Annotation of html5/workers/Overview.html, revision 1.118
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1.117 ihickson 145: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><!-- ZZZ ED vs WD --><div class="head">
1.115 ihickson 146: <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
1.54 ihickson 147: <h1>Web Workers</h1>
1.109 ihickson 148: <!--ZZZ:-->
1.117 ihickson 149: <!--<h2 class="no-num no-toc">W3C Working Draft 23 April 2009</h2>-->
1.118 ! ihickson 150: <h2 class="no-num no-toc" id="editor-s-draft-date-1-january-1970">Editor's Draft 26 April 2009</h2>
1.109 ihickson 151: <!--:ZZZ-->
1.117 ihickson 152: <dl><!-- ZZZ: update the month/day (twice), (un)comment out
153: <dt>This Version:</dt>
1.115 ihickson 154: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a></dd>
1.117 ihickson 155: :ZZZ --><dt>Latest Published Version:</dt>
1.115 ihickson 156: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 157: <dt>Latest Editor's Draft:</dt>
1.115 ihickson 158: <dd><a href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.117 ihickson 159: <!-- ZZZ: add the new version after it has shipped-->
1.2 ihickson 160: <dt>Previous Versions:</dt>
1.113 ihickson 161: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a>
1.117 ihickson 162: <!-- :ZZZ -->
1.81 ihickson 163: <dt>Editors:</dt>
1.115 ihickson 164: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
165: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
166: © 2009 <a href="http://www.w3.org/"><abbr title="World Wide
167: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
168: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.org/"><abbr title="European Research
169: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
170: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
171: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
172: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 173: use</a> rules apply.</p>
1.115 ihickson 174: </div><hr class="top"><h2 class="no-num no-toc" id="abstract">Abstract</h2><p>This specification defines an API that allows Web application
1.81 ihickson 175: authors to spawn background workers running scripts in parallel to
176: their main page. This allows for thread-like operation with
1.115 ihickson 177: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id="status-of-this-document">Status of this document</h2><!-- intro boilerplate (required) --><p><em>This section describes the status of this document at the
1.81 ihickson 178: time of its publication. Other documents may supersede this
179: document. A list of current W3C publications and the most recently
180: formally published revision of this technical report can be found in
1.115 ihickson 181: the <a href="http://www.w3.org/TR/">W3C technical reports index</a>
1.116 ihickson 182: at http://www.w3.org/TR/.</em></p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- XXX this section will be moved back to just below the copyright
183: notice in the header by October 2009 unless the spec as a whole has
184: been transitioned to a more permissive license by that time. --><!-- XXX when moving this text, add: class="alt copyright" --><p>The <a href="http://www.whatwg.org/specs/web-workers/current-work/">WHATWG
185: version</a> of this specification is available under a license that
186: permits reuse of the specification text.</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- where to send feedback (required) --><p>If you wish to make comments regarding this document, please send
1.115 ihickson 187: them to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a>
1.90 ihickson 188: (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
1.115 ihickson 189: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>)
1.81 ihickson 190:
191: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.115 ihickson 192: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
193: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.110 ihickson 194: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.1 ihickson 195:
1.81 ihickson 196: All feedback is welcome.</p><!-- stability (required) --><p>Implementors should be aware that this specification is not
197: stable. <strong>Implementors who are not taking part in the
198: discussions are likely to find the specification changing out from
199: under them in incompatible ways.</strong> Vendors interested in
200: implementing this specification before it eventually reaches the
201: Candidate Recommendation stage should join the aforementioned
202: mailing lists and take part in the discussions.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) --><p>The latest stable version of the editor's draft of this
1.115 ihickson 203: specification is always available on <a href="http://dev.w3.org/html5/workers/Overview.html">the W3C CVS
204: server</a> and in the <a href="http://svn.whatwg.org/webworkers/">WHATWG Subversion
1.81 ihickson 205: repository</a>. The latest editor's working copy (which may contain
1.115 ihickson 206: unfinished text in the process of being prepared) is available <a href="http://www.whatwg.org/specs/web-workers/current-work/">on the
1.81 ihickson 207: WHATWG site</a>. Detailed change history can be obtained from the
1.115 ihickson 208: following locations:</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><ul><li>Twitter messages (non-editorial changes only): <a href="http://twitter.com/WHATWG">http://twitter.com/WHATWG</a></li>
209: <li>Interactive Web interface: <a href="http://html5.org/tools/web-workers-tracker">http://html5.org/tools/web-workers-tracker</a></li>
210: <li>Commit-Watchers mailing list: <a href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></li>
211: <li>Subversion interface: <a href="http://svn.whatwg.org/webworkers/">http://svn.whatwg.org/webworkers/</a></li>
212: <li>CVS log: <a href="http://dev.w3.org/cvsweb/html5/workers/Overview.html">http://dev.w3.org/cvsweb/html5/workers/Overview.html</a></li>
213: </ul><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) --><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Apps
1.81 ihickson 214: Working Group</a> is the W3C working group responsible for this
215: specification's progress along the W3C Recommendation track.
216: <!--ZZZ:-->
1.117 ihickson 217: <!--This specification is the 23 April 2009 Working Draft.-->
1.118 ! ihickson 218: This specification is the 26 April 2009 Editor's Draft.
1.81 ihickson 219: <!--:ZZZ-->
1.115 ihickson 220: </p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- relationship to other work (required) --><p>This specification is also being produced by the <a href="http://www.whatwg.org/">WHATWG</a>. The two specifications are
1.81 ihickson 221: identical from the table of contents onwards.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) --><p>This specification is intended to specify a part of the Web
222: platform closely related to HTML5. It is defined in a separate
1.115 ihickson 223: document primarily to ease the cognitive load on reviewers.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- required patent boilerplate --><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5
224: February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of
1.81 ihickson 225: any patent disclosures</a> made in connection with the deliverables
226: of the group; that page also includes instructions for disclosing a
227: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 228: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
229: Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
230: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of contents</h2>
1.81 ihickson 231: <!--begin-toc-->
1.115 ihickson 232: <ol class="toc">
233: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 234: <ol>
1.115 ihickson 235: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
236: <li><a href="#tutorial"><span class="secno">1.2 </span>Tutorial</a>
1.81 ihickson 237: <ol>
1.115 ihickson 238: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
239: <li><a href="#a-worker-for-updating-a-client-side-database"><span class="secno">1.2.2 </span>A worker for updating a client-side database</a></li>
240: <li><a href="#worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</a></li>
241: <li><a href="#shared-workers"><span class="secno">1.2.4 </span>Shared workers</a></li>
242: <li><a href="#delegation"><span class="secno">1.2.5 </span>Delegation</a></li>
243: <li><a href="#providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</a></ol></ol></li>
244: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 245: <ol>
1.115 ihickson 246: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
247: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
248: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
1.81 ihickson 249: <ol>
1.115 ihickson 250: <li><a href="#the-global-scope"><span class="secno">4.1 </span>The global scope</a>
1.81 ihickson 251: <ol>
1.115 ihickson 252: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
253: <li><a href="#dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.1.2 </span>Dedicated workers and the <code>DedicatedWorkerGlobalScope</code> interface</a></li>
254: <li><a href="#shared-workers-and-the-sharedworkerglobalscope-inteface"><span class="secno">4.1.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> inteface</a></ol></li>
255: <li><a href="#base-urls-and-origins-of-workers"><span class="secno">4.2 </span>Base URLs and origins of workers</a></li>
256: <li><a href="#decoding-scripts"><span class="secno">4.3 </span>Decoding scripts</a></li>
257: <li><a href="#the-event-loop"><span class="secno">4.4 </span>The event loop</a></li>
258: <li><a href="#the-worker-s-ports"><span class="secno">4.5 </span>The worker's ports</a></li>
259: <li><a href="#processing-model"><span class="secno">4.6 </span>Processing model</a></li>
260: <li><a href="#runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</a></li>
261: <li><a href="#creating-workers"><span class="secno">4.8 </span>Creating workers</a>
1.81 ihickson 262: <ol>
1.115 ihickson 263: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
264: <li><a href="#dedicated-workers-and-the-worker-interface"><span class="secno">4.8.2 </span>Dedicated workers and the <code>Worker</code> interface</a></li>
265: <li><a href="#shared-workers-and-the-sharedworker-interface"><span class="secno">4.8.3 </span>Shared workers and the <code>SharedWorker</code> interface</a></ol></ol></li>
266: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 267: <ol>
1.115 ihickson 268: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
269: <li><a href="#the-navigator-object"><span class="secno">5.2 </span>The <code title="worker-Navigator">Navigator</code> object</a></li>
270: <li><a href="#apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</a></li>
271: <li><a href="#interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</a></li>
272: <li><a href="#worker-locations"><span class="secno">5.5 </span>Worker locations</a></ol></li>
273: <li><a class="no-num" href="#references">References</a></li>
274: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
275: <!--end-toc--><hr><h2 id="introduction"><span class="secno">1 </span>Introduction</h2><h3 id="scope"><span class="secno">1.1 </span>Scope</h3><p><em>This section is non-normative.</em><p>This specification defines an API for running scripts in the
1.81 ihickson 276: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
277: scripts that respond to clicks or other user interactions, and
278: allows long tasks to be executed without yielding to keep the page
279: responsive.<p>Workers (as these background scripts are called herein) are
280: relatively heavy-weight, and are not intended to be used in large
281: numbers. For example, it would be inappropriate to launch one worker
282: for each pixel of a four megapixel image. The examples below show
283: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
1.115 ihickson 284: start-up performance cost, and a high per-instance memory cost.<h3 id="tutorial"><span class="secno">1.2 </span>Tutorial</h3><p><em>This section is non-normative.</em><p>There are a variety of uses that workers can be put to. The
285: following subsections show various examples of this use.<h4 id="a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</h4><p><em>This section is non-normative.</em><p>The simplest use of workers is for performing a computationally
1.81 ihickson 286: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
287: (naïvely) compute prime numbers, and progressively displays the
288: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
289: <html>
290: <head>
291: <title>Worker example: One-core computation</title>
292: </head>
293: <body>
294: <p>The highest prime number discovered so far is: <output id="result"></output></p>
295: <script>
1.50 ihickson 296: var worker = new Worker('worker.js');
297: worker.onmessage = function (event) {
1.54 ihickson 298: document.getElementById('result').textContent = event.data;
1.29 ihickson 299: };
1.81 ihickson 300: </script>
301: </body>
1.115 ihickson 302: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
303: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 304: representing that worker, which is used to communicate with the
1.115 ihickson 305: worker. That object's <code title="handler-Worker-onmessage"><a href="#handler-worker-onmessage">onmessage</a></code> event handler
1.81 ihickson 306: attribute allows the code to receive messages from the worker.<p>The worker itself is as follows:<pre>var n = 1;
1.29 ihickson 307: search: while (true) {
308: n += 1;
309: for (var i = 2; i <= Math.sqrt(n); i += 1)
310: if (n % i == 0)
311: continue search;
312: // found a prime!
