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

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

diff --git a/vendor/itertools-0.8.2/src/pad_tail.rs b/vendor/itertools-0.8.2/src/pad_tail.rs
new file mode 100644 (file)
index 0000000..c9cfe6a
--- /dev/null
+++ b/vendor/itertools-0.8.2/src/pad_tail.rs
@@ -0,0 +1,83 @@
+use std::iter::Fuse;
+use size_hint;
+
+/// An iterator adaptor that pads a sequence to a minimum length by filling
+/// missing elements using a closure.
+///
+/// Iterator element type is `I::Item`.
+///
+/// See [`.pad_using()`](../trait.Itertools.html#method.pad_using) for more information.
+#[derive(Clone)]
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+pub struct PadUsing<I, F> {
+    iter: Fuse<I>,
+    min: usize,
+    pos: usize,
+    filler: F,
+}
+
+/// Create a new **PadUsing** iterator.
+pub fn pad_using<I, F>(iter: I, min: usize, filler: F) -> PadUsing<I, F>
+    where I: Iterator,
+          F: FnMut(usize) -> I::Item
+{
+    PadUsing {
+        iter: iter.fuse(),
+        min: min,
+        pos: 0,
+        filler: filler,
+    }
+}
+
+impl<I, F> Iterator for PadUsing<I, F>
+    where I: Iterator,
+          F: FnMut(usize) -> I::Item
+{
+    type Item = I::Item;
+
+    #[inline]
+    fn next(&mut self) -> Option<I::Item> {
+        match self.iter.next() {
+            None => {
+                if self.pos < self.min {
+                    let e = Some((self.filler)(self.pos));
+                    self.pos += 1;
+                    e
+                } else {
+                    None
+                }
+            },
+            e => {
+                self.pos += 1;
+                e
+            }
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let tail = self.min.saturating_sub(self.pos);
+        size_hint::max(self.iter.size_hint(), (tail, Some(tail)))
+    }
+}
+
+impl<I, F> DoubleEndedIterator for PadUsing<I, F>
+    where I: DoubleEndedIterator + ExactSizeIterator,
+          F: FnMut(usize) -> I::Item
+{
+    fn next_back(&mut self) -> Option<I::Item> {
+        if self.min == 0 {
+            self.iter.next_back()
+        } else if self.iter.len() >= self.min {
+            self.min -= 1;
+            self.iter.next_back()
+        } else {
+            self.min -= 1;
+            Some((self.filler)(self.min))
+        }
+    }
+}
+
+impl<I, F> ExactSizeIterator for PadUsing<I, F>
+    where I: ExactSizeIterator,
+          F: FnMut(usize) -> I::Item
+{}