447 lines
8.9 KiB
JavaScript
447 lines
8.9 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* eslint-disable no-restricted-syntax, no-invalid-this */
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'use strict';
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// MODULES //
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var setReadOnly = require( './../../define-nonenumerable-read-only-property' );
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var setReadOnlyAccessor = require( './../../define-nonenumerable-read-only-accessor' );
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var iteratorSymbol = require( '@stdlib/symbol/iterator' );
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var Node = require( './node.js' ); // eslint-disable-line stdlib/no-redeclare
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// MAIN //
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/**
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* First-in-first-out queue constructor.
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*
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* @constructor
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* @returns {FIFO} FIFO queue instance
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Remove the first value:
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* var v = queue.pop();
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* // returns 'foo'
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*
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* // Add a new value to the queue:
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* queue.push( 'beep' );
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*
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* // Remove the "oldest" queue value:
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* v = queue.pop();
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* // returns 'bar'
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*/
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function FIFO() {
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if ( !(this instanceof FIFO) ) {
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return new FIFO();
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}
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this._length = 0;
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this._first = null;
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this._last = null;
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return this;
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}
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/**
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* Clears the queue.
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*
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* @name clear
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {FIFO} queue instance
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Peek at the first value:
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* var v = queue.first();
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* // returns 'foo'
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*
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* // Examine the queue length:
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* var len = queue.length;
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* // returns 2
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*
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* // Clear all queue items:
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* queue.clear();
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*
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* // Peek at the first value:
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* v = queue.first();
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* // returns undefined
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*
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* // Examine the queue length:
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* len = queue.length;
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* // returns 0
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*/
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setReadOnly( FIFO.prototype, 'clear', function clear() {
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this._length = 0;
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this._first = null;
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this._last = null;
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return this;
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});
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/**
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* Returns the "oldest" queue value (i.e., the value which is "first-out").
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*
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* @name first
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {(*|void)} "oldest" queue value
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Peek at the first value:
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* var v = queue.first();
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* // returns 'foo'
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*/
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setReadOnly( FIFO.prototype, 'first', function first() {
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if ( this._length ) {
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return this._first.value;
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}
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});
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/**
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* Returns an iterator for iterating over a queue.
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*
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* ## Notes
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*
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* - In order to prevent confusion arising from queue mutation during iteration, a returned iterator **always** iterates over a queue "snapshot", which is defined as the list of queue elements at the time of this method's invocation.
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*
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* @name iterator
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {Iterator} iterator
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Create an iterator:
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* var it = queue.iterator();
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*
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* // Iterate over the queue...
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* var v = it.next().value;
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* // returns 'foo'
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*
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* v = it.next().value;
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* // returns 'bar'
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*
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* var bool = it.next().done;
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* // returns true
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*/
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setReadOnly( FIFO.prototype, 'iterator', function iterator() {
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var values;
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var iter;
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var self;
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var FLG;
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var i;
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self = this;
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// Initialize the iteration index:
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i = -1;
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// Create a copy of queue values (necessary in order to "snapshot" the queue; otherwise, values could come and go between calls to `next`):
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values = this.toArray();
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// Create an iterator protocol-compliant object:
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iter = {};
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setReadOnly( iter, 'next', next );
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setReadOnly( iter, 'return', end );
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if ( iteratorSymbol ) {
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setReadOnly( iter, iteratorSymbol, factory );
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}
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return iter;
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/**
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* Returns an iterator protocol-compliant object containing the next iterated value.
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*
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* @private
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* @returns {Object} iterator protocol-compliant object
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*/
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function next() {
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i += 1;
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if ( FLG || i >= values.length ) {
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return {
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'done': true
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};
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}
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return {
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'value': values[ i ],
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'done': false
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};
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}
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/**
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* Finishes an iterator.
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*
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* @private
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* @param {*} [value] - value to return
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* @returns {Object} iterator protocol-compliant object
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*/
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function end( value ) {
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FLG = true;
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if ( arguments.length ) {
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return {
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'value': value,
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'done': true
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};
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}
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return {
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'done': true
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};
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}
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/**
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* Returns a new iterator.
