feat(core): implemented and exported lru map
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teidesu
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3 changed files with 268 additions and 0 deletions
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@ -7,6 +7,7 @@ export * from './utils/crypto'
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export * from './utils/peer-utils'
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export * from './utils/tl-json'
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export * from './utils/async-lock'
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export * from './utils/lru-map'
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export { BinaryReader } from './utils/binary/binary-reader'
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export { BinaryWriter } from './utils/binary/binary-writer'
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184
packages/core/src/utils/lru-map.ts
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184
packages/core/src/utils/lru-map.ts
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@ -0,0 +1,184 @@
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interface TwoWayLinkedList<K, T> {
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// k = key
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k: K
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// v = value
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v: T
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// p = previous
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p?: TwoWayLinkedList<K, T>
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// n = next
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n?: TwoWayLinkedList<K, T>
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}
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/**
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* Simple class implementing LRU-like behaviour for a map,
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* falling back to objects when `Map` is not available.
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*
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* Can be used to handle local cache of *something*
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*
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* Uses two-way linked list internally to keep track of insertion/access order
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*/
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export class LruMap<K extends keyof any, V> {
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private _capacity: number
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private _first?: TwoWayLinkedList<K, V>
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private _last?: TwoWayLinkedList<K, V>
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private _size = 0
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constructor(capacity: number, useObject = false) {
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this._capacity = capacity
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if (typeof Map === 'undefined' || useObject) {
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const obj = {} as any
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this._set = (k, v) => obj[k] = v
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this._has = (k) => k in obj
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this._get = (k) => obj[k]
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this._del = (k) => delete obj[k]
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} else {
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const map = new Map()
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this._set = map.set.bind(map)
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this._has = map.has.bind(map)
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this._get = map.get.bind(map)
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this._del = map.delete.bind(map)
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}
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}
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private readonly _set: (key: K, value: V) => void
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private readonly _has: (key: K) => boolean
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private readonly _get: (key: K) => TwoWayLinkedList<K, V> | undefined
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private readonly _del: (key: K) => void
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private _markUsed(item: TwoWayLinkedList<K, V>): void {
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if (item === this._first) {
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return // already the most recently used
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}
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if (item.p) {
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if (item === this._last) {
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this._last = item.p
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}
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item.p.n = item.n
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}
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if (item.n) {
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item.n.p = item.p
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}
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item.p = undefined
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item.n = this._first
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if (this._first) {
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this._first.p = item
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}
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this._first = item
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}
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get(key: K): V | undefined {
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const item = this._get(key)
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if (!item) return undefined
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this._markUsed(item)
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return item.v
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}
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has(key: K): boolean {
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return this._has(key)
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}
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set(key: K, value: V): void {
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let item = this._get(key)
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if (item) {
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// already in cache, update
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item.v = value
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this._markUsed(item)
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return
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}
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item = {
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k: key,
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v: value
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}
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this._set(key, item as any)
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if (this._first) {
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this._first.p = item
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item.n = this._first
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} else {
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// first item ever
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this._last = item
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}
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this._first = item
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this._size += 1
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if (this._size > this._capacity) {
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// remove the last item
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const oldest = this._last
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if (oldest) {
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if (oldest.p) {
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this._last = oldest.p
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this._last!.n = undefined
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} else {
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// exhausted
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this._last = undefined
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this._first = undefined
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}
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// remove strong refs to and from the item
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oldest.p = oldest.n = undefined
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this._del(oldest.k)
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this._size -= 1
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}
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}
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}
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// private _setForMap(key: K, value: V) {
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// const old = this._items[key]
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//
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// if (old) {
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// bring old one to the beginning
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//
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// }
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// if (!this._first) this._first = { v: str }
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// if (!this._last) this._last = this._first
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// else {
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// this._last.n = { v: str }
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// this._last = this._last.n
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// }
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//
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// this._set!.add(str)
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//
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// if (this._set!.size > this._capacity && this._first) {
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// // remove least recently used
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// this._set!.delete(this._first.v)
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// this._first = this._first.n
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// }
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// }
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// private _hasForMap(str: string) {
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// return this._set!.has(str)
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// }
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// private _setForObj(str: string) {
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// if (str in this._obj!) return
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//
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// if (!this._first) this._first = { v: str }
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// if (!this._last) this._last = this._first
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// else {
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// this._last.n = { v: str }
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// this._last = this._last.n
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// }
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//
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// this._obj![str] = true
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//
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// if (this._objSize === this._capacity) {
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// // remove least recently used
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// delete this._obj![this._first.v]
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// this._first = this._first.n
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// } else {
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// this._objSize! += 1
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// }
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// }
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//
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// private _hasForObj(str: string) {
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// return str in this._obj!
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// }
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}
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83
packages/core/tests/lru-map.spec.ts
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83
packages/core/tests/lru-map.spec.ts
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@ -0,0 +1,83 @@
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import { describe, it } from 'mocha'
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import { expect } from 'chai'
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import { LruMap } from '../src'
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describe('LruMap', () => {
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it('Map backend', () => {
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const lru = new LruMap<string, number>(2)
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lru.set('first', 1)
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expect(lru.has('first')).true
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expect(lru.has('second')).false
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expect(lru.get('first')).eq(1)
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lru.set('first', 42)
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expect(lru.has('first')).true
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expect(lru.has('second')).false
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expect(lru.get('first')).eq(42)
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lru.set('second', 2)
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expect(lru.has('first')).true
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expect(lru.has('second')).true
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expect(lru.get('first')).eq(42)
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expect(lru.get('second')).eq(2)
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lru.set('third', 3)
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expect(lru.has('first')).false
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expect(lru.has('second')).true
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expect(lru.has('third')).true
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expect(lru.get('first')).eq(undefined)
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expect(lru.get('second')).eq(2)
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expect(lru.get('third')).eq(3)
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lru.get('second') // update lru so that last = third
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lru.set('fourth', 4)
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expect(lru.has('first')).false
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expect(lru.has('second')).true
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expect(lru.has('third')).false
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expect(lru.has('fourth')).true
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expect(lru.get('first')).eq(undefined)
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expect(lru.get('second')).eq(2)
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expect(lru.get('third')).eq(undefined)
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expect(lru.get('fourth')).eq(4)
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})
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it('Object backend', () => {
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const lru = new LruMap<string, number>(2, true)
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lru.set('first', 1)
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expect(lru.has('first')).true
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expect(lru.has('second')).false
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expect(lru.get('first')).eq(1)
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lru.set('first', 42)
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expect(lru.has('first')).true
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expect(lru.has('second')).false
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expect(lru.get('first')).eq(42)
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lru.set('second', 2)
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expect(lru.has('first')).true
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expect(lru.has('second')).true
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expect(lru.get('first')).eq(42)
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expect(lru.get('second')).eq(2)
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lru.set('third', 3)
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expect(lru.has('first')).false
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expect(lru.has('second')).true
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expect(lru.has('third')).true
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expect(lru.get('first')).eq(undefined)
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expect(lru.get('second')).eq(2)
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expect(lru.get('third')).eq(3)
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lru.get('second') // update lru so that last = third
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lru.set('fourth', 4)
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expect(lru.has('first')).false
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expect(lru.has('second')).true
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expect(lru.has('third')).false
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expect(lru.has('fourth')).true
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expect(lru.get('first')).eq(undefined)
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expect(lru.get('second')).eq(2)
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expect(lru.get('third')).eq(undefined)
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expect(lru.get('fourth')).eq(4)
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})
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})
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