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BTreeMap: lightly refactor range_search #81331

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BTreeMap: lightly refactor range_search #81331

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62 changes: 38 additions & 24 deletions library/alloc/src/collections/btree/navigate.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
use core::borrow::Borrow;
use core::cmp::Ordering;
use core::ops::Bound::{Excluded, Included, Unbounded};
use core::ops::RangeBounds;
use core::ops::{Bound, RangeBounds};
use core::ptr;

use super::node::{marker, ForceResult::*, Handle, NodeRef};
Expand Down Expand Up @@ -31,61 +30,76 @@ where
let start = range.start_bound();
let end = range.end_bound();
match (start, end) {
(Excluded(s), Excluded(e)) if s == e => {
(Bound::Excluded(s), Bound::Excluded(e)) if s == e => {
panic!("range start and end are equal and excluded in BTreeMap")
}
(Included(s) | Excluded(s), Included(e) | Excluded(e)) if s > e => {
(Bound::Included(s) | Bound::Excluded(s), Bound::Included(e) | Bound::Excluded(e))
if s > e =>
{
panic!("range start is greater than range end in BTreeMap")
}
_ => {}
};

enum FullBound<T> {
FullyIncluded,
Included(T),
Excluded(T),
FullyExcluded,
}
use FullBound::*;
impl<T> FullBound<T> {
fn from(ops_bound: Bound<T>) -> Self {
match ops_bound {
Bound::Included(t) => Included(t),
Bound::Excluded(t) => Excluded(t),
Bound::Unbounded => FullyIncluded,
}
}
}

let mut min_node = root1;
let mut max_node = root2;
let mut min_found = false;
let mut max_found = false;
let mut min_bound = FullBound::from(start);
let mut max_bound = FullBound::from(end);

loop {
// Using `range` again would be unsound (#81138)
let front = match (min_found, start) {
(false, Included(key)) => match min_node.search_node(key) {
let front = match min_bound {
Included(key) => match min_node.search_node(key) {
SearchResult::Found(kv) => {
min_found = true;
min_bound = FullyExcluded;
kv.left_edge()
}
SearchResult::GoDown(edge) => edge,
},
(false, Excluded(key)) => match min_node.search_node(key) {
Excluded(key) => match min_node.search_node(key) {
SearchResult::Found(kv) => {
min_found = true;
min_bound = FullyIncluded;
kv.right_edge()
}
SearchResult::GoDown(edge) => edge,
},
(true, Included(_)) => min_node.last_edge(),
(true, Excluded(_)) => min_node.first_edge(),
(_, Unbounded) => min_node.first_edge(),
FullyExcluded => min_node.last_edge(),
FullyIncluded => min_node.first_edge(),
};

// Using `range` again would be unsound (#81138)
let back = match (max_found, end) {
(false, Included(key)) => match max_node.search_node(key) {
let back = match max_bound {
Included(key) => match max_node.search_node(key) {
SearchResult::Found(kv) => {
max_found = true;
max_bound = FullyExcluded;
kv.right_edge()
}
SearchResult::GoDown(edge) => edge,
},
(false, Excluded(key)) => match max_node.search_node(key) {
Excluded(key) => match max_node.search_node(key) {
SearchResult::Found(kv) => {
max_found = true;
max_bound = FullyIncluded;
kv.left_edge()
}
SearchResult::GoDown(edge) => edge,
},
(true, Included(_)) => max_node.first_edge(),
(true, Excluded(_)) => max_node.last_edge(),
(_, Unbounded) => max_node.last_edge(),
FullyExcluded => max_node.first_edge(),
FullyIncluded => max_node.last_edge(),
};

if front.partial_cmp(&back) == Some(Ordering::Greater) {
Expand Down