Annotation of html5/workers/Overview.html, revision 1.114
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1.114 ! ihickson 145: </style><link href=http://www.w3.org/StyleSheets/TR/W3C-WD rel=stylesheet type=text/css><!-- ZZZ ED vs WD --><div class=head>
1.81 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:-->
1.113 ihickson 149: <h2 class="no-num no-toc" id=w3c-working-draft-23-april-year>W3C Working Draft 23 April 2009</h2>
1.114 ! ihickson 150: <!--<h2 class="no-num no-toc">Editor's Draft 22 April 2009</h2>-->
1.109 ihickson 151: <!--:ZZZ-->
152: <dl><!-- ZZZ: update the month/day (twice), (un)comment out--><dt>This Version:</dt>
1.113 ihickson 153: <dd><a href=http://www.w3.org/TR/2009/WD-workers-20090423/>http://www.w3.org/TR/2009/WD-workers-20090423/</a></dd>
1.109 ihickson 154: <!-- :ZZZ -->
1.2 ihickson 155: <dt>Latest Published Version:</dt>
1.109 ihickson 156: <dd><a href=http://www.w3.org/TR/workers/>http://www.w3.org/TR/workers/</a></dd>
157: <dt>Latest Editor's Draft:</dt>
1.81 ihickson 158: <dd><a href=http://dev.w3.org/html5/workers/>http://dev.w3.org/html5/workers/</a></dd>
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>
1.2 ihickson 162: :ZZZ -->
1.81 ihickson 163: <dt>Editors:</dt>
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>
1.109 ihickson 166: © 2009 <a href=http://www.w3.org/><abbr title="World Wide
1.81 ihickson 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
173: use</a> rules apply.</p>
1.1 ihickson 174:
175: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.81 ihickson 176: <p class="alt copyright">The <a href=http://www.whatwg.org/specs/web-workers/current-work/>WHATWG
177: version</a> of this specification is available under a more
178: permissive license.</p>
1.1 ihickson 179: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
180:
1.112 ihickson 181: </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 182: authors to spawn background workers running scripts in parallel to
183: their main page. This allows for thread-like operation with
184: 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
185: time of its publication. Other documents may supersede this
186: document. A list of current W3C publications and the most recently
187: formally published revision of this technical report can be found in
188: the <a href=http://www.w3.org/TR/>W3C technical reports index</a>
189: at http://www.w3.org/TR/.</em></p><!-- where to send feedback (required) --><p>If you wish to make comments regarding this document, please send
1.90 ihickson 190: them to <a href=mailto:public-webapps@w3.org>public-webapps@w3.org</a>
191: (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
192: <a href=http://lists.w3.org/Archives/Public/public-webapps/>archives</a>)
1.81 ihickson 193:
194: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
195: or <a href=mailto:whatwg@whatwg.org>whatwg@whatwg.org</a> (<a href=http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org>subscribe</a>,
196: <a href=http://lists.whatwg.org/pipermail/whatwg-whatwg.org/>archives</a>).
1.110 ihickson 197: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.1 ihickson 198:
1.81 ihickson 199: All feedback is welcome.</p><!-- stability (required) --><p>Implementors should be aware that this specification is not
200: stable. <strong>Implementors who are not taking part in the
201: discussions are likely to find the specification changing out from
202: under them in incompatible ways.</strong> Vendors interested in
203: implementing this specification before it eventually reaches the
204: Candidate Recommendation stage should join the aforementioned
205: 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
206: specification is always available on <a href=http://dev.w3.org/html5/workers/Overview.html>the W3C CVS
207: server</a> and in the <a href=http://svn.whatwg.org/webworkers/>WHATWG Subversion
208: repository</a>. The latest editor's working copy (which may contain
209: unfinished text in the process of being prepared) is available <a href=http://www.whatwg.org/specs/web-workers/current-work/>on the
210: WHATWG site</a>. Detailed change history can be obtained from the
211: 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>
212: <li>Interactive Web interface: <a href=http://html5.org/tools/web-workers-tracker>http://html5.org/tools/web-workers-tracker</a></li>
213: <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>
214: <li>Subversion interface: <a href=http://svn.whatwg.org/webworkers/>http://svn.whatwg.org/webworkers/</a></li>
215: <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>
216: </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
217: Working Group</a> is the W3C working group responsible for this
218: specification's progress along the W3C Recommendation track.
