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Improve the Pairs Iterator type #112

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Jun 2, 2021
Merged

Improve the Pairs Iterator type #112

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fdd0d45
Introduce an enhanced version of the Pairs Iterator
Kerollmops Jun 2, 2021
39d3506
Improve the xor ops readability by using the Pairs iterator
Kerollmops Jun 2, 2021
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92 changes: 55 additions & 37 deletions src/bitmap/cmp.rs
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Original file line number Diff line number Diff line change
@@ -1,16 +1,11 @@
use std::borrow::Borrow;
use std::cmp::Ordering;
use std::iter::Peekable;
use std::slice;

use super::container::Container;
use crate::RoaringBitmap;

struct Pairs<'a>(Peekable<slice::Iter<'a, Container>>, Peekable<slice::Iter<'a, Container>>);

impl RoaringBitmap {
fn pairs<'a>(&'a self, other: &'a RoaringBitmap) -> Pairs<'a> {
Pairs(self.containers.iter().peekable(), other.containers.iter().peekable())
}

/// Returns true if the set has no elements in common with other. This is equivalent to
/// checking for an empty intersection.
///
Expand All @@ -32,9 +27,9 @@ impl RoaringBitmap {
///
/// ```
pub fn is_disjoint(&self, other: &Self) -> bool {
self.pairs(other)
.filter(|&(c1, c2)| c1.is_some() && c2.is_some())
.all(|(c1, c2)| c1.unwrap().is_disjoint(c2.unwrap()))
Pairs::new(&self.containers, &other.containers)
.filter_map(|(c1, c2)| c1.zip(c2))
.all(|(c1, c2)| c1.is_disjoint(c2))
}

/// Returns `true` if this set is a subset of `other`.
Expand All @@ -60,12 +55,10 @@ impl RoaringBitmap {
/// assert_eq!(rb1.is_subset(&rb2), false);
/// ```
pub fn is_subset(&self, other: &Self) -> bool {
for pair in self.pairs(other) {
for pair in Pairs::new(&self.containers, &other.containers) {
match pair {
(None, _) => (),
(_, None) => {
return false;
}
(_, None) => return false,
(Some(c1), Some(c2)) => {
if !c1.is_subset(c2) {
return false;
Expand Down Expand Up @@ -103,32 +96,57 @@ impl RoaringBitmap {
}
}

impl<'a> Iterator for Pairs<'a> {
type Item = (Option<&'a Container>, Option<&'a Container>);
/// An helping Iterator over pairs of containers.
///
/// Returns the smallest container according to its key
/// or both if the key is the same. It is useful when you need
/// to iterate over two containers to do operations on them.
pub struct Pairs<I, J, L, R>
where
I: Iterator<Item = L>,
J: Iterator<Item = R>,
L: Borrow<Container>,
R: Borrow<Container>,
{
left: Peekable<I>,
right: Peekable<J>,
}

impl<I, J, L, R> Pairs<I, J, L, R>
where
I: Iterator<Item = L>,
J: Iterator<Item = R>,
L: Borrow<Container>,
R: Borrow<Container>,
{
pub fn new<A, B>(left: A, right: B) -> Pairs<I, J, L, R>
where
A: IntoIterator<Item = L, IntoIter = I>,
B: IntoIterator<Item = R, IntoIter = J>,
{
Pairs { left: left.into_iter().peekable(), right: right.into_iter().peekable() }
}
}

impl<I, J, L, R> Iterator for Pairs<I, J, L, R>
where
I: Iterator<Item = L>,
J: Iterator<Item = R>,
L: Borrow<Container>,
R: Borrow<Container>,
{
type Item = (Option<L>, Option<R>);

fn next(&mut self) -> Option<Self::Item> {
enum Which {
Left,
Right,
Both,
None,
}
let which = match (self.0.peek(), self.1.peek()) {
(None, None) => Which::None,
(Some(_), None) => Which::Left,
(None, Some(_)) => Which::Right,
(Some(c1), Some(c2)) => match (c1.key, c2.key) {
(key1, key2) if key1 == key2 => Which::Both,
(key1, key2) if key1 < key2 => Which::Left,
(key1, key2) if key1 > key2 => Which::Right,
(_, _) => unreachable!(),
match (self.left.peek(), self.right.peek()) {
(None, None) => None,
(Some(_), None) => Some((self.left.next(), None)),
(None, Some(_)) => Some((None, self.right.next())),
(Some(c1), Some(c2)) => match c1.borrow().key.cmp(&c2.borrow().key) {
Ordering::Equal => Some((self.left.next(), self.right.next())),
Ordering::Less => Some((self.left.next(), None)),
Ordering::Greater => Some((None, self.right.next())),
},
};
match which {
Which::Left => Some((self.0.next(), None)),
Which::Right => Some((None, self.1.next())),
Which::Both => Some((self.0.next(), self.1.next())),
Which::None => None,
}
}
}
1 change: 1 addition & 0 deletions src/bitmap/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ mod iter;
mod ops;
mod serialization;