1.50 ihickson 313: postMessage(n);
1.105 ihickson 314: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.115 ihickson 315: number. To send a message back to the page, the <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
316: method is used to post a message when a prime is found.<p><a href="http://www.whatwg.org/demos/workers/primes/page.html">View this example online</a>.<h4 id="a-worker-for-updating-a-client-side-database"><span class="secno">1.2.2 </span>A worker for updating a client-side database</h4><p><em>This section is non-normative.</em><p>In this example, the main document spawns a worker whose only
1.81 ihickson 317: task is to listen for notifications from the server, and, when
318: appropriate, either add or remove data from the client-side
319: database.<p>Since no communication occurs between the worker and the main
320: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 321: new Worker('worker.js');
1.81 ihickson 322: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 323: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 324: server.onmessage = function (event) {
325: // data is in the format "command key value"
1.54 ihickson 326: var data = event.data.split(' ');
1.31 ihickson 327: switch (data[0]) {
328: case '+':
329: database.transaction(function(tx) {
330: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
331: });
332: case '-':
333: database.transaction(function(tx) {
334: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
335: });
336: }
1.81 ihickson 337: };</pre><p>This connects to the server using the <code>WebSocket</code>
338: mechanism and opens the local database (which, we presume, has been
339: created earlier). The worker then just listens for messages from the
340: server and acts on them as appropriate, forever (or until the main
1.115 ihickson 341: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 342: this example online</a>. (This example will not actually function,
343: since the server does not actually exist and the database is not
1.115 ihickson 344: created by this sample code.)<h4 id="worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</h4><p><em>This section is non-normative.</em><p>In this example, the main document uses two workers, one for
1.81 ihickson 345: fetching stock updates for at regular intervals, and one for
346: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
347: <html>
348: <head>
349: <title>Worker example: Stock ticker</title>
350: <script>
1.33 ihickson 351: // TICKER
352: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 353: var ticker = new Worker('ticker.js');
1.33 ihickson 354:
355: // SEARCHER
1.50 ihickson 356: var searcher = new Worker('searcher.js');
1.33 ihickson 357: function search(query) {
1.50 ihickson 358: searcher.postMessage(query);
1.33 ihickson 359: }
360:
361: // SYMBOL SELECTION UI
362: function select(newSymbol) {
363: symbol = newSymbol;
1.50 ihickson 364: ticker.postMessage(symbol);
1.33 ihickson 365: }
1.81 ihickson 366: </script>
367: </head>
368: <body>
369: <p><output id="symbol"></output> <output id="value"></output></p>
370: <script>
1.50 ihickson 371: ticker.onmessage = function (event) {
1.54 ihickson 372: var data = event.data.split(' ');
1.33 ihickson 373: document.getElementById('symbol').textContent = data[0];
374: document.getElementById('value').textContent = data[1];
375: };
1.50 ihickson 376: ticker.postMessage(symbol);
1.81 ihickson 377: </script>
378: <p><label>Search: <input type="text" oninput="search(this.value)"></label></p>
379: <ul id="results"></ul>
380: <script>
1.50 ihickson 381: searcher.onmessage = function (event) {
1.54 ihickson 382: var data = event.data.split(' ');
1.33 ihickson 383: var results = document.getElementById('results');
384: while (results.hasChildNodes()) // clear previous results
385: results.removeChild(results.firstChild);
386: for (var i = 0; i < data.length; i += 1) {
387: // add a list item with a button for each result
388: var li = document.createElement('li');
389: var button = document.createElement('button');
390: button.value = data[i];
391: button.type = 'button';
392: button.onclick = function () { select(this.value); };
393: button.textContent = data[i];
394: li.appendChild(button);
395: results.appendChild(li);
396: }
397: };
1.81 ihickson 398: </script>
399: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
400: </body>
401: </html></pre><p>The two workers use a common library for performing the actual
402: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 403: try {
404: var xhr = new XMLHttpRequest();
405: xhr.open('GET', url, false);
406: xhr.send();
407: return xhr.responseText;
408: } catch (e) {
409: return ''; // turn all errors into empty results
410: }
1.81 ihickson 411: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 412: var timer;
413: var symbol;
414: function update() {
1.50 ihickson 415: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 416: timer = setTimeout(update, 10000);
417: }
1.50 ihickson 418: onmessage = function (event) {
1.33 ihickson 419: if (timer)
420: clearTimeout(timer);
1.54 ihickson 421: symbol = event.data;
1.33 ihickson 422: update();
1.81 ihickson 423: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 424: onmessage = function (event) {
1.54 ihickson 425: postMessage(get('search.cgi?' + event.data));
1.115 ihickson 426: };</pre><p><a href="http://www.whatwg.org/demos/workers/stocks/page.html">View this example online</a>.<h4 id="shared-workers"><span class="secno">1.2.4 </span>Shared workers</h4><p><em>This section is non-normative.</em><p>In this example, multiple windows (viewers) can be opened that
1.81 ihickson 427: are all viewing the same map. All the windows share the same map
428: information, with a single worker coordinating all the viewers. Each
429: viewer can move around independently, but if they set any data on
430: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
431: the viewers:<pre><!DOCTYPE HTML>
432: <html>
433: <head>
434: <title>Workers example: Multiviewer</title>
435: <script>
1.36 ihickson 436: function openViewer() {
437: window.open('viewer.html');
438: }
1.81 ihickson 439: </script>
440: </head>
441: <body>
442: <p><button type=button onclick="openViewer()">Open a new
443: viewer</button></p>
444: <p>Each viewer opens in a new window. You can have as many viewers
445: as you like, they all view the same data.</p>
446: </body>
447: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
448: <html>
449: <head>
450: <title>Workers example: Multiviewer viewer</title>
451: <script>
1.50 ihickson 452: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 453:
454: // CONFIGURATION
455: function configure(event) {
1.54 ihickson 456: if (event.data.substr(0, 4) != 'cfg ') return;
457: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 458: // update display to mention our name is name
459: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
460: // no longer need this listener
1.43 ihickson 461: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 462: }
1.53 ihickson 463: worker.port.addEventListener('message', configure, false);
1.36 ihickson 464:
465: // MAP
466: function paintMap(event) {
1.54 ihickson 467: if (event.data.substr(0, 4) != 'map ') return;
468: var data = event.data.substr(4).split(',');
1.36 ihickson 469: // display tiles data[0] .. data[8]
470: var canvas = document.getElementById('map');
471: var context = canvas.getContext('2d');
472: for (var y = 0; y < 3; y += 1) {
473: for (var x = 0; x < 3; x += 1) {
474: var tile = data[y * 3 + x];
475: if (tile == '0')
476: context.fillStyle = 'green';
477: else
478: context.fillStyle = 'maroon';
479: fillRect(x * 50, y * 50, 50, 50);
480: }
481: }
482: }
1.53 ihickson 483: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 484:
485: // PUBLIC CHAT
486: function updatePublicChat(event) {
1.54 ihickson 487: if (event.data.substr(0, 4) != 'txt ') return;
488: var name = event.data.substr(4).split(' ', 1);
489: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 490: // display "<name> message" in public chat
1.36 ihickson 491: var dialog = document.getElementById('public');
492: var dt = document.createElement('dt');
493: dt.textContent = name;
494: dialog.appendChild(dt);
495: var dd = document.createElement('dd');
496: dd.textContent = message;
497: dialog.appendChild(dd);
498: }
1.53 ihickson 499: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 500:
501: // PRIVATE CHAT
502: function startPrivateChat(event) {
1.54 ihickson 503: if (event.data.substr(0, 4) != 'msg ') return;
504: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 505: var port = event.ports[0];
1.36 ihickson 506: // display a private chat UI
507: var ul = document.getElementById('private');
508: var li = document.createElement('li');
509: var h3 = document.createElement('h3');
510: h3.textContent = 'Private chat with ' + name;
511: li.appendChild(h3);
512: var dialog = document.createElement('dialog');
513: var addMessage = function(name, message) {
514: var dt = document.createElement('dt');
515: dt.textContent = name;
516: dialog.appendChild(dt);
517: var dd = document.createElement('dd');
518: dd.textContent = message;
519: dialog.appendChild(dd);
520: };
521: port.onmessage = function (event) {
1.54 ihickson 522: addMessage(name, event.data);
1.36 ihickson 523: };
524: li.appendChild(dialog);
525: var form = document.createElement('form');
526: var p = document.createElement('p');
527: var input = document.createElement('input');
528: input.size = 50;
529: p.appendChild(input);
530: p.appendChild(document.createTextNode(' '));
531: var button = document.createElement('button');
532: button.textContent = 'Post';
533: p.appendChild(button);
534: form.onsubmit = function () {
535: port.postMessage(input.value);
536: addMessage('me', input.value);
537: input.value = '';
538: return false;
539: };
540: form.appendChild(p);
541: li.appendChild(form);
542: }
1.53 ihickson 543: worker.port.addEventListener('message', startPrivateChat, false);
1.81 ihickson 544: </script>
545: </head>
546: <body>
547: <h1>Viewer</h1>
548: <h2>Map</h2>
549: <p><canvas id="map" height=150 width=150></canvas></p>
550: <p>
551: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
552: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
553: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
554: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
555: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
556: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
557: </p>
558: <h2>Public Chat</h2>
559: <dialog id="public"></dialog>
560: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
561: <p>
562: <input type="text" name="message" size="50">
563: <button>Post</button>
564: </p>
565: </form>
566: <h2>Private Chat</h2>
567: <ul id="private"></ul>
568: </body>
569: </html>
570: </pre><p>There are several key things worth noting about the way the
571: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
572: processing function, the code here attaches multiple event
573: listeners, each one performing a quick check to see if it is
574: relevant for the message. In this example it doesn't make much
575: difference, but if multiple authors wanted to collaborate using a
576: single port to communicate with a worker, it would allow for
577: independent code instead of changes having to all be made to a
578: single event handling function.<p>Registering event listeners in this way also allows you to
579: unregister specific listeners when you are done with them, as is
580: done with the <code title="">configure()</code> method in this
581: example.<p>Finally, the worker:<pre>
1.36 ihickson 582: var nextName = 0;
583: function getNextName() {
584: // this could use more friendly names
585: // but for now just return a number
586: return nextName++;
587: }
588:
589: var map = [
590: [0, 0, 0, 0, 0, 0, 0],
591: [1, 1, 0, 1, 0, 1, 1],
592: [0, 1, 0, 1, 0, 0, 0],
593: [0, 1, 0, 1, 0, 1, 1],
594: [0, 0, 0, 1, 0, 0, 0],
595: [1, 0, 0, 1, 1, 1, 1],
596: [1, 1, 0, 1, 1, 0, 1],
597: ];
598:
599: function wrapX(x) {
600: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 601: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 602: return x;
