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| 1 | +'use strict' |
| 2 | + |
| 3 | +// A linked list to keep track of recently-used-ness |
| 4 | +const Yallist = require('yallist') |
| 5 | + |
| 6 | +const MAX = Symbol('max') |
| 7 | +const LENGTH = Symbol('length') |
| 8 | +const LENGTH_CALCULATOR = Symbol('lengthCalculator') |
| 9 | +const ALLOW_STALE = Symbol('allowStale') |
| 10 | +const MAX_AGE = Symbol('maxAge') |
| 11 | +const DISPOSE = Symbol('dispose') |
| 12 | +const NO_DISPOSE_ON_SET = Symbol('noDisposeOnSet') |
| 13 | +const LRU_LIST = Symbol('lruList') |
| 14 | +const CACHE = Symbol('cache') |
| 15 | +const UPDATE_AGE_ON_GET = Symbol('updateAgeOnGet') |
| 16 | + |
| 17 | +const naiveLength = () => 1 |
| 18 | + |
| 19 | +// lruList is a yallist where the head is the youngest |
| 20 | +// item, and the tail is the oldest. the list contains the Hit |
| 21 | +// objects as the entries. |
| 22 | +// Each Hit object has a reference to its Yallist.Node. This |
| 23 | +// never changes. |
| 24 | +// |
| 25 | +// cache is a Map (or PseudoMap) that matches the keys to |
| 26 | +// the Yallist.Node object. |
| 27 | +class LRUCache { |
| 28 | + constructor (options) { |
| 29 | + if (typeof options === 'number') |
| 30 | + options = { max: options } |
| 31 | + |
| 32 | + if (!options) |
| 33 | + options = {} |
| 34 | + |
| 35 | + if (options.max && (typeof options.max !== 'number' || options.max < 0)) |
| 36 | + throw new TypeError('max must be a non-negative number') |
| 37 | + // Kind of weird to have a default max of Infinity, but oh well. |
| 38 | + const max = this[MAX] = options.max || Infinity |
| 39 | + |
| 40 | + const lc = options.length || naiveLength |
| 41 | + this[LENGTH_CALCULATOR] = (typeof lc !== 'function') ? naiveLength : lc |
| 42 | + this[ALLOW_STALE] = options.stale || false |
| 43 | + if (options.maxAge && typeof options.maxAge !== 'number') |
| 44 | + throw new TypeError('maxAge must be a number') |
| 45 | + this[MAX_AGE] = options.maxAge || 0 |
| 46 | + this[DISPOSE] = options.dispose |
| 47 | + this[NO_DISPOSE_ON_SET] = options.noDisposeOnSet || false |
| 48 | + this[UPDATE_AGE_ON_GET] = options.updateAgeOnGet || false |
| 49 | + this.reset() |
| 50 | + } |
| 51 | + |
| 52 | + // resize the cache when the max changes. |
| 53 | + set max (mL) { |
| 54 | + if (typeof mL !== 'number' || mL < 0) |
| 55 | + throw new TypeError('max must be a non-negative number') |
| 56 | + |
| 57 | + this[MAX] = mL || Infinity |
| 58 | + trim(this) |
| 59 | + } |
| 60 | + get max () { |
| 61 | + return this[MAX] |
| 62 | + } |
| 63 | + |
| 64 | + set allowStale (allowStale) { |
| 65 | + this[ALLOW_STALE] = !!allowStale |
| 66 | + } |
| 67 | + get allowStale () { |
| 68 | + return this[ALLOW_STALE] |
| 69 | + } |
| 70 | + |
| 71 | + set maxAge (mA) { |
| 72 | + if (typeof mA !== 'number') |
| 73 | + throw new TypeError('maxAge must be a non-negative number') |
| 74 | + |
| 75 | + this[MAX_AGE] = mA |
| 76 | + trim(this) |
| 77 | + } |
| 78 | + get maxAge () { |
| 79 | + return this[MAX_AGE] |
| 80 | + } |
| 81 | + |
| 82 | + // resize the cache when the lengthCalculator changes. |
| 83 | + set lengthCalculator (lC) { |
| 84 | + if (typeof lC !== 'function') |
| 85 | + lC = naiveLength |
| 86 | + |
| 87 | + if (lC !== this[LENGTH_CALCULATOR]) { |
| 88 | + this[LENGTH_CALCULATOR] = lC |
| 89 | + this[LENGTH] = 0 |
| 90 | + this[LRU_LIST].forEach(hit => { |
| 91 | + hit.length = this[LENGTH_CALCULATOR](hit.value, hit.key) |
| 92 | + this[LENGTH] += hit.length |
| 93 | + }) |
| 94 | + } |
| 95 | + trim(this) |
| 96 | + } |
| 97 | + get lengthCalculator () { return this[LENGTH_CALCULATOR] } |
| 98 | + |