use self::cmp::Pairs;
pub use self::iter::IntoIter;
pub use self::iter::Iter;

Expand Down
80 changes: 19 additions & 61 deletions src/bitmap/ops.rs
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
use std::cmp::Ordering;
use std::mem;
use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Sub, SubAssign};

use retain_mut::RetainMut;

use crate::bitmap::container::Container;
use crate::bitmap::Pairs;
use crate::RoaringBitmap;

impl RoaringBitmap {
Expand Down Expand Up @@ -416,38 +416,17 @@ impl BitXor<&RoaringBitmap> for &RoaringBitmap {
impl BitXorAssign<RoaringBitmap> for RoaringBitmap {
/// A `symmetric difference` between two sets.
fn bitxor_assign(&mut self, rhs: RoaringBitmap) {
let mut left = mem::take(&mut self.containers).into_iter().peekable();
let mut right = rhs.containers.into_iter().peekable();

loop {
match (left.peek(), right.peek()) {
(None, None) => break,
(Some(_), None) => {
self.containers.extend(left);
break;
}
(None, Some(_)) => {
self.containers.extend(right);
break;
}
(Some(l), Some(r)) => match l.key.cmp(&r.key) {
Ordering::Equal => {
let mut lhs = left.next().unwrap();
let rhs = right.next().unwrap();
BitXorAssign::bitxor_assign(&mut lhs, rhs);
if lhs.len != 0 {
self.containers.push(lhs);
}
}
Ordering::Less => {
let lhs = left.next().unwrap();
for pair in Pairs::new(mem::take(&mut self.containers), rhs.containers) {
match pair {
(Some(mut lhs), Some(rhs)) => {
BitXorAssign::bitxor_assign(&mut lhs, rhs);
if lhs.len != 0 {
self.containers.push(lhs);
}
Ordering::Greater => {
let rhs = right.next().unwrap();
self.containers.push(rhs);
}
},
}
(Some(lhs), None) => self.containers.push(lhs),
(None, Some(rhs)) => self.containers.push(rhs),
(None, None) => break,
}
}
}
Expand All @@ -456,38 +435,17 @@ impl BitXorAssign<RoaringBitmap> for RoaringBitmap {
impl BitXorAssign<&RoaringBitmap> for RoaringBitmap {
/// A `symmetric difference` between two sets.
fn bitxor_assign(&mut self, rhs: &RoaringBitmap) {
let mut left = mem::take(&mut self.containers).into_iter().peekable();
let mut right = rhs.containers.iter().peekable();

loop {
match (left.peek(), right.peek()) {
(None, None) => break,
(Some(_), None) => {
self.containers.extend(left);
break;
}
(None, Some(_)) => {
self.containers.extend(right.cloned());
break;
}
(Some(l), Some(r)) => match l.key.cmp(&r.key) {
Ordering::Equal => {
let mut lhs = left.next().unwrap();
let rhs = right.next().unwrap();
BitXorAssign::bitxor_assign(&mut lhs, rhs);
if lhs.len != 0 {
self.containers.push(lhs);
}
}
Ordering::Less => {
let lhs = left.next().unwrap();
for pair in Pairs::new(mem::take(&mut self.containers), &rhs.containers) {
match pair {
(Some(mut lhs), Some(rhs)) => {
BitXorAssign::bitxor_assign(&mut lhs, rhs);
if lhs.len != 0 {
self.containers.push(lhs);
}
Ordering::Greater => {
let rhs = right.next().unwrap();
self.containers.push(rhs.clone());
}
},
}
(Some(lhs), None) => self.containers.push(lhs),
(None, Some(rhs)) => self.containers.push(rhs.clone()),
(None, None) => break,
}
}
}
Expand Down