rust/protover: add ProtoSet::and_not_in()

This is a way more efficient version of retain().
This commit is contained in:
cypherpunks 2018-08-09 21:25:18 +00:00
parent 281854bab7
commit 578f7326ed

View File

@ -4,6 +4,8 @@
//! Sets for lazily storing ordered, non-overlapping ranges of integers.
use std::cmp;
use std::iter;
use std::slice;
use std::str::FromStr;
use std::u32;
@ -269,6 +271,57 @@ impl ProtoSet {
expanded.retain(f);
*self = expanded.into();
}
/// Returns all the `Version`s in `self` which are not also in the `other`
/// `ProtoSet`.
///
/// # Examples
///
/// ```
/// # use protover::errors::ProtoverError;
/// use protover::protoset::ProtoSet;
///
/// # fn do_test() -> Result<bool, ProtoverError> {
/// let protoset: ProtoSet = "1,3-6,10-12,15-16".parse()?;
/// let other: ProtoSet = "2,5-7,9-11,14-20".parse()?;
///
/// let subset: ProtoSet = protoset.and_not_in(&other);
///
/// assert_eq!(subset.expand(), vec![1, 3, 4, 12]);
/// #
/// # Ok(true)
/// # }
/// # fn main() { do_test(); } // wrap the test so we can use the ? operator
/// ```
pub fn and_not_in(&self, other: &Self) -> Self {
if self.is_empty() || other.is_empty() {
return self.clone();
}
let pairs = self.iter().flat_map(|&(lo, hi)| {
let the_end = (hi + 1, hi + 1); // special case to mark the end of the range.
let excluded_ranges = other
.iter()
.cloned() // have to be owned tuples, to match iter::once(the_end).
.skip_while(move|&(_, hi2)| hi2 < lo) // skip the non-overlapping ranges.
.take_while(move|&(lo2, _)| lo2 <= hi) // take all the overlapping ones.
.chain(iter::once(the_end));
let mut nextlo = lo;
excluded_ranges.filter_map(move |(excluded_lo, excluded_hi)| {
let pair = if nextlo < excluded_lo {
Some((nextlo, excluded_lo - 1))
} else {
None
};
nextlo = cmp::min(excluded_hi, u32::MAX - 1) + 1;
pair
})
});
let pairs = pairs.collect();
ProtoSet::is_ok(ProtoSet{ pairs }).expect("should be already sorted")
}
}
impl FromStr for ProtoSet {