| 99 | + get length () { return this[LENGTH] } |
| 100 | + get itemCount () { return this[LRU_LIST].length } |
| 101 | + |
| 102 | + rforEach (fn, thisp) { |
| 103 | + thisp = thisp || this |
| 104 | + for (let walker = this[LRU_LIST].tail; walker !== null;) { |
| 105 | + const prev = walker.prev |
| 106 | + forEachStep(this, fn, walker, thisp) |
| 107 | + walker = prev |
| 108 | + } |
| 109 | + } |
| 110 | + |
| 111 | + forEach (fn, thisp) { |
| 112 | + thisp = thisp || this |
| 113 | + for (let walker = this[LRU_LIST].head; walker !== null;) { |
| 114 | + const next = walker.next |
| 115 | + forEachStep(this, fn, walker, thisp) |
| 116 | + walker = next |
| 117 | + } |
| 118 | + } |
| 119 | + |
| 120 | + keys () { |
| 121 | + return this[LRU_LIST].toArray().map(k => k.key) |
| 122 | + } |
| 123 | + |
| 124 | + values () { |
| 125 | + return this[LRU_LIST].toArray().map(k => k.value) |
| 126 | + } |
| 127 | + |
| 128 | + reset () { |
| 129 | + if (this[DISPOSE] && |
| 130 | + this[LRU_LIST] && |
| 131 | + this[LRU_LIST].length) { |
| 132 | + this[LRU_LIST].forEach(hit => this[DISPOSE](hit.key, hit.value)) |
| 133 | + } |
| 134 | + |
| 135 | + this[CACHE] = new Map() // hash of items by key |
| 136 | + this[LRU_LIST] = new Yallist() // list of items in order of use recency |
| 137 | + this[LENGTH] = 0 // length of items in the list |
| 138 | + } |
| 139 | + |
| 140 | + dump () { |
| 141 | + return this[LRU_LIST].map(hit => |
| 142 | + isStale(this, hit) ? false : { |
| 143 | + k: hit.key, |
| 144 | + v: hit.value, |
| 145 | + e: hit.now + (hit.maxAge || 0) |
| 146 | + }).toArray().filter(h => h) |
| 147 | + } |
| 148 | + |
| 149 | + dumpLru () { |
| 150 | + return this[LRU_LIST] |
| 151 | + } |
| 152 | + |
| 153 | + set (key, value, maxAge) { |
| 154 | + maxAge = maxAge || this[MAX_AGE] |
| 155 | + |
| 156 | + if (maxAge && typeof maxAge !== 'number') |
| 157 | + throw new TypeError('maxAge must be a number') |
| 158 | + |
| 159 | + const now = maxAge ? Date.now() : 0 |
| 160 | + const len = this[LENGTH_CALCULATOR](value, key) |
| 161 | + |
| 162 | + if (this[CACHE].has(key)) { |
| 163 | + if (len > this[MAX]) { |
| 164 | + del(this, this[CACHE].get(key)) |
| 165 | + return false |
| 166 | + } |
| 167 | + |
| 168 | + const node = this[CACHE].get(key) |
| 169 | + const item = node.value |
| 170 | + |
| 171 | + // dispose of the old one before overwriting |
| 172 | + // split out into 2 ifs for better coverage tracking |
| 173 | + if (this[DISPOSE]) { |
| 174 | + if (!this[NO_DISPOSE_ON_SET]) |
| 175 | + this[DISPOSE](key, item.value) |
| 176 | + } |
| 177 | + |
| 178 | + item.now = now |
| 179 | + item.maxAge = maxAge |
| 180 | + item.value = value |
| 181 | + this[LENGTH] += len - item.length |
| 182 | + item.length = len |
| 183 | + this.get(key) |
| 184 | + trim(this) |
| 185 | + return true |
| 186 | + } |
| 187 | + |
| 188 | + const hit = new Entry(key, value, len, now, maxAge) |
| 189 | + |
| 190 | + // oversized objects fall out of cache automatically. |
| 191 | + if (hit.length > this[MAX]) { |
| 192 | + if (this[DISPOSE]) |
| 193 | + this[DISPOSE](key, value) |
| 194 | + |
| 195 | + return false |
| 196 | + } |
| 197 | + |
| 198 | + this[LENGTH] += hit.length |
| 199 | + this[LRU_LIST].unshift(hit) |
| 200 | + this[CACHE].set(key, this[LRU_LIST].head) |
| 201 | + trim(this) |
| 202 | + return true |
| 203 | + } |
| 204 | + |
| 205 | + has (key) { |
| 206 | + if (!this[CACHE].has(key)) return false |
| 207 | + const hit = this[CACHE].get(key).value |
| 208 | + return !isStale(this, hit) |
| 209 | + } |
| 210 | + |
| 211 | + get (key) { |
| 212 | + return get(this, key, true) |
| 213 | + } |
| 214 | + |
