mirror of
https://github.com/meilisearch/MeiliSearch
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94 lines
2.6 KiB
Rust
94 lines
2.6 KiB
Rust
use std::collections::BTreeMap;
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#[derive(Debug)]
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pub struct CappedBTreeMap<K, V> {
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inner: BTreeMap<K, V>,
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capacity: usize,
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}
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#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
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pub enum Insertion<V> {
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OldValue(V),
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Evicted(V), // FIXME give (key *and* value)
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Nothing,
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}
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impl<K: Ord, V> CappedBTreeMap<K, V> {
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pub fn new(capacity: usize) -> Self {
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assert!(capacity != 0, "It is invalid to set the capacity to zero.");
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Self {
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inner: BTreeMap::new(),
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capacity: capacity,
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}
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}
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pub fn clear(&mut self) {
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self.inner.clear()
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}
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/// This method insert the `key`, `value` pair in the tree *but* will
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/// remove the _smallest_ one, if the capacity is already reached,
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/// before insertion.
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///
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/// The _smallest_ `value` is not removed if the `key` inserted is already
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/// present in the tree, in this case, the old replaced `value` is returned.
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///
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/// ```
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/// # extern crate raptor;
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/// use raptor::{CappedBTreeMap, Insertion};
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///
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/// let mut tree = CappedBTreeMap::new(3);
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///
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/// let res = tree.insert(1, "a");
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/// assert_eq!(res, Insertion::Nothing);
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///
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/// tree.insert(2, "b");
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/// tree.insert(3, "c");
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///
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/// assert_eq!(tree.insert(4, "d"), Insertion::Evicted("c"));
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///
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/// assert_eq!(tree.insert(1, "d"), Insertion::OldValue("a"));
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/// ```
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///
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pub fn insert(&mut self, key: K, value: V) -> Insertion<V>
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where K: Clone,
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{
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if self.len() == self.capacity {
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if self.inner.contains_key(&key) {
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let value = self.inner.insert(key, value).unwrap();
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Insertion::OldValue(value)
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}
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else {
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let evicted_value = {
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// it is not possible to panic because we have reached
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// the capacity and the capacity cannot be set to zero.
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// FIXME remove this clone, find a way to remove
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// the smallest key/value avoid borrowing problems
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let key = self.inner.keys().next_back().unwrap().clone();
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self.inner.remove(&key).unwrap()
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};
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self.inner.insert(key, value);
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Insertion::Evicted(evicted_value)
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}
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}
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else {
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self.inner.insert(key, value);
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Insertion::Nothing
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}
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}
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pub fn len(&self) -> usize {
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self.inner.len()
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}
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pub fn is_empty(&self) -> bool {
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self.inner.is_empty()
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}
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pub fn capacity(&self) -> usize {
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self.capacity
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}
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}
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