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*
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* @private
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* @returns {Iterator} iterator
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*/
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function factory() {
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return self.iterator();
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}
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});
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/**
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* Returns the "newest" queue value (i.e., the value which is currently "last-out").
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*
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* @name last
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {(*|void)} "newest" queue value
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Peek at the last value:
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* var v = queue.last();
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* // returns 'bar'
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*/
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setReadOnly( FIFO.prototype, 'last', function last() {
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if ( this._length ) {
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return this._last.value;
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}
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});
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/**
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* Queue length.
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*
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* @name length
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* @memberof FIFO.prototype
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* @type {NonNegativeInteger}
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*
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* @example
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* var queue = new FIFO();
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*
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* // Examine the initial queue length:
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* var len = queue.length;
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* // returns 0
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Retrieve the current queue length:
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* len = queue.length;
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* // returns 2
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*/
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setReadOnlyAccessor( FIFO.prototype, 'length', function get() {
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return this._length;
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});
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/**
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* Removes a value from the queue.
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*
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* @name pop
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {(*|void)} removed value
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Remove the first value:
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* var v = queue.pop();
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* // returns 'foo'
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*
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* // Add a new value to the queue:
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* queue.push( 'beep' );
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*
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* // Remove the "oldest" queue value:
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* v = queue.pop();
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* // returns 'bar'
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*/
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setReadOnly( FIFO.prototype, 'pop', function pop() {
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var value;
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if ( this._length ) {
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// Retrieve the "first-out" value:
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value = this._first.value;
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// Check whether we have a new "first-out" or whether we have drained the queue...
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if ( this._first.next ) {
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this._first = this._first.next;
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this._first.prev = null;
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} else {
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// Queue is empty:
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this._first = null;
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this._last = null;
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}
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// Decrement the queue length:
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this._length -= 1;
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}
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return value;
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});
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/**
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* Adds a value to the queue.
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*
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* @name push
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {FIFO} queue instance
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Remove the first value:
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* var v = queue.pop();
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* // returns 'foo'
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*
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* // Add a new value to the queue:
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* queue.push( 'beep' );
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*
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* // Remove the "oldest" queue value:
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* v = queue.pop();
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* // returns 'bar'
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*/
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setReadOnly( FIFO.prototype, 'push', function push( value ) {
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var node;
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// Create a new queue node:
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node = new Node( value );
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// Check whether the queue is currently empty...
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if ( this._length === 0 ) {
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// This is the only queued node, making it both the first and last node:
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this._first = node;
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this._last = node;
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} else {
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// Link the node to the previous most "recent" node:
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node.prev = this._last;
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// Link the previous most "recent" node to the new node:
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this._last.next = node;
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// Update the queue pointer for the "last" node to the new node:
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this._last = node;
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}
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// Increment the queue length:
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this._length += 1;
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return this;
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});
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/**
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* Returns an array of queue values.
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*
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* @name toArray
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {Array} queue values
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Get an array of queue values:
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* var vals = queue.toArray();
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* // returns [ 'foo', 'bar' ]
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*/
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setReadOnly( FIFO.prototype, 'toArray', function toArray() {
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var node;
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var out;
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var i;
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out = [];
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node = this._first;
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for ( i = 0; i < this._length; i++ ) {
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out.push( node.value );
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node = node.next;
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}
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return out;
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});
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/**
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* Serializes a queue as JSON.
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*
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* ## Notes
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*
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* - `JSON.stringify()` implicitly calls this method when stringifying a `FIFO` instance.
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*
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* @name toJSON
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* @memberof FIFO.prototype
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* @type {Function}
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* @returns {Object} serialized queue
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*
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* @example
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* var queue = new FIFO();
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*
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* // Add values to the queue:
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* queue.push( 'foo' ).push( 'bar' );
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*
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* // Serialize to JSON:
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* var o = queue.toJSON();
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* // returns { 'type': 'fifo', 'data': [ 'foo', 'bar' ] }
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*/
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setReadOnly( FIFO.prototype, 'toJSON', function toJSON() {
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var out = {};
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out.type = 'fifo';
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out.data = this.toArray();
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return out;
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});
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// EXPORTS //
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module.exports = FIFO;
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