Struct Map

pub struct Map<K: Ord + Clone, V: Clone, const SIZE: usize>(/* private fields */);

This Map uses a similar strategy to BTreeMap to ensure cache efficient performance on modern hardware while still providing log(N) get, insert, and remove operations.

For good performance, it is very important to understand that clone is a fundamental operation, it needs to be fast for your key and data types, because it’s going to be called a lot whenever you change the map.

Why

1. Multiple threads can read this structure even while one thread is updating it. Using a library like arc_swap you can avoid ever blocking readers.

2. Snapshotting this structure is free.

Examples

use alloc::string::String;
use self::immutable_chunkmap::map::MapM;

let m =
   MapM::new()
   .insert(String::from("1"), 1).0
   .insert(String::from("2"), 2).0
   .insert(String::from("3"), 3).0;

assert_eq!(m.get("1"), Option::Some(&1));
assert_eq!(m.get("2"), Option::Some(&2));
assert_eq!(m.get("3"), Option::Some(&3));
assert_eq!(m.get("4"), Option::None);

for (k, v) in &m {
  println!("key {}, val: {}", k, v)
}

Implementations

impl<K, V, const SIZE: usize> Map<K, V, SIZE>

where K: Ord + Clone, V: Clone,

pub fn new() -> Self

Create a new empty map

pub fn downgrade(&self) -> WeakMapRef<K, V, SIZE>

Create a weak reference to this map

pub fn strong_count(&self) -> usize

Return the number of strong references to this map (see Arc)

pub fn weak_count(&self) -> usize

Return the number of weak references to this map (see Arc)

pub fn insert_many<E: IntoIterator<Item = (K, V)>>(&self, elts: E) -> Self

This will insert many elements at once, and is potentially a lot faster than inserting one by one, especially if the data is sorted. It is just a wrapper around the more general update_many method.

#Examples

 use self::immutable_chunkmap::map::MapM;

 let mut v = vec![(1, 3), (10, 1), (-12, 2), (44, 0), (50, -1)];
 v.sort_unstable_by_key(|&(k, _)| k);

 let m = MapM::new().insert_many(v.iter().map(|(k, v)| (*k, *v)));

 for (k, v) in &v {
   assert_eq!(m.get(k), Option::Some(v))
 }

pub fn remove_many<Q, E>(&self, elts: E) -> Self

where E: IntoIterator<Item = Q>, Q: Ord, K: Borrow<Q>,

This will remove many elements at once, and is potentially a lot faster than removing elements one by one, especially if the data is sorted. It is just a wrapper around the more general update_many method.

pub fn update_many<Q, D, E, F>(&self, elts: E, f: F) -> Self

where E: IntoIterator<Item = (Q, D)>, Q: Ord, K: Borrow<Q>, F: FnMut(Q, D, Option<(&K, &V)>) -> Option<(K, V)>,

This method updates multiple bindings in one call. Given an iterator of an arbitrary type (Q, D), where Q is any borrowed form of K, an update function taking Q, D, the current binding in the map, if any, and producing the new binding, if any, this method will produce a new map with updated bindings of many elements at once. It will skip intermediate node allocations where possible. If the data in elts is sorted, it will be able to skip many more intermediate allocations, and can produce a speedup of about 10x compared to inserting/updating one by one. In any case it should always be faster than inserting elements one by one, even with random unsorted keys.

#Examples

use core::iter::FromIterator;
use self::immutable_chunkmap::map::MapM;

let m = MapM::from_iter((0..4).map(|k| (k, k)));
let m = m.update_many(
    (0..4).map(|x| (x, ())),
    |k, (), cur| cur.map(|(_, c)| (k, c + 1))
);
assert_eq!(
    m.into_iter().map(|(k, v)| (*k, *v)).collect::<Vec<_>>(),
    vec![(0, 1), (1, 2), (2, 3), (3, 4)]
);

pub fn insert(&self, k: K, v: V) -> (Self, Option<V>)

return a new map with (k, v) inserted into it. If k already exists in the old map, the old binding will be returned, and the new map will contain the new binding. In fact this method is just a wrapper around update.

pub fn insert_cow(&mut self, k: K, v: V) -> Option<V>

insert in place using copy on write semantics if self is not a unique reference to the map. see update_cow.

pub fn update<Q, D, F>(&self, q: Q, d: D, f: F) -> (Self, Option<V>)

where Q: Ord, K: Borrow<Q>, F: FnMut(Q, D, Option<(&K, &V)>) -> Option<(K, V)>,

return a new map with the binding for q, which can be any borrowed form of k, updated to the result of f. If f returns None, the binding will be removed from the new map, otherwise it will be inserted. This function is more efficient than calling get and then insert, since it makes only one tree traversal instead of two. This method runs in log(N) time and space where N is the size of the map.

