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Mini Shell
Mini Shell
const perf =
typeof performance === 'object' &&
performance &&
typeof performance.now === 'function'
? performance
: Date
const hasAbortController = typeof AbortController === 'function'
// minimal backwards-compatibility polyfill
// this doesn't have nearly all the checks and whatnot that
// actual AbortController/Signal has, but it's enough for
// our purposes, and if used properly, behaves the same.
const AC = hasAbortController
? AbortController
: class AbortController {
constructor() {
this.signal = new AS()
}
abort() {
this.signal.dispatchEvent('abort')
}
}
const hasAbortSignal = typeof AbortSignal === 'function'
// Some polyfills put this on the AC class, not global
const hasACAbortSignal = typeof AC.AbortSignal === 'function'
const AS = hasAbortSignal
? AbortSignal
: hasACAbortSignal
? AC.AbortController
: class AbortSignal {
constructor() {
this.aborted = false
this._listeners = []
}
dispatchEvent(type) {
if (type === 'abort') {
this.aborted = true
const e = { type, target: this }
this.onabort(e)
this._listeners.forEach(f => f(e), this)
}
}
onabort() {}
addEventListener(ev, fn) {
if (ev === 'abort') {
this._listeners.push(fn)
}
}
removeEventListener(ev, fn) {
if (ev === 'abort') {
this._listeners = this._listeners.filter(f => f !== fn)
}
}
}
const warned = new Set()
const deprecatedOption = (opt, instead) => {
const code = `LRU_CACHE_OPTION_${opt}`
if (shouldWarn(code)) {
warn(code, `${opt} option`, `options.${instead}`, LRUCache)
}
}
const deprecatedMethod = (method, instead) => {
const code = `LRU_CACHE_METHOD_${method}`
if (shouldWarn(code)) {
const { prototype } = LRUCache
const { get } = Object.getOwnPropertyDescriptor(prototype, method)
warn(code, `${method} method`, `cache.${instead}()`, get)
}
}
const deprecatedProperty = (field, instead) => {
const code = `LRU_CACHE_PROPERTY_${field}`
if (shouldWarn(code)) {
const { prototype } = LRUCache
const { get } = Object.getOwnPropertyDescriptor(prototype, field)
warn(code, `${field} property`, `cache.${instead}`, get)
}
}
const emitWarning = (...a) => {
typeof process === 'object' &&
process &&
typeof process.emitWarning === 'function'
? process.emitWarning(...a)
: console.error(...a)
}
const shouldWarn = code => !warned.has(code)
const warn = (code, what, instead, fn) => {
warned.add(code)
const msg = `The ${what} is deprecated. Please use ${instead} instead.`
emitWarning(msg, 'DeprecationWarning', code, fn)
}
const isPosInt = n => n && n === Math.floor(n) && n > 0 && isFinite(n)
/* istanbul ignore next - This is a little bit ridiculous, tbh.
* The maximum array length is 2^32-1 or thereabouts on most JS impls.
* And well before that point, you're caching the entire world, I mean,
* that's ~32GB of just integers for the next/prev links, plus whatever
* else to hold that many keys and values. Just filling the memory with
* zeroes at init time is brutal when you get that big.
* But why not be complete?
* Maybe in the future, these limits will have expanded. */
const getUintArray = max =>
!isPosInt(max)
? null
: max <= Math.pow(2, 8)
? Uint8Array
: max <= Math.pow(2, 16)
? Uint16Array
: max <= Math.pow(2, 32)
? Uint32Array
: max <= Number.MAX_SAFE_INTEGER
? ZeroArray
: null
class ZeroArray extends Array {
constructor(size) {
super(size)
this.fill(0)
}
}
class Stack {
constructor(max) {
if (max === 0) {
return []
}
const UintArray = getUintArray(max)
this.heap = new UintArray(max)
this.length = 0
}
push(n) {
this.heap[this.length++] = n
}
pop() {
return this.heap[--this.length]
}
}
class LRUCache {
constructor(options = {}) {
const {
max = 0,
ttl,
ttlResolution = 1,
ttlAutopurge,
updateAgeOnGet,
updateAgeOnHas,
allowStale,
dispose,
disposeAfter,
noDisposeOnSet,
noUpdateTTL,
maxSize = 0,
sizeCalculation,
fetchMethod,
fetchContext,
noDeleteOnFetchRejection,
noDeleteOnStaleGet,
} = options
// deprecated options, don't trigger a warning for getting them if
// the thing being passed in is another LRUCache we're copying.