603: }
604:
605: function wrapY(y) {
606: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 607: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 608: return y;
609: }
610:
1.50 ihickson 611: function sendMapData(callback) {
1.36 ihickson 612: var data = '';
613: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
614: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
615: if (data != '')
616: data += ',';
617: data += map[y][x];
618: }
619: }
1.50 ihickson 620: callback('map ' + data);
1.36 ihickson 621: }
622:
623: var viewers = {};
624: onconnect = function (event) {
1.84 ihickson 625: event.ports[0]._name = getNextName();
626: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
627: viewers[event.ports[0]._name] = event.port._data;
628: event.ports[0].postMessage('cfg ' + name);
629: event.ports[0].onmessage = getMessage;
630: sendMapData(event.ports[0].postMessage);
1.36 ihickson 631: };
632:
633: function getMessage(event) {
1.54 ihickson 634: switch (event.data.substr(0, 4)) {
1.36 ihickson 635: case 'mov ':
1.54 ihickson 636: var direction = event.data.substr(4);
1.36 ihickson 637: var dx = 0;
638: var dy = 0;
639: switch (direction) {
640: case 'up': dy = -1; break;
641: case 'down': dy = 1; break;
642: case 'left': dx = -1; break;
643: case 'right': dx = 1; break;
644: }
645: event.target._data.x = wrapX(event.target._data.x + dx);
646: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 647: sendMapData(event.target.postMessage);
1.36 ihickson 648: break;
649: case 'set ':
1.54 ihickson 650: var value = event.data.substr(4);
1.36 ihickson 651: map[event.target._data.y][event.target._data.x] = value;
652: for (var viewer in viewers)
1.50 ihickson 653: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 654: break;
655: case 'txt ':
656: var name = event.target._name;
1.54 ihickson 657: var message = event.data.substr(4);
1.36 ihickson 658: for (var viewer in viewers)
659: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
660: break;
661: case 'msg ':
662: var party1 = event._data;
1.54 ihickson 663: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 664: if (party2) {
665: var channel = new MessageChannel();
1.84 ihickson 666: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
667: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 668: }
669: break;
670: }
1.81 ihickson 671: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 672: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.81 ihickson 673: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
674: "msg" message from one viewer naming another viewer, it sets up a
675: direct connection between the two, so that the two viewers can
676: communicate directly without the worker having to proxy all the
1.115 ihickson 677: messages.<p><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">View this example online</a>.<h4 id="delegation"><span class="secno">1.2.5 </span>Delegation</h4><p><em>This section is non-normative.</em><p>With multicore CPUs becoming prevalent, one way to obtain better
1.81 ihickson 678: performance is to split computationally expensive tasks amongst
679: multiple workers. In this example, a computationally expensive task
680: that is to be performed for every number from 1 to 10,000,000 is
681: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
682: <html>
683: <head>
684: <title>Worker example: One-core computation</title>
685: </head>
686: <body>
687: <p>The highest prime number discovered so far is: <output id="result"></output></p>
688: <script>
1.50 ihickson 689: var worker = new Worker('worker.js');
690: worker.onmessage = function (event) {
1.54 ihickson 691: document.getElementById('result').textContent = event.data;
1.40 ihickson 692: };
1.81 ihickson 693: </script>
694: </body>
695: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 696: var num_workers = 10;
697: var items_per_worker = 1000000;
698:
699: // start the workers
700: var result = 0;
701: var pending_workers = num_workers;
702: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 703: var worker = new Worker('core.js');
704: worker.postMessage(i * items_per_worker);
705: worker.postMessage((i+1) * items_per_worker);
706: worker.onmessage = storeResult;
1.40 ihickson 707: }
708:
709: // handle the results
710: function storeResult(event) {
1.54 ihickson 711: result += 1*event.data;
1.40 ihickson 712: pending_workers -= 1;
713: if (pending_workers <= 0)
1.50 ihickson 714: postMessage(result); // finished!
1.81 ihickson 715: }</pre><p>It consists of a loop to start the subworkers, and then a handler
716: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 717: onmessage = getStart;
1.40 ihickson 718: function getStart(event) {
1.54 ihickson 719: start = 1*event.data;
1.40 ihickson 720: onmessage = getEnd;
721: }
722:
723: var end;
724: function getEnd(event) {
1.54 ihickson 725: end = 1*event.data;
1.40 ihickson 726: onmessage = null;
1.66 ihickson 727: work();
1.40 ihickson 728: }
729:
1.66 ihickson 730: function work() {
1.40 ihickson 731: var result = 0;
732: for (var i = start; i < end; i += 1) {
733: // perform some complex calculation here
734: result += 1;
735: }
1.50 ihickson 736: postMessage(result);
737: close();
1.81 ihickson 738: }</pre><p>They receive two numbers in two events, perform the computation
739: for the range of numbers thus specified, and then report the result
1.115 ihickson 740: back to the parent.<p><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View this example online</a>.<h4 id="providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</h4><p><em>This section is non-normative.</em><p>Suppose that a cryptography library is made available that
1.81 ihickson 741: provides three tasks:<dl><dt>Generate a public/private key pair</dt>
742:
743: <dd>Takes a port, on which it will send two messages, first the
744: public key and then the private key.</dd>
745:
746: <dt>Given a plaintext and a public key, return the corresponding cyphertext</dt>
747:
748: <dd>Takes a port, to which any number of messages can be sent, the
749: first giving the public key, and the remainder giving the
750: plaintext, each of which is encrypted and then sent on that same
751: channel as the cyphertext. The user can close the port when it is
752: done encrypting content.</dd>
753:
754: <dt>Given a cyphertext and a private key, return the corresponding plaintext</dt>
755:
756: <dd>Takes a port, to which any number of messages can be sent, the
757: first giving the private key, and the remainder giving the
758: cyphertext, each of which is decrypted and then sent on that same
759: channel as the plaintext. The user can close the port when it is
760: done decrypting content.</dd>
1.49 ihickson 761:
1.81 ihickson 762: </dl><p>The library itself is as follows:<pre>function handleMessage(e) {
1.54 ihickson 763: if (e.data == "genkeys")
1.84 ihickson 764: genkeys(e.ports[0]);
1.54 ihickson 765: else if (e.data == "encrypt")
1.84 ihickson 766: encrypt(e.ports[0]);
1.54 ihickson 767: else if (e.data == "decrypt")
1.84 ihickson 768: decrypt(e.ports[0]);
1.49 ihickson 769: }
770:
771: function genkeys(p) {
772: var keys = _generateKeyPair();
773: p.postMessage(keys[0]);
774: p.postMessage(keys[1]);
775: }
776:
777: function encrypt(p) {
778: var key, state = 0;
779: p.onmessage = function (e) {
780: if (state == 0) {
1.54 ihickson 781: key = e.data;
1.49 ihickson 782: state = 1;
783: } else {
1.54 ihickson 784: p.postMessage(_encrypt(key, e.data));
1.49 ihickson 785: }
786: };
787: }
788:
789: function decrypt(p) {
790: var key, state = 0;
791: p.onmessage = function (e) {
792: if (state == 0) {
1.54 ihickson 793: key = e.data;
1.49 ihickson 794: state = 1;
795: } else {
1.54 ihickson 796: p.postMessage(_decrypt(key, e.data));
1.49 ihickson 797: }
798: };
799: }
800:
1.50 ihickson 801: // support being used as a shared worker as well as a dedicated worker
802: if (this.onmessage) // dedicated worker
803: onmessage = handleMessage;
804: else // shared worker
805: onconnect = function (e) { e.port.onmessage = handleMessage; }
1.49 ihickson 806:
807:
808: // the "crypto" functions:
809:
810: function _generateKeyPair() {
811: return [Math.random(), Math.random()];
812: }
813:
814: function _encrypt(k, s) {
815: return 'encrypted-' + k + ' ' + s;
816: }
817:
818: function _decrypt(k, s) {
819: return s.substr(s.indexOf(' ')+1);
1.81 ihickson 820: }</pre><p>Note that the crypto functions here are just stubs and don't do
821: real cryptography.<p>This library could be used as follows:<pre><!DOCTYPE HTML>
822: <html>
823: <head>
824: <title>Worker example: Crypto library</title>
825: <script>
1.50 ihickson 826: var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
1.49 ihickson 827: function getKeys() {
828: var state = 0;
1.50 ihickson 829: cryptoLib.startConversation("genkeys").onmessage = function (e) {
1.49 ihickson 830: if (state == 0)
1.54 ihickson 831: document.getElementById('public').value = e.data;
1.49 ihickson 832: else if (state == 1)
1.54 ihickson 833: document.getElementById('private').value = e.data;
1.49 ihickson 834: state += 1;
835: };
836: }
837: function enc() {
1.50 ihickson 838: var port = cryptoLib.startConversation("encrypt");
839: port.postMessage(document.getElementById('public').value);
840: port.postMessage(document.getElementById('input').value);
841: port.onmessage = function (e) {
1.54 ihickson 842: document.getElementById('input').value = e.data;
1.50 ihickson 843: port.close();
1.49 ihickson 844: };
845: }
846: function dec() {
1.50 ihickson 847: var port = cryptoLib.startConversation("decrypt");
848: port.postMessage(document.getElementById('private').value);
849: port.postMessage(document.getElementById('input').value);
850: port.onmessage = function (e) {
1.54 ihickson 851: document.getElementById('input').value = e.data;
1.50 ihickson 852: port.close();
1.49 ihickson 853: };
854: }
1.81 ihickson 855: </script>
856: <style>
1.49 ihickson 857: textarea { display: block; }
1.81 ihickson 858: </style>
859: </head>
860: <body onload="getKeys()">
861: <fieldset>
862: <legend>Keys</legend>
863: <p><label>Public Key: <textarea id="public"></textarea></label></p>
864: <p><label>Private Key: <textarea id="private"></textarea></label></p>
865: </fieldset>
866: <p><label>Input: <textarea id="input"></textarea></label></p>
867: <p><button onclick="enc()">Encrypt</button> <button onclick="dec()">Decrypt</button></p>
868: </body>
869: </html></pre><p>A later version of the API, though, might want to offload all the
870: crypto work onto subworkers. This could be done as follows:<pre>function handleMessage(e) {
1.54 ihickson 871: if (e.data == "genkeys")
1.84 ihickson 872: genkeys(e.ports[0]);
1.54 ihickson 873: else if (e.data == "encrypt")
1.84 ihickson 874: encrypt(e.ports[0]);
1.54 ihickson 875: else if (e.data == "decrypt")
1.84 ihickson 876: decrypt(e.ports[0]);
1.49 ihickson 877: }
878:
879: function genkeys(p) {
1.50 ihickson 880: var generator = new Worker('libcrypto-v2-generator.js');
1.84 ihickson 881: generator.postMessage('', [p]);
1.49 ihickson 882: }
883:
884: function encrypt(p) {
885: p.onmessage = function (e) {
1.54 ihickson 886: var key = e.data;
1.50 ihickson 887: var encryptor = new Worker('libcrypto-v2-encryptor.js');
1.84 ihickson 888: encryptor.postMessage(key, [p]);
1.49 ihickson 889: };
890: }
891:
892: function encrypt(p) {
893: p.onmessage = function (e) {
1.54 ihickson 894: var key = e.data;
1.50 ihickson 895: var decryptor = new Worker('libcrypto-v2-decryptor.js');
1.84 ihickson 896: decryptor.postMessage(key, [p]);
1.49 ihickson 897: };
898: }
899:
1.50 ihickson 900: // support being used as a shared worker as well as a dedicated worker
901: if (this.onmessage) // dedicated worker
902: onmessage = handleMessage;
903: else // shared worker
1.84 ihickson 904: onconnect = function (e) { e.ports[0].onmessage = handleMessage };
1.81 ihickson 905: </pre><p>The little subworkers would then be as follows.<p>For generating key pairs:<pre>onmessage = function (e) {
1.50 ihickson 906: var k = _generateKeyPair();
1.84 ihickson 907: e.ports[0].postMessage(k[0]);
908: e.ports[0].postMessage(k[1]);
1.49 ihickson 909: close();
910: }
1.50 ihickson 911:
912: function _generateKeyPair() {