219: <!--ZZZ:-->
1.113 ihickson 220: This specification is the 23 April 2009 First Public Working Draft.
1.114 ! ihickson 221: <!-- This specification is the 22 April 2009 Editor's Draft. -->
1.81 ihickson 222: <!--:ZZZ-->
223: </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
224: 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
225: platform closely related to HTML5. It is defined in a separate
226: 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
227: 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
228: any patent disclosures</a> made in connection with the deliverables
229: of the group; that page also includes instructions for disclosing a
230: patent. An individual who has actual knowledge of a patent which the
231: individual believes contains <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential>Essential
232: Claim(s)</a> must disclose the information in accordance with <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure>section
233: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id=contents>Table of contents</h2>
234: <!--begin-toc-->
235: <ol class=toc>
236: <li><a href=#introduction><span class=secno>1 </span>Introduction</a>
237: <ol>
238: <li><a href=#scope><span class=secno>1.1 </span>Scope</a></li>
239: <li><a href=#tutorial><span class=secno>1.2 </span>Tutorial</a>
240: <ol>
241: <li><a href=#a-background-number-crunching-worker><span class=secno>1.2.1 </span>A background number-crunching worker</a></li>
242: <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>
243: <li><a href=#worker-used-for-background-i-o><span class=secno>1.2.3 </span>Worker used for background I/O</a></li>
244: <li><a href=#shared-workers><span class=secno>1.2.4 </span>Shared workers</a></li>
245: <li><a href=#delegation><span class=secno>1.2.5 </span>Delegation</a></li>
1.82 ihickson 246: <li><a href=#providing-libraries><span class=secno>1.2.6 </span>Providing libraries</a></ol></ol></li>
247: <li><a href=#conformance-requirements><span class=secno>2 </span>Conformance requirements</a>
248: <ol>
249: <li><a href=#dependencies><span class=secno>2.1 </span>Dependencies</a></ol></li>
250: <li><a href=#terminology><span class=secno>3 </span>Terminology</a></li>
251: <li><a href=#infrastructure><span class=secno>4 </span>Infrastructure</a>
1.81 ihickson 252: <ol>
1.82 ihickson 253: <li><a href=#the-global-scope><span class=secno>4.1 </span>The global scope</a>
1.81 ihickson 254: <ol>
1.82 ihickson 255: <li><a href=#the-workerglobalscope-abstract-interface><span class=secno>4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
256: <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>
257: <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>
258: <li><a href=#base-urls-and-origins-of-workers><span class=secno>4.2 </span>Base URLs and origins of workers</a></li>
1.85 ihickson 259: <li><a href=#decoding-scripts><span class=secno>4.3 </span>Decoding scripts</a></li>
260: <li><a href=#the-event-loop><span class=secno>4.4 </span>The event loop</a></li>
261: <li><a href=#the-worker-s-ports><span class=secno>4.5 </span>The worker's ports</a></li>
1.99 ihickson 262: <li><a href=#processing-model><span class=secno>4.6 </span>Processing model</a></li>
263: <li><a href=#runtime-script-errors><span class=secno>4.7 </span>Runtime script errors</a></li>
264: <li><a href=#creating-workers><span class=secno>4.8 </span>Creating workers</a>
1.81 ihickson 265: <ol>
1.99 ihickson 266: <li><a href=#the-abstractworker-abstract-interface><span class=secno>4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
267: <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>
268: <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>
1.82 ihickson 269: <li><a href=#apis-available-to-workers><span class=secno>5 </span>APIs available to workers</a>
1.81 ihickson 270: <ol>
1.82 ihickson 271: <li><a href=#importing-scripts-and-libraries><span class=secno>5.1 </span>Importing scripts and libraries</a></li>
1.93 ihickson 272: <li><a href=#the-navigator-object><span class=secno>5.2 </span>The <code title=worker-Navigator>Navigator</code> object</a></li>
1.82 ihickson 273: <li><a href=#apis-defined-in-other-specifications><span class=secno>5.3 </span>APIs defined in other specifications</a></li>
274: <li><a href=#interface-objects-and-constructors><span class=secno>5.4 </span>Interface objects and constructors</a></li>
