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Bundle and document 6 BTreeMap navigation algorithms

This commit is contained in:
Stein Somers 2019-11-19 13:55:55 +01:00
parent ecde10fc28
commit 3cf724d0c1
4 changed files with 314 additions and 236 deletions
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278
src/liballoc/collections/btree/map.rs
View File

@ -6,10 +6,11 @@ use core::iter::{FromIterator, FusedIterator, Peekable};
use core::marker::PhantomData;
use core::ops::Bound::{Excluded, Included, Unbounded};
use core::ops::{Index, RangeBounds};
use core::{fmt, intrinsics, mem, ptr};
use core::{fmt, mem, ptr};
use super::node::{self, marker, ForceResult::*, Handle, InsertResult::*, NodeRef};
use super::search::{self, SearchResult::*};
use super::unwrap_unchecked;
use Entry::*;
use UnderflowResult::*;
@ -645,7 +646,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
T: Ord,
K: Borrow<T>,
{
let front = first_leaf_edge(self.root.as_ref());
let front = self.root.as_ref().first_leaf_edge();
front.right_kv().ok().map(Handle::into_kv)
}
@ -706,7 +707,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
T: Ord,
K: Borrow<T>,
{
let back = last_leaf_edge(self.root.as_ref());
let back = self.root.as_ref().last_leaf_edge();
back.left_kv().ok().map(Handle::into_kv)
}
@ -1073,7 +1074,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
self.ensure_root_is_owned();
let mut cur_node = last_leaf_edge(self.root.as_mut()).into_node();
let mut cur_node = self.root.as_mut().last_leaf_edge().into_node();
// Iterate through all key-value pairs, pushing them into nodes at the right level.
for (key, value) in iter {
// Try to push key-value pair into the current leaf node.
@ -1113,7 +1114,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
open_node.push(key, value, right_tree);
// Go down to the right-most leaf again.
cur_node = last_leaf_edge(open_node.forget_type()).into_node();
cur_node = open_node.forget_type().last_leaf_edge().into_node();
}
self.length += 1;
@ -1411,10 +1412,8 @@ impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
None
} else {
self.length -= 1;
unsafe {
let (k, v) = self.range.next_unchecked();
Some((k, v)) // coerce k from `&mut K` to `&K`
}
let (k, v) = unsafe { self.range.next_unchecked() };
Some((k, v)) // coerce k from `&mut K` to `&K`
}
}
@ -1434,7 +1433,8 @@ impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
None
} else {
self.length -= 1;
unsafe { Some(self.range.next_back_unchecked()) }
let (k, v) = unsafe { self.range.next_back_unchecked() };
Some((k, v)) // coerce k from `&mut K` to `&K`
}
}
}
@ -1460,7 +1460,7 @@ impl<K, V> IntoIterator for BTreeMap<K, V> {
let len = self.length;
mem::forget(self);
IntoIter { front: first_leaf_edge(root1), back: last_leaf_edge(root2), length: len }
IntoIter { front: root1.first_leaf_edge(), back: root2.last_leaf_edge(), length: len }
}
}
@ -1475,9 +1475,9 @@ impl<K, V> Drop for IntoIter<K, V> {
}
if let Some(first_parent) = leaf_node.deallocate_and_ascend() {
let mut cur_node = first_parent.into_node();
while let Some(parent) = cur_node.deallocate_and_ascend() {
cur_node = parent.into_node()
let mut cur_internal_node = first_parent.into_node();
while let Some(parent) = cur_internal_node.deallocate_and_ascend() {
cur_internal_node = parent.into_node()
}
}
}
@ -1490,37 +1490,10 @@ impl<K, V> Iterator for IntoIter<K, V> {
fn next(&mut self) -> Option<(K, V)> {
if self.length == 0 {
return None;
None
} else {
self.length -= 1;
}
let handle = unsafe { ptr::read(&self.front) };
let mut cur_handle = match handle.right_kv() {
Ok(kv) => {
let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
self.front = kv.right_edge();
return Some((k, v));
}
Err(last_edge) => unsafe {
unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
},
};
loop {
match cur_handle.right_kv() {
Ok(kv) => {
let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
self.front = first_leaf_edge(kv.right_edge().descend());
return Some((k, v));
}
Err(last_edge) => unsafe {
cur_handle = unwrap_unchecked(last_edge.into_node().deallocate_and_ascend());
},
}
Some(unsafe { self.front.next_unchecked() })
}
}
@ -1533,37 +1506,10 @@ impl<K, V> Iterator for IntoIter<K, V> {
impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
fn next_back(&mut self) -> Option<(K, V)> {
if self.length == 0 {
return None;
None
} else {