const { length, maxAge, stale } =
options instanceof LRUCache ? {} : options
if (max !== 0 && !isPosInt(max)) {
throw new TypeError('max option must be a nonnegative integer')
}
const UintArray = max ? getUintArray(max) : Array
if (!UintArray) {
throw new Error('invalid max value: ' + max)
}
this.max = max
this.maxSize = maxSize
this.sizeCalculation = sizeCalculation || length
if (this.sizeCalculation) {
if (!this.maxSize) {
throw new TypeError(
'cannot set sizeCalculation without setting maxSize'
)
}
if (typeof this.sizeCalculation !== 'function') {
throw new TypeError('sizeCalculation set to non-function')
}
}
this.fetchMethod = fetchMethod || null
if (this.fetchMethod && typeof this.fetchMethod !== 'function') {
throw new TypeError(
'fetchMethod must be a function if specified'
)
}
this.fetchContext = fetchContext
if (!this.fetchMethod && fetchContext !== undefined) {
throw new TypeError(
'cannot set fetchContext without fetchMethod'
)
}
this.keyMap = new Map()
this.keyList = new Array(max).fill(null)
this.valList = new Array(max).fill(null)
this.next = new UintArray(max)
this.prev = new UintArray(max)
this.head = 0
this.tail = 0
this.free = new Stack(max)
this.initialFill = 1
this.size = 0
if (typeof dispose === 'function') {
this.dispose = dispose
}
if (typeof disposeAfter === 'function') {
this.disposeAfter = disposeAfter
this.disposed = []
} else {
this.disposeAfter = null
this.disposed = null
}
this.noDisposeOnSet = !!noDisposeOnSet
this.noUpdateTTL = !!noUpdateTTL
this.noDeleteOnFetchRejection = !!noDeleteOnFetchRejection
if (this.maxSize !== 0) {
if (!isPosInt(this.maxSize)) {
throw new TypeError(
'maxSize must be a positive integer if specified'
)
}
this.initializeSizeTracking()
}
this.allowStale = !!allowStale || !!stale
this.noDeleteOnStaleGet = !!noDeleteOnStaleGet
this.updateAgeOnGet = !!updateAgeOnGet
this.updateAgeOnHas = !!updateAgeOnHas
this.ttlResolution =
isPosInt(ttlResolution) || ttlResolution === 0
? ttlResolution
: 1
this.ttlAutopurge = !!ttlAutopurge
this.ttl = ttl || maxAge || 0
if (this.ttl) {
if (!isPosInt(this.ttl)) {
throw new TypeError(
'ttl must be a positive integer if specified'
)
}
this.initializeTTLTracking()
}
// do not allow completely unbounded caches
if (this.max === 0 && this.ttl === 0 && this.maxSize === 0) {
throw new TypeError(
'At least one of max, maxSize, or ttl is required'
)
}
if (!this.ttlAutopurge && !this.max && !this.maxSize) {
const code = 'LRU_CACHE_UNBOUNDED'
if (shouldWarn(code)) {
warned.add(code)
const msg =
'TTL caching without ttlAutopurge, max, or maxSize can ' +
'result in unbounded memory consumption.'
