forked from Deuxfleurs/garage
125 lines
3.3 KiB
Rust
125 lines
3.3 KiB
Rust
use std::iter::{FromIterator, IntoIterator};
|
|
|
|
use serde::{Deserialize, Serialize};
|
|
|
|
use crate::crdt::crdt::*;
|
|
|
|
/// Simple CRDT Map
|
|
///
|
|
/// This types defines a CRDT for a map from keys to values. Values are CRDT types which
|
|
/// can have their own updating logic.
|
|
///
|
|
/// Internally, the map is stored as a vector of keys and values, sorted by ascending key order.
|
|
/// This is why the key type `K` must implement `Ord` (and also to ensure a unique serialization,
|
|
/// such that two values can be compared for equality based on their hashes). As a consequence,
|
|
/// insertions take `O(n)` time. This means that Map should be used for reasonably small maps.
|
|
/// However, note that even if we were using a more efficient data structure such as a `BTreeMap`,
|
|
/// the serialization cost `O(n)` would still have to be paid at each modification, so we are
|
|
/// actually not losing anything here.
|
|
#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
|
|
pub struct Map<K, V> {
|
|
vals: Vec<(K, V)>,
|
|
}
|
|
|
|
impl<K, V> Map<K, V>
|
|
where
|
|
K: Clone + Ord,
|
|
V: Clone + Crdt,
|
|
{
|
|
/// Create a new empty map CRDT
|
|
pub fn new() -> Self {
|
|
Self { vals: vec![] }
|
|
}
|
|
|
|
/// Returns a map that contains a single mapping from the specified key to the specified value.
|
|
/// This can be used to build a delta-mutator:
|
|
/// when merged with another map, the value will be added or CRDT-merged if a previous
|
|
/// value already exists.
|
|
#[must_use = "CRDT mutators are meant to be merged into a CRDT and not ignored."]
|
|
pub fn put_mutator(k: K, v: V) -> Self {
|
|
Self { vals: vec![(k, v)] }
|
|
}
|
|
|
|
/// Add a value to the map
|
|
pub fn put(&mut self, k: K, v: V) {
|
|
self.merge(&Self::put_mutator(k, v));
|
|
}
|
|
|
|
/// Removes all values from the map
|
|
pub fn clear(&mut self) {
|
|
self.vals.clear();
|
|
}
|
|
|
|
/// Get a reference to the value assigned to a key
|
|
pub fn get(&self, k: &K) -> Option<&V> {
|
|
match self.vals.binary_search_by(|(k2, _)| k2.cmp(k)) {
|
|
Ok(i) => Some(&self.vals[i].1),
|
|
Err(_) => None,
|
|
}
|
|
}
|
|
/// Gets a reference to all of the items, as a slice. Usefull to iterate on all map values.
|
|
pub fn items(&self) -> &[(K, V)] {
|
|
&self.vals[..]
|
|
}
|
|
/// Returns the number of items in the map
|
|
pub fn len(&self) -> usize {
|
|
self.vals.len()
|
|
}
|
|
|
|
/// Returns true if the map is empty
|
|
pub fn is_empty(&self) -> bool {
|
|
self.len() == 0
|
|
}
|
|
}
|
|
|
|
impl<K, V> Crdt for Map<K, V>
|
|
where
|
|
K: Clone + Ord,
|
|
V: Clone + Crdt,
|
|
{
|
|
fn merge(&mut self, other: &Self) {
|
|
for (k, v2) in other.vals.iter() {
|
|
match self.vals.binary_search_by(|(k2, _)| k2.cmp(k)) {
|
|
Ok(i) => {
|
|
self.vals[i].1.merge(v2);
|
|
}
|
|
Err(i) => {
|
|
self.vals.insert(i, (k.clone(), v2.clone()));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<K, V> Default for Map<K, V>
|
|
where
|
|
K: Clone + Ord,
|
|
V: Clone + Crdt,
|
|
{
|
|
fn default() -> Self {
|
|
Self::new()
|
|
}
|
|
}
|
|
|
|
/// A crdt map can be created from an iterator of key-value pairs.
|
|
/// Note that all keys in the iterator must be distinct:
|
|
/// this function will throw a panic if it is not the case.
|
|
impl<K, V> FromIterator<(K, V)> for Map<K, V>
|
|
where
|
|
K: Clone + Ord,
|
|
V: Clone + Crdt,
|
|
{
|
|
fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
|
|
let mut vals: Vec<(K, V)> = iter.into_iter().collect();
|
|
vals.sort_by_cached_key(|tup| tup.0.clone());
|
|
|
|
// sanity check
|
|
for i in 1..vals.len() {
|
|
if vals[i - 1].0 == vals[i].0 {
|
|
panic!("Duplicate key in crdt::Map resulting from .from_iter() or .collect()");
|
|
}
|
|
}
|
|
|
|
Self { vals }
|
|
}
|
|
}
|