mirror of
https://codeberg.org/tacerus/teddit.git
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438 lines
11 KiB
JavaScript
438 lines
11 KiB
JavaScript
'use strict';
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/**
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* Custom implementation of a double ended queue.
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*/
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function Denque(array) {
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this._head = 0;
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this._tail = 0;
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this._capacityMask = 0x3;
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this._list = new Array(4);
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if (Array.isArray(array)) {
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this._fromArray(array);
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}
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}
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/**
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* -------------
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* PUBLIC API
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* -------------
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*/
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/**
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* Returns the item at the specified index from the list.
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* 0 is the first element, 1 is the second, and so on...
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* Elements at negative values are that many from the end: -1 is one before the end
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* (the last element), -2 is two before the end (one before last), etc.
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* @param index
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* @returns {*}
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*/
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Denque.prototype.peekAt = function peekAt(index) {
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var i = index;
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// expect a number or return undefined
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if ((i !== (i | 0))) {
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return void 0;
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}
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var len = this.size();
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if (i >= len || i < -len) return undefined;
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if (i < 0) i += len;
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i = (this._head + i) & this._capacityMask;
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return this._list[i];
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};
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/**
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* Alias for peakAt()
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* @param i
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* @returns {*}
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*/
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Denque.prototype.get = function get(i) {
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return this.peekAt(i);
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};
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/**
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* Returns the first item in the list without removing it.
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* @returns {*}
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*/
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Denque.prototype.peek = function peek() {
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if (this._head === this._tail) return undefined;
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return this._list[this._head];
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};
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/**
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* Alias for peek()
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* @returns {*}
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*/
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Denque.prototype.peekFront = function peekFront() {
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return this.peek();
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};
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/**
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* Returns the item that is at the back of the queue without removing it.
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* Uses peekAt(-1)
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*/
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Denque.prototype.peekBack = function peekBack() {
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return this.peekAt(-1);
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};
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/**
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* Returns the current length of the queue
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* @return {Number}
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*/
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Object.defineProperty(Denque.prototype, 'length', {
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get: function length() {
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return this.size();
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}
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});
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/**
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* Return the number of items on the list, or 0 if empty.
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* @returns {number}
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*/
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Denque.prototype.size = function size() {
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if (this._head === this._tail) return 0;
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if (this._head < this._tail) return this._tail - this._head;
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else return this._capacityMask + 1 - (this._head - this._tail);
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};
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/**
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* Add an item at the beginning of the list.
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* @param item
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*/
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Denque.prototype.unshift = function unshift(item) {
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if (item === undefined) return this.size();
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var len = this._list.length;
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this._head = (this._head - 1 + len) & this._capacityMask;
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this._list[this._head] = item;
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if (this._tail === this._head) this._growArray();
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if (this._head < this._tail) return this._tail - this._head;
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else return this._capacityMask + 1 - (this._head - this._tail);
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};
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/**
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* Remove and return the first item on the list,
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* Returns undefined if the list is empty.
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* @returns {*}
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*/
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Denque.prototype.shift = function shift() {
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var head = this._head;
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if (head === this._tail) return undefined;
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var item = this._list[head];
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this._list[head] = undefined;
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this._head = (head + 1) & this._capacityMask;
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if (head < 2 && this._tail > 10000 && this._tail <= this._list.length >>> 2) this._shrinkArray();
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return item;
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};
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/**
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* Add an item to the bottom of the list.
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* @param item
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*/
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Denque.prototype.push = function push(item) {
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if (item === undefined) return this.size();
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var tail = this._tail;
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this._list[tail] = item;
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this._tail = (tail + 1) & this._capacityMask;
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if (this._tail === this._head) {
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this._growArray();
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}
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if (this._head < this._tail) return this._tail - this._head;
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else return this._capacityMask + 1 - (this._head - this._tail);
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};
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/**
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* Remove and return the last item on the list.
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* Returns undefined if the list is empty.