emitWarning(msg, 'UnboundedCacheWarning', code, LRUCache)
}
}
if (stale) {
deprecatedOption('stale', 'allowStale')
}
if (maxAge) {
deprecatedOption('maxAge', 'ttl')
}
if (length) {
deprecatedOption('length', 'sizeCalculation')
}
}
getRemainingTTL(key) {
return this.has(key, { updateAgeOnHas: false }) ? Infinity : 0
}
initializeTTLTracking() {
this.ttls = new ZeroArray(this.max)
this.starts = new ZeroArray(this.max)
this.setItemTTL = (index, ttl, start = perf.now()) => {
this.starts[index] = ttl !== 0 ? start : 0
this.ttls[index] = ttl
if (ttl !== 0 && this.ttlAutopurge) {
const t = setTimeout(() => {
if (this.isStale(index)) {
this.delete(this.keyList[index])
}
}, ttl + 1)
/* istanbul ignore else - unref() not supported on all platforms */
if (t.unref) {
t.unref()
}
}
}
this.updateItemAge = index => {
this.starts[index] = this.ttls[index] !== 0 ? perf.now() : 0
}
// debounce calls to perf.now() to 1s so we're not hitting
// that costly call repeatedly.
let cachedNow = 0
const getNow = () => {
const n = perf.now()
if (this.ttlResolution > 0) {
cachedNow = n
const t = setTimeout(
() => (cachedNow = 0),
this.ttlResolution
)
/* istanbul ignore else - not available on all platforms */
if (t.unref) {
t.unref()
}
}
return n
}
this.getRemainingTTL = key => {
const index = this.keyMap.get(key)
if (index === undefined) {
return 0
}
return this.ttls[index] === 0 || this.starts[index] === 0
? Infinity
: this.starts[index] +
this.ttls[index] -
(cachedNow || getNow())
}
this.isStale = index => {
return (
this.ttls[index] !== 0 &&
this.starts[index] !== 0 &&
(cachedNow || getNow()) - this.starts[index] >
this.ttls[index]
)
}
}
updateItemAge(index) {}
setItemTTL(index, ttl, start) {}
isStale(index) {
return false
}
initializeSizeTracking() {
this.calculatedSize = 0
this.sizes = new ZeroArray(this.max)
this.removeItemSize = index => {
this.calculatedSize -= this.sizes[index]
this.sizes[index] = 0
}
this.requireSize = (k, v, size, sizeCalculation) => {
if (!isPosInt(size)) {
if (sizeCalculation) {
if (typeof sizeCalculation !== 'function') {
throw new TypeError('sizeCalculation must be a function')
}
size = sizeCalculation(v, k)
if (!isPosInt(size)) {
throw new TypeError(
'sizeCalculation return invalid (expect positive integer)'
)
}
} else {
throw new TypeError(
'invalid size value (must be positive integer)'
)
}
}
return size
}
this.addItemSize = (index, size) => {
this.sizes[index] = size
const maxSize = this.maxSize - this.sizes[index]
while (this.calculatedSize > maxSize) {
this.evict(true)
}
this.calculatedSize += this.sizes[index]
}
}
removeItemSize(index) {}
addItemSize(index, size) {}
requireSize(k, v, size, sizeCalculation) {
if (size || sizeCalculation) {
throw new TypeError(
'cannot set size without setting maxSize on cache'
)
}
}
*indexes({ allowStale = this.allowStale } = {}) {
if (this.size) {
for (let i = this.tail; true; ) {
if (!this.isValidIndex(i)) {
break
}
if (allowStale || !this.isStale(i)) {
yield i
}
if (i === this.head) {
break
} else {
i = this.prev[i]
}
}
}
}
*rindexes({ allowStale = this.allowStale } = {}) {
if (this.size) {
for (let i = this.head; true; ) {
if (!this.isValidIndex(i)) {
break
}
if (allowStale || !this.isStale(i)) {
yield i
}
if (i === this.tail) {
break
} else {
i = this.next[i]
}
}
}
}
isValidIndex(index) {
return this.keyMap.get(this.keyList[index]) === index
}
*entries() {
for (const i of this.indexes()) {
yield [this.keyList[i], this.valList[i]]
}
}
*rentries() {
for (const i of this.rindexes()) {
yield [this.keyList[i], this.valList[i]]
}
}
*keys() {
for (const i of this.indexes()) {
yield this.keyList[i]
}
}
*rkeys() {
for (const i of this.rindexes()) {