275: <li><a href=#worker-locations><span class=secno>5.5 </span>Worker locations</a></ol></li>
1.81 ihickson 276: <li><a class=no-num href=#references>References</a></li>
277: <li><a class=no-num href=#acknowledgements>Acknowledgements</a></ol>
278: <!--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
279: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
280: scripts that respond to clicks or other user interactions, and
281: allows long tasks to be executed without yielding to keep the page
282: responsive.<p>Workers (as these background scripts are called herein) are
283: relatively heavy-weight, and are not intended to be used in large
284: numbers. For example, it would be inappropriate to launch one worker
285: for each pixel of a four megapixel image. The examples below show
286: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
287: 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
288: 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
289: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
290: (naïvely) compute prime numbers, and progressively displays the
291: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
292: <html>
293: <head>
294: <title>Worker example: One-core computation</title>
295: </head>
296: <body>
297: <p>The highest prime number discovered so far is: <output id="result"></output></p>
298: <script>
1.50 ihickson 299: var worker = new Worker('worker.js');
300: worker.onmessage = function (event) {
1.54 ihickson 301: document.getElementById('result').textContent = event.data;
1.29 ihickson 302: };
1.81 ihickson 303: </script>
304: </body>
305: </html></pre><p>The <code title=dom-Worker><a href=#dom-worker>Worker()</a></code> constructor call
306: creates a worker and returns a <code><a href=#worker>Worker</a></code> object
307: representing that worker, which is used to communicate with the
308: worker. That object's <code title=handler-Worker-onmessage><a href=#handler-worker-onmessage>onmessage</a></code> event handler
309: attribute allows the code to receive messages from the worker.<p>The worker itself is as follows:<pre>var n = 1;
1.29 ihickson 310: search: while (true) {
311: n += 1;
312: for (var i = 2; i <= Math.sqrt(n); i += 1)
313: if (n % i == 0)
314: continue search;
315: // found a prime!
1.50 ihickson 316: postMessage(n);
1.105 ihickson 317: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.81 ihickson 318: number. To send a message back to the page, the <code title=dom-DedicatedWorkerGlobalScope-postMessage><a href=#dom-dedicatedworkerglobalscope-postmessage>postMessage()</a></code>
319: 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
320: task is to listen for notifications from the server, and, when
321: appropriate, either add or remove data from the client-side
322: database.<p>Since no communication occurs between the worker and the main
323: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 324: new Worker('worker.js');
1.81 ihickson 325: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 326: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 327: server.onmessage = function (event) {
328: // data is in the format "command key value"
1.54 ihickson 329: var data = event.data.split(' ');
1.31 ihickson 330: switch (data[0]) {
331: case '+':
332: database.transaction(function(tx) {
333: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
334: });
335: case '-':
336: database.transaction(function(tx) {
337: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
338: });
339: }
1.81 ihickson 340: };</pre><p>This connects to the server using the <code>WebSocket</code>
341: mechanism and opens the local database (which, we presume, has been
342: created earlier). The worker then just listens for messages from the
343: server and acts on them as appropriate, forever (or until the main
344: page is closed).<p><a href=http://www.whatwg.org/demos/workers/database-updater/page.html>View
345: this example online</a>. (This example will not actually function,
346: since the server does not actually exist and the database is not
347: 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
348: fetching stock updates for at regular intervals, and one for
349: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
350: <html>
351: <head>
352: <title>Worker example: Stock ticker</title>
353: <script>
1.33 ihickson 354: // TICKER
