1 files changed, 79 insertions, 0 deletions
diff --git a/vendor/itertools/src/lazy_buffer.rs b/vendor/itertools/src/lazy_buffer.rs
new file mode 100644
index 00000000..fafa5f72
--- /dev/null
+++ b/vendor/itertools/src/lazy_buffer.rs
@@ -0,0 +1,79 @@
+use alloc::vec::Vec;
+use std::iter::Fuse;
+use std::ops::Index;
+
+use crate::size_hint::{self, SizeHint};
+
+#[derive(Debug, Clone)]
+pub struct LazyBuffer<I: Iterator> {
+    it: Fuse<I>,
+    buffer: Vec<I::Item>,
+}
+
+impl<I> LazyBuffer<I>
+where
+    I: Iterator,
+{
+    pub fn new(it: I) -> Self {
+        Self {
+            it: it.fuse(),
+            buffer: Vec::new(),
+        }
+    }
+
+    pub fn len(&self) -> usize {
+        self.buffer.len()
+    }
+
+    pub fn size_hint(&self) -> SizeHint {
+        size_hint::add_scalar(self.it.size_hint(), self.len())
+    }
+
+    pub fn count(self) -> usize {
+        self.len() + self.it.count()
+    }
+
+    pub fn get_next(&mut self) -> bool {
+        if let Some(x) = self.it.next() {
+            self.buffer.push(x);
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn prefill(&mut self, len: usize) {
+        let buffer_len = self.buffer.len();
+        if len > buffer_len {
+            let delta = len - buffer_len;
+            self.buffer.extend(self.it.by_ref().take(delta));
+        }
+    }
+}
+
+impl<I> LazyBuffer<I>
+where
+    I: Iterator,
+    I::Item: Clone,
+{
+    pub fn get_at(&self, indices: &[usize]) -> Vec<I::Item> {
+        indices.iter().map(|i| self.buffer[*i].clone()).collect()
+    }
+
+    pub fn get_array<const K: usize>(&self, indices: [usize; K]) -> [I::Item; K] {
+        indices.map(|i| self.buffer[i].clone())
+    }
+}
+
+impl<I, J> Index<J> for LazyBuffer<I>
+where
+    I: Iterator,
+    I::Item: Sized,
+    Vec<I::Item>: Index<J>,
+{
+    type Output = <Vec<I::Item> as Index<J>>::Output;
+
+    fn index(&self, index: J) -> &Self::Output {
+        self.buffer.index(index)
+    }
+}