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BTreeMap: various tweaks

This commit is contained in:
Stein Somers 2020-08-09 12:25:20 +02:00
parent 3965524570
commit 55fa8afe94
1 changed files with 50 additions and 61 deletions
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111
library/alloc/src/collections/btree/node.rs
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@ -47,8 +47,7 @@ const KV_IDX_CENTER: usize = B - 1;
const EDGE_IDX_LEFT_OF_CENTER: usize = B - 1;
const EDGE_IDX_RIGHT_OF_CENTER: usize = B;
/// The underlying representation of leaf nodes.
#[repr(C)]
/// The underlying representation of leaf nodes and part of the representation of internal nodes.
struct LeafNode<K, V> {
/// We want to be covariant in `K` and `V`.
parent: Option<NonNull<InternalNode<K, V>>>,
@ -59,9 +58,6 @@ struct LeafNode<K, V> {
parent_idx: MaybeUninit<u16>,
/// The number of keys and values this node stores.
///
/// This next to `parent_idx` to encourage the compiler to join `len` and
/// `parent_idx` into the same 32-bit word, reducing space overhead.
len: u16,
/// The arrays storing the actual data of the node. Only the first `len` elements of each
@ -92,7 +88,9 @@ impl<K, V> LeafNode<K, V> {
/// node, allowing code to act on leaf and internal nodes generically without having to even check
/// which of the two a pointer is pointing at. This property is enabled by the use of `repr(C)`.
#[repr(C)]
// gdb_providers.py uses this type name for introspection.
struct InternalNode<K, V> {
// gdb_providers.py uses this field name for introspection.
data: LeafNode<K, V>,
/// The pointers to the children of this node. `len + 1` of these are considered
@ -183,9 +181,9 @@ impl<K, V> Root<K, V> {
NodeRef { height: self.height, node: self.node.as_ptr(), _marker: PhantomData }
}
/// Adds a new internal node with a single edge, pointing to the previous root, and make that
/// new node the root. This increases the height by 1 and is the opposite of
/// `pop_internal_level`.
/// Adds a new internal node with a single edge pointing to the previous root node,
/// make that new node the root node, and return it. This increases the height by 1
/// and is the opposite of `pop_internal_level`.
pub fn push_internal_level(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::Internal> {
let mut new_node = Box::new(unsafe { InternalNode::new() });
new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
@ -322,7 +320,7 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
NodeRef { height: self.height, node: self.node, _marker: PhantomData }
}
/// Exposes the leaf "portion" of any leaf or internal node.
/// Exposes the leaf portion of any leaf or internal node.
/// If the node is a leaf, this function simply opens up its data.
/// If the node is an internal node, so not a leaf, it does have all the data a leaf has
/// (header, keys and values), and this function exposes that.
@ -472,7 +470,7 @@ impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
NodeRef { height: self.height, node: self.node, _marker: PhantomData }
}
/// Exposes the leaf "portion" of any leaf or internal node for writing.
/// Exposes the leaf portion of any leaf or internal node for writing.
/// If the node is a leaf, this function simply opens up its data.
/// If the node is an internal node, so not a leaf, it does have all the data a leaf has
/// (header, keys and values), and this function exposes that.
@ -498,18 +496,38 @@ impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
unsafe { self.reborrow_mut().into_val_mut_at(idx) }
}
fn keys_mut(&mut self) -> &mut [K] {
fn keys_mut(&mut self) -> &mut [K]
where
K: 'a,
V: 'a,
{
// 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
// for the lifetime of the borrow.
unsafe { self.reborrow_mut().into_key_slice_mut() }
// SAFETY: The keys of a node must always be initialized up to length.
unsafe {
slice::from_raw_parts_mut(
MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().keys),
self.len(),
)
}
}
fn vals_mut(&mut self) -> &mut [V] {
fn vals_mut(&mut self) -> &mut [V]
where
K: 'a,
V: 'a,
{
// SAFETY: the caller will not be able to call further methods on self
// until the value slice reference is dropped, as we have unique access
// for the lifetime of the borrow.
unsafe { self.reborrow_mut().into_val_slice_mut() }
// SAFETY: The values of a node must always be initialized up to length.
unsafe {
slice::from_raw_parts_mut(
MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().vals),
self.len(),
)
}
}
}
@ -539,26 +557,6 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
}
impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
fn into_key_slice_mut(mut self) -> &'a mut [K] {
// SAFETY: The keys of a node must always be initialized up to length.
unsafe {
slice::from_raw_parts_mut(
MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().keys),
self.len(),
)
}
}
fn into_val_slice_mut(mut self) -> &'a mut [V] {
// SAFETY: The values of a node must always be initialized up to length.