Examples

use self::immutable_chunkmap::map::MapM;

let (m, _) = MapM::new().update(0, 0, |k, d, _| Some((k, d)));
let (m, _) = m.update(1, 1, |k, d, _| Some((k, d)));
let (m, _) = m.update(2, 2, |k, d, _| Some((k, d)));
assert_eq!(m.get(&0), Some(&0));
assert_eq!(m.get(&1), Some(&1));
assert_eq!(m.get(&2), Some(&2));

let (m, _) = m.update(0, (), |k, (), v| v.map(move |(_, v)| (k, v + 1)));
assert_eq!(m.get(&0), Some(&1));
assert_eq!(m.get(&1), Some(&1));
assert_eq!(m.get(&2), Some(&2));

let (m, _) = m.update(1, (), |_, (), _| None);
assert_eq!(m.get(&0), Some(&1));
assert_eq!(m.get(&1), None);
assert_eq!(m.get(&2), Some(&2));

pub fn update_cow<Q, D, F>(&mut self, q: Q, d: D, f: F) -> Option<V>

where Q: Ord, K: Borrow<Q>, F: FnMut(Q, D, Option<(&K, &V)>) -> Option<(K, V)>,

Perform a copy on write update to the map. In the case that self is a unique reference to the map, then the update will be performed completly in place. self will be mutated, and no previous version will be available. In the case that self has a clone, or clones, then only the parts of the map that need to be mutated will be copied before the update is performed. self will reference the mutated copy, and previous versions of the map will not be modified. self will still share all the parts of the map that did not need to be mutated with any pre existing clones.

COW semantics are a flexible middle way between full peristance and full mutability. Needless to say in the case where you have a unique reference to the map, using update_cow is a lot faster than using update, and a lot more flexible than update_many.

Other than copy on write the semanics of this method are identical to those of update.

#Examples

 use self::immutable_chunkmap::map::MapM;

 let mut m = MapM::new().update(0, 0, |k, d, _| Some((k, d))).0;
 let orig = m.clone();
 m.update_cow(1, 1, |k, d, _| Some((k, d))); // copies the original chunk
 m.update_cow(2, 2, |k, d, _| Some((k, d))); // doesn't copy anything
 assert_eq!(m.len(), 3);
 assert_eq!(orig.len(), 1);
 assert_eq!(m.get(&0), Some(&0));
 assert_eq!(m.get(&1), Some(&1));
 assert_eq!(m.get(&2), Some(&2));
 assert_eq!(orig.get(&0), Some(&0));
 assert_eq!(orig.get(&1), None);
 assert_eq!(orig.get(&2), None);

pub fn union<F>(&self, other: &Map<K, V, SIZE>, f: F) -> Self

where F: FnMut(&K, &V, &V) -> Option<V>,

Merge two maps together. Bindings that exist in both maps will be passed to f, which may elect to remove the binding by returning None. This function runs in O(log(n) + m) time and space, where n is the size of the largest map, and m is the number of intersecting chunks. It will never be slower than calling update_many on the first map with an iterator over the second, and will be significantly faster if the intersection is minimal or empty.

Examples

use core::iter::FromIterator;
use self::immutable_chunkmap::map::MapM;

let m0 = MapM::from_iter((0..10).map(|k| (k, 1)));
let m1 = MapM::from_iter((10..20).map(|k| (k, 1)));
let m2 = m0.union(&m1, |_k, _v0, _v1| panic!("no intersection expected"));

for i in 0..20 {
    assert!(m2.get(&i).is_some())
}

let m3 = MapM::from_iter((5..9).map(|k| (k, 1)));
let m4 = m3.union(&m2, |_k, v0, v1| Some(v0 + v1));

for i in 0..20 {
   assert!(
       *m4.get(&i).unwrap() ==
       *m3.get(&i).unwrap_or(&0) + *m2.get(&i).unwrap_or(&0)
   )
}

pub fn intersect<F>(&self, other: &Map<K, V, SIZE>, f: F) -> Self

where F: FnMut(&K, &V, &V) -> Option<V>,

Produce a map containing the mapping over F of the intersection (by key) of two maps. The function f runs on each intersecting element, and has the option to omit elements from the intersection by returning None, or change the value any way it likes. Runs in O(log(N) + M) time and space where N is the size of the smallest map, and M is the number of intersecting chunks.

