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BTreeMap: avoid slices even more #76790

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Sep 18, 2020
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BTreeMap: avoid slices even more #76790

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45 changes: 29 additions & 16 deletions library/alloc/src/collections/btree/node.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -465,6 +465,22 @@ impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
unsafe { &mut (*self.node.as_ptr()) }
}

/// Borrows a mutable reference to one of the keys stored in the node.
///
/// # Safety
/// The node has more than `idx` initialized elements.
pub unsafe fn key_mut_at(&mut self, idx: usize) -> &mut K {
unsafe { self.reborrow_mut().into_key_mut_at(idx) }
}

/// Borrows a mutable reference to one of the values stored in the node.
///
/// # Safety
/// The node has more than `idx` initialized elements.
pub unsafe fn val_mut_at(&mut self, idx: usize) -> &mut V {
unsafe { self.reborrow_mut().into_val_mut_at(idx) }
}

fn keys_mut(&mut self) -> &mut [K] {
// SAFETY: the caller will not be able to call further methods on self
// until the key slice reference is dropped, as we have unique access
Expand Down Expand Up @@ -555,15 +571,14 @@ impl<'a, K, V, Type> NodeRef<marker::ValMut<'a>, K, V, Type> {
impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
/// Adds a key/value pair to the end of the node.
pub fn push(&mut self, key: K, val: V) {
assert!(self.len() < CAPACITY);

let idx = self.len();

let len = &mut self.as_leaf_mut().len;
let idx = *len as usize;
assert!(idx < CAPACITY);
*len += 1;
unsafe {
ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
ptr::write(self.key_mut_at(idx), key);
ptr::write(self.val_mut_at(idx), val);
}
self.as_leaf_mut().len += 1;
}

/// Adds a key/value pair to the beginning of the node.
Expand Down Expand Up @@ -600,17 +615,15 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
/// the end of the node.
pub fn push(&mut self, key: K, val: V, edge: Root<K, V>) {
assert!(edge.height == self.height - 1);
assert!(self.len() < CAPACITY);

let idx = self.len();

let len = &mut self.as_leaf_mut().len;
let idx = *len as usize;
assert!(idx < CAPACITY);
*len += 1;
unsafe {
ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
ptr::write(self.key_mut_at(idx), key);
ptr::write(self.val_mut_at(idx), val);
self.as_internal_mut().edges.get_unchecked_mut(idx + 1).write(edge.node);

self.as_leaf_mut().len += 1;

Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
}
}
Expand Down Expand Up @@ -903,7 +916,7 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
/// The returned pointer points to the inserted value.
fn insert_fit(&mut self, key: K, val: V) -> *mut V {
self.leafy_insert_fit(key, val);
unsafe { self.node.vals_mut().get_unchecked_mut(self.idx) }
unsafe { self.node.val_mut_at(self.idx) }
}
}

Expand Down