334 lines
8 KiB
JavaScript
334 lines
8 KiB
JavaScript
'use strict'
|
|
|
|
// A linked list to keep track of recently-used-ness
|
|
const Yallist = require('yallist')
|
|
|
|
const MAX = Symbol('max')
|
|
const LENGTH = Symbol('length')
|
|
const LENGTH_CALCULATOR = Symbol('lengthCalculator')
|
|
const ALLOW_STALE = Symbol('allowStale')
|
|
const MAX_AGE = Symbol('maxAge')
|
|
const DISPOSE = Symbol('dispose')
|
|
const NO_DISPOSE_ON_SET = Symbol('noDisposeOnSet')
|
|
const LRU_LIST = Symbol('lruList')
|
|
const CACHE = Symbol('cache')
|
|
const UPDATE_AGE_ON_GET = Symbol('updateAgeOnGet')
|
|
|
|
const naiveLength = () => 1
|
|
|
|
// lruList is a yallist where the head is the youngest
|
|
// item, and the tail is the oldest. the list contains the Hit
|
|
// objects as the entries.
|
|
// Each Hit object has a reference to its Yallist.Node. This
|
|
// never changes.
|
|
//
|
|
// cache is a Map (or PseudoMap) that matches the keys to
|
|
// the Yallist.Node object.
|
|
class LRUCache {
|
|
constructor (options) {
|
|
if (typeof options === 'number')
|
|
options = { max: options }
|
|
|
|
if (!options)
|
|
options = {}
|
|
|
|
if (options.max && (typeof options.max !== 'number' || options.max < 0))
|
|
throw new TypeError('max must be a non-negative number')
|
|
// Kind of weird to have a default max of Infinity, but oh well.
|
|
const max = this[MAX] = options.max || Infinity
|
|
|
|
const lc = options.length || naiveLength
|
|
this[LENGTH_CALCULATOR] = (typeof lc !== 'function') ? naiveLength : lc
|
|
this[ALLOW_STALE] = options.stale || false
|
|
if (options.maxAge && typeof options.maxAge !== 'number')
|
|
throw new TypeError('maxAge must be a number')
|
|
this[MAX_AGE] = options.maxAge || 0
|
|
this[DISPOSE] = options.dispose
|
|
this[NO_DISPOSE_ON_SET] = options.noDisposeOnSet || false
|
|
this[UPDATE_AGE_ON_GET] = options.updateAgeOnGet || false
|
|
this.reset()
|
|
}
|
|
|
|
// resize the cache when the max changes.
|
|
set max (mL) {
|
|
if (typeof mL !== 'number' || mL < 0)
|
|
throw new TypeError('max must be a non-negative number')
|
|
|
|
this[MAX] = mL || Infinity
|
|
trim(this)
|
|
}
|
|
get max () {
|
|
return this[MAX]
|
|
}
|
|
|
|
set allowStale (allowStale) {
|
|
this[ALLOW_STALE] = !!allowStale
|
|
}
|
|
get allowStale () {
|
|
return this[ALLOW_STALE]
|
|
}
|
|
|
|
set maxAge (mA) {
|
|
if (typeof mA !== 'number')
|
|
throw new TypeError('maxAge must be a non-negative number')
|
|
|
|
this[MAX_AGE] = mA
|
|
trim(this)
|
|
}
|
|
get maxAge () {
|
|
return this[MAX_AGE]
|
|
}
|
|
|
|
// resize the cache when the lengthCalculator changes.