355: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 356: var ticker = new Worker('ticker.js');
1.33 ihickson 357:
358: // SEARCHER
1.50 ihickson 359: var searcher = new Worker('searcher.js');
1.33 ihickson 360: function search(query) {
1.50 ihickson 361: searcher.postMessage(query);
1.33 ihickson 362: }
363:
364: // SYMBOL SELECTION UI
365: function select(newSymbol) {
366: symbol = newSymbol;
1.50 ihickson 367: ticker.postMessage(symbol);
1.33 ihickson 368: }
1.81 ihickson 369: </script>
370: </head>
371: <body>
372: <p><output id="symbol"></output> <output id="value"></output></p>
373: <script>
1.50 ihickson 374: ticker.onmessage = function (event) {
1.54 ihickson 375: var data = event.data.split(' ');
1.33 ihickson 376: document.getElementById('symbol').textContent = data[0];
377: document.getElementById('value').textContent = data[1];
378: };
1.50 ihickson 379: ticker.postMessage(symbol);
1.81 ihickson 380: </script>
381: <p><label>Search: <input type="text" oninput="search(this.value)"></label></p>
382: <ul id="results"></ul>
383: <script>
1.50 ihickson 384: searcher.onmessage = function (event) {
1.54 ihickson 385: var data = event.data.split(' ');
1.33 ihickson 386: var results = document.getElementById('results');
387: while (results.hasChildNodes()) // clear previous results
388: results.removeChild(results.firstChild);
389: for (var i = 0; i < data.length; i += 1) {
390: // add a list item with a button for each result
391: var li = document.createElement('li');
392: var button = document.createElement('button');
393: button.value = data[i];
394: button.type = 'button';
395: button.onclick = function () { select(this.value); };
396: button.textContent = data[i];
397: li.appendChild(button);
398: results.appendChild(li);
399: }
400: };
1.81 ihickson 401: </script>
402: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
403: </body>
404: </html></pre><p>The two workers use a common library for performing the actual
405: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 406: try {
407: var xhr = new XMLHttpRequest();
408: xhr.open('GET', url, false);
409: xhr.send();
410: return xhr.responseText;
411: } catch (e) {
412: return ''; // turn all errors into empty results
413: }
1.81 ihickson 414: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 415: var timer;
416: var symbol;
417: function update() {
1.50 ihickson 418: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 419: timer = setTimeout(update, 10000);
420: }
1.50 ihickson 421: onmessage = function (event) {
1.33 ihickson 422: if (timer)
423: clearTimeout(timer);
1.54 ihickson 424: symbol = event.data;
1.33 ihickson 425: update();
1.81 ihickson 426: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 427: onmessage = function (event) {
1.54 ihickson 428: postMessage(get('search.cgi?' + event.data));
1.81 ihickson 429: };</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
430: are all viewing the same map. All the windows share the same map
431: information, with a single worker coordinating all the viewers. Each
432: viewer can move around independently, but if they set any data on
433: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
434: the viewers:<pre><!DOCTYPE HTML>
435: <html>
436: <head>
437: <title>Workers example: Multiviewer</title>
438: <script>
1.36 ihickson 439: function openViewer() {
440: window.open('viewer.html');
441: }
1.81 ihickson 442: </script>
443: </head>
444: <body>
445: <p><button type=button onclick="openViewer()">Open a new
446: viewer</button></p>
447: <p>Each viewer opens in a new window. You can have as many viewers
448: as you like, they all view the same data.</p>
449: </body>
450: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
451: <html>
452: <head>
453: <title>Workers example: Multiviewer viewer</title>
454: <script>
1.50 ihickson 455: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 456:
457: // CONFIGURATION
458: function configure(event) {
1.54 ihickson 459: if (event.data.substr(0, 4) != 'cfg ') return;
460: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 461: // update display to mention our name is name
462: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
463: // no longer need this listener
1.43 ihickson 464: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 465: }
1.53 ihickson 466: worker.port.addEventListener('message', configure, false);
1.36 ihickson 467:
468: // MAP
469: function paintMap(event) {