913: return [Math.random(), Math.random()];
1.81 ihickson 914: }</pre><p>For encrypting:<pre>onmessage = function (e) {
1.54 ihickson 915: var key = e.data;
1.84 ihickson 916: e.ports[0].onmessage = function (e) {
1.54 ihickson 917: var s = e.data;
1.50 ihickson 918: postMessage(_encrypt(key, s));
1.49 ihickson 919: }
1.84 ihickson 920: e.ports[0].onclose = function (e) {
1.49 ihickson 921: close();
922: }
1.50 ihickson 923: }
924:
925: function _encrypt(k, s) {
926: return 'encrypted-' + k + ' ' + s;
1.81 ihickson 927: }</pre><p>For decrypting:<pre>onmessage = function (e) {
1.54 ihickson 928: var key = e.data;
1.84 ihickson 929: e.ports[0].onmessage = function (e) {
1.54 ihickson 930: var s = e.data;
1.50 ihickson 931: postMessage(_decrypt(key, s));
1.49 ihickson 932: }
1.84 ihickson 933: e.ports[0].onclose = function (e) {
1.49 ihickson 934: close();
935: }
1.50 ihickson 936: }
937:
938: function _decrypt(k, s) {
939: return s.substr(s.indexOf(' ')+1);
1.81 ihickson 940: }</pre><p>Notice how the users of the API don't have to even know that this
941: is happening — the API hasn't changed; the library can
942: delegate to subworkers without changing its API, even though it is
1.115 ihickson 943: accepting data using message channels.<p><a href="http://www.whatwg.org/demos/workers/crypto/page.html">View this example online</a>.<h2 id="conformance-requirements"><span class="secno">2 </span>Conformance requirements</h2><p>All diagrams, examples, and notes in this specification are
1.81 ihickson 944: non-normative, as are all sections explicitly marked non-normative.
945: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
946: NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
947: "OPTIONAL" in the normative parts of this document are to be
948: interpreted as described in RFC2119. For readability, these words do
1.115 ihickson 949: not appear in all uppercase letters in this specification. <a href="#references">[RFC2119]</a><p>Requirements phrased in the imperative as part of algorithms
1.81 ihickson 950: (such as "strip any leading space characters" or "return false and
951: abort these steps") are to be interpreted with the meaning of the
952: key word ("must", "should", "may", etc) used in introducing the
953: algorithm.<p>Some conformance requirements are phrased as requirements on
954: attributes, methods or objects. Such requirements are to be
955: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
956: may be implemented in any manner, so long as the end result is
957: equivalent. (In particular, the algorithms defined in this
958: specification are intended to be easy to follow, and not intended to
959: be performant.)<p>The only conformance class defined by this specification is user
960: agents.<p>User agents may impose implementation-specific limits on
961: otherwise unconstrained inputs, e.g. to prevent denial of service
962: attacks, to guard against running out of memory, or to work around
1.115 ihickson 963: platform-specific limitations.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
1.81 ihickson 964: specifications.<dl><dt>HTML5</dt>
1.49 ihickson 965:
1.81 ihickson 966: <dd>
1.49 ihickson 967:
1.81 ihickson 968: <p>Many fundamental concepts from HTML5 are used by this
1.115 ihickson 969: specification. <a href="#references">[HTML5]</a></p>
1.49 ihickson 970:
1.81 ihickson 971: </dd>
1.1 ihickson 972:
1.81 ihickson 973: <dt>WebIDL</dt>
1.1 ihickson 974:
975: <dd>
976:
1.81 ihickson 977: <p>The IDL blocks in this specification use the semantics of the
1.115 ihickson 978: WebIDL specification. <a href="#references">[WebIDL]</a></p>
1.1 ihickson 979:
1.81 ihickson 980: </dd>
1.1 ihickson 981:
1.115 ihickson 982: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 983: <code title="">Foo</code> is actually an interface, is sometimes
984: used instead of the more accurate "an object implementing the
985: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
986: scripts in Web applications, and does not necessarily imply the
987: existence of an actual <code>Document</code> object or of any other
988: <code>Node</code> objects as defined in the DOM Core
1.115 ihickson 989: specifications. <a href="#references">[DOM3CORE]</a><p>A DOM attribute is said to be <em>getting</em> when its value is
1.81 ihickson 990: being retrieved (e.g. by author script), and is said to be
1.103 ihickson 991: <em>setting</em> when a new value is assigned to it.<p>The term "JavaScript" is used to refer to ECMA262, rather than
992: the official term ECMAScript, since the term JavaScript is more
1.115 ihickson 993: widely known. <a href="#references">[ECMA262]</a><h2 id="infrastructure"><span class="secno">4 </span>Infrastructure</h2><p>There are two kinds of workers; dedicated workers, and shared
1.81 ihickson 994: workers. Dedicated workers, once created, and are linked to their
995: creator; but message ports can be used to communicate from a
996: dedicated worker to multiple other browsing contexts or
997: workers. Shared workers, on the other hand, are named, and once
998: created any script running in the same <span>origin</span> can
1.115 ihickson 999: obtain a reference to that worker and communicate with it.<h3 id="the-global-scope"><span class="secno">4.1 </span>The global scope</h3><p>The global scope is the "inside" of a worker.<h4 id="the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> abstract interface</h4><pre class="idl">interface <dfn id="workerglobalscope">WorkerGlobalScope</dfn> {
1000: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1001: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1002: // also implements everything on <a href="#workerutils">WorkerUtils</a>
1003:
1004: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1005: attribute <span>EventListener</span> <a href="#handler-workerglobalscope-onclose" title="handler-WorkerGlobalScope-onclose">onclose</a>;
1006: attribute <span>EventListener</span> <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1007: };</pre><p>Objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> interface
1008: must also implement the <code>EventTarget</code> interface.<p>The <dfn id="dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self"><code>self</code></dfn> attribute
1009: must return the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object itself.<p>The <dfn id="dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location"><code>location</code></dfn>
1010: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1011: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1012: created. It represents the <span>absolute URL</span> of the script
1.115 ihickson 1013: that was used to initialize the worker.<hr><p>When a script invokes the <dfn id="dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close"><code>close()</code></dfn> method on
1014: a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.81 ihickson 1015: following steps:<ol><li><p><span>Queue a task</span> to <span>fire a simple
1.115 ihickson 1016: event</span> called <code title="event-close">close</code> at the
1017: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object.</li>
1.81 ihickson 1018:
1.115 ihickson 1019: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1020: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1021: true.</li>
1022:
1023: <li><p>For each <code>MessagePort</code> object that is entangled
1024: with another port and that has one (but only one) port whose owner
1.115 ihickson 1025: is the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object on which the method
1.81 ihickson 1026: was invoked (this would include, for instance, the implicit port in
1.107 ihickson 1027: used for dedicated workers), disentangle the two ports.</li>
1.81 ihickson 1028:
1.102 ihickson 1029: </ol><p>The following are the <span>event handler attributes</span> (and their corresponding <span title="event handler event type">event handler event types</span>)
1030: that must be supported, as DOM attributes, by objects implementing
1.115 ihickson 1031: the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> interface:<table><thead><tr><th><span title="event handler attributes">event handler attribute</span> <th><span>Event handler event type</span>
1032: <tbody><tr><td><dfn id="handler-workerglobalscope-onclose" title="handler-WorkerGlobalScope-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code>
1033: <tr><td><dfn id="handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1034: </table><h4 id="dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.1.2 </span>Dedicated workers and the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface</h4><!-- the XXX below is for collapsing this interface onto WorkerGlobalScope so it looks like just one interface - the inheritance is a spec fiction only --><pre class="idl">[NoInterfaceObject, XXX] interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1035: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(in any message, [Optional] in <span>MessagePortArray</span> ports);<!--
1.77 ihickson 1036: <span>MessagePort</span> <span title="dom-DedicatedWorkerGlobalScope-startConversation">startConversation</span>(in any message);-->
1.115 ihickson 1037: attribute <span>EventListener</span> <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1038: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.81 ihickson 1039: had an implicit <code>MessagePort</code> associated with them. This
1040: port is part of a channel that is set up when the worker is created,
1041: but it is not exposed. This object must never be garbage collected
1.115 ihickson 1042: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1043: at the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>The <dfn id="dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage"><code>postMessage()</code></dfn><!--
1.64 ihickson 1044: and <dfn
1045: title="dom-DedicatedWorkerGlobalScope-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1046: method<!--s (startConversation)--> on
1.115 ihickson 1047: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.81 ihickson 1048: invoked, it<!--/they (startConversation)--> immediately invoked the
1049: method of the same name on the port, with the same arguments, and
1.102 ihickson 1050: returned the same return value.<p>The following are the <span>event handler attributes</span> (and their corresponding <span title="event handler event type">event handler event types</span>)
1051: that must be supported, as DOM attributes, by objects implementing
1.115 ihickson 1052: the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface:<table><thead><tr><th><span title="event handler attributes">event handler attribute</span> <th><span>Event handler event type</span>
1053: <tbody><tr><td><dfn id="handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1.102 ihickson 1054: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1055: networking model, a dedicated worker is an extension of the
1.115 ihickson 1056: <span>cache host</span> from which it was created.<h4 id="shared-workers-and-the-sharedworkerglobalscope-inteface"><span class="secno">4.1.3 </span>Shared workers and the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> inteface</h4><!-- the XXX below is for collapsing this interface onto WorkerGlobalScope so it looks like just one interface - the inheritance is a spec fiction only --><pre class="idl">[NoInterfaceObject, XXX] interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1057: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1058: readonly attribute <span>ApplicationCache</span> <a href="#dom-sharedworkerglobalscope-applicationcache" title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</a>;
1059: attribute <span>EventListener</span> <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1060: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1061: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1062: attribute must return the value it was assigned when the
1.115 ihickson 1063: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1064: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1065: that can be used to obtain a reference to the worker using the