self.length -= 1;
}
let handle = unsafe { ptr::read(&self.back) };
let mut cur_handle = match handle.left_kv() {
Ok(kv) => {
let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
self.back = kv.left_edge();
return Some((k, v));
}
Err(last_edge) => unsafe {
unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
},
};
loop {
match cur_handle.left_kv() {
Ok(kv) => {
let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
self.back = last_leaf_edge(kv.left_edge().descend());
return Some((k, v));
}
Err(last_edge) => unsafe {
cur_handle = unwrap_unchecked(last_edge.into_node().deallocate_and_ascend());
},
}
Some(unsafe { self.back.next_back_unchecked() })
}
}
}
@ -1665,7 +1611,7 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
type Item = (&'a K, &'a V);
fn next(&mut self) -> Option<(&'a K, &'a V)> {
if self.front == self.back { None } else { unsafe { Some(self.next_unchecked()) } }
if self.is_empty() { None } else { unsafe { Some(self.next_unchecked()) } }
}
fn last(mut self) -> Option<(&'a K, &'a V)> {
@ -1708,73 +1654,25 @@ impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
impl<'a, K, V> Range<'a, K, V> {
fn is_empty(&self) -> bool {
self.front == self.back
}
unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
let handle = self.front;
let mut cur_handle = match handle.right_kv() {
Ok(kv) => {
let ret = kv.into_kv();
self.front = kv.right_edge();
return ret;
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
};
loop {
match cur_handle.right_kv() {
Ok(kv) => {
let ret = kv.into_kv();
self.front = first_leaf_edge(kv.right_edge().descend());
return ret;
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
cur_handle = unwrap_unchecked(next_level);
}
}
}
self.front.next_unchecked()
}
}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
if self.front == self.back { None } else { unsafe { Some(self.next_back_unchecked()) } }
if self.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
}
}
impl<'a, K, V> Range<'a, K, V> {
unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
let handle = self.back;
let mut cur_handle = match handle.left_kv() {
Ok(kv) => {
let ret = kv.into_kv();
self.back = kv.left_edge();
return ret;
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
};
loop {
match cur_handle.left_kv() {
Ok(kv) => {
let ret = kv.into_kv();
self.back = last_leaf_edge(kv.left_edge().descend());
return ret;
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
cur_handle = unwrap_unchecked(next_level);
}
}
}
self.back.next_back_unchecked()
}
}
@ -1796,10 +1694,8 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
if self.is_empty() {
None
} else {
unsafe {
let (k, v) = self.next_unchecked();
Some((k, v)) // coerce k from `&mut K` to `&K`
}
let (k, v) = unsafe { self.next_unchecked() };
Some((k, v)) // coerce k from `&mut K` to `&K`
}
}
@ -1814,42 +1710,19 @@ impl<'a, K, V> RangeMut<'a, K, V> {
}
unsafe fn next_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
let handle = ptr::read(&self.front);
let mut cur_handle = match handle.right_kv() {
Ok(kv) => {
self.front = ptr::read(&kv).right_edge();
// Doing the descend invalidates the references returned by `into_kv_mut`,
// so we have to do this last.
return kv.into_kv_mut();
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
};
loop {
match cur_handle.right_kv() {
Ok(kv) => {
self.front = first_leaf_edge(ptr::read(&kv).right_edge().descend());
// Doing the descend invalidates the references returned by `into_kv_mut`,
// so we have to do this last.
return kv.into_kv_mut();
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
cur_handle = unwrap_unchecked(next_level);
}
}
}
self.front.next_unchecked()
}
}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
if self.is_empty() { None } else { unsafe { Some(self.next_back_unchecked()) } }
if self.is_empty() {
None
} else {
let (k, v) = unsafe { self.next_back_unchecked() };
Some((k, v)) // coerce k from `&mut K` to `&K`
}
}
}
@ -1857,38 +1730,8 @@ impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
impl<'a, K, V> RangeMut<'a, K, V> {
unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
let handle = ptr::read(&self.back);
let mut cur_handle = match handle.left_kv() {
Ok(kv) => {
self.back = ptr::read(&kv).left_edge();
// Doing the descend invalidates the references returned by `into_kv_mut`,
// so we have to do this last.