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* @returns {*}
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*/
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Denque.prototype.pop = function pop() {
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var tail = this._tail;
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if (tail === this._head) return undefined;
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var len = this._list.length;
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this._tail = (tail - 1 + len) & this._capacityMask;
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var item = this._list[this._tail];
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this._list[this._tail] = undefined;
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if (this._head < 2 && tail > 10000 && tail <= len >>> 2) this._shrinkArray();
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return item;
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};
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/**
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* Remove and return the item at the specified index from the list.
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* Returns undefined if the list is empty.
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* @param index
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* @returns {*}
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*/
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Denque.prototype.removeOne = function removeOne(index) {
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var i = index;
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// expect a number or return undefined
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if ((i !== (i | 0))) {
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return void 0;
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}
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if (this._head === this._tail) return void 0;
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var size = this.size();
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var len = this._list.length;
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if (i >= size || i < -size) return void 0;
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if (i < 0) i += size;
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i = (this._head + i) & this._capacityMask;
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var item = this._list[i];
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var k;
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if (index < size / 2) {
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for (k = index; k > 0; k--) {
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this._list[i] = this._list[i = (i - 1 + len) & this._capacityMask];
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}
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this._list[i] = void 0;
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this._head = (this._head + 1 + len) & this._capacityMask;
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} else {
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for (k = size - 1 - index; k > 0; k--) {
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this._list[i] = this._list[i = ( i + 1 + len) & this._capacityMask];
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}
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this._list[i] = void 0;
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this._tail = (this._tail - 1 + len) & this._capacityMask;
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}
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return item;
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};
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/**
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* Remove number of items from the specified index from the list.
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* Returns array of removed items.
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* Returns undefined if the list is empty.
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* @param index
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* @param count
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* @returns {array}
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*/
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Denque.prototype.remove = function remove(index, count) {
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var i = index;
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var removed;
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var del_count = count;
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// expect a number or return undefined
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if ((i !== (i | 0))) {
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return void 0;
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}
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if (this._head === this._tail) return void 0;
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var size = this.size();
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var len = this._list.length;
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if (i >= size || i < -size || count < 1) return void 0;
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if (i < 0) i += size;
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if (count === 1 || !count) {
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removed = new Array(1);
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removed[0] = this.removeOne(i);
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return removed;
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}
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if (i === 0 && i + count >= size) {
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removed = this.toArray();
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this.clear();
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return removed;
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}
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if (i + count > size) count = size - i;
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var k;
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removed = new Array(count);
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for (k = 0; k < count; k++) {
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removed[k] = this._list[(this._head + i + k) & this._capacityMask];
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}
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i = (this._head + i) & this._capacityMask;
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if (index + count === size) {
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this._tail = (this._tail - count + len) & this._capacityMask;
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for (k = count; k > 0; k--) {
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this._list[i = (i + 1 + len) & this._capacityMask] = void 0;
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}
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return removed;
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}
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if (index === 0) {
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this._head = (this._head + count + len) & this._capacityMask;
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for (k = count - 1; k > 0; k--) {
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this._list[i = (i + 1 + len) & this._capacityMask] = void 0;
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}
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return removed;
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}
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if (i < size / 2) {
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this._head = (this._head + index + count + len) & this._capacityMask;
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for (k = index; k > 0; k--) {
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this.unshift(this._list[i = (i - 1 + len) & this._capacityMask]);
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}
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i = (this._head - 1 + len) & this._capacityMask;
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while (del_count > 0) {
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this._list[i = (i - 1 + len) & this._capacityMask] = void 0;
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del_count--;
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}
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if (index < 0) this._tail = i;
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} else {
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this._tail = i;
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i = (i + count + len) & this._capacityMask;
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for (k = size - (count + index); k > 0; k--) {
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this.push(this._list[i++]);
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}
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i = this._tail;
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while (del_count > 0) {
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this._list[i = (i + 1 + len) & this._capacityMask] = void 0;
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del_count--;
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}
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}
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if (this._head < 2 && this._tail > 10000 && this._tail <= len >>> 2) this._shrinkArray();
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return removed;
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};
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/**
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* Native splice implementation.
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* Remove number of items from the specified index from the list and/or add new elements.
