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introduce the Comparable trait for btree internals #144506

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introduce the Comparable trait for btree internals #144506

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52 changes: 52 additions & 0 deletions library/alloc/src/collections/btree/cmp.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,52 @@
//! Complements to the [`core::cmp`] module

use core::borrow::Borrow;
use core::cmp::Ordering;

/// Key equivalence trait.
///
/// This trait allows hash table lookup to be customized. It has one blanket
/// implementation that uses the regular solution with `Borrow` and `Eq`, just
/// like `HashMap` does, so that you can pass `&str` to lookup into a map with
/// `String` keys and so on.
///
/// # Contract
///
/// The implementor **must** hash like `Q`, if it is hashable.
pub(crate) trait Equivalent<Q: ?Sized> {
// /// Compare self to `key` and return `true` if they are equal.
// fn equivalent(&self, key: &Q) -> bool;
}

impl<K: ?Sized, Q: ?Sized> Equivalent<Q> for K
where
K: Borrow<Q>,
Q: Eq,
{
// #[inline]
// fn equivalent(&self, key: &Q) -> bool {
// PartialEq::eq(self.borrow(), key)
// }
}

/// Key ordering trait.
///
/// This trait allows ordered map lookup to be customized. It has one blanket
/// implementation that uses the regular solution with `Borrow` and `Ord`, just
/// like `BTreeMap` does, so that you can pass `&str` to lookup into a map with
/// `String` keys and so on.
pub(crate) trait Comparable<Q: ?Sized>: Equivalent<Q> {
/// Compare self to `key` and return their ordering.
fn compare(&self, key: &Q) -> Ordering;
}

impl<K: ?Sized, Q: ?Sized> Comparable<Q> for K
where
K: Borrow<Q>,
Q: Ord,
{
#[inline]
fn compare(&self, key: &Q) -> Ordering {
Ord::cmp(self.borrow(), key)
}
}
1 change: 1 addition & 0 deletions library/alloc/src/collections/btree/mod.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
mod append;
mod borrow;
mod cmp;
mod dedup_sorted_iter;
mod fix;
pub(super) mod map;
Expand Down
14 changes: 6 additions & 8 deletions library/alloc/src/collections/btree/navigate.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use core::borrow::Borrow;
use core::ops::RangeBounds;
use core::{hint, ptr};

use super::cmp::Comparable;
use super::node::ForceResult::*;
use super::node::{Handle, NodeRef, marker};
use super::search::SearchBound;
Expand Down Expand Up @@ -267,7 +267,7 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
) -> LeafRange<BorrowType, K, V>
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
R: RangeBounds<Q>,
{
match self.search_tree_for_bifurcation(&range) {
Expand Down Expand Up @@ -316,7 +316,7 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>
pub(super) fn range_search<Q, R>(self, range: R) -> LeafRange<marker::Immut<'a>, K, V>
where
Q: ?Sized + Ord,
K: Borrow<Q>,
K: Comparable<Q>,
R: RangeBounds<Q>,
{
// SAFETY: our borrow type is immutable.
Expand All @@ -342,7 +342,7 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::ValMut<'a>, K, V, marker::LeafOrInternal>
pub(super) fn range_search<Q, R>(self, range: R) -> LeafRange<marker::ValMut<'a>, K, V>
where
Q: ?Sized + Ord,
K: Borrow<Q>,
K: Comparable<Q>,
R: RangeBounds<Q>,
{
unsafe { self.find_leaf_edges_spanning_range(range) }
Expand Down Expand Up @@ -746,8 +746,7 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
mut bound: SearchBound<&Q>,
) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
{
let mut node = self;
loop {
Expand All @@ -769,8 +768,7 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
mut bound: SearchBound<&Q>,
) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
{
let mut node = self;
loop {
Expand Down
35 changes: 16 additions & 19 deletions library/alloc/src/collections/btree/search.rs
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
use core::borrow::Borrow;
use core::cmp::Ordering;
use core::ops::{Bound, RangeBounds};

use SearchBound::*;
use SearchResult::*;

use super::cmp::Comparable;
use super::node::ForceResult::*;
use super::node::{Handle, NodeRef, marker};

Expand Down Expand Up @@ -51,8 +51,7 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
key: &Q,
) -> SearchResult<BorrowType, K, V, marker::LeafOrInternal, marker::Leaf>
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
{
loop {
self = match self.search_node(key) {
Expand Down Expand Up @@ -95,7 +94,7 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
>
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
R: RangeBounds<Q>,
{
// Determine if map or set is being searched
Expand Down Expand Up @@ -161,8 +160,8 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
bound: SearchBound<&'r Q>,
) -> (Handle<Self, marker::Edge>, SearchBound<&'r Q>)
where
Q: ?Sized + Ord,
K: Borrow<Q>,
Q: ?Sized,
K: Comparable<Q>,
{
let (edge_idx, bound) = self.find_lower_bound_index(bound);
let edge = unsafe { Handle::new_edge(self, edge_idx) };
Expand All @@ -175,8 +174,8 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Lea
bound: SearchBound<&'r Q>,
) -> (Handle<Self, marker::Edge>, SearchBound<&'r Q>)
where
Q: ?Sized + Ord,
K: Borrow<Q>,
Q: ?Sized,
K: Comparable<Q>,
{
let (edge_idx, bound) = unsafe { self.find_upper_bound_index(bound, 0) };
let edge = unsafe { Handle::new_edge(self, edge_idx) };
Expand All @@ -197,8 +196,7 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
key: &Q,
) -> SearchResult<BorrowType, K, V, Type, Type>
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
{
match unsafe { self.find_key_index(key, 0) } {
IndexResult::KV(idx) => Found(unsafe { Handle::new_kv(self, idx) }),
Expand All @@ -216,17 +214,16 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
/// `start_index` must be a valid edge index for the node.
unsafe fn find_key_index<Q: ?Sized>(&self, key: &Q, start_index: usize) -> IndexResult
where
Q: Ord,
K: Borrow<Q>,
K: Comparable<Q>,
{
let node = self.reborrow();
let keys = node.keys();
debug_assert!(start_index <= keys.len());
for (offset, k) in unsafe { keys.get_unchecked(start_index..) }.iter().enumerate() {
match key.cmp(k.borrow()) {
Ordering::Greater => {}
match k.compare(key) {
Ordering::Less => {}
Ordering::Equal => return IndexResult::KV(start_index + offset),
Ordering::Less => return IndexResult::Edge(start_index + offset),
Ordering::Greater => return IndexResult::Edge(start_index + offset),
}
}
IndexResult::Edge(keys.len())
Expand All @@ -242,8 +239,8 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
bound: SearchBound<&'r Q>,
) -> (usize, SearchBound<&'r Q>)
where
Q: ?Sized + Ord,
K: Borrow<Q>,
Q: ?Sized,
K: Comparable<Q>,
{
match bound {
Included(key) => match unsafe { self.find_key_index(key, 0) } {
Expand All @@ -270,8 +267,8 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
start_index: usize,
) -> (usize, SearchBound<&'r Q>)
where
Q: ?Sized + Ord,
K: Borrow<Q>,
Q: ?Sized,
K: Comparable<Q>,
{
match bound {
Included(key) => match unsafe { self.find_key_index(key, start_index) } {
Expand Down
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