let (k, v) = kv.into_kv_mut();
return (k, v); // coerce k from `&mut K` to `&K`
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
};
loop {
match cur_handle.left_kv() {
Ok(kv) => {
self.back = last_leaf_edge(ptr::read(&kv).left_edge().descend());
// Doing the descend invalidates the references returned by `into_kv_mut`,
// so we have to do this last.
let (k, v) = kv.into_kv_mut();
return (k, v); // coerce k from `&mut K` to `&K`
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
cur_handle = unwrap_unchecked(next_level);
}
}
}
unsafe fn next_back_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
self.back.next_back_unchecked()
}
}
@ -1987,32 +1830,6 @@ where
}
}
fn first_leaf_edge<BorrowType, K, V>(
mut node: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
loop {
match node.force() {
Leaf(leaf) => return leaf.first_edge(),
Internal(internal) => {
node = internal.first_edge().descend();
}
}
}
}
fn last_leaf_edge<BorrowType, K, V>(
mut node: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
loop {
match node.force() {
Leaf(leaf) => return leaf.last_edge(),
Internal(internal) => {
node = internal.last_edge().descend();
}
}
}
}
fn range_search<BorrowType, K, V, Q: ?Sized, R: RangeBounds<Q>>(
root1: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
root2: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
@ -2116,17 +1933,6 @@ where
}
}
#[inline(always)]
unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
val.unwrap_or_else(|| {
if cfg!(debug_assertions) {
panic!("'unchecked' unwrap on None in BTreeMap");
} else {
intrinsics::unreachable();
}
})
}
impl<K, V> BTreeMap<K, V> {
/// Gets an iterator over the entries of the map, sorted by key.
///
@ -2153,8 +1959,8 @@ impl<K, V> BTreeMap<K, V> {
pub fn iter(&self) -> Iter<'_, K, V> {
Iter {
range: Range {
front: first_leaf_edge(self.root.as_ref()),
back: last_leaf_edge(self.root.as_ref()),
front: self.root.as_ref().first_leaf_edge(),
back: self.root.as_ref().last_leaf_edge(),
},
length: self.length,
}
@ -2187,8 +1993,8 @@ impl<K, V> BTreeMap<K, V> {
let root2 = unsafe { ptr::read(&root1) };
IterMut {
range: RangeMut {
front: first_leaf_edge(root1),
back: last_leaf_edge(root2),
front: root1.first_leaf_edge(),
back: root2.last_leaf_edge(),
_marker: PhantomData,
},
length: self.length,
@ -2691,7 +2497,7 @@ impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
let key_loc = internal.kv_mut().0 as *mut K;
let val_loc = internal.kv_mut().1 as *mut V;
let to_remove = first_leaf_edge(internal.right_edge().descend()).right_kv().ok();
let to_remove = internal.right_edge().descend().first_leaf_edge().right_kv().ok();
let to_remove = unsafe { unwrap_unchecked(to_remove) };
let (hole, key, val) = to_remove.remove();

12
src/liballoc/collections/btree/mod.rs
View File

@ -1,4 +1,5 @@
pub mod map;
mod navigate;
mod node;
mod search;
pub mod set;
@ -11,3 +12,14 @@ trait Recover<Q: ?Sized> {
fn take(&mut self, key: &Q) -> Option<Self::Key>;
fn replace(&mut self, key: Self::Key) -> Option<Self::Key>;
}
#[inline(always)]
pub unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
val.unwrap_or_else(|| {
if cfg!(debug_assertions) {
panic!("'unchecked' unwrap on None in BTreeMap");
} else {
core::intrinsics::unreachable();
}
})
}

244
src/liballoc/collections/btree/navigate.rs Normal file
View File

@ -0,0 +1,244 @@
use core::ptr;
use super::node::{marker, ForceResult::*, Handle, NodeRef};
use super::unwrap_unchecked;
macro_rules! def_next {
{ unsafe fn $name:ident : $next_kv:ident $next_edge:ident $initial_leaf_edge:ident } => {
/// Given a leaf edge handle into an immutable tree, returns a handle to the next
/// leaf edge and references to the key and value between these edges.
