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Auto merge of #3028 - ttsugriy:range-map-find-offset, r=RalfJung

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Replace hand-written binary search with Vec::binary_search_by.

It's similar to https://github.com/rust-lang/miri/pull/3021 and should improve maintainability.
This commit is contained in:
bors 2023-08-16 07:26:49 +00:00
commit edc6fc12e3
1 changed files with 15 additions and 20 deletions
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35
src/tools/miri/src/range_map.rs
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@ -36,26 +36,21 @@ pub fn new(size: Size, init: T) -> RangeMap<T> {
/// Finds the index containing the given offset.
fn find_offset(&self, offset: u64) -> usize {
// We do a binary search.
let mut left = 0usize; // inclusive
let mut right = self.v.len(); // exclusive
loop {
debug_assert!(left < right, "find_offset: offset {offset} is out-of-bounds");
let candidate = left.checked_add(right).unwrap() / 2;
let elem = &self.v[candidate];
if offset < elem.range.start {
// We are too far right (offset is further left).
debug_assert!(candidate < right); // we are making progress
right = candidate;
} else if offset >= elem.range.end {
// We are too far left (offset is further right).
debug_assert!(candidate >= left); // we are making progress
left = candidate + 1;
} else {
// This is it!
return candidate;
}
}
self.v
.binary_search_by(|elem| -> std::cmp::Ordering {
if offset < elem.range.start {
// We are too far right (offset is further left).
// (`Greater` means that `elem` is greater than the desired target.)
std::cmp::Ordering::Greater
} else if offset >= elem.range.end {
// We are too far left (offset is further right).
std::cmp::Ordering::Less
} else {
// This is it!
std::cmp::Ordering::Equal
}
})
.unwrap()
}
/// Provides read-only iteration over everything in the given range. This does