1.115 ihickson 1066: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handler attributes</span> (and their corresponding <span title="event handler event type">event handler event types</span>)
1.102 ihickson 1067: that must be supported, as DOM attributes, by objects implementing
1.115 ihickson 1068: the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> interface:<table><thead><tr><th><span title="event handler attributes">event handler attribute</span> <th><span>Event handler event type</span>
1069: <tbody><tr><td><dfn id="handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect"><code>onconnect</code></dfn> <td> <code title="event-connect">connect</code>
1.102 ihickson 1070: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1071: networking model, a shared worker is its own <span>cache
1.115 ihickson 1072: host</span>. The <a href="#run-a-worker">run a worker</a> algorithm takes care of
1073: associating the worker with an <span>application cache</span>.<p class="note">The <dfn id="dom-sharedworkerglobalscope-applicationcache" title="dom-SharedWorkerGlobalScope-applicationCache"><code>applicationCache</code></dfn>
1.101 ihickson 1074: returns the <code>ApplicationCache</code> object for the
1075: worker.</p><!-- normative conf criteria is in the appcache section
1.115 ihickson 1076: --><h3 id="base-urls-and-origins-of-workers"><span class="secno">4.2 </span>Base URLs and origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1077: origin</span> of scripts running in workers are the
1078: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1079: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1080: represents.<h3 id="decoding-scripts"><span class="secno">4.3 </span>Decoding scripts</h3><p>When a user agent is to <dfn id="decode-a-script-resource">decode a script resource</dfn> to
1.85 ihickson 1081: obtain its source in Unicode, it must run the following steps:<ol><li>
1082:
1083: <p>Let <var title="">character encoding</var> be <i title="">unknown</i>.</p>
1084:
1085: </li>
1086:
1087: <li>
1088:
1089: <p>For each of the rows in the following table, starting with the
1090: first one and going down, if the resource has as many or more
1091: bytes available than the number of bytes in the first column, and
1092: the first bytes of the resource match the bytes given in the first
1093: column, then let <var title="">character encoding</var> be the
1094: encoding given in the cell in the second column of that row:</p>
1095:
1096: <!-- this table is present in several forms in this file; keep them in sync -->
1097: <table><thead><tr><th>Bytes in Hexadecimal
1098: <th>Encoding
1099: <tbody><!-- nobody uses this
1100: <tr>
1101: <td>00 00 FE FF
1102: <td>UTF-32BE
1103: <tr>
1104: <td>FF FE 00 00
1105: <td>UTF-32LE
1106: --><tr><td>FE FF
1107: <td>UTF-16BE
1108: <tr><td>FF FE
1109: <td>UTF-16LE
1110: <tr><td>EF BB BF
1111: <td>UTF-8
1112: <!-- nobody uses this
1113: <tr>
1114: <td>DD 73 66 73
1115: <td>UTF-EBCDIC
1116: -->
1.115 ihickson 1117: </table><p class="note">This step looks for Unicode Byte Order Marks
1.85 ihickson 1118: (BOMs).</p>
1119:
1120: </li>
1121:
1122: <li>
1123:
1124: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, apply the <span>algorithm for extracting an
1.115 ihickson 1125: encoding from a Content-Type</span> to the resource's <span title="Content-Type">Content Type metadata</span>; if this returns
1.85 ihickson 1126: an encoding, and the user agent supports that encoding, then let
1127: <var title="">character encoding</var> be that encoding.</p>
1128:
1129: </li>
1130:
1131: <li>
1132:
1133: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, then let <var title="">character
1134: encoding</var> be UTF-8.</p>
1135:
1136: </li>
1137:
1138: <li>
1139:
1140: <p>Convert the resource to Unicode using the character encoding
1141: given by <var title="">character encoding</var>.</p>
1142:
1143: <p>Return the text that is so obtained.</p>
1144:
1145: </li>
1146:
1.115 ihickson 1147: </ol><h3 id="the-event-loop"><span class="secno">4.4 </span>The event loop</h3><p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is asssociated with a
1.81 ihickson 1148: <span>event loop</span>. This <span>event loop</span> has no
1149: associated <span>browsing context</span>, and its <span title="task
1150: queue">task queues</span> only have events, callbacks, and
1.115 ihickson 1151: networking activity as <span title="concept-task">tasks</span>. The
1.81 ihickson 1152: processing model of these <span title="event loop">event
1.115 ihickson 1153: loops</span> is defined below in the <a href="#run-a-worker">run a worker</a>
1154: algorithm.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object also has a <dfn id="dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</dfn> flag, which must
1.81 ihickson 1155: initially be false, but which can get set to true by the algorithms
1.115 ihickson 1156: in the processing model section below.<p>Once the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set to
1.81 ihickson 1157: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1158: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.81 ihickson 1159: already on the queue are unaffected unless otherwise
1.115 ihickson 1160: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1161: timers stop firing, notifications for all pending asynchronous
1.115 ihickson 1162: operations are dropped, etc.<h3 id="the-worker-s-ports"><span class="secno">4.5 </span>The worker's ports</h3><p>Workers communicate with other workers and with <span title="browsing context">browsing contexts</span> through <span title="channel messaging">message channels</span> and their
1163: <code>MessagePort</code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1164: scope</var> has a list of <dfn id="the-worker-s-ports-0">the worker's ports</dfn>, which
1.81 ihickson 1165: consists of all the <code>MessagePort</code> objects that are
1166: entangled with another port and that have one (but only one) port
1167: owned by <var title="">worker global scope</var>. This list includes
1168: <!--all the <code>MessagePort</code> objects that are in events
1.68 ihickson 1169: pending in the <span>event loop</span>, as well as (commented out
1170: because in practice it makes no difference either way as far as I
1171: can tell, and it would be hard to strictly implement since these
1.81 ihickson 1172: ports might not yet be across the thread boundary)--> the implicit
1.115 ihickson 1173: <code>MessagePort</code> in the case of <a href="#dedicatedworkerglobalscope" title="DedicatedWorkerGlobalScope">dedicated workers</a>.<hr><p>A worker is said to be a <dfn id="permissible-worker">permissible worker</dfn> if
1.81 ihickson 1174: either:<ul><li>at some point past or present a <code>MessagePort</code> owned
1175: by the worker was entangled with a <code>MessagePort</code> <var title="">p</var> whose owner is a <code>Window</code> object whose
1176: <span>active document</span> is the <code>Document</code> that was
1177: that <span>browsing context</span>'s <span>active document</span>
1178: when <var title="">p</var> was created, and that
1179: <code>Document</code> is <span>fully active</span>, or</li>
1180:
1181: <li>at some point past or present a <code>MessagePort</code> owned
1182: by the worker was entangled with a <code>MessagePort</code> owned
1.115 ihickson 1183: by another worker that is currently a <a href="#permissible-worker">permissible
1.81 ihickson 1184: worker</a>.</li>
1185:
1.115 ihickson 1186: </ul><hr><p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if
1.81 ihickson 1187: either:<ul><li>it has outstanding timers, database transactions, or network
1.115 ihickson 1188: connections, and is a <a href="#permissible-worker">permissible worker</a>, or</li>
1.81 ihickson 1189:
1.115 ihickson 1190: <li>there is a <a href="#protected-worker">protected worker</a> that at some point
1.81 ihickson 1191: past or present owned a <code>MessagePort</code> that was entangled
1192: with a <code>MessagePort</code> owned by this worker.</li>
1193:
1.115 ihickson 1194: </ul><hr><p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if either:
1.81 ihickson 1195:
1.115 ihickson 1196: <ul><li>the worker is a <a href="#protected-worker">protected worker</a>, or</li>
1.81 ihickson 1197:
1.115 ihickson 1198: <li>at least one of the <a href="#the-worker-s-ports-0">the worker's ports</a> is
1.81 ihickson 1199: entangled with a <code>MessagePort</code> <var title="">p</var>
1200: whose owner is a <code>Window</code> object whose <span>active
1201: document</span> is the <code>Document</code> that was that
1202: <span>browsing context</span>'s <span>active document</span> when
1203: that <code>MessagePort</code> <var title="">p</var> was created,
1204: and that <code>Document</code> is <span>fully active</span>,
1205: or</li>
1206:
1.115 ihickson 1207: <li>at least one of the <a href="#the-worker-s-ports-0">the worker's ports</a> has an
1.81 ihickson 1208: entangled <code>MessagePort</code> owned by a
1.115 ihickson 1209: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object that is itself an
1210: <a href="#active-needed-worker">active needed worker</a>.</li>
1.81 ihickson 1211:
1.115 ihickson 1212: </ul><hr><p>A worker is said to be a <dfn id="suspendable-worker">suspendable worker</dfn> if it is
1213: not an <a href="#active-needed-worker">active needed worker</a> but either:<ul><li>at least one of the <a href="#the-worker-s-ports-0">the worker's ports</a> has an
1.81 ihickson 1214: entangled <code>MessagePort</code> owned by a <code>Window</code>
1215: object, or</li>
1216:
1.115 ihickson 1217: <li>at least one of the <a href="#the-worker-s-ports-0">the worker's ports</a> has an
1.81 ihickson 1218: entangled <code>MessagePort</code> owned by a
1.115 ihickson 1219: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object that is itself a <span>needed
1.81 ihickson 1220: worker</span>.</li>
1221:
1.115 ihickson 1222: </ul><h3 id="processing-model"><span class="secno">4.6 </span>Processing model</h3><p>When a user agent is to <dfn id="run-a-worker">run a worker</dfn> for a script with
1.81 ihickson 1223: <span>URL</span> <var title="">url</var>, a browsing context <var title="">owner browsing context</var>, and with global scope <var title="">worker global scope</var>, it must run the following
1224: steps:<ol><li>
1225:
1226: <p>Create a completely separate and parallel execution environment
1227: (i.e. a separate thread or process or equivalent construct), and
1.106 ihickson 1228: run the rest of these steps asynchronously in that context.</p>
1.81 ihickson 1229:
1230: </li>
1.4 ihickson 1231:
1.101 ihickson 1232: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1233: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1234: shared worker), and there are any <span title="relevant application
1235: cache">relevant application caches</span> that are identified by a
1236: manifest URL with the <span>same origin</span> as <var title="">url</var> and that have <var title="">url</var> as one of
1.115 ihickson 1237: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1238: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1239: cache</span> of those that match.</li>
1240:
1.4 ihickson 1241: <li>
1.52 ihickson 1242:
1.81 ihickson 1243: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>.</p>
1244:
1.115 ihickson 1245: <p>If the attempt fails, then for each <code><a href="#worker">Worker</a></code> or
1246: <code><a href="#sharedworker">SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1247: <span>fire a simple event</span> called <code title="event-error">error</code> at that object. Abort these
1.81 ihickson 1248: steps.</p>
1.7 ihickson 1249:
1.115 ihickson 1250: <p>If the attempt succeeds, then <a href="#decode-a-script-resource" title="decode a script
1.85 ihickson 1251: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1.81 ihickson 1252:
1.68 ihickson 1253: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1254:
1.115 ihickson 1255: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1256: type of the script is ignored. Unlike with <code>script</code>
1257: elements, there is no way to override the type. It's always