/// Unsafe because the caller must ensure that the given leaf edge has a successor.
unsafe fn $name <'a, K: 'a, V: 'a>(
leaf_edge: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
) -> (Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>, &'a K, &'a V) {
let mut cur_handle = match leaf_edge.$next_kv() {
Ok(leaf_kv) => {
let (k, v) = leaf_kv.into_kv();
let next_leaf_edge = leaf_kv.$next_edge();
return (next_leaf_edge, k, v);
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
};
loop {
cur_handle = match cur_handle.$next_kv() {
Ok(internal_kv) => {
let (k, v) = internal_kv.into_kv();
let next_internal_edge = internal_kv.$next_edge();
let next_leaf_edge = next_internal_edge.descend().$initial_leaf_edge();
return (next_leaf_edge, k, v);
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
}
}
}
};
}
macro_rules! def_next_mut {
{ unsafe fn $name:ident : $next_kv:ident $next_edge:ident $initial_leaf_edge:ident } => {
/// Given a leaf edge handle into a mutable tree, returns handles to the next
/// leaf edge and to the KV between these edges.
/// Unsafe for two reasons:
/// - the caller must ensure that the given leaf edge has a successor;
/// - both returned handles represent mutable references into the same tree
/// that can easily invalidate each other, even on immutable use.
unsafe fn $name <'a, K: 'a, V: 'a>(
leaf_edge: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
) -> (Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>) {
let mut cur_handle = match leaf_edge.$next_kv() {
Ok(leaf_kv) => {
let next_leaf_edge = ptr::read(&leaf_kv).$next_edge();
return (next_leaf_edge, leaf_kv.forget_node_type());
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
};
loop {
cur_handle = match cur_handle.$next_kv() {
Ok(internal_kv) => {
let next_internal_edge = ptr::read(&internal_kv).$next_edge();
let next_leaf_edge = next_internal_edge.descend().$initial_leaf_edge();
return (next_leaf_edge, internal_kv.forget_node_type());
}
Err(last_edge) => {
let next_level = last_edge.into_node().ascend().ok();
unwrap_unchecked(next_level)
}
}
}
}
};
}
macro_rules! def_next_dealloc {
{ unsafe fn $name:ident : $next_kv:ident $next_edge:ident $initial_leaf_edge:ident } => {
/// Given a leaf edge handle into an owned tree, returns a handle to the next
/// leaf edge and the key and value between these edges, while deallocating
/// any node left behind.
/// Unsafe for two reasons:
/// - the caller must ensure that the given leaf edge has a successor;
/// - the node pointed at by the given handle, and its ancestors, may be deallocated,
/// while the reference to those nodes in the surviving ancestors is left dangling;
/// thus using the returned handle is dangerous.
unsafe fn $name <K, V>(
leaf_edge: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
) -> (Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>, K, V) {
let mut cur_handle = match leaf_edge.$next_kv() {
Ok(leaf_kv) => {
let k = ptr::read(leaf_kv.reborrow().into_kv().0);
let v = ptr::read(leaf_kv.reborrow().into_kv().1);
let next_leaf_edge = leaf_kv.$next_edge();
return (next_leaf_edge, k, v);
}
Err(last_edge) => {
unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
}
};
loop {
cur_handle = match cur_handle.$next_kv() {
Ok(internal_kv) => {
let k = ptr::read(internal_kv.reborrow().into_kv().0);
let v = ptr::read(internal_kv.reborrow().into_kv().1);
let next_internal_edge = internal_kv.$next_edge();
let next_leaf_edge = next_internal_edge.descend().$initial_leaf_edge();
return (next_leaf_edge, k, v);
}
Err(last_edge) => {
unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
}
}
}
}
};
}
def_next! {unsafe fn next_unchecked: right_kv right_edge first_leaf_edge}
def_next! {unsafe fn next_back_unchecked: left_kv left_edge last_leaf_edge}
def_next_mut! {unsafe fn next_unchecked_mut: right_kv right_edge first_leaf_edge}
def_next_mut! {unsafe fn next_back_unchecked_mut: left_kv left_edge last_leaf_edge}
def_next_dealloc! {unsafe fn next_unchecked_deallocating: right_kv right_edge first_leaf_edge}
def_next_dealloc! {unsafe fn next_back_unchecked_deallocating: left_kv left_edge last_leaf_edge}
impl<'a, K, V> Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge> {
/// Moves the leaf edge handle to the next leaf edge and returns references to the
/// key and value in between.
