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Diffstat (limited to 'tools/addon-sdk-1.3/packages/api-utils/lib/cortex.js')
-rw-r--r-- | tools/addon-sdk-1.3/packages/api-utils/lib/cortex.js | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/tools/addon-sdk-1.3/packages/api-utils/lib/cortex.js b/tools/addon-sdk-1.3/packages/api-utils/lib/cortex.js new file mode 100644 index 0000000..059d9de --- /dev/null +++ b/tools/addon-sdk-1.3/packages/api-utils/lib/cortex.js @@ -0,0 +1,139 @@ +/* vim:set ts=2 sw=2 sts=2 + * ***** BEGIN LICENSE BLOCK ***** + * Version: MPL 1.1/GPL 2.0/LGPL 2.1 + * + * The contents of this file are subject to the Mozilla Public License Version + * 1.1 (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * http://www.mozilla.org/MPL/ + * + * Software distributed under the License is distributed on an "AS IS" basis, + * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License + * for the specific language governing rights and limitations under the + * License. + * + * The Initial Developer of the Original Code is Mozilla. + * Portions created by the Initial Developer are Copyright (C) 2010 + * the Initial Developer. All Rights Reserved. + * + * Contributor(s): + * Irakli Gozalishvili <gozala@mozilla.com> (Original author) + * + * Alternatively, the contents of this file may be used under the terms of + * either the GNU General Public License Version 2 or later (the "GPL"), or + * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), + * in which case the provisions of the GPL or the LGPL are applicable instead + * of those above. If you wish to allow use of your version of this file only + * under the terms of either the GPL or the LGPL, and not to allow others to + * use your version of this file under the terms of the MPL, indicate your + * decision by deleting the provisions above and replace them with the notice + * and other provisions required by the GPL or the LGPL. If you do not delete + * the provisions above, a recipient may use your version of this file under + * the terms of any one of the MPL, the GPL or the LGPL. + * + * ***** END LICENSE BLOCK ***** */ + +"use strict"; + +// `var` is being used in the module in order to make it reusable in +// environments in which `let` and `const` is not yet supported. + +// Returns `object`'s property value, where `name` is a name of the property. +function get(object, name) { + return object[name]; +} + +// Assigns `value` to the `object`'s property, where `name` is the name of the +// property. +function set(object, name, value) { + return object[name] = value; +} + +/** + * Given an `object` containing a property with the given `name`, create + * a property descriptor that can be used to define alias/proxy properties + * on other objects. A change in the value of an alias will propagate + * to the aliased property and vice versa. + */ +function createAliasProperty(object, name) { + // Getting own property descriptor of an `object` for the given `name` as + // we are going to create proxy analog. + var property = Object.getOwnPropertyDescriptor(object, name); + var descriptor = { + configurable: property.configurable, + enumerable: property.enumerable, + alias: true + }; + + // If the original property has a getter and/or setter, bind a + // corresponding getter/setter in the alias descriptor to the original + // object, so the `this` object in the getter/setter is the original object + // rather than the alias. + if ("get" in property && property.get) + descriptor.get = property.get.bind(object); + if ("set" in property && property.set) + descriptor.set = property.set.bind(object); + + // If original property was a value property. + if ("value" in property) { + // If original property is a method using it's `object` bounded copy. + if (typeof property.value === "function") { + descriptor.value = property.value.bind(object); + // Also preserving writability of the original property. + descriptor.writable = property.writable; + } + + // If the original property was just a data property, we create proxy + // accessors using our custom get/set functions to propagate changes to the + // original `object` and vice versa. + else { + descriptor.get = get.bind(null, object, name); + descriptor.set = set.bind(null, object, name); + } + } + return descriptor; +} + +// Defines property on `object` object with a name `alias` if given if not +// defaults to `name` that represents an alias of `source[name]`. If aliased +// property was an assessor or a method `this` pseudo-variable will be `source` +// when invoked. If aliased property was a data property changes on any of the +// aliases will propagate to the `source[name]` and also other way round. +function defineAlias(source, target, name, alias) { + return Object.defineProperty(target, alias || name, + createAliasProperty(source, name)); +} + +/** + * Function takes any `object` and returns a proxy for its own public + * properties. By default properties are considered to be public if they don't + * start with `"_"`, but default behavior can be overridden if needed, by + * passing array of public property `names` as a second argument. By default + * returned object will be direct decedent of the given `object`'s prototype, + * but this can be overridden by passing third optional argument, that will be + * used as `prototype` instead. + * @param {Object} object + * Object to create cortex for. + * @param {String[]} [names] + * Optional array of public property names. + * @param {Object} [prototype] + * Optional argument that will be used as `prototype` of the returned object, + * if not provided `Object.getPrototypeOf(object)` is used instead. + */ +exports.Cortex = function Cortex(object, names, prototype) { + // Creating a cortex object from the given `prototype`, if one was not + // provided then `prototype` of a given `object` is used. This allows + // consumer to define expected behavior `instanceof`. In common case + // `prototype` argument can be omitted to preserve same behavior of + // `instanceof` as on original `object`. + var cortex = Object.create(prototype || Object.getPrototypeOf(object)); + // Creating alias properties on the `cortex` object for all the own + // properties of the original `object` that are contained in `names` array. + // If `names` array is not provided then all the properties that don't + // start with `"_"` are aliased. + Object.getOwnPropertyNames(object).forEach(function (name) { + if ((!names && "_" !== name.charAt(0)) || (names && ~names.indexOf(name))) + defineAlias(object, cortex, name); + }); + return cortex; +} |