73 lines
1.6 KiB
JavaScript
73 lines
1.6 KiB
JavaScript
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// https://github.com/rsms/js-lru
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var Cache = new function() {
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// jshint ignore:line
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function LRU(maxLength) {
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this.size = 0
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this.limit = maxLength
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this.head = this.tail = void 0
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this._keymap = {}
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}
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var p = LRU.prototype
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p.put = function(key, value) {
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var entry = {
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key: key,
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value: value
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}
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this._keymap[key] = entry
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if (this.tail) {
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this.tail.newer = entry
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entry.older = this.tail
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} else {
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this.head = entry
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}
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this.tail = entry
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if (this.size === this.limit) {
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this.shift()
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} else {
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this.size++
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}
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return value
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}
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p.shift = function() {
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var entry = this.head
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if (entry) {
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this.head = this.head.newer
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this.head.older = entry.newer = entry.older = this._keymap[
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entry.key
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] = void 0
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delete this._keymap[entry.key] //#1029
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}
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}
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p.get = function(key) {
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var entry = this._keymap[key]
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if (entry === void 0) return
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if (entry === this.tail) {
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return entry.value
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}
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// HEAD--------------TAIL
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// <.older .newer>
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// <--- add direction --
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// A B C <D> E
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if (entry.newer) {
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if (entry === this.head) {
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this.head = entry.newer
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}
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entry.newer.older = entry.older // C <-- E.
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}
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if (entry.older) {
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entry.older.newer = entry.newer // C. --> E
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}
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entry.newer = void 0 // D --x
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entry.older = this.tail // D. --> E
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if (this.tail) {
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this.tail.newer = entry // E. <-- D
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}
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this.tail = entry
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return entry.value
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}
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return LRU
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}() // jshint ignore:line
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