yield this.keyList[i]
}
}
*values() {
for (const i of this.indexes()) {
yield this.valList[i]
}
}
*rvalues() {
for (const i of this.rindexes()) {
yield this.valList[i]
}
}
[Symbol.iterator]() {
return this.entries()
}
find(fn, getOptions = {}) {
for (const i of this.indexes()) {
if (fn(this.valList[i], this.keyList[i], this)) {
return this.get(this.keyList[i], getOptions)
}
}
}
forEach(fn, thisp = this) {
for (const i of this.indexes()) {
fn.call(thisp, this.valList[i], this.keyList[i], this)
}
}
rforEach(fn, thisp = this) {
for (const i of this.rindexes()) {
fn.call(thisp, this.valList[i], this.keyList[i], this)
}
}
get prune() {
deprecatedMethod('prune', 'purgeStale')
return this.purgeStale
}
purgeStale() {
let deleted = false
for (const i of this.rindexes({ allowStale: true })) {
if (this.isStale(i)) {
this.delete(this.keyList[i])
deleted = true
}
}
return deleted
}
dump() {
const arr = []
for (const i of this.indexes({ allowStale: true })) {
const key = this.keyList[i]
const v = this.valList[i]
const value = this.isBackgroundFetch(v)
? v.__staleWhileFetching
: v
const entry = { value }
if (this.ttls) {
entry.ttl = this.ttls[i]
// always dump the start relative to a portable timestamp
// it's ok for this to be a bit slow, it's a rare operation.
const age = perf.now() - this.starts[i]
entry.start = Math.floor(Date.now() - age)
}
if (this.sizes) {
entry.size = this.sizes[i]
}
arr.unshift([key, entry])
}
return arr
}
load(arr) {
this.clear()
for (const [key, entry] of arr) {
if (entry.start) {
// entry.start is a portable timestamp, but we may be using
// node's performance.now(), so calculate the offset.
// it's ok for this to be a bit slow, it's a rare operation.
const age = Date.now() - entry.start
entry.start = perf.now() - age
}
this.set(key, entry.value, entry)
}
}
dispose(v, k, reason) {}
set(
k,
v,
{
ttl = this.ttl,
start,
noDisposeOnSet = this.noDisposeOnSet,
size = 0,
sizeCalculation = this.sizeCalculation,
noUpdateTTL = this.noUpdateTTL,
} = {}
) {
size = this.requireSize(k, v, size, sizeCalculation)
// if the item doesn't fit, don't do anything
if (this.maxSize && size > this.maxSize) {
return this
}
let index = this.size === 0 ? undefined : this.keyMap.get(k)
if (index === undefined) {
// addition
index = this.newIndex()
this.keyList[index] = k
this.valList[index] = v
this.keyMap.set(k, index)
this.next[this.tail] = index
this.prev[index] = this.tail
this.tail = index
this.size++
this.addItemSize(index, size)
noUpdateTTL = false
} else {
// update
const oldVal = this.valList[index]
if (v !== oldVal) {
if (this.isBackgroundFetch(oldVal)) {
oldVal.__abortController.abort()
} else {
if (!noDisposeOnSet) {
this.dispose(oldVal, k, 'set')
if (this.disposeAfter) {
this.disposed.push([oldVal, k, 'set'])
}
}
}
this.removeItemSize(index)
this.valList[index] = v
this.addItemSize(index, size)
}
this.moveToTail(index)
}
if (ttl !== 0 && this.ttl === 0 && !this.ttls) {
this.initializeTTLTracking()
}
if (!noUpdateTTL) {
this.setItemTTL(index, ttl, start)
}
if (this.disposeAfter) {
while (this.disposed.length) {
this.disposeAfter(...this.disposed.shift())
}
}
return this
}
newIndex() {
if (this.size === 0) {
return this.tail
}
if (this.size === this.max && this.max !== 0) {
return this.evict(false)
}
if (this.free.length !== 0) {
return this.free.pop()
}
// initial fill, just keep writing down the list
return this.initialFill++
}
pop() {
if (this.size) {
const val = this.valList[this.head]
this.evict(true)
return val
}
}
evict(free) {
const head = this.head
const k = this.keyList[head]
const v = this.valList[head]
if (this.isBackgroundFetch(v)) {
v.__abortController.abort()
} else {
this.dispose(v, k, 'evict')
