(),
+        index: 0,
+    }
+}
+
+impl<I> MultiPeek<I>
+    where I: Iterator
+{
+    /// Reset the peeking “cursor”
+    pub fn reset_peek(&mut self) {
+        self.index = 0;
+    }
+}
+
+impl<I: Iterator> MultiPeek<I> {
+    /// Works exactly like `.next()` with the only difference that it doesn't
+    /// advance itself. `.peek()` can be called multiple times, to peek
+    /// further ahead.
+    /// When `.next()` is called, reset the peeking “cursor”.
+    pub fn peek(&mut self) -> Option<&I::Item> {
+        let ret = if self.index < self.buf.len() {
+            Some(&self.buf[self.index])
+        } else {
+            match self.iter.next() {
+                Some(x) => {
+                    self.buf.push_back(x);
+                    Some(&self.buf[self.index])
+                }
+                None => return None,
+            }
+        };
+
+        self.index += 1;
+        ret
+    }
+}
+
+impl<I> PeekingNext for MultiPeek<I>
+    where I: Iterator,
+{
+    fn peeking_next<F>(&mut self, accept: F) -> Option<Self::Item>
+        where F: FnOnce(&Self::Item) -> bool
+    {
+        if self.buf.is_empty() {
+            if let Some(r) = self.peek() {
+                if !accept(r) { return None }
+            }
+        } else {
+            if let Some(r) = self.buf.get(0) {
+                if !accept(r) { return None }
+            }
+        }
+        self.next()
+    }
+}
+
+impl<I> Iterator for MultiPeek<I>
+    where I: Iterator
+{
+    type Item = I::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.index = 0;
+        self.buf.pop_front().or_else(|| self.iter.next())
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        size_hint::add_scalar(self.iter.size_hint(), self.buf.len())
+    }
+}
+
+// Same size
+impl<I> ExactSizeIterator for MultiPeek<I>
+    where I: ExactSizeIterator
+{}
+
+