1258: assumed to be JavaScript.</p> <!-- XXX people will complain about
1.7 ihickson 1259: this. I guess we might want to examine the MIME type... -->
1.81 ihickson 1260:
1261: </li>
1.7 ihickson 1262:
1263: <li>
1.68 ihickson 1264:
1.115 ihickson 1265: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1266: created, as follows.</p>
1267:
1268: <p>Create a new <span>script execution environment</span>
1269: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1270:
1.68 ihickson 1271: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1272: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1273: entry-points</span>; set the <i>initial code entry-point</i> to
1274: the entry-point for any executable code to be immediately run.</p>
1275:
1276: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1277:
1278: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1279:
1.83 ihickson 1280: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1281: UTF-8. (This is just used for encoding non-ASCII characters in the
1282: query component of URLs.)</p>
1.68 ihickson 1283:
1284: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1285:
1.115 ihickson 1286: <p>Create a new <span>script group</span> and add the <span title="concept-script">script</span> to it.</p>
1.81 ihickson 1287:
1288: </li>
1.4 ihickson 1289:
1290: <li>
1.81 ihickson 1291:
1292: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.115 ihickson 1293: worker such that as soon as it stops being either an <a href="#active-needed-worker">active
1294: needed worker</a> or a <a href="#suspendable-worker">suspendable worker</a>, <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1295: to true and <span title="queue a task">a task is queued</span> to
1.115 ihickson 1296: <span>fire a simple event</span> called <code title="event-close">close</code> at <var title="">worker global
1.81 ihickson 1297: scope</var>.</p>
1298:
1299: </li>
1.9 ihickson 1300:
1301: <li>
1.7 ihickson 1302:
1.81 ihickson 1303: <p><strong>Suspending workers</strong>: Start monitoring the
1304: worker, such that whenever <var title="">worker global
1.115 ihickson 1305: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1306: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1307: agent suspends execution of script in that worker until such time
1.115 ihickson 1308: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1309: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1310: worker</a>.</p>
1.4 ihickson 1311:
1.81 ihickson 1312: </li>
1.68 ihickson 1313:
1314: <li>
1.4 ihickson 1315:
1.81 ihickson 1316: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1317: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1318: entry-point</i>, and let that run until it either returns, fails
1319: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1320: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1321: algorithms defined below.</p>
1322:
1.115 ihickson 1323: <p class="note">If the script gets aborted by the "<a href="#kill-a-worker">kill a
1.81 ihickson 1324: worker</a>" algorithm, then that same algorithm will cause
1.115 ihickson 1325: there to only be a single <span title="concept-task">task</span>
1.81 ihickson 1326: in the <span>event loop</span> at the next step, namely the task
1.115 ihickson 1327: for the <code title="message-close">close</code> event. The
1328: "<a href="#terminate-a-worker">terminate a worker</a>" algorithm removes all the
1.81 ihickson 1329: events.</p>
1.4 ihickson 1330:
1.81 ihickson 1331: </li>
1.4 ihickson 1332:
1.95 ihickson 1333: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1334: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.95 ihickson 1335: a dedicated worker), then open the <span>port message queue</span>
1336: of the worker's implicit port.</li>
1337:
1.4 ihickson 1338: <li>
1.68 ihickson 1339:
1.115 ihickson 1340: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1341: loop</span>'s <span title="task queue">task queues</span> or <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1342: to true.</p>
1.43 ihickson 1343:
1.81 ihickson 1344: </li>
1.4 ihickson 1345:
1346: <li>
1347:
1.81 ihickson 1348: <p>Run the oldest task on one of the <span>event loop</span>'s
1349: <span title="task queue">task queues</span>, if any. The user
1350: agent may pick any <span>task queue</span>.</p>
1351:
1.115 ihickson 1352: <p class="note">The handling of events or the execution of
1353: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1354: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1355: defined below.</p>
1.8 ihickson 1356:
1.81 ihickson 1357: </li>
1.4 ihickson 1358:
1359: <li>
1360:
1.81 ihickson 1361: <p>Remove the task run in the previous step, if any, from its
1362: <span>task queue</span>.</p>
1.4 ihickson 1363:
1.81 ihickson 1364: </li>
1.4 ihickson 1365:
1366: <li>
1.8 ihickson 1367:
1.81 ihickson 1368: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1369: <span title="task queue">task queues</span> or if <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1370: to false, then jump back to the step above labeled <i>event
1371: loop</i>.</p>
1.8 ihickson 1372:
1.81 ihickson 1373: </li>
1.8 ihickson 1374:
1375: <li>
1.71 ihickson 1376:
1.81 ihickson 1377: <p>Freeze the <span>script group</span>.</p>
1.50 ihickson 1378:
1.115 ihickson 1379: <p class="note">This kills timers, database transactions, etc.</p>
1.50 ihickson 1380:
1.81 ihickson 1381: </li>
1.50 ihickson 1382:
1.81 ihickson 1383: <li>
1.50 ihickson 1384:
1.115 ihickson 1385: <p>For each <code><a href="#worker">Worker</a></code> or <code><a href="#sharedworker">SharedWorker</a></code>
1.81 ihickson 1386: object associated with <var title="">worker global scope</var>,
1387: <span>queue a task</span> to <span>fire a simple event</span>
1.115 ihickson 1388: called <code title="event-close">close</code> at that object.</p>
1.5 ihickson 1389:
1.81 ihickson 1390: </li>
1.50 ihickson 1391:
1.115 ihickson 1392: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1393: run the following steps in parallel with the worker's main loop (the
1.115 ihickson 1394: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1395: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is
1.81 ihickson 1396: false, <span>queue a task</span> to <span>fire a simple
1.115 ihickson 1397: event</span> called <code title="event-close">close</code> at the
1398: worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object.</li>
1.81 ihickson 1399:
1.115 ihickson 1400: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1401: true.</li>
1402:
1.115 ihickson 1403: <li><p>Wait a user-agent-defined amount of time. If the "<a href="#run-a-worker">run
1.81 ihickson 1404: a worker</a>" processing model defined above immediately starts
1.115 ihickson 1405: running event listeners registered for the <code title="event-close">close</code> event, this time should not be
1406: zero — the idea is that the <code title="event-close">close</code> event can be used to clean up
1.81 ihickson 1407: when shutting down unexpectedly.</li>
1408:
1.115 ihickson 1409: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1410: queued in the <span>event loop</span>'s <span title="task
1.115 ihickson 1411: queue">task queues</span> other than the <code title="event-close">close</code> event that this algorithm just
1.81 ihickson 1412: added, discard them without processing them.</li>
1413:
1.115 ihickson 1414: <li><p>If the <code title="event-close">close</code> event that
1.81 ihickson 1415: this algorithm just queued hasn't yet been dispatched, then abort
1416: the script currently running in the worker.</li>
1417:
1418: <li><p>Wait a user-agent-defined amount of time.</li>
1419:
1420: <li><p>Abort the script currently running in the worker (if any
1.115 ihickson 1421: script is running, then it will be a handler for the <code title="event-close">close</code> event).</li>
1.81 ihickson 1422:
1.115 ihickson 1423: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1424: processing model on a worker at any time, e.g. in response to user
1425: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1426: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1427: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1428: set to true.<hr><p>When a user agent is to <dfn id="terminate-a-worker">terminate a worker</dfn> it must run
1.81 ihickson 1429: the following steps in parallel with the worker's main loop (the
1.115 ihickson 1430: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1431: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1432: true.</li>
1433:
1.115 ihickson 1434: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1435: queued in the <span>event loop</span>'s <span title="task
1436: queue">task queues</span>, discard them without processing
1437: them.</li>
1438:
1439: <li><p>Abort the script currently running in the worker.</li>
1440:
1.115 ihickson 1441: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1442: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1443: worker is a dedicated worker), then empty the <span>port message
1444: queue</span> of the port that the worker's implicit port is
1445: entangled with.</li>
1446:
1.115 ihickson 1447: </ol><h3 id="runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</h3><p>Whenever a runtime script error occurs in one of the worker's
1.81 ihickson 1448: scripts, if the error did not occur while handling a previous script
1.118 ! ihickson 1449: error, the user agent must <span>queue a task</span> to <span>fire a
! 1450: simple event</span> called <code title="event-error">error</code> at
! 1451: the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object.<p>For shared workers, if the error is still <i title="">not
1.81 ihickson 1452: handled</i> afterwards, or if the error occured while handling a
1453: previous script error, the error should be reported to the user.<p>For dedicated workers, if the error is still <i title="">not
1454: handled</i> afterwards, or if the error occured while handling a
1455: previous script error, the user agent must further <span>queue a
1.118 ! ihickson 1456: task</span> to <a href="#fire-a-worker-error-event">fire a worker error event</a> at the
! 1457: <code><a href="#worker">Worker</a></code> object associated with the worker.<p>When the user agent is to <dfn id="fire-a-worker-error-event">fire a worker error event</dfn> at
! 1458: a <code><a href="#worker">Worker</a></code> object, it must dispatch an event that uses
! 1459: the <code><a href="#errorevent">ErrorEvent</a></code> interface, with the name <code title="event-error">error</code>, that doesn't bubble and is
1.115 ihickson 1460: cancelable, with its <code title="dom-ErrorEvent-message"><a href="#dom-errorevent-message">message</a></code>, <code title="dom-ErrorEvent-filename"><a href="#dom-errorevent-filename">filename</a></code>, and <code title="dom-ErrorEvent-lineno"><a href="#dom-errorevent-lineno">lineno</a></code> attributes set
1.81 ihickson 1461: appropriately. The default action of this event depends on whether
1.115 ihickson 1462: the <code><a href="#worker">Worker</a></code> object is itself in a worker. If it is, and
1.81 ihickson 1463: that worker is also a dedicated worker, then the user agent must
1.118 ! ihickson 1464: again <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
! 1465: event</a> at the <code><a href="#worker">Worker</a></code> object associated with
! 1466: <em>that</em> worker. Otherwise, then the error should be reported
! 1467: to the user.<hr><pre class="idl">interface <dfn id="errorevent">ErrorEvent</dfn> : Event {
1.115 ihickson 1468: readonly attribute DOMObject <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1469: readonly attribute DOMObject <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1470: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1471: void <a href="#dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent">initErrorEvent</a>(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMObject messageArg, in DOMObject filenameArg, in unsigned long linenoArg);
