Struct LWWMap 

pub struct LWWMap<K: Ord + Clone, V: Clone> { /* private fields */ }

A last-writer-wins map (LWW-Map).

Each key maps to a value with a HybridTimestamp. Concurrent writes to the same key resolve by keeping the value with the highest timestamp. Keys can be removed; a remove is stored as a tombstone with a timestamp so that stale puts don’t resurrect deleted keys.

Example

use crdt_kit::prelude::*;
use crdt_kit::clock::HybridTimestamp;

let ts = |ms, node| HybridTimestamp { physical: ms, logical: 0, node_id: node };

let mut m1 = LWWMap::new();
m1.insert("color", "red", ts(100, 1));

let mut m2 = LWWMap::new();
m2.insert("color", "blue", ts(200, 2));

m1.merge(&m2);
assert_eq!(m1.get(&"color"), Some(&"blue")); // later timestamp wins

Implementations

impl<K: Ord + Clone, V: Clone> LWWMap<K, V>

pub fn new() -> Self

Create a new empty LWW-Map.

pub fn insert(&mut self, key: K, value: V, timestamp: HybridTimestamp)

Insert or update a key-value pair with the given timestamp.

If the key already exists with a newer or equal timestamp, this is a no-op.

pub fn remove(&mut self, key: &K, timestamp: HybridTimestamp) -> bool

Remove a key with the given timestamp.

The removal only takes effect if its timestamp is greater than the current entry’s timestamp. Returns true if the key was removed.

pub fn get(&self, key: &K) -> Option<&V>

Get the value associated with a key, if it exists and is alive.

pub fn contains_key(&self, key: &K) -> bool

Check if a key is present and alive in the map.

pub fn len(&self) -> usize

Get the number of alive keys.

pub fn is_empty(&self) -> bool

Check if the map has no alive keys.

pub fn iter(&self) -> impl Iterator<Item = (&K, &V)>

Iterate over alive key-value pairs.

pub fn keys(&self) -> impl Iterator<Item = &K>

Get all alive keys.

pub fn values(&self) -> impl Iterator<Item = &V>

Get all alive values.

Trait Implementations

impl<K: Clone + Ord + Clone, V: Clone + Clone> Clone for LWWMap<K, V>

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

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<K: Ord + Clone, V: Clone> Crdt for LWWMap<K, V>

fn merge(&mut self, other: &Self)

Merge another replica’s state into this one.

impl<K: Debug + Ord + Clone, V: Debug + Clone> Debug for LWWMap<K, V>

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

Formats the value using the given formatter.

impl<K: Ord + Clone, V: Clone> Default for LWWMap<K, V>

fn default() -> Self

Returns the “default value” for a type.

impl<K: Ord + Clone, V: Clone> DeltaCrdt for LWWMap<K, V>

type Delta = LWWMapDelta<K, V>

The type of delta produced by this CRDT.

fn delta(&self, other: &Self) -> LWWMapDelta<K, V>

Generate a delta containing changes in self that other does not have.

fn apply_delta(&mut self, delta: &LWWMapDelta<K, V>)

Apply a delta to this replica’s state.

impl<K: PartialEq + Ord + Clone, V: PartialEq + Clone> PartialEq for LWWMap<K, V>

fn eq(&self, other: &LWWMap<K, V>) -> 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: Ord + Clone, V: Clone> Versioned for LWWMap<K, V>

const CURRENT_VERSION: u8 = 1

Current schema version for this CRDT type’s serialization format.

const CRDT_TYPE: CrdtType = CrdtType::LWWMap

The CRDT type identifier for the envelope.

impl<K: Eq + Ord + Clone, V: Eq + Clone> Eq for LWWMap<K, V>

impl<K: Ord + Clone, V: Clone> StructuralPartialEq for LWWMap<K, V>