if (this.disposeAfter) {
this.disposed.push([v, k, 'evict'])
}
}
this.removeItemSize(head)
// if we aren't about to use the index, then null these out
if (free) {
this.keyList[head] = null
this.valList[head] = null
this.free.push(head)
}
this.head = this.next[head]
this.keyMap.delete(k)
this.size--
return head
}
has(k, { updateAgeOnHas = this.updateAgeOnHas } = {}) {
const index = this.keyMap.get(k)
if (index !== undefined) {
if (!this.isStale(index)) {
if (updateAgeOnHas) {
this.updateItemAge(index)
}
return true
}
}
return false
}
// like get(), but without any LRU updating or TTL expiration
peek(k, { allowStale = this.allowStale } = {}) {
const index = this.keyMap.get(k)
if (index !== undefined && (allowStale || !this.isStale(index))) {
const v = this.valList[index]
// either stale and allowed, or forcing a refresh of non-stale value
return this.isBackgroundFetch(v) ? v.__staleWhileFetching : v
}
}
backgroundFetch(k, index, options, context) {
const v = index === undefined ? undefined : this.valList[index]
if (this.isBackgroundFetch(v)) {
return v
}
const ac = new AC()
const fetchOpts = {
signal: ac.signal,
options,
context,
}
const cb = v => {
if (!ac.signal.aborted) {
this.set(k, v, fetchOpts.options)
}
return v
}
const eb = er => {
if (this.valList[index] === p) {
const del =
!options.noDeleteOnFetchRejection ||
p.__staleWhileFetching === undefined
if (del) {
this.delete(k)
} else {
// still replace the *promise* with the stale value,
// since we are done with the promise at this point.
this.valList[index] = p.__staleWhileFetching
}
}
if (p.__returned === p) {
throw er
}
}
const pcall = res => res(this.fetchMethod(k, v, fetchOpts))
const p = new Promise(pcall).then(cb, eb)
p.__abortController = ac
p.__staleWhileFetching = v
p.__returned = null
if (index === undefined) {
this.set(k, p, fetchOpts.options)
index = this.keyMap.get(k)
} else {
this.valList[index] = p
}
return p
}
isBackgroundFetch(p) {
return (
p &&
typeof p === 'object' &&
typeof p.then === 'function' &&
Object.prototype.hasOwnProperty.call(
p,
'__staleWhileFetching'
) &&
Object.prototype.hasOwnProperty.call(p, '__returned') &&
(p.__returned === p || p.__returned === null)
)
}
// this takes the union of get() and set() opts, because it does both
async fetch(
k,
{
// get options
allowStale = this.allowStale,
updateAgeOnGet = this.updateAgeOnGet,
noDeleteOnStaleGet = this.noDeleteOnStaleGet,
// set options
ttl = this.ttl,
noDisposeOnSet = this.noDisposeOnSet,
size = 0,
sizeCalculation = this.sizeCalculation,
noUpdateTTL = this.noUpdateTTL,
// fetch exclusive options
noDeleteOnFetchRejection = this.noDeleteOnFetchRejection,
fetchContext = this.fetchContext,
forceRefresh = false,
} = {}
) {
if (!this.fetchMethod) {
return this.get(k, {
allowStale,
updateAgeOnGet,
noDeleteOnStaleGet,
})
}
const options = {
allowStale,
updateAgeOnGet,
noDeleteOnStaleGet,
ttl,
noDisposeOnSet,
size,
sizeCalculation,
noUpdateTTL,
noDeleteOnFetchRejection,
}
let index = this.keyMap.get(k)
if (index === undefined) {
const p = this.backgroundFetch(k, index, options, fetchContext)
return (p.__returned = p)
} else {
// in cache, maybe already fetching
const v = this.valList[index]
if (this.isBackgroundFetch(v)) {
return allowStale && v.__staleWhileFetching !== undefined
? v.__staleWhileFetching
: (v.__returned = v)
}
// if we force a refresh, that means do NOT serve the cached value,
// unless we are already in the process of refreshing the cache.
if (!forceRefresh && !this.isStale(index)) {
this.moveToTail(index)
if (updateAgeOnGet) {
this.updateItemAge(index)
}
return v
}
// ok, it is stale or a forced refresh, and not already fetching.
