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183 lines
3.7 KiB
183 lines
3.7 KiB
5 years ago
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/**
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* Module dependencies.
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*/
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var Symbol = require('es6-symbol');
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var debug = require('debug')('array-index');
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var get = Symbol('get');
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var set = Symbol('set');
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var length = Symbol('length');
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/**
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* JavaScript Array "length" is bound to an unsigned 32-bit int.
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* See: http://stackoverflow.com/a/6155063/376773
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*/
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var MAX_LENGTH = Math.pow(2, 32);
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/**
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* Module exports.
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*/
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module.exports = ArrayIndex;
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ArrayIndex.get = get;
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ArrayIndex.set = set;
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/**
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* Subclass this.
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*/
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function ArrayIndex (_length) {
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Object.defineProperty(this, 'length', {
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get: getLength,
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set: setLength,
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enumerable: false,
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configurable: true
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});
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this[length] = 0;
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if (arguments.length > 0) {
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setLength.call(this, _length);
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}
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}
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/**
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* You overwrite the "get" Symbol in your subclass.
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*/
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ArrayIndex.prototype[ArrayIndex.get] = function () {
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throw new Error('you must implement the `ArrayIndex.get` Symbol');
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};
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/**
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* You overwrite the "set" Symbol in your subclass.
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*/
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ArrayIndex.prototype[ArrayIndex.set] = function () {
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throw new Error('you must implement the `ArrayIndex.set` Symbol');
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};
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/**
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* Converts this array class into a real JavaScript Array. Note that this
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* is a "flattened" array and your defined getters and setters won't be invoked
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* when you interact with the returned Array. This function will call the
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* getter on every array index of the object.
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*
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* @return {Array} The flattened array
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* @api public
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*/
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ArrayIndex.prototype.toArray = function toArray () {
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var i = 0;
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var l = this.length;
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var array = new Array(l);
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for (; i < l; i++) {
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array[i] = this[i];
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}
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return array;
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};
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/**
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* Basic support for `JSON.stringify()`.
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*/
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ArrayIndex.prototype.toJSON = function toJSON () {
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return this.toArray();
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};
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/**
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* toString() override. Use Array.prototype.toString().
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*/
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ArrayIndex.prototype.toString = function toString () {
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var a = this.toArray();
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return a.toString.apply(a, arguments);
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};
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/**
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* inspect() override. For the REPL.
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*/
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ArrayIndex.prototype.inspect = function inspect () {
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var a = this.toArray();
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Object.keys(this).forEach(function (k) {
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a[k] = this[k];
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}, this);
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return a;
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};
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/**
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* Getter for the "length" property.
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* Returns the value of the "length" Symbol.
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*/
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function getLength () {
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debug('getting "length": %o', this[length]);
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return this[length];
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};
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/**
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* Setter for the "length" property.
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* Calls "ensureLength()", then sets the "length" Symbol.
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*/
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function setLength (v) {
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debug('setting "length": %o', v);
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return this[length] = ensureLength(this, v);
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};
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/**
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* Ensures that getters/setters from 0 up to "_newLength" have been defined
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* on `Object.getPrototypeOf(this)`.
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*
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* @api private
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*/
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function ensureLength (self, _newLength) {
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var newLength;
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if (_newLength > MAX_LENGTH) {
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newLength = MAX_LENGTH;
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} else {
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newLength = _newLength | 0;
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}
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var proto = Object.getPrototypeOf(self);
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var cur = proto[length] | 0;
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var num = newLength - cur;
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if (num > 0) {
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var desc = {};
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debug('creating a descriptor object with %o entries', num);
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for (var i = cur; i < newLength; i++) {
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desc[i] = setup(i);
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}
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debug('calling `Object.defineProperties()` with %o entries', num);
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Object.defineProperties(proto, desc);
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proto[length] = newLength;
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}
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return newLength;
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}
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/**
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* Returns a property descriptor for the given "index", with "get" and "set"
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* functions created within the closure.
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*
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* @api private
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*/
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function setup (index) {
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function get () {
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return this[ArrayIndex.get](index);
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}
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function set (v) {
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return this[ArrayIndex.set](index, v);
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}
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return {
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enumerable: true,
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configurable: true,
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get: get,
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set: set
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};
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}
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