better doubling

Signed-off-by: Moritz Hoffmann <[email protected]>

src/impls/slice_copy.rs

@@ -110,18 +110,14 @@ where
 {
     #[inline]
     fn push(&mut self, item: [T; N]) -> <OwnedRegion<T> as Region>::Index {
-        let start = self.slices.len();
-        self.slices.extend(item);
-        (start, self.slices.len())
+        (self.slices.len(), self.slices.extend(item))
     }
 }
 
 impl<T: Clone, S: Storage<T>, const N: usize> Push<&[T; N]> for OwnedRegion<T, S> {
     #[inline]
     fn push(&mut self, item: &[T; N]) -> <OwnedRegion<T> as Region>::Index {
-        let start = self.slices.len();
-        self.slices.extend_from_slice(item);
-        (start, self.slices.len())
+        self.push(item.as_slice())
     }
 }
 
@@ -145,9 +141,7 @@ impl<'b, T: Clone, S: Storage<T>, const N: usize> ReserveItems<&'b [T; N]> for O
 impl<T: Clone, S: Storage<T>> Push<&[T]> for OwnedRegion<T, S> {
     #[inline]
     fn push(&mut self, item: &[T]) -> <OwnedRegion<T, S> as Region>::Index {
-        let start = self.slices.len();
-        self.slices.extend_from_slice(item);
-        (start, self.slices.len())
+        (self.slices.len(), self.slices.extend_from_slice(item))
     }
 }
 
@@ -182,9 +176,7 @@ where
 {
     #[inline]
     fn push(&mut self, mut item: Vec<T>) -> <OwnedRegion<T, S> as Region>::Index {
-        let start = self.slices.len();
-        self.slices.append(&mut item);
-        (start, self.slices.len())
+        (self.slices.len(), self.slices.append(&mut item))
     }
 }
 
@@ -212,9 +204,7 @@ where
 impl<T: Clone, S: Storage<T>, I: IntoIterator<Item = T>> Push<CopyIter<I>> for OwnedRegion<T, S> {
     #[inline]
     fn push(&mut self, item: CopyIter<I>) -> <OwnedRegion<T, S> as Region>::Index {
-        let start = self.slices.len();
-        self.slices.extend(item.0);
-        (start, self.slices.len())
+        (self.slices.len(), self.slices.extend(item.0))
     }
 }
 

src/impls/storage.rs

@@ -134,7 +134,7 @@ impl<T> Default for Doubling<T> {
     }
 }
 
-impl<T: Clone> Storage<T> for Doubling<T> {
+impl<T> Storage<T> for Doubling<T> {
     #[inline]
     fn with_capacity(capacity: usize) -> Self {
         Self {
@@ -179,7 +179,10 @@ impl<T: Clone> Storage<T> for Doubling<T> {
 
     #[inline]
     fn clear(&mut self) {
-        self.inner.clear();
+        self.inner.drain(..self.len().saturating_sub(1));
+        if let Some(last) = self.inner.last_mut() {
+            last.clear();
+        }
     }
 
     #[inline]
@@ -192,8 +195,15 @@ impl<T: Clone> Storage<T> for Doubling<T> {
 
     #[inline]
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) -> usize {
-        let vec: Vec<T> = iter.into_iter().collect();
-        self.extend_from_slice(&vec)
+        let mut iter = iter.into_iter().peekable();
+        while iter.peek().is_some() {
+            if let Some(last) = self.inner.last_mut().filter(|last| last.len() < last.capacity()) {
+                Extend::extend(last, (&mut iter).take(last.capacity() - last.len()));
+            }
+            let (lo, hi) = iter.size_hint();
+            self.reserve(hi.unwrap_or(lo));
+        }
+        self.len()
     }
 
     #[inline]