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The ISC License | ||
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Copyright (c) Isaac Z. Schlueter and Contributors | ||
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Permission to use, copy, modify, and/or distribute this software for any | ||
purpose with or without fee is hereby granted, provided that the above | ||
copyright notice and this permission notice appear in all copies. | ||
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | ||
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | ||
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | ||
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | ||
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | ||
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR | ||
IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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'use strict' | ||
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// A linked list to keep track of recently-used-ness | ||
const Yallist = require('yallist') | ||
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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') | ||
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const naiveLength = () => 1 | ||
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// 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 } | ||
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if (!options) | ||
options = {} | ||
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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 | ||
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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() | ||
} | ||
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// 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') | ||
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this[MAX] = mL || Infinity | ||
trim(this) | ||
} | ||
get max () { | ||
return this[MAX] | ||
} | ||
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set allowStale (allowStale) { | ||
this[ALLOW_STALE] = !!allowStale | ||
} | ||
get allowStale () { | ||
return this[ALLOW_STALE] | ||
} | ||
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set maxAge (mA) { | ||
if (typeof mA !== 'number') | ||
throw new TypeError('maxAge must be a non-negative number') | ||
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this[MAX_AGE] = mA | ||
trim(this) | ||
} | ||
get maxAge () { | ||
return this[MAX_AGE] | ||
} | ||
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// resize the cache when the lengthCalculator changes. | ||
set lengthCalculator (lC) { | ||
if (typeof lC !== 'function') | ||
lC = naiveLength | ||
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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] } | ||
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get length () { return this[LENGTH] } | ||
get itemCount () { return this[LRU_LIST].length } | ||
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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 | ||
} | ||
} | ||
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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 | ||
} | ||
} | ||
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keys () { | ||
return this[LRU_LIST].toArray().map(k => k.key) | ||
} | ||
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values () { | ||
return this[LRU_LIST].toArray().map(k => k.value) | ||
} | ||
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reset () { | ||
if (this[DISPOSE] && | ||
this[LRU_LIST] && | ||
this[LRU_LIST].length) { | ||
this[LRU_LIST].forEach(hit => this[DISPOSE](hit.key, hit.value)) | ||
} | ||
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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 | ||
} | ||
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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) | ||
} | ||
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dumpLru () { | ||
return this[LRU_LIST] | ||
} | ||
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set (key, value, maxAge) { | ||
maxAge = maxAge || this[MAX_AGE] | ||
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if (maxAge && typeof maxAge !== 'number') | ||
throw new TypeError('maxAge must be a number') | ||
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const now = maxAge ? Date.now() : 0 | ||
const len = this[LENGTH_CALCULATOR](value, key) | ||
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if (this[CACHE].has(key)) { | ||
if (len > this[MAX]) { | ||
del(this, this[CACHE].get(key)) | ||
return false | ||
} | ||
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const node = this[CACHE].get(key) | ||
const item = node.value | ||
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// 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) | ||
} | ||
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item.now = now | ||
item.maxAge = maxAge | ||
item.value = value | ||
this[LENGTH] += len - item.length | ||
item.length = len | ||
this.get(key) | ||
trim(this) | ||
return true | ||
} | ||
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const hit = new Entry(key, value, len, now, maxAge) | ||
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// oversized objects fall out of cache automatically. | ||
if (hit.length > this[MAX]) { | ||
if (this[DISPOSE]) | ||
this[DISPOSE](key, value) | ||
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return false | ||
} | ||
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this[LENGTH] += hit.length | ||
this[LRU_LIST].unshift(hit) | ||
this[CACHE].set(key, this[LRU_LIST].head) | ||
trim(this) | ||
return true | ||
} | ||
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has (key) { | ||
if (!this[CACHE].has(key)) return false | ||
const hit = this[CACHE].get(key).value | ||
return !isStale(this, hit) | ||
} | ||
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get (key) { | ||
return get(this, key, true) | ||
} | ||
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peek (key) { | ||
return get(this, key, false) | ||
} | ||
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pop () { | ||
const node = this[LRU_LIST].tail | ||
if (!node) | ||
return null | ||
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del(this, node) | ||
return node.value | ||
} | ||
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del (key) { | ||
del(this, this[CACHE].get(key)) | ||
} | ||
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load (arr) { | ||
// reset the cache | ||
this.reset() | ||
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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) | ||
} | ||
} | ||
} | ||
} | ||
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prune () { | ||
this[CACHE].forEach((value, key) => get(this, key, false)) | ||
} | ||
} | ||
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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 | ||
} | ||
} | ||
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const isStale = (self, hit) => { | ||
if (!hit || (!hit.maxAge && !self[MAX_AGE])) | ||
return false | ||
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const diff = Date.now() - hit.now | ||
return hit.maxAge ? diff > hit.maxAge | ||
: self[MAX_AGE] && (diff > self[MAX_AGE]) | ||
} | ||
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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 | ||
} | ||
} | ||
} | ||
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const del = (self, node) => { | ||
if (node) { | ||
const hit = node.value | ||
if (self[DISPOSE]) | ||
self[DISPOSE](hit.key, hit.value) | ||
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self[LENGTH] -= hit.length | ||
self[CACHE].delete(hit.key) | ||
self[LRU_LIST].removeNode(node) | ||
} | ||
} | ||
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class Entry { | ||
constructor (key, value, length, now, maxAge) { | ||
this.key = key | ||
this.value = value | ||
this.length = length | ||
this.now = now | ||
this.maxAge = maxAge || 0 | ||
} | ||
} | ||
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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) | ||
} | ||
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module.exports = LRUCache |
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