| 215 | + peek (key) { |
| 216 | + return get(this, key, false) |
| 217 | + } |
| 218 | + |
| 219 | + pop () { |
| 220 | + const node = this[LRU_LIST].tail |
| 221 | + if (!node) |
| 222 | + return null |
| 223 | + |
| 224 | + del(this, node) |
| 225 | + return node.value |
| 226 | + } |
| 227 | + |
| 228 | + del (key) { |
| 229 | + del(this, this[CACHE].get(key)) |
| 230 | + } |
| 231 | + |
| 232 | + load (arr) { |
| 233 | + // reset the cache |
| 234 | + this.reset() |
| 235 | + |
| 236 | + const now = Date.now() |
| 237 | + // A previous serialized cache has the most recent items first |
| 238 | + for (let l = arr.length - 1; l >= 0; l--) { |
| 239 | + const hit = arr[l] |
| 240 | + const expiresAt = hit.e || 0 |
| 241 | + if (expiresAt === 0) |
| 242 | + // the item was created without expiration in a non aged cache |
| 243 | + this.set(hit.k, hit.v) |
| 244 | + else { |
| 245 | + const maxAge = expiresAt - now |
| 246 | + // dont add already expired items |
| 247 | + if (maxAge > 0) { |
| 248 | + this.set(hit.k, hit.v, maxAge) |
| 249 | + } |
| 250 | + } |
| 251 | + } |
| 252 | + } |
| 253 | + |
| 254 | + prune () { |
| 255 | + this[CACHE].forEach((value, key) => get(this, key, false)) |
| 256 | + } |
| 257 | +} |
| 258 | + |
| 259 | +const get = (self, key, doUse) => { |
| 260 | + const node = self[CACHE].get(key) |
| 261 | + if (node) { |
| 262 | + const hit = node.value |
| 263 | + if (isStale(self, hit)) { |
| 264 | + del(self, node) |
| 265 | + if (!self[ALLOW_STALE]) |
| 266 | + return undefined |
| 267 | + } else { |
| 268 | + if (doUse) { |
| 269 | + if (self[UPDATE_AGE_ON_GET]) |
| 270 | + node.value.now = Date.now() |
| 271 | + self[LRU_LIST].unshiftNode(node) |
| 272 | + } |
| 273 | + } |
| 274 | + return hit.value |
| 275 | + } |
| 276 | +} |
| 277 | + |
| 278 | +const isStale = (self, hit) => { |
| 279 | + if (!hit || (!hit.maxAge && !self[MAX_AGE])) |
| 280 | + return false |
| 281 | + |
| 282 | + const diff = Date.now() - hit.now |
| 283 | + return hit.maxAge ? diff > hit.maxAge |
| 284 | + : self[MAX_AGE] && (diff > self[MAX_AGE]) |
| 285 | +} |
| 286 | + |
| 287 | +const trim = self => { |
| 288 | + if (self[LENGTH] > self[MAX]) { |
| 289 | + for (let walker = self[LRU_LIST].tail; |
| 290 | + self[LENGTH] > self[MAX] && walker !== null;) { |
| 291 | + // We know that we're about to delete this one, and also |
| 292 | + // what the next least recently used key will be, so just |
| 293 | + // go ahead and set it now. |
| 294 | + const prev = walker.prev |
| 295 | + del(self, walker) |
| 296 | + walker = prev |
| 297 | + } |
| 298 | + } |
| 299 | +} |
| 300 | + |
| 301 | +const del = (self, node) => { |
| 302 | + if (node) { |
| 303 | + const hit = node.value |
| 304 | + if (self[DISPOSE]) |
| 305 | + self[DISPOSE](hit.key, hit.value) |
| 306 | + |
| 307 | + self[LENGTH] -= hit.length |
| 308 | + self[CACHE].delete(hit.key) |
| 309 | + self[LRU_LIST].removeNode(node) |
| 310 | + } |
| 311 | +} |
| 312 | + |
| 313 | +class Entry { |
| 314 | + constructor (key, value, length, now, maxAge) { |
| 315 | + this.key = key |
| 316 | + this.value = value |
| 317 | + this.length = length |
| 318 | + this.now = now |
| 319 | + this.maxAge = maxAge || 0 |
| 320 | + } |
| 321 | +} |
| 322 | + |
| 323 | +const forEachStep = (self, fn, node, thisp) => { |
| 324 | + let hit = node.value |
| 325 | + if (isStale(self, hit)) { |
| 326 | + del(self, node) |
| 327 | + if (!self[ALLOW_STALE]) |
| 328 | + hit = undefined |
| 329 | + } |
| 330 | + if (hit) |
| 331 | + fn.call(thisp, hit.value, hit.key, self) |
| 332 | +} |
| 333 | + |
| 334 | +module.exports = LRUCache |
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