use std::iter::{Chain, FromIterator}; use std::ops::RangeInclusive; use roaring::bitmap::{IntoIter, RoaringBitmap}; pub struct AvailableDocumentsIds { iter: Chain>, } impl AvailableDocumentsIds { pub fn from_documents_ids(docids: &RoaringBitmap) -> AvailableDocumentsIds { match docids.max() { Some(last_id) => { let mut available = RoaringBitmap::from_iter(0..last_id); available -= docids; let iter = match last_id.checked_add(1) { Some(id) => id..=u32::max_value(), None => 1..=0, // empty range iterator }; AvailableDocumentsIds { iter: available.into_iter().chain(iter) } } None => { let empty = RoaringBitmap::new().into_iter(); AvailableDocumentsIds { iter: empty.chain(0..=u32::max_value()) } } } } } impl Iterator for AvailableDocumentsIds { type Item = u32; fn next(&mut self) -> Option { self.iter.next() } } #[cfg(test)] mod tests { use super::*; #[test] fn empty() { let base = RoaringBitmap::new(); let left = AvailableDocumentsIds::from_documents_ids(&base); let right = 0..=u32::max_value(); left.zip(right).take(500).for_each(|(l, r)| assert_eq!(l, r)); } #[test] fn scattered() { let mut base = RoaringBitmap::new(); base.insert(0); base.insert(10); base.insert(100); base.insert(405); let left = AvailableDocumentsIds::from_documents_ids(&base); let right = (0..=u32::max_value()).filter(|&n| n != 0 && n != 10 && n != 100 && n != 405); left.zip(right).take(500).for_each(|(l, r)| assert_eq!(l, r)); } }