|
|
set lengthCalculator (lC) {
|
|
if (typeof lC !== 'function')
|
|
lC = naiveLength
|
|
|
|
if (lC !== this[LENGTH_CALCULATOR]) {
|
|
this[LENGTH_CALCULATOR] = lC
|
|
this[LENGTH] = 0
|
|
this[LRU_LIST].forEach(hit => {
|
|
hit.length = this[LENGTH_CALCULATOR](hit.value, hit.key)
|
|
this[LENGTH] += hit.length
|
|
})
|
|
}
|
|
trim(this)
|
|
}
|
|
get lengthCalculator () { return this[LENGTH_CALCULATOR] }
|
|
|
|
get length () { return this[LENGTH] }
|
|
get itemCount () { return this[LRU_LIST].length }
|
|
|
|
rforEach (fn, thisp) {
|
|
thisp = thisp || this
|
|
for (let walker = this[LRU_LIST].tail; walker !== null;) {
|
|
const prev = walker.prev
|
|
forEachStep(this, fn, walker, thisp)
|
|
walker = prev
|
|
}
|
|
}
|
|
|
|
forEach (fn, thisp) {
|
|
thisp = thisp || this
|
|
for (let walker = this[LRU_LIST].head; walker !== null;) {
|
|
const next = walker.next
|
|
forEachStep(this, fn, walker, thisp)
|
|
walker = next
|
|
}
|
|
}
|
|
|
|
keys () {
|
|
return this[LRU_LIST].toArray().map(k => k.key)
|
|
}
|
|
|
|
values () {
|
|
return this[LRU_LIST].toArray().map(k => k.value)
|
|
}
|
|
|
|
reset () {
|
|
if (this[DISPOSE] &&
|
|
this[LRU_LIST] &&
|
|
this[LRU_LIST].length) {
|
|
this[LRU_LIST].forEach(hit => this[DISPOSE](hit.key, hit.value))
|
|
}
|
|
|
|
this[CACHE] = new Map() // hash of items by key
|
|
this[LRU_LIST] = new Yallist() // list of items in order of use recency
|
|
this[LENGTH] = 0 // length of items in the list
|
|
}
|
|
|
|
dump () {
|
|
return this[LRU_LIST].map(hit =>
|
|
isStale(this, hit) ? false : {
|
|
k: hit.key,
|
|
v: hit.value,
|
|
e: hit.now + (hit.maxAge || 0)
|
|
}).toArray().filter(h => h)
|
|
}
|
|
|
|
dumpLru () {
|
|
return this[LRU_LIST]
|
|
}
|
|
|
|
set (key, value, maxAge) {
|
|
maxAge = maxAge || this[MAX_AGE]
|
|
|
|
if (maxAge && typeof maxAge !== 'number')
|
|
throw new TypeError('maxAge must be a number')
|
|
|
|
const now = maxAge ? Date.now() : 0
|
|
const len = this[LENGTH_CALCULATOR](value, key)
|
|
|
|
if (this[CACHE].has(key)) {
|
|
if (len > this[MAX]) {
|
|
del(this, this[CACHE].get(key))
|
|
return false
|
|
}
|
|
|
|
const node = this[CACHE].get(key)
|
|
const item = node.value
|
|
|
|
// dispose of the old one before overwriting
|
|
// split out into 2 ifs for better coverage tracking
|
|
if (this[DISPOSE]) {
|
|
if (!this[NO_DISPOSE_ON_SET])
|
|
this[DISPOSE](key, item.value)
|
|
}
|
|
|
|
item.now = now
|
|
item.maxAge = maxAge
|
|
item.value = value
|
|
this[LENGTH] += len - item.length
|
|
item.length = len
|
|
this.get(key)
|
|
trim(this)
|
|
return true
|
|
}
|
|
|
|
const hit = new Entry(key, value, len, now, maxAge)
|
|
|
|
// oversized objects fall out of cache automatically.
