all: split reusable components into workspace crates

utils/src/vecdeque_ext.rs

@@ -0,0 +1,35 @@
+use std::{
+    collections::{Bound, VecDeque},
+    ops::RangeBounds,
+};
+
+pub trait VecDequeExt<T> {
+    fn get_slices(&self, range: impl RangeBounds<usize>) -> (&[T], &[T]);
+}
+
+impl<T> VecDequeExt<T> for VecDeque<T> {
+    fn get_slices(&self, range: impl RangeBounds<usize>) -> (&[T], &[T]) {
+        let (l, r) = self.as_slices();
+        let start = match range.start_bound().cloned() {
+            Bound::Included(n) => n,
+            Bound::Excluded(n) => n + 1,
+            Bound::Unbounded => 0,
+        };
+        let end = match range.end_bound().cloned() {
+            Bound::Included(n) => n + 1,
+            Bound::Excluded(n) => n,
+            Bound::Unbounded => self.len(),
+        };
+        let left = {
+            let lo = start.min(l.len());
+            let hi = end.min(l.len());
+            &l[lo..hi]
+        };
+        let right = {
+            let lo = start.saturating_sub(l.len());
+            let hi = end.saturating_sub(l.len());
+            &r[lo..hi]
+        };
+        (left, right)
+    }
+}