Examples

 use core::iter::FromIterator;
 use self::immutable_chunkmap::map::MapM;

 let m0 = MapM::from_iter((0..100000).map(|k| (k, 1)));
 let m1 = MapM::from_iter((50..30000).map(|k| (k, 1)));
 let m2 = m0.intersect(&m1, |_k, v0, v1| Some(v0 + v1));

 for i in 0..100000 {
     if i >= 30000 || i < 50 {
         assert!(m2.get(&i).is_none());
     } else {
         assert!(*m2.get(&i).unwrap() == 2);
     }
 }

pub fn diff<F>(&self, other: &Map<K, V, SIZE>, f: F) -> Self

where F: FnMut(&K, &V, &V) -> Option<V>, K: Debug, V: Debug,

Produce a map containing the second map subtracted from the first. The function F is called for each intersecting element, and ultimately decides whether it appears in the result, for example, to compute a classical set diff, the function should always return None.

Examples

 use core::iter::FromIterator;
 use self::immutable_chunkmap::map::MapM;

 let m0 = MapM::from_iter((0..10000).map(|k| (k, 1)));
 let m1 = MapM::from_iter((50..3000).map(|k| (k, 1)));
 let m2 = m0.diff(&m1, |_k, _v0, _v1| None);

 m2.invariant();
 dbg!(m2.len());
 assert!(m2.len() == 10000 - 2950);
 for i in 0..10000 {
     if i >= 3000 || i < 50 {
         assert!(*m2.get(&i).unwrap() == 1);
     } else {
         assert!(m2.get(&i).is_none());
     }
 }

pub fn get<'a, Q: ?Sized + Ord>(&'a self, k: &Q) -> Option<&'a V>

where K: Borrow<Q>,

lookup the mapping for k. If it doesn’t exist return None. Runs in log(N) time and constant space. where N is the size of the map.

pub fn get_key<'a, Q: ?Sized + Ord>(&'a self, k: &Q) -> Option<&'a K>

where K: Borrow<Q>,

lookup the mapping for k. Return the key. If it doesn’t exist return None. Runs in log(N) time and constant space. where N is the size of the map.

pub fn get_full<'a, Q: ?Sized + Ord>(&'a self, k: &Q) -> Option<(&'a K, &'a V)>

where K: Borrow<Q>,

lookup the mapping for k. Return both the key and the value. If it doesn’t exist return None. Runs in log(N) time and constant space. where N is the size of the map.

pub fn get_mut_cow<'a, Q: ?Sized + Ord>( &'a mut self, k: &Q, ) -> Option<&'a mut V>

where K: Borrow<Q>,

Get a mutable reference to the value mapped to k using copy on write semantics. This works as Arc::make_mut, it will only clone the parts of the tree that are,

• required to reach k
• have a strong count > 1

This operation is also triggered by mut indexing on the map, e.g. &mut m[k] calls get_mut_cow on m

Example

use core::iter::FromIterator;
use self::immutable_chunkmap::map::MapM as Map;
  
let mut m = Map::from_iter((0..100).map(|k| (k, Map::from_iter((0..100).map(|k| (k, 1))))));
let orig = m.clone();

if let Some(inner) = m.get_mut_cow(&0) {
    if let Some(v) = inner.get_mut_cow(&0) {
        *v += 1
    }
}

assert_eq!(m.get(&0).and_then(|m| m.get(&0)), Some(&2));
assert_eq!(orig.get(&0).and_then(|m| m.get(&0)), Some(&1));

pub fn get_or_insert_cow<'a, F>(&'a mut self, k: K, f: F) -> &'a mut V

where F: FnOnce() -> V,

Same as get_mut_cow except if the value is not in the map it will first be inserted by calling f

pub fn remove<Q: Sized + Ord>(&self, k: &Q) -> (Self, Option<V>)

where K: Borrow<Q>,

return a new map with the mapping under k removed. If the binding existed in the old map return it. Runs in log(N) time and log(N) space, where N is the size of the map.

pub fn remove_cow<Q: Sized + Ord>(&mut self, k: &Q) -> Option<V>

where K: Borrow<Q>,

remove in place using copy on write semantics if self is not a unique reference to the map. see update_cow.

pub fn len(&self) -> usize

get the number of elements in the map O(1) time and space

pub fn range<'a, Q, R>(&'a self, r: R) -> Iter<'a, R, Q, K, V, SIZE>

where Q: Ord + ?Sized + 'a, K: Borrow<Q>, R: RangeBounds<Q> + 'a,

return an iterator over the subset of elements in the map that are within the specified range.

