Extremely fast and lightweight double-ended queue implementation with zero dependencies.
This script should not be not be installed directly. It is a library for other scripts to include with the meta directive // @require https://update.greasyfork.org/scripts/428422/943850/Denque.js
/**
* Copyright (c) 2018 Mike Diarmid (Salakar) <mike.diarmid@gmail.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this library except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
/**
* Custom implementation of a double ended queue.
*/
function Denque(array, options) {
var options = options || {};
this._head = 0;
this._tail = 0;
this._capacity = options.capacity;
this._capacityMask = 0x3;
this._list = new Array(4);
if (Array.isArray(array)) {
this._fromArray(array);
}
}
/**
* -------------
* PUBLIC API
* -------------
*/
/**
* Returns the item at the specified index from the list.
* 0 is the first element, 1 is the second, and so on...
* Elements at negative values are that many from the end: -1 is one before the end
* (the last element), -2 is two before the end (one before last), etc.
* @param index
* @returns {*}
*/
Denque.prototype.peekAt = function peekAt(index) {
var i = index;
// expect a number or return undefined
if ((i !== (i | 0))) {
return void 0;
}
var len = this.size();
if (i >= len || i < -len) return undefined;
if (i < 0) i += len;
i = (this._head + i) & this._capacityMask;
return this._list[i];
};
/**
* Alias for peekAt()
* @param i
* @returns {*}
*/
Denque.prototype.get = function get(i) {
return this.peekAt(i);
};
/**
* Returns the first item in the list without removing it.
* @returns {*}
*/
Denque.prototype.peek = function peek() {
if (this._head === this._tail) return undefined;
return this._list[this._head];
};
/**
* Alias for peek()
* @returns {*}
*/
Denque.prototype.peekFront = function peekFront() {
return this.peek();
};
/**
* Returns the item that is at the back of the queue without removing it.
* Uses peekAt(-1)
*/
Denque.prototype.peekBack = function peekBack() {
return this.peekAt(-1);
};
/**
* Returns the current length of the queue
* @return {Number}
*/
Object.defineProperty(Denque.prototype, 'length', {
get: function length() {
return this.size();
}
});
/**
* Return the number of items on the list, or 0 if empty.
* @returns {number}
*/
Denque.prototype.size = function size() {
if (this._head === this._tail) return 0;
if (this._head < this._tail) return this._tail - this._head;
else return this._capacityMask + 1 - (this._head - this._tail);
};
/**
* Add an item at the beginning of the list.
* @param item
*/
Denque.prototype.unshift = function unshift(item) {
if (item === undefined) return this.size();
var len = this._list.length;
this._head = (this._head - 1 + len) & this._capacityMask;
this._list[this._head] = item;
if (this._tail === this._head) this._growArray();
if (this._capacity && this.size() > this._capacity) this.pop();
if (this._head < this._tail) return this._tail - this._head;
else return this._capacityMask + 1 - (this._head - this._tail);
};
/**
* Remove and return the first item on the list,
* Returns undefined if the list is empty.
* @returns {*}
*/
Denque.prototype.shift = function shift() {
var head = this._head;
if (head === this._tail) return undefined;
var item = this._list[head];
this._list[head] = undefined;
this._head = (head + 1) & this._capacityMask;
if (head < 2 && this._tail > 10000 && this._tail <= this._list.length >>> 2) this._shrinkArray();
return item;
};
/**
* Add an item to the bottom of the list.
* @param item
*/
Denque.prototype.push = function push(item) {
if (item === undefined) return this.size();
var tail = this._tail;
this._list[tail] = item;
this._tail = (tail + 1) & this._capacityMask;
if (this._tail === this._head) {
this._growArray();
}
if (this._capacity && this.size() > this._capacity) {
this.shift();
}
if (this._head < this._tail) return this._tail - this._head;
else return this._capacityMask + 1 - (this._head - this._tail);
};
/**
* Remove and return the last item on the list.
* Returns undefined if the list is empty.
* @returns {*}
*/
Denque.prototype.pop = function pop() {
var tail = this._tail;
if (tail === this._head) return undefined;
var len = this._list.length;
this._tail = (tail - 1 + len) & this._capacityMask;
var item = this._list[this._tail];
this._list[this._tail] = undefined;
if (this._head < 2 && tail > 10000 && tail <= len >>> 2) this._shrinkArray();
return item;
};
/**
* Remove and return the item at the specified index from the list.
* Returns undefined if the list is empty.
* @param index
* @returns {*}
*/
Denque.prototype.removeOne = function removeOne(index) {
var i = index;
// expect a number or return undefined
if ((i !== (i | 0))) {
return void 0;
}
if (this._head === this._tail) return void 0;
var size = this.size();
var len = this._list.length;
if (i >= size || i < -size) return void 0;
if (i < 0) i += size;
i = (this._head + i) & this._capacityMask;
var item = this._list[i];
var k;
if (index < size / 2) {
for (k = index; k > 0; k--) {
this._list[i] = this._list[i = (i - 1 + len) & this._capacityMask];
}
this._list[i] = void 0;
this._head = (this._head + 1 + len) & this._capacityMask;
} else {
for (k = size - 1 - index; k > 0; k--) {
this._list[i] = this._list[i = ( i + 1 + len) & this._capacityMask];
}
this._list[i] = void 0;
this._tail = (this._tail - 1 + len) & this._capacityMask;
}
return item;
};
/**
* Remove number of items from the specified index from the list.
* Returns array of removed items.
* Returns undefined if the list is empty.
