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BTreeMap: more expressive local variables in merge

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This commit is contained in:
Stein Somers 2020-11-23 14:41:53 +01:00
parent 12813159a9
commit 94fd1d325c
1 changed files with 27 additions and 28 deletions
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55
library/alloc/src/collections/btree/node.rs
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@ -1352,66 +1352,65 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
/// ///
/// Panics unless we `.can_merge()`. /// Panics unless we `.can_merge()`.
pub fn merge( pub fn merge(
mut self, self,
track_edge_idx: Option<LeftOrRight<usize>>, track_edge_idx: Option<LeftOrRight<usize>>,
) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::Edge> { ) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::Edge> {
let Handle { node: mut parent_node, idx: parent_idx, _marker } = self.parent;
let old_parent_len = parent_node.len();
let mut left_node = self.left_child; let mut left_node = self.left_child;
let left_len = left_node.len(); let old_left_len = left_node.len();
let right_node = self.right_child; let right_node = self.right_child;
let right_len = right_node.len(); let right_len = right_node.len();
let new_left_len = old_left_len + 1 + right_len;
assert!(left_len + right_len < CAPACITY); assert!(new_left_len <= CAPACITY);
assert!(match track_edge_idx { assert!(match track_edge_idx {
None => true, None => true,
Some(LeftOrRight::Left(idx)) => idx <= left_len, Some(LeftOrRight::Left(idx)) => idx <= old_left_len,
Some(LeftOrRight::Right(idx)) => idx <= right_len, Some(LeftOrRight::Right(idx)) => idx <= right_len,
}); });
unsafe { unsafe {
*left_node.reborrow_mut().into_len_mut() += right_len as u16 + 1; *left_node.reborrow_mut().into_len_mut() = new_left_len as u16;
let parent_key = slice_remove( let parent_key =
self.parent.node.reborrow_mut().into_key_area_slice(), slice_remove(parent_node.reborrow_mut().into_key_area_slice(), parent_idx);
self.parent.idx, left_node.reborrow_mut().into_key_area_mut_at(old_left_len).write(parent_key);
);
left_node.reborrow_mut().into_key_area_mut_at(left_len).write(parent_key);
ptr::copy_nonoverlapping( ptr::copy_nonoverlapping(
right_node.reborrow().key_area().as_ptr(), right_node.reborrow().key_area().as_ptr(),
left_node.reborrow_mut().into_key_area_slice().as_mut_ptr().add(left_len + 1), left_node.reborrow_mut().into_key_area_slice().as_mut_ptr().add(old_left_len + 1),
right_len, right_len,
); );
let parent_val = slice_remove( let parent_val =
self.parent.node.reborrow_mut().into_val_area_slice(), slice_remove(parent_node.reborrow_mut().into_val_area_slice(), parent_idx);
self.parent.idx, left_node.reborrow_mut().into_val_area_mut_at(old_left_len).write(parent_val);
);
left_node.reborrow_mut().into_val_area_mut_at(left_len).write(parent_val);
ptr::copy_nonoverlapping( ptr::copy_nonoverlapping(
right_node.reborrow().val_area().as_ptr(), right_node.reborrow().val_area().as_ptr(),
left_node.reborrow_mut().into_val_area_slice().as_mut_ptr().add(left_len + 1), left_node.reborrow_mut().into_val_area_slice().as_mut_ptr().add(old_left_len + 1),
right_len, right_len,
); );
slice_remove( slice_remove(&mut parent_node.reborrow_mut().into_edge_area_slice(), parent_idx + 1);
&mut self.parent.node.reborrow_mut().into_edge_area_slice(), parent_node.correct_childrens_parent_links(parent_idx + 1..old_parent_len);
self.parent.idx + 1, *parent_node.reborrow_mut().into_len_mut() -= 1;
);
let parent_old_len = self.parent.node.len();
self.parent.node.correct_childrens_parent_links(self.parent.idx + 1..parent_old_len);
*self.parent.node.reborrow_mut().into_len_mut() -= 1;
if self.parent.node.height > 1 { if parent_node.height > 1 {
// SAFETY: the height of the nodes being merged is one below the height // SAFETY: the height of the nodes being merged is one below the height
// of the node of this edge, thus above zero, so they are internal. // of the node of this edge, thus above zero, so they are internal.
let mut left_node = left_node.reborrow_mut().cast_to_internal_unchecked(); let mut left_node = left_node.reborrow_mut().cast_to_internal_unchecked();
let right_node = right_node.cast_to_internal_unchecked(); let right_node = right_node.cast_to_internal_unchecked();
ptr::copy_nonoverlapping( ptr::copy_nonoverlapping(
right_node.reborrow().edge_area().as_ptr(), right_node.reborrow().edge_area().as_ptr(),
left_node.reborrow_mut().into_edge_area_slice().as_mut_ptr().add(left_len + 1), left_node
.reborrow_mut()
.into_edge_area_slice()
.as_mut_ptr()
.add(old_left_len + 1),
right_len + 1, right_len + 1,
); );
left_node.correct_childrens_parent_links(left_len + 1..=left_len + 1 + right_len); left_node.correct_childrens_parent_links(old_left_len + 1..new_left_len + 1);
Global.deallocate(right_node.node.cast(), Layout::new::<InternalNode<K, V>>()); Global.deallocate(right_node.node.cast(), Layout::new::<InternalNode<K, V>>());
} else { } else {
@ -1421,7 +1420,7 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
let new_idx = match track_edge_idx { let new_idx = match track_edge_idx {
None => 0, None => 0,
Some(LeftOrRight::Left(idx)) => idx, Some(LeftOrRight::Left(idx)) => idx,
Some(LeftOrRight::Right(idx)) => left_len + 1 + idx, Some(LeftOrRight::Right(idx)) => old_left_len + 1 + idx,
}; };
Handle::new_edge(left_node, new_idx) Handle::new_edge(left_node, new_idx)
} }