The returned iterator runs in O(log(N) + M) time, and constant space. N is the number of elements in the tree, and M is the number of elements you examine.

if lbound >= ubound the returned iterator will be empty

pub fn range_mut_cow<'a, Q, R>( &'a mut self, r: R, ) -> IterMut<'a, R, Q, K, V, SIZE>

where Q: Ord + ?Sized + 'a, K: Borrow<Q>, R: RangeBounds<Q> + 'a,

return a mutable iterator over the subset of elements in the map that are within the specified range. The iterator will copy on write the part of the tree that it visits, specifically it will be as if you ran get_mut_cow on every element you visit.

The returned iterator runs in O(log(N) + M) time, and constant space. N is the number of elements in the tree, and M is the number of elements you examine.

if lbound >= ubound the returned iterator will be empty

pub fn iter_mut_cow<'a>(&'a mut self) -> IterMut<'a, RangeFull, K, K, V, SIZE>

return a mutable iterator over the entire map. The iterator will copy on write every element in the tree, specifically it will be as if you ran get_mut_cow on every element.

The returned iterator runs in O(log(N) + M) time, and constant space. N is the number of elements in the tree, and M is the number of elements you examine.

impl<K, V, const SIZE: usize> Map<K, V, SIZE>

where K: Ord + Clone, V: Clone + Default,

pub fn get_or_default_cow<'a>(&'a mut self, k: K) -> &'a mut V

Same as get_mut_cow except if the value isn’t in the map it will be added by calling V::default

impl<K, V, const SIZE: usize> Map<K, V, SIZE>

where K: Ord + Clone + Debug, V: Clone + Debug,

pub fn invariant(&self)

Trait Implementations

impl<K: Clone + Ord + Clone, V: Clone + Clone, const SIZE: usize> Clone for Map<K, V, SIZE>

fn clone(&self) -> Map<K, V, SIZE>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<K, V, const SIZE: usize> Debug for Map<K, V, SIZE>

where K: Debug + Ord + Clone, V: Debug + Clone,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<K, V, const SIZE: usize> Default for Map<K, V, SIZE>

where K: Ord + Clone, V: Clone,

fn default() -> Map<K, V, SIZE>

Returns the “default value” for a type.

impl<K, V, const SIZE: usize> FromIterator<(K, V)> for Map<K, V, SIZE>

where K: Ord + Clone, V: Clone,

fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self

Creates a value from an iterator.

impl<K, V, const SIZE: usize> Hash for Map<K, V, SIZE>

where K: Hash + Ord + Clone, V: Hash + Clone,

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'a, Q, K, V, const SIZE: usize> Index<&'a Q> for Map<K, V, SIZE>

where Q: Ord, K: Ord + Clone + Borrow<Q>, V: Clone,

type Output = V

The returned type after indexing.

fn index(&self, k: &Q) -> &V

Performs the indexing (container[index]) operation.

impl<'a, Q, K, V, const SIZE: usize> IndexMut<&'a Q> for Map<K, V, SIZE>

where Q: Ord, K: Ord + Clone + Borrow<Q>, V: Clone,

fn index_mut(&mut self, k: &'a Q) -> &mut Self::Output

Performs the mutable indexing (container[index]) operation.

impl<'a, K, V, const SIZE: usize> IntoIterator for &'a Map<K, V, SIZE>

where K: 'a + Ord + Clone, V: 'a + Clone,

type Item = (&'a K, &'a V)

The type of the elements being iterated over.

type IntoIter = Iter<'a, RangeFull, K, K, V, SIZE>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<K, V, const SIZE: usize> Ord for Map<K, V, SIZE>

where K: Ord + Clone, V: Ord + Clone,

fn cmp(&self, other: &Map<K, V, SIZE>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<K, V, const SIZE: usize> PartialEq for Map<K, V, SIZE>

where K: PartialEq + Ord + Clone, V: PartialEq + Clone,

fn eq(&self, other: &Map<K, V, SIZE>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<K, V, const SIZE: usize> PartialOrd for Map<K, V, SIZE>

where K: Ord + Clone, V: PartialOrd + Clone,

fn partial_cmp(&self, other: &Map<K, V, SIZE>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<K, V, const SIZE: usize> Eq for Map<K, V, SIZE>

where K: Eq + Ord + Clone, V: Eq + Clone,