histogram

Added

• QuantilesResult::into_entries() — consumes the result and returns the quantile-to-bucket BTreeMap by value, allowing iterator transformations without borrowing from the original result.

Added

• Midpoint-based mean() on the borrowed CumulativeROHistogramRef / CumulativeROHistogram32Ref views. The mean is stored on the view (computed once at construction, or carried over from the owned histogram's cached value), so mean() is a cheap field access exposed just like count() — no per-call streaming computation — letting a zero-alloc reducer fold it in directly. Returns None for an empty histogram.

Changed

• CumulativeROHistogramRef / CumulativeROHistogram32Ref no longer implement Eq (they now carry an f64 mean); PartialEq is retained.

Added

• CumulativeROHistogramRef<'a> / CumulativeROHistogram32Ref<'a> and SparseHistogramRef<'a> / SparseHistogram32Ref<'a> — borrowed views over histogram storage that mirror the read-only API surface of the owned types. Lets columnar consumers compute quantiles directly off &[u32] slices without per-snapshot allocation or revalidation.
• from_parts_unchecked constructor on each ref type for hot-path use where invariants are already known to hold; from_parts validates as before.
• as_ref() on CumulativeROHistogram* and SparseHistogram* returning the matching ref view; From<&Owned> for OwnedRef<'_> for trait-based conversion.
• SampleQuantiles impl on each ref type.

Added

• Histogram32, AtomicHistogram32, SparseHistogram32, and CumulativeROHistogram32 — u32-counter sibling types for all four histogram variants, generated from shared declarative macros
• Sealed Count and AtomicCount traits abstracting the bucket counter width (implemented for u32/u64 and their atomic counterparts)
• Cross-width widening From conversions (u32 → u64) for all four histogram families
• Cross-width narrowing TryFrom conversions (u64 → u32) for Histogram, SparseHistogram, and CumulativeROHistogram
• Cross-variant + narrowing TryFrom paths for the snapshot pipeline: Histogram → CumulativeROHistogram32, Histogram → SparseHistogram32, and SparseHistogram → CumulativeROHistogram32
• u32 benchmark cases for Histogram and AtomicHistogram
• rezolus_memory example comparing Histogram, SparseHistogram, and CumulativeROHistogram memory footprints from Rezolus parquet recordings
• README "Counter Width" and "Recommended Pipeline" sections, with matching rustdoc in lib.rs

Changed

• CumulativeROHistogram cache-line threshold for linear-vs-binary search is now count-type-dependent (64 / size_of::<C>()); total_count and individual_count continue to return u64

Added

• CumulativeROHistogram, a read-only histogram variant with cumulative (prefix-sum) counts that enables O(log n) quantile lookups via binary search (with a linear-scan fallback for cache-line-sized data)
• From<&Histogram> and From<&SparseHistogram> conversions for constructing a CumulativeROHistogram
• Quantile range query methods on CumulativeROHistogram for analytics use cases

Added

• SampleQuantiles trait with quantiles() and quantile() methods, implemented for both Histogram and SparseHistogram
• QuantilesResult struct returning a BTreeMap<Quantile, Bucket> with total_count, min, and max bucket metadata
• Quantile newtype wrapping validated f64 in 0.0..=1.0, implementing Ord/Eq for use as a BTreeMap key
• Error::InvalidQuantile variant for quantile validation errors

Deprecated

• Histogram::percentiles() and Histogram::percentile() — use SampleQuantiles trait methods instead
• SparseHistogram::percentiles() and SparseHistogram::percentile() — use SampleQuantiles trait methods instead
• Error::InvalidPercentile — use Error::InvalidQuantile instead

First release with changelog.