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index.js
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index.js
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'use strict';
class LRU {
constructor(max) {
this.max = max;
this.size = 0;
this.cache = new Map();
this._cache = new Map();
}
get(key, options) {
let item = this.cache.get(key);
const maxAge = options && options.maxAge;
// only call Date.now() when necessary
let now;
function getNow() {
now = now || Date.now();
return now;
}
if (item) {
// check expired
if (item.expired && getNow() > item.expired) {
item.expired = 0;
item.value = undefined;
} else {
// update expired in get
if (maxAge !== undefined) {
const expired = maxAge ? getNow() + maxAge : 0;
item.expired = expired;
}
}
return item.value;
}
// try to read from _cache
item = this._cache.get(key);
if (item) {
// check expired
if (item.expired && getNow() > item.expired) {
item.expired = 0;
item.value = undefined;
} else {
// not expired, save to cache
this._update(key, item);
// update expired in get
if (maxAge !== undefined) {
const expired = maxAge ? getNow() + maxAge : 0;
item.expired = expired;
}
}
return item.value;
}
}
set(key, value, options) {
const maxAge = options && options.maxAge;
const expired = maxAge ? Date.now() + maxAge : 0;
let item = this.cache.get(key);
if (item) {
item.expired = expired;
item.value = value;
} else {
item = {
value,
expired,
};
this._update(key, item);
}
}
keys() {
const cacheKeys = new Set();
const now = Date.now();
for (const entry of this.cache.entries()) {
checkEntry(entry);
}
for (const entry of this._cache.entries()) {
checkEntry(entry);
}
function checkEntry(entry) {
const key = entry[0];
const item = entry[1];
if (entry[1].value && (!entry[1].expired) || item.expired >= now) {
cacheKeys.add(key);
}
}
return Array.from(cacheKeys.keys());
}
reset() {
this.size = 0;
this.cache.clear();
this._cache.clear();
}
_update(key, item) {
this.cache.set(key, item);
this.size++;
if (this.size >= this.max) {
this.size = 0;
this._cache = this.cache;
this.cache = new Map();
}
}
}
module.exports = LRU;