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* Returns array of removed items or empty array if count == 0.
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* Returns undefined if the list is empty.
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*
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* @param index
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* @param count
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* @param {...*} [elements]
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* @returns {array}
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*/
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Denque.prototype.splice = function splice(index, count) {
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var i = index;
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// expect a number or return undefined
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if ((i !== (i | 0))) {
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return void 0;
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}
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var size = this.size();
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if (i < 0) i += size;
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if (i > size) return void 0;
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if (arguments.length > 2) {
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var k;
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var temp;
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var removed;
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var arg_len = arguments.length;
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var len = this._list.length;
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var arguments_index = 2;
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if (!size || i < size / 2) {
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temp = new Array(i);
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for (k = 0; k < i; k++) {
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temp[k] = this._list[(this._head + k) & this._capacityMask];
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}
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if (count === 0) {
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removed = [];
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if (i > 0) {
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this._head = (this._head + i + len) & this._capacityMask;
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}
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} else {
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removed = this.remove(i, count);
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this._head = (this._head + i + len) & this._capacityMask;
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}
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while (arg_len > arguments_index) {
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this.unshift(arguments[--arg_len]);
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}
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for (k = i; k > 0; k--) {
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this.unshift(temp[k - 1]);
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}
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} else {
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temp = new Array(size - (i + count));
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var leng = temp.length;
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for (k = 0; k < leng; k++) {
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temp[k] = this._list[(this._head + i + count + k) & this._capacityMask];
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}
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if (count === 0) {
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removed = [];
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if (i != size) {
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this._tail = (this._head + i + len) & this._capacityMask;
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}
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} else {
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removed = this.remove(i, count);
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this._tail = (this._tail - leng + len) & this._capacityMask;
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}
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while (arguments_index < arg_len) {
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this.push(arguments[arguments_index++]);
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}
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for (k = 0; k < leng; k++) {
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this.push(temp[k]);
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}
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}
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return removed;
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} else {
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return this.remove(i, count);
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}
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};
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/**
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* Soft clear - does not reset capacity.
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*/
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Denque.prototype.clear = function clear() {
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this._head = 0;
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this._tail = 0;
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};
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/**
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* Returns true or false whether the list is empty.
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* @returns {boolean}
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*/
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Denque.prototype.isEmpty = function isEmpty() {
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return this._head === this._tail;
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};
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/**
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* Returns an array of all queue items.
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* @returns {Array}
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*/
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Denque.prototype.toArray = function toArray() {
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return this._copyArray(false);
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};
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/**
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* -------------
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* INTERNALS
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* -------------
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*/
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/**
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* Fills the queue with items from an array
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* For use in the constructor
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* @param array
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* @private
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*/
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Denque.prototype._fromArray = function _fromArray(array) {
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for (var i = 0; i < array.length; i++) this.push(array[i]);
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};
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/**
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*
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* @param fullCopy
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* @returns {Array}
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* @private
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*/
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Denque.prototype._copyArray = function _copyArray(fullCopy) {
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var newArray = [];
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var list = this._list;
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var len = list.length;
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var i;
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if (fullCopy || this._head > this._tail) {
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for (i = this._head; i < len; i++) newArray.push(list[i]);
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for (i = 0; i < this._tail; i++) newArray.push(list[i]);
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} else {
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for (i = this._head; i < this._tail; i++) newArray.push(list[i]);
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}
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return newArray;
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};
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/**
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* Grows the internal list array.
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* @private
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*/
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Denque.prototype._growArray = function _growArray() {
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if (this._head) {
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// copy existing data, head to end, then beginning to tail.
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this._list = this._copyArray(true);
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this._head = 0;
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}
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// head is at 0 and array is now full, safe to extend
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this._tail = this._list.length;
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this._list.length *= 2;
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this._capacityMask = (this._capacityMask << 1) | 1;
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};
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/**
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* Shrinks the internal list array.
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* @private
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*/
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Denque.prototype._shrinkArray = function _shrinkArray() {
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this._list.length >>>= 1;
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this._capacityMask >>>= 1;
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};
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module.exports = Denque;
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