/// Unsafe because the caller must ensure that the leaf edge is not the last one in the tree.
pub unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
let (next_edge, k, v) = next_unchecked(*self);
*self = next_edge;
(k, v)
}
/// Moves the leaf edge handle to the previous leaf edge and returns references to the
/// key and value in between.
/// Unsafe because the caller must ensure that the leaf edge is not the first one in the tree.
pub unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
let (next_edge, k, v) = next_back_unchecked(*self);
*self = next_edge;
(k, v)
}
}
impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
/// Moves the leaf edge handle to the next leaf edge and returns references to the
/// key and value in between.
/// Unsafe for two reasons:
/// - The caller must ensure that the leaf edge is not the last one in the tree.
/// - Using the updated handle may well invalidate the returned references.
pub unsafe fn next_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
let (next_edge, kv) = next_unchecked_mut(ptr::read(self));
*self = next_edge;
// Doing the descend (and perhaps another move) invalidates the references
// returned by `into_kv_mut`, so we have to do this last.
kv.into_kv_mut()
}
/// Moves the leaf edge handle to the previous leaf and returns references to the
/// key and value in between.
/// Unsafe for two reasons:
/// - The caller must ensure that the leaf edge is not the first one in the tree.
/// - Using the updated handle may well invalidate the returned references.
pub unsafe fn next_back_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
let (next_edge, kv) = next_back_unchecked_mut(ptr::read(self));
*self = next_edge;
// Doing the descend (and perhaps another move) invalidates the references
// returned by `into_kv_mut`, so we have to do this last.
kv.into_kv_mut()
}
}
impl<K, V> Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge> {
/// Moves the leaf edge handle to the next leaf edge and returns the key and value
/// in between, while deallocating any node left behind.
/// Unsafe for three reasons:
/// - The caller must ensure that the leaf edge is not the last one in the tree
/// and is not a handle previously resulting from counterpart `next_back_unchecked`.
/// - If the leaf edge is the last edge of a node, that node and possibly ancestors
/// will be deallocated, while the reference to those nodes in the surviving ancestor
/// is left dangling; thus further use of the leaf edge handle is dangerous.
/// It is, however, safe to call this method again on the updated handle.
/// if the two preconditions above hold.
/// - Using the updated handle may well invalidate the returned references.
pub unsafe fn next_unchecked(&mut self) -> (K, V) {
let (next_edge, k, v) = next_unchecked_deallocating(ptr::read(self));
*self = next_edge;
(k, v)
}
/// Moves the leaf edge handle to the previous leaf edge and returns the key
/// and value in between, while deallocating any node left behind.
/// Unsafe for three reasons:
/// - The caller must ensure that the leaf edge is not the first one in the tree
/// and is not a handle previously resulting from counterpart `next_unchecked`.
/// - If the lead edge is the first edge of a node, that node and possibly ancestors
/// will be deallocated, while the reference to those nodes in the surviving ancestor
/// is left dangling; thus further use of the leaf edge handle is dangerous.
/// It is, however, safe to call this method again on the updated handle.
/// if the two preconditions above hold.
/// - Using the updated handle may well invalidate the returned references.
pub unsafe fn next_back_unchecked(&mut self) -> (K, V) {
let (next_edge, k, v) = next_back_unchecked_deallocating(ptr::read(self));
*self = next_edge;
(k, v)
}
}
impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
/// Returns the leftmost leaf edge in or underneath a node - in other words, the edge
/// you need first when navigating forward (or last when navigating backward).
#[inline]
pub fn first_leaf_edge(self) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
let mut node = self;
loop {
match node.force() {
Leaf(leaf) => return leaf.first_edge(),
Internal(internal) => node = internal.first_edge().descend(),
}
}
}
/// Returns the rightmost leaf edge in or underneath a node - in other words, the edge
/// you need last when navigating forward (or first when navigating backward).
#[inline]
pub fn last_leaf_edge(self) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
let mut node = self;
loop {
match node.force() {
Leaf(leaf) => return leaf.last_edge(),
Internal(internal) => node = internal.last_edge().descend(),
}
}
}
}

16
src/liballoc/collections/btree/node.rs
View File

@ -1418,6 +1418,22 @@ unsafe fn move_edges<K, V>(
dest.correct_childrens_parent_links(dest_offset, dest_offset + count);
}
impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::KV> {
pub fn forget_node_type(
self,
) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
}
}
impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::KV> {
pub fn forget_node_type(
self,
) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
}
}
impl<BorrowType, K, V, HandleType>
Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, HandleType>
{