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264 lines
5.2 KiB
JavaScript

'use strict';
class QuickLRU {
constructor(options = {}) {
if (!(options.maxSize && options.maxSize > 0)) {
throw new TypeError('`maxSize` must be a number greater than 0');
}
if (typeof options.maxAge === 'number' && options.maxAge === 0) {
throw new TypeError('`maxAge` must be a number greater than 0');
}
this.maxSize = options.maxSize;
this.maxAge = options.maxAge || Infinity;
this.onEviction = options.onEviction;
this.cache = new Map();
this.oldCache = new Map();
this._size = 0;
}
_emitEvictions(cache) {
if (typeof this.onEviction !== 'function') {
return;
}
for (const [key, item] of cache) {
this.onEviction(key, item.value);
}
}
_deleteIfExpired(key, item) {
if (typeof item.expiry === 'number' && item.expiry <= Date.now()) {
if (typeof this.onEviction === 'function') {
this.onEviction(key, item.value);
}
return this.delete(key);
}
return false;
}
_getOrDeleteIfExpired(key, item) {
const deleted = this._deleteIfExpired(key, item);
if (deleted === false) {
return item.value;
}
}
_getItemValue(key, item) {
return item.expiry ? this._getOrDeleteIfExpired(key, item) : item.value;
}
_peek(key, cache) {
const item = cache.get(key);
return this._getItemValue(key, item);
}
_set(key, value) {
this.cache.set(key, value);
this._size++;
if (this._size >= this.maxSize) {
this._size = 0;
this._emitEvictions(this.oldCache);
this.oldCache = this.cache;
this.cache = new Map();
}
}
_moveToRecent(key, item) {
this.oldCache.delete(key);
this._set(key, item);
}
* _entriesAscending() {
for (const item of this.oldCache) {
const [key, value] = item;
if (!this.cache.has(key)) {
const deleted = this._deleteIfExpired(key, value);
if (deleted === false) {
yield item;
}
}
}
for (const item of this.cache) {
const [key, value] = item;
const deleted = this._deleteIfExpired(key, value);
if (deleted === false) {
yield item;
}
}
}
get(key) {
if (this.cache.has(key)) {
const item = this.cache.get(key);
return this._getItemValue(key, item);
}
if (this.oldCache.has(key)) {
const item = this.oldCache.get(key);
if (this._deleteIfExpired(key, item) === false) {
this._moveToRecent(key, item);
return item.value;
}
}
}
set(key, value, {maxAge = this.maxAge === Infinity ? undefined : Date.now() + this.maxAge} = {}) {
if (this.cache.has(key)) {
this.cache.set(key, {
value,
maxAge
});
} else {
this._set(key, {value, expiry: maxAge});
}
}
has(key) {
if (this.cache.has(key)) {
return !this._deleteIfExpired(key, this.cache.get(key));
}
if (this.oldCache.has(key)) {
return !this._deleteIfExpired(key, this.oldCache.get(key));
}
return false;
}
peek(key) {
if (this.cache.has(key)) {
return this._peek(key, this.cache);
}
if (this.oldCache.has(key)) {
return this._peek(key, this.oldCache);
}
}
delete(key) {
const deleted = this.cache.delete(key);
if (deleted) {
this._size--;
}
return this.oldCache.delete(key) || deleted;
}
clear() {
this.cache.clear();
this.oldCache.clear();
this._size = 0;
}
resize(newSize) {
if (!(newSize && newSize > 0)) {
throw new TypeError('`maxSize` must be a number greater than 0');
}
const items = [...this._entriesAscending()];
const removeCount = items.length - newSize;
if (removeCount < 0) {
this.cache = new Map(items);
this.oldCache = new Map();
this._size = items.length;
} else {
if (removeCount > 0) {
this._emitEvictions(items.slice(0, removeCount));
}
this.oldCache = new Map(items.slice(removeCount));
this.cache = new Map();
this._size = 0;
}
this.maxSize = newSize;
}
* keys() {
for (const [key] of this) {
yield key;
}
}
* values() {
for (const [, value] of this) {
yield value;
}
}
* [Symbol.iterator]() {
for (const item of this.cache) {
const [key, value] = item;
const deleted = this._deleteIfExpired(key, value);
if (deleted === false) {
yield [key, value.value];
}
}
for (const item of this.oldCache) {
const [key, value] = item;
if (!this.cache.has(key)) {
const deleted = this._deleteIfExpired(key, value);
if (deleted === false) {
yield [key, value.value];
}
}
}
}
* entriesDescending() {
let items = [...this.cache];
for (let i = items.length - 1; i >= 0; --i) {
const item = items[i];
const [key, value] = item;
const deleted = this._deleteIfExpired(key, value);
if (deleted === false) {
yield [key, value.value];
}
}
items = [...this.oldCache];
for (let i = items.length - 1; i >= 0; --i) {
const item = items[i];
const [key, value] = item;
if (!this.cache.has(key)) {
const deleted = this._deleteIfExpired(key, value);
if (deleted === false) {
yield [key, value.value];
}
}
}
}
* entriesAscending() {
for (const [key, value] of this._entriesAscending()) {
yield [key, value.value];
}
}
get size() {
if (!this._size) {
return this.oldCache.size;
}
let oldCacheSize = 0;
for (const key of this.oldCache.keys()) {
if (!this.cache.has(key)) {
oldCacheSize++;
}
}
return Math.min(this._size + oldCacheSize, this.maxSize);
}
}
module.exports = QuickLRU;