// refresh the cache.
const p = this.backgroundFetch(k, index, options, fetchContext)
return allowStale && p.__staleWhileFetching !== undefined
? p.__staleWhileFetching
: (p.__returned = p)
}
}
get(
k,
{
allowStale = this.allowStale,
updateAgeOnGet = this.updateAgeOnGet,
noDeleteOnStaleGet = this.noDeleteOnStaleGet,
} = {}
) {
const index = this.keyMap.get(k)
if (index !== undefined) {
const value = this.valList[index]
const fetching = this.isBackgroundFetch(value)
if (this.isStale(index)) {
// delete only if not an in-flight background fetch
if (!fetching) {
if (!noDeleteOnStaleGet) {
this.delete(k)
}
return allowStale ? value : undefined
} else {
return allowStale ? value.__staleWhileFetching : undefined
}
} else {
// if we're currently fetching it, we don't actually have it yet
// it's not stale, which means this isn't a staleWhileRefetching,
// so we just return undefined
if (fetching) {
return undefined
}
this.moveToTail(index)
if (updateAgeOnGet) {
this.updateItemAge(index)
}
return value
}
}
}
connect(p, n) {
this.prev[n] = p
this.next[p] = n
}
moveToTail(index) {
// if tail already, nothing to do
// if head, move head to next[index]
// else
// move next[prev[index]] to next[index] (head has no prev)
// move prev[next[index]] to prev[index]
// prev[index] = tail
// next[tail] = index
// tail = index
if (index !== this.tail) {
if (index === this.head) {
this.head = this.next[index]
} else {
this.connect(this.prev[index], this.next[index])
}
this.connect(this.tail, index)
this.tail = index
}
}
get del() {
deprecatedMethod('del', 'delete')
return this.delete
}
delete(k) {
let deleted = false
if (this.size !== 0) {
const index = this.keyMap.get(k)
if (index !== undefined) {
deleted = true
if (this.size === 1) {
this.clear()
} else {
this.removeItemSize(index)
const v = this.valList[index]
if (this.isBackgroundFetch(v)) {
v.__abortController.abort()
} else {
this.dispose(v, k, 'delete')
if (this.disposeAfter) {
this.disposed.push([v, k, 'delete'])
}
}
this.keyMap.delete(k)
this.keyList[index] = null
this.valList[index] = null
if (index === this.tail) {
this.tail = this.prev[index]
} else if (index === this.head) {
this.head = this.next[index]
} else {
this.next[this.prev[index]] = this.next[index]
this.prev[this.next[index]] = this.prev[index]
}
this.size--
this.free.push(index)
}
}
}
if (this.disposed) {
while (this.disposed.length) {
this.disposeAfter(...this.disposed.shift())
}
}
return deleted
}
clear() {
for (const index of this.rindexes({ allowStale: true })) {
const v = this.valList[index]
if (this.isBackgroundFetch(v)) {
v.__abortController.abort()
} else {
const k = this.keyList[index]
this.dispose(v, k, 'delete')
if (this.disposeAfter) {
this.disposed.push([v, k, 'delete'])
}
}
}
this.keyMap.clear()
this.valList.fill(null)
this.keyList.fill(null)
if (this.ttls) {
this.ttls.fill(0)
this.starts.fill(0)
}
if (this.sizes) {
this.sizes.fill(0)
}
this.head = 0
this.tail = 0
this.initialFill = 1
this.free.length = 0
this.calculatedSize = 0
this.size = 0
if (this.disposed) {
while (this.disposed.length) {
this.disposeAfter(...this.disposed.shift())
}
}
}
get reset() {
deprecatedMethod('reset', 'clear')
return this.clear
}
get length() {
deprecatedProperty('length', 'size')
return this.size
}
static get AbortController() {
return AC
}
static get AbortSignal() {
return AS
}
}
module.exports = LRUCache
Zerion Mini Shell 1.0