* @param index
* @param count
* @returns {array}
*/
Denque.prototype.remove = function remove(index, count) {
var i = index;
var removed;
var del_count = count;
// expect a number or return undefined
if ((i !== (i | 0))) {
return void 0;
}
if (this._head === this._tail) return void 0;
var size = this.size();
var len = this._list.length;
if (i >= size || i < -size || count < 1) return void 0;
if (i < 0) i += size;
if (count === 1 || !count) {
removed = new Array(1);
removed[0] = this.removeOne(i);
return removed;
}
if (i === 0 && i + count >= size) {
removed = this.toArray();
this.clear();
return removed;
}
if (i + count > size) count = size - i;
var k;
removed = new Array(count);
for (k = 0; k < count; k++) {
removed[k] = this._list[(this._head + i + k) & this._capacityMask];
}
i = (this._head + i) & this._capacityMask;
if (index + count === size) {
this._tail = (this._tail - count + len) & this._capacityMask;
for (k = count; k > 0; k--) {
this._list[i = (i + 1 + len) & this._capacityMask] = void 0;
}
return removed;
}
if (index === 0) {
this._head = (this._head + count + len) & this._capacityMask;
for (k = count - 1; k > 0; k--) {
this._list[i = (i + 1 + len) & this._capacityMask] = void 0;
}
return removed;
}
if (i < size / 2) {
this._head = (this._head + index + count + len) & this._capacityMask;
for (k = index; k > 0; k--) {
this.unshift(this._list[i = (i - 1 + len) & this._capacityMask]);
}
i = (this._head - 1 + len) & this._capacityMask;
while (del_count > 0) {
this._list[i = (i - 1 + len) & this._capacityMask] = void 0;
del_count--;
}
if (index < 0) this._tail = i;
} else {
this._tail = i;
i = (i + count + len) & this._capacityMask;
for (k = size - (count + index); k > 0; k--) {
this.push(this._list[i++]);
}
i = this._tail;
while (del_count > 0) {
this._list[i = (i + 1 + len) & this._capacityMask] = void 0;
del_count--;
}
}
if (this._head < 2 && this._tail > 10000 && this._tail <= len >>> 2) this._shrinkArray();
return removed;
};
/**
* Native splice implementation.
* Remove number of items from the specified index from the list and/or add new elements.
* Returns array of removed items or empty array if count == 0.
* Returns undefined if the list is empty.
*
* @param index
* @param count
* @param {...*} [elements]
* @returns {array}
*/
Denque.prototype.splice = function splice(index, count) {
var i = index;
// expect a number or return undefined
if ((i !== (i | 0))) {
return void 0;
}
var size = this.size();
if (i < 0) i += size;
if (i > size) return void 0;
if (arguments.length > 2) {
var k;
var temp;
var removed;
var arg_len = arguments.length;
var len = this._list.length;
var arguments_index = 2;
if (!size || i < size / 2) {
temp = new Array(i);
for (k = 0; k < i; k++) {
temp[k] = this._list[(this._head + k) & this._capacityMask];
}
if (count === 0) {
removed = [];
if (i > 0) {
this._head = (this._head + i + len) & this._capacityMask;
}
} else {
removed = this.remove(i, count);
this._head = (this._head + i + len) & this._capacityMask;
}
while (arg_len > arguments_index) {
this.unshift(arguments[--arg_len]);
}
for (k = i; k > 0; k--) {
this.unshift(temp[k - 1]);
}
} else {
temp = new Array(size - (i + count));
var leng = temp.length;
for (k = 0; k < leng; k++) {
temp[k] = this._list[(this._head + i + count + k) & this._capacityMask];
}
if (count === 0) {
removed = [];
if (i != size) {
this._tail = (this._head + i + len) & this._capacityMask;
}
} else {
removed = this.remove(i, count);
this._tail = (this._tail - leng + len) & this._capacityMask;
}
while (arguments_index < arg_len) {
this.push(arguments[arguments_index++]);
}
for (k = 0; k < leng; k++) {
this.push(temp[k]);
}
}
return removed;
} else {
return this.remove(i, count);
}
};
/**
* Soft clear - does not reset capacity.
*/
Denque.prototype.clear = function clear() {
this._head = 0;
this._tail = 0;
};
/**
* Returns true or false whether the list is empty.
* @returns {boolean}
*/
Denque.prototype.isEmpty = function isEmpty() {
return this._head === this._tail;
};
/**
* Returns an array of all queue items.
* @returns {Array}
*/
Denque.prototype.toArray = function toArray() {
return this._copyArray(false);
};
/**
* -------------
* INTERNALS
* -------------
*/
/**
* Fills the queue with items from an array
* For use in the constructor
* @param array
* @private
*/
Denque.prototype._fromArray = function _fromArray(array) {
for (var i = 0; i < array.length; i++) this.push(array[i]);
};
/**
*
* @param fullCopy
* @returns {Array}
* @private
*/
Denque.prototype._copyArray = function _copyArray(fullCopy) {
var newArray = [];
var list = this._list;
var len = list.length;
var i;
if (fullCopy || this._head > this._tail) {
for (i = this._head; i < len; i++) newArray.push(list[i]);
for (i = 0; i < this._tail; i++) newArray.push(list[i]);
} else {
for (i = this._head; i < this._tail; i++) newArray.push(list[i]);
}
return newArray;
};
/**
* Grows the internal list array.
* @private
*/
Denque.prototype._growArray = function _growArray() {
if (this._head) {
// copy existing data, head to end, then beginning to tail.
this._list = this._copyArray(true);
this._head = 0;
}
// head is at 0 and array is now full, safe to extend
this._tail = this._list.length;
this._list.length *= 2;
this._capacityMask = (this._capacityMask << 1) | 1;
};
/**
* Shrinks the internal list array.
* @private
*/
Denque.prototype._shrinkArray = function _shrinkArray() {
this._list.length >>>= 1;
this._capacityMask >>>= 1;
};
window.Denque = Denque;