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/* |
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Copyright 2013 Rob Wu <gwnRob@gmail.com> |
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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// Target: Chrome 20+
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// W3-compliant Worker proxy.
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// This module replaces the global Worker object.
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// When invoked, the default Worker object is called.
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// If this call fails with SECURITY_ERR, the script is fetched
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// using async XHR, and transparently proxies all calls and
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// setters/getters to the new Worker object.
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// Note: This script does not magically circumvent the Same origin policy.
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(function() { |
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'use strict'; |
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var Worker_ = window.Worker; |
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var URL = window.URL || window.webkitURL; |
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// Create dummy worker for the following purposes:
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// 1. Don't override the global Worker object if the fallback isn't
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// going to work (future API changes?)
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// 2. Use it to trigger early validation of postMessage calls
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// Note: Blob constructor is supported since Chrome 20, but since
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// some of the used Chrome APIs are only supported as of Chrome 20,
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// I don't bother adding a BlobBuilder fallback.
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var dummyWorker = new Worker_( |
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URL.createObjectURL(new Blob([], {type: 'text/javascript'}))); |
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window.Worker = function Worker(scriptURL) { |
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if (arguments.length === 0) { |
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throw new TypeError('Not enough arguments'); |
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} |
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try { |
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return new Worker_(scriptURL); |
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} catch (e) { |
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if (e.code === 18/*DOMException.SECURITY_ERR*/) { |
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return new WorkerXHR(scriptURL); |
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} else { |
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throw e; |
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} |
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} |
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}; |
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// Bind events and replay queued messages
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function bindWorker(worker, workerURL) { |
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if (worker._terminated) { |
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return; |
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} |
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worker.Worker = new Worker_(workerURL); |
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worker.Worker.onerror = worker._onerror; |
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worker.Worker.onmessage = worker._onmessage; |
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var o; |
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while ( (o = worker._replayQueue.shift()) ) { |
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worker.Worker[o.method].apply(worker.Worker, o.arguments); |
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} |
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while ( (o = worker._messageQueue.shift()) ) { |
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worker.Worker.postMessage.apply(worker.Worker, o); |
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} |
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} |
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function WorkerXHR(scriptURL) { |
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var worker = this; |
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var x = new XMLHttpRequest(); |
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x.responseType = 'blob'; |
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x.onload = function() { |
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// http://stackoverflow.com/a/10372280/938089
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var workerURL = URL.createObjectURL(x.response); |
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bindWorker(worker, workerURL); |
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}; |
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x.open('GET', scriptURL); |
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x.send(); |
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worker._replayQueue = []; |
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worker._messageQueue = []; |
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} |
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WorkerXHR.prototype = { |
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constructor: Worker_, |
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terminate: function() { |
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if (!this._terminated) { |
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this._terminated = true; |
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if (this.Worker) |
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this.Worker.terminate(); |
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} |
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}, |
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postMessage: function(message, transfer) { |
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if (!(this instanceof WorkerXHR)) |
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throw new TypeError('Illegal invocation'); |
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if (this.Worker) { |
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this.Worker.postMessage.apply(this.Worker, arguments); |
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} else { |
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// Trigger validation:
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dummyWorker.postMessage(message); |
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// Alright, push the valid message to the queue.
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this._messageQueue.push(arguments); |
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} |
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} |
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}; |
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// Implement the EventTarget interface
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[ |
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'addEventListener', |
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'removeEventListener', |
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'dispatchEvent' |
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].forEach(function(method) { |
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WorkerXHR.prototype[method] = function() { |
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if (!(this instanceof WorkerXHR)) { |
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throw new TypeError('Illegal invocation'); |
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} |
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if (this.Worker) { |
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this.Worker[method].apply(this.Worker, arguments); |
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} else { |
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this._replayQueue.push({method: method, arguments: arguments}); |
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} |
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}; |
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}); |
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Object.defineProperties(WorkerXHR.prototype, { |
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onmessage: { |
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get: function() {return this._onmessage || null;}, |
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set: function(func) { |
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this._onmessage = typeof func === 'function' ? func : null; |
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} |
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}, |
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onerror: { |
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get: function() {return this._onerror || null;}, |
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set: function(func) { |
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this._onerror = typeof func === 'function' ? func : null; |
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} |
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} |
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}); |
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})(); |
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