diff --git a/src/range.rs b/src/range.rs index be7ff250..91933e61 100644 --- a/src/range.rs +++ b/src/range.rs @@ -51,6 +51,7 @@ //! If we do not see practical bugs, or we get a formal proof that the code cannot lead to error states, then we may remove this warning. use crate::{internal::small_vec::SmallVec, version_set::VersionSet}; +use std::cmp::Ordering; use std::ops::RangeBounds; use std::{ fmt::{Debug, Display, Formatter}, @@ -202,23 +203,37 @@ impl Range { /// Returns true if the this Range contains the specified value. pub fn contains(&self, v: &V) -> bool { for segment in self.segments.iter() { - if match segment { - (Unbounded, Unbounded) => true, - (Unbounded, Included(end)) => v <= end, - (Unbounded, Excluded(end)) => v < end, - (Included(start), Unbounded) => v >= start, - (Included(start), Included(end)) => v >= start && v <= end, - (Included(start), Excluded(end)) => v >= start && v < end, - (Excluded(start), Unbounded) => v > start, - (Excluded(start), Included(end)) => v > start && v <= end, - (Excluded(start), Excluded(end)) => v > start && v < end, - } { - return true; + match within_bounds(v, segment) { + Ordering::Less => return false, + Ordering::Equal => return true, + Ordering::Greater => (), } } false } + /// Returns true if the this Range contains the specified values. + /// + /// The `versions` iterator must be sorted. + /// Functionally equivalent to `versions.map(|v| self.contains(v))`. + /// Except it runs in `O(size_of_range + len_of_versions)` not `O(size_of_range * len_of_versions)` + pub fn contains_many<'s, I>(&'s self, versions: I) -> impl Iterator + 's + where + I: Iterator + 's, + V: 's, + { + versions.scan(0, move |i, v| { + while let Some(segment) = self.segments.get(*i) { + match within_bounds(v, segment) { + Ordering::Less => return Some(false), + Ordering::Equal => return Some(true), + Ordering::Greater => *i += 1, + } + } + Some(false) + }) + } + /// Construct a simple range from anything that impls [RangeBounds] like `v1..v2`. pub fn from_range_bounds(bounds: R) -> Self where @@ -264,6 +279,26 @@ impl Range { } } +fn within_bounds(v: &V, segment: &Interval) -> Ordering { + let below_lower_bound = match segment { + (Excluded(start), _) => v <= start, + (Included(start), _) => v < start, + (Unbounded, _) => false, + }; + if below_lower_bound { + return Ordering::Less; + } + let below_upper_bound = match segment { + (_, Unbounded) => true, + (_, Included(end)) => v <= end, + (_, Excluded(end)) => v < end, + }; + if below_upper_bound { + return Ordering::Equal; + } + Ordering::Greater +} + fn valid_segment(start: &Bound, end: &Bound) -> bool { match (start, end) { (Included(s), Included(e)) => s <= e, @@ -274,6 +309,36 @@ fn valid_segment(start: &Bound, end: &Bound) -> bool { } } +/// Group adjacent versions locations. +/// +/// ```text +/// [None, 3, 6, 7, None] -> [(3, 7)] +/// [3, 6, 7, None] -> [(None, 7)] +/// [3, 6, 7] -> [(None, None)] +/// [None, 1, 4, 7, None, None, None, 8, None, 9] -> [(1, 7), (8, 8), (9, None)] +/// ``` +fn group_adjacent_locations( + mut locations: impl Iterator>, +) -> impl Iterator, Option)> { + // If the first version matched, then the lower bound of that segment is not needed + let mut seg = locations.next().flatten().map(|ver| (None, Some(ver))); + std::iter::from_fn(move || { + for ver in locations.by_ref() { + if let Some(ver) = ver { + // As long as were still matching versions, we keep merging into the currently matching segment + seg = Some((seg.map_or(Some(ver), |(s, _)| s), Some(ver))); + } else { + // If we have found a version that doesn't match, then right the merge segment and prepare for a new one. + if seg.is_some() { + return seg.take(); + } + } + } + // If the last version matched, then write out the merged segment but the upper bound is not needed. + seg.take().map(|(s, _)| (s, None)) + }) +} + impl Range { /// Computes the union of this `Range` and another. pub fn union(&self, other: &Self) -> Self { @@ -321,6 +386,54 @@ impl Range { Self { segments }.check_invariants() } + + /// Returns a simpler Range that contains the same versions + /// + /// For every one of the Versions provided in versions the existing range and + /// the simplified range will agree on whether it is contained. + /// The simplified version may include or exclude versions that are not in versions as the implementation wishes. + /// For example: + /// - If all the versions are contained in the original than the range will be simplified to `full`. + /// - If none of the versions are contained in the original than the range will be simplified to `empty`. + /// + /// If versions are not sorted the correctness of this function is not guaranteed. + pub fn simplify<'v, I>(&self, versions: I) -> Self + where + I: Iterator + 'v, + V: 'v, + { + // Return the segment index in the range for each version in the range, None otherwise + let version_locations = versions.scan(0, move |i, v| { + while let Some(segment) = self.segments.get(*i) { + match within_bounds(v, segment) { + Ordering::Less => return Some(None), + Ordering::Equal => return Some(Some(*i)), + Ordering::Greater => *i += 1, + } + } + Some(None) + }); + let kept_segments = group_adjacent_locations(version_locations); + self.keep_segments(kept_segments) + } + + /// Create a new range with a subset of segments at given location bounds. + /// + /// Each new segment is constructed from a pair of segments, taking the + /// start of the first and the end of the second. + fn keep_segments( + &self, + kept_segments: impl Iterator, Option)>, + ) -> Range { + let mut segments = SmallVec::Empty; + for (s, e) in kept_segments { + segments.push(( + s.map_or(Unbounded, |s| self.segments[s].0.clone()), + e.map_or(Unbounded, |e| self.segments[e].1.clone()), + )); + } + Self { segments }.check_invariants() + } } impl VersionSet for Range { @@ -600,5 +713,32 @@ pub mod tests { let rv2: Range = rv.bounding_range().map(Range::from_range_bounds::<_, u32>).unwrap_or_else(Range::empty); assert_eq!(rv, rv2); } + + #[test] + fn contains(range in strategy(), versions in proptest::collection::vec(version_strat(), ..30)) { + for v in versions { + assert_eq!(range.contains(&v), range.segments.iter().any(|s| RangeBounds::contains(s, &v))); + } + } + + #[test] + fn contains_many(range in strategy(), mut versions in proptest::collection::vec(version_strat(), ..30)) { + versions.sort(); + assert_eq!(versions.len(), range.contains_many(versions.iter()).count()); + for (a, b) in versions.iter().zip(range.contains_many(versions.iter())) { + assert_eq!(range.contains(a), b); + } + } + + #[test] + fn simplify(range in strategy(), mut versions in proptest::collection::vec(version_strat(), ..30)) { + versions.sort(); + let simp = range.simplify(versions.iter()); + + for v in versions { + assert_eq!(range.contains(&v), simp.contains(&v)); + } + assert!(simp.segments.len() <= range.segments.len()) + } } }