1472: void <a href="#dom-errorevent-initerroreventns" title="dom-ErrorEvent-initErrorEventNS">initErrorEventNS</a>(in DOMString namespaceURIArg, in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMObject messageArg, in DOMObject filenameArg, in unsigned long linenoArg);
1473: };</pre><p>The <dfn id="dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent"><code>initErrorEvent()</code></dfn>
1474: and <dfn id="dom-errorevent-initerroreventns" title="dom-ErrorEvent-initErrorEventNS"><code>initErrorEventNS()</code></dfn>
1.81 ihickson 1475: methods must initialize the event in a manner analogous to the
1.115 ihickson 1476: similarly-named methods in the DOM3 Events interfaces. <a href="#references">[DOM3EVENTS]</a><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn>
1477: attribute represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1.81 ihickson 1478: attribute represents the <span>absolute URL</span> of the script in
1.115 ihickson 1479: which the error originally occured.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.81 ihickson 1480: attribute represents the line number where the error occured in the
1.115 ihickson 1481: script.<h3 id="creating-workers"><span class="secno">4.8 </span>Creating workers</h3><h4 id="the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code><a href="#abstractworker">AbstractWorker</a></code> abstract interface</h4><pre class="idl">interface <dfn id="abstractworker">AbstractWorker</dfn> {
1482: attribute <span>EventListener</span> <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1483: attribute <span>EventListener</span> <a href="#handler-abstractworker-onclose" title="handler-AbstractWorker-onclose">onclose</a>;
1484: };</pre><p>Objects implementing the <code><a href="#abstractworker">AbstractWorker</a></code> interface
1.102 ihickson 1485: must also implement the <code>EventTarget</code> interface.<p>The following are the <span>event handler attributes</span> (and their corresponding <span title="event handler event type">event handler event types</span>)
1486: that must be supported, as DOM attributes, by objects implementing
1.115 ihickson 1487: the <code><a href="#abstractworker">AbstractWorker</a></code> interface:<table><thead><tr><th><span title="event handler attributes">event handler attribute</span> <th><span>Event handler event type</span>
1488: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1489: <tr><td><dfn id="handler-abstractworker-onclose" title="handler-AbstractWorker-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code>
1490: </table><h4 id="dedicated-workers-and-the-worker-interface"><span class="secno">4.8.2 </span>Dedicated workers and the <code><a href="#worker">Worker</a></code> interface</h4><pre class="idl">[<a href="#dom-worker" title="dom-Worker">Constructor</a>(in DOMString scriptURL)]
1491: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1492: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1493:
1.115 ihickson 1494: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(in any message, [Optional] in <span>MessagePortArray</span> ports);<!--
1.81 ihickson 1495: <span>MessagePort</span> <span title="dom-Worker-startConversation">startConversation</span>(in any message);-->
1.115 ihickson 1496: attribute <span>EventListener</span> <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1497: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1498: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1499: algorithm to be run on the worker with with the object is
1.115 ihickson 1500: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.81 ihickson 1501: <code>MessagePort</code> associated with them. This port is part of
1502: a channel that is set up when the worker is created, but it is not
1503: exposed. This object must never be garbage collected before the
1.115 ihickson 1504: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1505: at the <code><a href="#worker">Worker</a></code> object.<p>The <dfn id="dom-worker-postmessage" title="dom-Worker-postMessage"><code>postMessage()</code></dfn><!--
1.64 ihickson 1506: and <dfn
1507: title="dom-Worker-startConversation"><code>startConversation()</code></dfn>-->
1.115 ihickson 1508: method<!--s (startConversation)--> on <code><a href="#worker">Worker</a></code> objects
1.81 ihickson 1509: must act as if, when invoked, it<!--/they (startConversation)-->
1510: immediately invoked the method of the same name on the port, with
1.102 ihickson 1511: the same arguments, and returned the same return value.<p>The following are the <span>event handler attributes</span> (and their corresponding <span title="event handler event type">event handler event types</span>)
1512: that must be supported, as DOM attributes, by objects implementing
1.115 ihickson 1513: the <code><a href="#worker">Worker</a></code> interface:<table><thead><tr><th><span title="event handler attributes">event handler attribute</span> <th><span>Event handler event type</span>
1514: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1515: </table><hr><p>When the <dfn id="dom-worker" title="dom-Worker"><code>Worker(<var title="">scriptURL</var>)</code></dfn> constructor is invoked, the
1.81 ihickson 1516: user agent must run the following steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.9 ihickson 1517:
1.81 ihickson 1518: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1519: exception.</li>
1.9 ihickson 1520:
1.81 ihickson 1521: <li><p>If the <span>origin</span> of the resulting <span>absolute
1522: URL</span> is not the <span title="same origin">same</span> as the
1523: origin of the script that invoked the constructor, then throw a
1524: <span>security exception</span>.</li>
1.9 ihickson 1525:
1.115 ihickson 1526: <li><p><span>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1.81 ihickson 1527: object</span>. Let <var title="">worker global scope</var> be this
1528: new object.</li>
1.9 ihickson 1529:
1.115 ihickson 1530: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1531: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1532:
1.81 ihickson 1533: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1534: by the <span>script execution context</span> of the script that
1535: invoked the method. Let this be the <var title="">outside
1536: port</var>.</li>
1.9 ihickson 1537:
1.81 ihickson 1538: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1539:
1.81 ihickson 1540: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1541: by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1542:
1.81 ihickson 1543: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1544:
1.81 ihickson 1545: <li><p><span>Entangle</span> <var title="">outside port</var> and
1546: <var title="">inside port</var>.</li>
1.50 ihickson 1547:
1.81 ihickson 1548: <li><p>Return <var title="">worker</var>, and run the following
1549: steps asynchronously.</li>
1.50 ihickson 1550:
1.81 ihickson 1551: <li><p>Open <var title="">inside port</var>'s <span>port message
1552: queue</span>.</li>
1.50 ihickson 1553:
1.81 ihickson 1554: <li><p>Open <var title="">outside port</var>'s <span>port message
1555: queue</span>.</li>
1.50 ihickson 1556:
1557: <li>
1.51 ihickson 1558:
1.115 ihickson 1559: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.81 ihickson 1560: URL</span>, with the <span>script browsing context</span> of the
1561: script that invoked the method as the <var title="">owner browsing
1562: context</var>, and with <var title="">worker global scope</var> as
1563: the global scope.</p>
1.9 ihickson 1564:
1.81 ihickson 1565: </li>
1.4 ihickson 1566:
1.115 ihickson 1567: </ol><h4 id="shared-workers-and-the-sharedworker-interface"><span class="secno">4.8.3 </span>Shared workers and the <code><a href="#sharedworker">SharedWorker</a></code> interface</h4><pre class="idl">[<a href="#dom-sharedworker" title="dom-SharedWorker">Constructor</a>(in DOMString scriptURL, in DOMString name)]
1568: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1569: readonly attribute <span>MessagePort</span> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1570: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1571: attribute must return the value it was assigned by the object's
1572: constructor. It represents the <code>MessagePort</code> for
1.115 ihickson 1573: communicating with the shared worker.<p>When the <dfn id="dom-sharedworker" title="dom-SharedWorker"><code>SharedWorker(<var title="">scriptURL</var>, <var title="">name</var>)</code></dfn>
1.81 ihickson 1574: constructor is invoked, the user agent must run the following
1575: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1576:
1577: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1578: exception.</li>
1579:
1580: <li><p>If the <span>origin</span> of the resulting <span>absolute
1581: URL</span> is not the <span title="same origin">same</span> as the
1582: origin of the script that invoked the constructor, then throw a
1583: <span>security exception</span>.</li>
1.9 ihickson 1584:
1585: <li>
1586:
1.50 ihickson 1587: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1588:
1.115 ihickson 1589: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1590: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1591: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1592:
1593: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1594: by the <span>script execution context</span> of the script that
1595: invoked the method. Let this be the <var title="">outside
1596: port</var>.</li>
1597:
1.115 ihickson 1598: <li><p>Assign <var title="">outside port</var> to the <code title="dom-SharedWorker-port"><a href="#dom-sharedworker-port">port</a></code> attribute of <var title="">worker</var>.</li>
1.81 ihickson 1599:
1.9 ihickson 1600: <li>
1601:
1.115 ihickson 1602: <p>If there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1603: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1604: flag is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1.81 ihickson 1605: exactly equal to the <var title="">name</var> argument, and
1.115 ihickson 1606: whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.81 ihickson 1607: represents an <span>absolute URL</span> that has the <span>same
1608: origin</span> as the resulting <span>absolute URL</span>, then
1609: run these substeps:</p>
1610:
1611: <ol><li><p>Let <var title="">worker global scope</var> be that
1.115 ihickson 1612: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1.81 ihickson 1613:
1.115 ihickson 1614: <li><p>If <var title="">worker global scope</var>'s <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code>
1.81 ihickson 1615: attribute represents an <span>absolute URL</span> that is not
1616: exactly equal to the resulting <span>absolute URL</span>, then
1617: throw a <code>URL_MISMATCH_ERR</code> exception and abort all
1.115 ihickson 1618: these steps. <span class="XXX">code 21</span></li>
1.81 ihickson 1619:
1620: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1621:
1622: <li><p><span>Create a <code>MessagePort</code> object</span>
1623: owned by <var title="">worker global scope</var>. Let this
1624: be the <var title="">inside port</var>.</li>
1625:
1626: <li><p><span>Entangle</span> <var title="">outside port</var>
1627: and <var title="">inside port</var>.</li>
1628:
1629: <li><p>Return <var title="">worker</var> and perform the next
1630: step asynchronously.</li>
1.9 ihickson 1631:
1.81 ihickson 1632: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1633: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ! ihickson 1634: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
! 1635: is the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
! 1636: value is an array containing only the newly created port, and
! 1637: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.43 ihickson 1638:
1.81 ihickson 1639: <li><p>Abort all these steps.</li>
1.9 ihickson 1640:
1.81 ihickson 1641: </ol></li>
1.9 ihickson 1642:
1.115 ihickson 1643: <li><p><span>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1.81 ihickson 1644: object</span>. Let <var title="">worker global scope</var> be
1645: this new object.</li>
1.9 ihickson 1646:
1.81 ihickson 1647: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1648:
1.115 ihickson 1649: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1650: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1651:
1.81 ihickson 1652: <li><p><span>Create a <code>MessagePort</code> object</span>
1653: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1654:
1.81 ihickson 1655: <li><p><span>Entangle</span> <var title="">outside port</var> and
1656: <var title="">inside port</var>.</li>
1.9 ihickson 1657:
1.81 ihickson 1658: </ol></li>
1.28 ihickson 1659:
1.81 ihickson 1660: <li><p>Return <var title="">worker</var> and perform the next step
1661: asynchronously.</li>
1.18 ihickson 1662:
1.81 ihickson 1663: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ! ihickson 1664: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1665: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.118 ! ihickson 1666: the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
! 1667: is an array containing only the newly created port, and <span>queue
! 1668: a task</span> to dispatch the event at <var title="">worker global
! 1669: scope</var>.</li>
1.26 ihickson 1670:
1671: <li>
1.46 ihickson 1672:
1.115 ihickson 1673: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.81 ihickson 1674: URL</span>, with the <span>script browsing context</span> of the
1675: script that invoked the method as the <var title="">owner browsing
1676: context</var>, and with <var title="">worker global scope</var> as
1677: the global scope.</p>
1.26 ihickson 1678:
1.60 ihickson 1679: </li>
1.81 ihickson 1680:
1.115 ihickson 1681: </ol><h2 id="apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</h2><!-- the XXX below is for collapsing this interface onto WorkerGlobalScope so it looks like just one interface - the inheritance is a spec fiction only --><pre class="idl">[NoInterfaceObject, ImplementedOn=WorkerGlobalScope, XXX] interface <dfn id="workerutils">WorkerUtils</dfn> {
1682: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>([Variadic] in DOMString urls);
1683: readonly attribute <a href="#worker-navigator" title="worker-Navigator">Navigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1684: <span>Database</span> <span title="dom-opendatabase">openDatabase</span>(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize);
1685: <span>DatabaseSync</span> <span title="dom-opendatabase-sync">openDatabaseSync</span>(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize);
1686: };</pre><p>Objects that implement the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1687: interface must also implement the <code><a href="#workerutils">WorkerUtils</a></code>
1688: interface.<p>Objects that implement the <code><a href="#workerutils">WorkerUtils</a></code> interface
1.81 ihickson 1689: must also implement the <code>WindowTimers</code> interface. (This
1690: interface provides the <code title="">setTimeout()</code> method and
1.104 ihickson 1691: its friends.)</p><!-- XXX ref --><!-- XXX ApplicationCache --><!-- XXX debugging: void log(in DOMString s); // log to console --><hr><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1692: objects, etc) are not available to workers in this version of this
1.115 ihickson 1693: specification.<h3 id="importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</h3><p>When a script invokes the <dfn id="dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts"><code>importScripts(<var title="">urls</var>)</code></dfn> method on a
1694: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.81 ihickson 1695: following steps:<ol><li><p>If there are no arguments, return without doing
1696: anything. Abort these steps.</li>
1697:
1698: <li><p><span title="resolve a url">Resolve</span> each
1699: argument.</li>
1700:
1701: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1702: exception.</li>
1703:
1704: <!--
1.67 ihickson 1705: <li><p>If any of the resulting <span title="absolute URL">absolute
1706: URLs</span> have an <span>origin</span> that is not the <span
1707: title="same origin">same</span> as the origin of the script that
1708: invoked the method, then throw a <span>security
1709: exception</span>.</p></li>
1710: -->
1.26 ihickson 1711:
1712: <li>
1.81 ihickson 1713:
1.45 ihickson 1714: <p>Attempt to <span>fetch</span> each resource identified by the
1.81 ihickson 1715: resulting <span title="absolute URLs">absolute URL</span>.</p>
1716:
1717: </li>
1.26 ihickson 1718:
1719: <li>
1720:
1.81 ihickson 1721: <p>For each argument in turn, in the order given, starting with
1722: the first one, run these substeps:</p>
1.26 ihickson 1723:
1.81 ihickson 1724: <ol><li>
1.26 ihickson 1725:
1.81 ihickson 1726: <p>Wait for the fetching attempt for the corresponding resource
1727: to complete.</p>
1.60 ihickson 1728:
1.81 ihickson 1729: <p>If the fetching attempt failed, throw a
1730: <code>NETWORK_ERR</code> exception and abort all these
1731: steps.</p>
1.45 ihickson 1732:
1.115 ihickson 1733: <p>If the attempt succeeds, then <a href="#decode-a-script-resource" title="decode a script
1.85 ihickson 1734: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1735:
1736: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1737:
1.115 ihickson 1738: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1739: always assumed to be JavaScript, regardless of the MIME
1740: type.</p> <!-- XXX -->
1.61 ihickson 1741:
1.81 ihickson 1742: </li>
1.26 ihickson 1743:
1.81 ihickson 1744: <li>
1.26 ihickson 1745:
1.81 ihickson 1746: <p><span>Create a script</span>, using <var title="">source</var> as the script source and <var title="">language</var> as the scripting language, using the
1747: same global object, browsing context, character encoding, base
1.115 ihickson 1748: URL, and script group as the <span title="concept-script">script</span> that was created by the
1749: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1750:
1.115 ihickson 1751: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1752: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1753: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1754: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1755:
1.81 ihickson 1756: <p>If it failed to parse, then throw a
1757: <code>SyntaxError</code><!-- XXX ref? --> exception and abort
1758: all these steps.</p>
1.63 ihickson 1759:
1.81 ihickson 1760: <p>If an exception was raised or if the script was prematurely
1761: aborted, then abort all these steps, letting the exception or
1762: aborting continue to be processed by the script that called the
1.115 ihickson 1763: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1764: method.</p>
1765:
1.115 ihickson 1766: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1767: worker</a>" algorithms abort the script then abort all these
1768: steps.</p>
1769:
1770: </li>
1771:
1772: </ol></li>
1773:
1.115 ihickson 1774: </ol><h3 id="the-navigator-object"><span class="secno">5.2 </span>The <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> object</h3><p>The <dfn id="dom-worker-navigator" title="dom-worker-navigator"><code>navigator</code></dfn> attribute
1775: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1776: the <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> interface, which
1.93 ihickson 1777: represents the identity and state of the user agent (the
1.115 ihickson 1778: client):<pre class="idl">interface <dfn id="worker-navigator" title="worker-Navigator">Navigator</dfn> {
1.81 ihickson 1779: // objects implementing this interface also implement the interfaces listed below
1.115 ihickson 1780: };</pre><p>Objects implementing the <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> interface must also
1.93 ihickson 1781: implement the <span>NavigatorID</span> and
1.81 ihickson 1782: <span>NavigatorOnLine</span> interfaces specified in the HTML5
1.115 ihickson 1783: specification. <a href="#references">[HTML5]</a><p class="note">The <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code>
1.93 ihickson 1784: interface defined in this specification is different than the one
1.115 ihickson 1785: defined in the HTML5 specification.<h3 id="apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</h3><p>The <code title="dom-opendatabase">openDatabase()</code> and
1786: <code title="dom-opendatabase-sync">openDatabaseSync()</code>
1787: methods are defined in the Web Storage specification. <a href="#references">[WEBSTORAGE]</a><h3 id="interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</h3><p>There must be no interface objects and constructors available in
1.81 ihickson 1788: the global scope of scripts whose <span>script execution
1.115 ihickson 1789: context</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.81 ihickson 1790: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1791: constructors defined by the XMLHttpRequest specifications, except
1792: that the <span>document response entity body</span> must always be
1.115 ihickson 1793: null. <a href="#references">[XHR]</a></li>
1.81 ihickson 1794:
1795: <li><p>The <code>WebSocket</code> interface object and
1.115 ihickson 1796: constructor. <a href="#references">[WEBSOCKET]</a></li>
1.81 ihickson 1797:
1798: <li><p>The <code>MessageChannel</code> interface object and
1.115 ihickson 1799: constructor. <a href="#references">[HTML5]</a></li>
1.81 ihickson 1800:
1.115 ihickson 1801: <li><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> and <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker(<var title="">url</var>)</a></code> constructors.</li>
1.81 ihickson 1802:
1.115 ihickson 1803: </ul><h3 id="worker-locations"><span class="secno">5.5 </span>Worker locations</h3><pre class="idl">interface <dfn id="workerlocation">WorkerLocation</dfn> {
1804: readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1805: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1806: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1807: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1808: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1809: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1810: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1811: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1812: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1813: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1814: attribute must return the <span>absolute URL</span> that the object
1.115 ihickson 1815: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1816: of <span>URL decomposition attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1817: <dfn id="dom-workerlocation-host" title="dom-WorkerLocation-host"><code>host</code></dfn>, <dfn id="dom-workerlocation-port" title="dom-WorkerLocation-port"><code>port</code></dfn>, <dfn id="dom-workerlocation-hostname" title="dom-WorkerLocation-hostname"><code>hostname</code></dfn>,
1818: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1819: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1820: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>. These must
1.81 ihickson 1821: follow the rules given for URL decomposition attributes, with the
1.115 ihickson 1822: <span title="concept-uda-input">input</span> being the
1.81 ihickson 1823: <span>absolute URL</span> that the object represents (same as the
1.115 ihickson 1824: <code title="dom-WorkerLocation-href"><a href="#dom-workerlocation-href">href</a></code> attribute), and
1825: the <span title="concept-uda-setter">common setter action</span>
1826: being a no-op, since the attributes are defined to be readonly. <a href="#references">[HTML5]</a><h2 class="no-num" id="references">References</h2><p class="big-issue">This section will be written in a future
1827: draft.<!--XXX--><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 1828:
1829: Aaron Boodman,
1830: Алексей Проскуряков (Alexey Proskuryakov),
1831: Anne van Kesteren,
1832: Ben Turner,
1833: Dmitry Titov,
1.96 ihickson 1834: Drew Wilson,
1.97 ihickson 1835: Jeremy Orlow,
1.81 ihickson 1836: Jonas Sicking,
1837: Justin James,
1838: Kevin Hakanson,
1839: Maciej Stachowiak,
1840: Michael Nordman,
1841: Mike Smith,
1842:
1843: and
1844:
1845: Philip Taylor
1846:
1847: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1848: technology and whose experience has been a huge influence on this
1849: specification.
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