unsafe {
slice::from_raw_parts_mut(
MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().vals),
self.len(),
)
}
}
/// # Safety
/// The node has more than `idx` initialized elements.
unsafe fn into_key_mut_at(mut self, idx: usize) -> &'a mut K {
@ -610,8 +608,8 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
}
/// Adds a key/value pair to the beginning of the node.
pub fn push_front(&mut self, key: K, val: V) {
assert!(self.len() < CAPACITY);
fn push_front(&mut self, key: K, val: V) {
debug_assert!(self.len() < CAPACITY);
unsafe {
slice_insert(self.keys_mut(), 0, key);
@ -683,10 +681,9 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
/// Removes a key/value pair from the end of this node and returns the pair.
/// If this is an internal node, also removes the edge that was to the right
/// of that pair and returns the orphaned node that this edge owned with its
/// parent erased.
pub fn pop(&mut self) -> (K, V, Option<Root<K, V>>) {
assert!(self.len() > 0);
/// of that pair and returns the orphaned node that this edge owned.
fn pop(&mut self) -> (K, V, Option<Root<K, V>>) {
debug_assert!(self.len() > 0);
let idx = self.len() - 1;
@ -708,10 +705,11 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
}
}
/// Removes a key/value pair from the beginning of this node. If this is an internal node,
/// also removes the edge that was to the left of that pair.
pub fn pop_front(&mut self) -> (K, V, Option<Root<K, V>>) {
assert!(self.len() > 0);
/// Removes a key/value pair from the beginning of this node and returns the pair.
/// If this is an internal node, also removes the edge that was to the left
/// of that pair and returns the orphaned node that this edge owned.
fn pop_front(&mut self) -> (K, V, Option<Root<K, V>>) {
debug_assert!(self.len() > 0);
let old_len = self.len();
@ -913,7 +911,6 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>
/// this edge. This method assumes that there is enough space in the node for the new
/// pair to fit.
fn leafy_insert_fit(&mut self, key: K, val: V) {
// Necessary for correctness, but in a private module
debug_assert!(self.node.len() < CAPACITY);
unsafe {
@ -951,18 +948,18 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
let (middle_kv_idx, insertion) = splitpoint(self.idx);
let middle = unsafe { Handle::new_kv(self.node, middle_kv_idx) };
let (mut left, k, v, mut right) = middle.split();
let val_ptr = match insertion {
let mut insertion_edge = match insertion {
InsertionPlace::Left(insert_idx) => unsafe {
Handle::new_edge(left.reborrow_mut(), insert_idx).insert_fit(key, val)
Handle::new_edge(left.reborrow_mut(), insert_idx)
},
InsertionPlace::Right(insert_idx) => unsafe {
Handle::new_edge(
right.node_as_mut().cast_unchecked::<marker::Leaf>(),
insert_idx,
)
.insert_fit(key, val)
},
};
let val_ptr = insertion_edge.insert_fit(key, val);
(InsertResult::Split(SplitResult { left: left.forget_type(), k, v, right }), val_ptr)
}
}
@ -985,8 +982,6 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
/// between this edge and the key/value pair to the right of this edge. This method assumes
/// that there is enough space in the node for the new pair to fit.
fn insert_fit(&mut self, key: K, val: V, edge: Root<K, V>) {
// Necessary for correctness, but in an internal module
debug_assert!(self.node.len() < CAPACITY);
debug_assert!(edge.height == self.node.height - 1);
unsafe {
@ -1136,12 +1131,12 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>
ptr::copy_nonoverlapping(
self.node.key_at(self.idx + 1),
new_node.keys.as_mut_ptr() as *mut K,
MaybeUninit::slice_as_mut_ptr(&mut new_node.keys),
new_len,
);
ptr::copy_nonoverlapping(
self.node.val_at(self.idx + 1),
new_node.vals.as_mut_ptr() as *mut V,
MaybeUninit::slice_as_mut_ptr(&mut new_node.vals),
new_len,
);
@ -1376,9 +1371,7 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
move_edges(left, new_left_len + 1, right, 0, count);
}
(ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
_ => {
unreachable!();
}
_ => unreachable!(),
}
}
}
@ -1433,9 +1426,7 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
right.correct_childrens_parent_links(0..=new_right_len);
}
(ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
_ => {
unreachable!();
}
_ => unreachable!(),
}
}
}
@ -1568,9 +1559,7 @@ impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, ma
move_edges(left, left_new_len + 1, right, 1, right_new_len);
}
(ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
_ => {
unreachable!();
}
_ => unreachable!(),
}
}
}