|
|
if (hit.length > this[MAX]) {
|
|
if (this[DISPOSE])
|
|
this[DISPOSE](key, value)
|
|
|
|
return false
|
|
}
|
|
|
|
this[LENGTH] += hit.length
|
|
this[LRU_LIST].unshift(hit)
|
|
this[CACHE].set(key, this[LRU_LIST].head)
|
|
trim(this)
|
|
return true
|
|
}
|
|
|
|
has (key) {
|
|
if (!this[CACHE].has(key)) return false
|
|
const hit = this[CACHE].get(key).value
|
|
return !isStale(this, hit)
|
|
}
|
|
|
|
get (key) {
|
|
return get(this, key, true)
|
|
}
|
|
|
|
peek (key) {
|
|
return get(this, key, false)
|
|
}
|
|
|
|
pop () {
|
|
const node = this[LRU_LIST].tail
|
|
if (!node)
|
|
return null
|
|
|
|
del(this, node)
|
|
return node.value
|
|
}
|
|
|
|
del (key) {
|
|
del(this, this[CACHE].get(key))
|
|
}
|
|
|
|
load (arr) {
|
|
// reset the cache
|
|
this.reset()
|
|
|
|
const now = Date.now()
|
|
// A previous serialized cache has the most recent items first
|
|
for (let l = arr.length - 1; l >= 0; l--) {
|
|
const hit = arr[l]
|
|
const expiresAt = hit.e || 0
|
|
if (expiresAt === 0)
|
|
// the item was created without expiration in a non aged cache
|
|
this.set(hit.k, hit.v)
|
|
else {
|
|
const maxAge = expiresAt - now
|
|
// dont add already expired items
|
|
if (maxAge > 0) {
|
|
this.set(hit.k, hit.v, maxAge)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
prune () {
|
|
this[CACHE].forEach((value, key) => get(this, key, false))
|
|
}
|
|
}
|
|
|
|
const get = (self, key, doUse) => {
|
|
const node = self[CACHE].get(key)
|
|
if (node) {
|
|
const hit = node.value
|
|
if (isStale(self, hit)) {
|
|
del(self, node)
|
|
if (!self[ALLOW_STALE])
|
|
return undefined
|
|
} else {
|
|
if (doUse) {
|
|
if (self[UPDATE_AGE_ON_GET])
|
|
node.value.now = Date.now()
|
|
self[LRU_LIST].unshiftNode(node)
|
|
}
|
|
}
|
|
return hit.value
|
|
}
|
|
}
|
|
|
|
const isStale = (self, hit) => {
|
|
if (!hit || (!hit.maxAge && !self[MAX_AGE]))
|
|
return false
|
|
|
|
const diff = Date.now() - hit.now
|
|
return hit.maxAge ? diff > hit.maxAge
|
|
: self[MAX_AGE] && (diff > self[MAX_AGE])
|
|
}
|
|
|
|
const trim = self => {
|
|
if (self[LENGTH] > self[MAX]) {
|
|
for (let walker = self[LRU_LIST].tail;
|
|
self[LENGTH] > self[MAX] && walker !== null;) {
|
|
// We know that we're about to delete this one, and also
|
|
// what the next least recently used key will be, so just
|
|
// go ahead and set it now.
|
|
const prev = walker.prev
|
|
del(self, walker)
|
|
walker = prev
|
|
}
|
|
}
|
|
}
|
|
|
|
const del = (self, node) => {
|
|
if (node) {
|
|
const hit = node.value
|
|
if (self[DISPOSE])
|
|
self[DISPOSE](hit.key, hit.value)
|
|
|
|
self[LENGTH] -= hit.length
|
|
self[CACHE].delete(hit.key)
|
|
self[LRU_LIST].removeNode(node)
|
|
}
|
|
}
|
|
|
|
class Entry {
|
|
constructor (key, value, length, now, maxAge) {
|
|
this.key = key
|
|
this.value = value
|
|
this.length = length
|
|
this.now = now
|
|
this.maxAge = maxAge || 0
|
|
}
|
|
}
|
|
|
|
const forEachStep = (self, fn, node, thisp) => {
|
|
let hit = node.value
|
|
if (isStale(self, hit)) {
|
|
del(self, node)
|
|
if (!self[ALLOW_STALE])
|
|
hit = undefined
|
|
}
|
|
if (hit)
|
|
fn.call(thisp, hit.value, hit.key, self)
|
|
}
|
|
|
|
module.exports = LRUCache
|