1.54 ihickson 470: if (event.data.substr(0, 4) != 'map ') return;
471: var data = event.data.substr(4).split(',');
1.36 ihickson 472: // display tiles data[0] .. data[8]
473: var canvas = document.getElementById('map');
474: var context = canvas.getContext('2d');
475: for (var y = 0; y < 3; y += 1) {
476: for (var x = 0; x < 3; x += 1) {
477: var tile = data[y * 3 + x];
478: if (tile == '0')
479: context.fillStyle = 'green';
480: else
481: context.fillStyle = 'maroon';
482: fillRect(x * 50, y * 50, 50, 50);
483: }
484: }
485: }
1.53 ihickson 486: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 487:
488: // PUBLIC CHAT
489: function updatePublicChat(event) {
1.54 ihickson 490: if (event.data.substr(0, 4) != 'txt ') return;
491: var name = event.data.substr(4).split(' ', 1);
492: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 493: // display "<name> message" in public chat
1.36 ihickson 494: var dialog = document.getElementById('public');
495: var dt = document.createElement('dt');
496: dt.textContent = name;
497: dialog.appendChild(dt);
498: var dd = document.createElement('dd');
499: dd.textContent = message;
500: dialog.appendChild(dd);
501: }
1.53 ihickson 502: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 503:
504: // PRIVATE CHAT
505: function startPrivateChat(event) {
1.54 ihickson 506: if (event.data.substr(0, 4) != 'msg ') return;
507: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 508: var port = event.ports[0];
1.36 ihickson 509: // display a private chat UI
510: var ul = document.getElementById('private');
511: var li = document.createElement('li');
512: var h3 = document.createElement('h3');
513: h3.textContent = 'Private chat with ' + name;
514: li.appendChild(h3);
515: var dialog = document.createElement('dialog');
516: var addMessage = function(name, message) {
517: var dt = document.createElement('dt');
518: dt.textContent = name;
519: dialog.appendChild(dt);
520: var dd = document.createElement('dd');
521: dd.textContent = message;
522: dialog.appendChild(dd);
523: };
524: port.onmessage = function (event) {
1.54 ihickson 525: addMessage(name, event.data);
1.36 ihickson 526: };
527: li.appendChild(dialog);
528: var form = document.createElement('form');
529: var p = document.createElement('p');
530: var input = document.createElement('input');
531: input.size = 50;
532: p.appendChild(input);
533: p.appendChild(document.createTextNode(' '));
534: var button = document.createElement('button');
535: button.textContent = 'Post';
536: p.appendChild(button);
537: form.onsubmit = function () {
538: port.postMessage(input.value);
539: addMessage('me', input.value);
540: input.value = '';
541: return false;
542: };
543: form.appendChild(p);
544: li.appendChild(form);
545: }
1.53 ihickson 546: worker.port.addEventListener('message', startPrivateChat, false);
1.81 ihickson 547: </script>
548: </head>
549: <body>
550: <h1>Viewer</h1>
551: <h2>Map</h2>
552: <p><canvas id="map" height=150 width=150></canvas></p>
553: <p>
554: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
555: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
556: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
557: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
558: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
559: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
560: </p>
561: <h2>Public Chat</h2>
562: <dialog id="public"></dialog>
563: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
564: <p>
565: <input type="text" name="message" size="50">
566: <button>Post</button>
567: </p>
568: </form>
569: <h2>Private Chat</h2>
570: <ul id="private"></ul>
571: </body>
572: </html>
573: </pre><p>There are several key things worth noting about the way the
574: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
575: processing function, the code here attaches multiple event
576: listeners, each one performing a quick check to see if it is
577: relevant for the message. In this example it doesn't make much
578: difference, but if multiple authors wanted to collaborate using a
579: single port to communicate with a worker, it would allow for
580: independent code instead of changes having to all be made to a
581: single event handling function.<p>Registering event listeners in this way also allows you to
582: unregister specific listeners when you are done with them, as is
583: done with the <code title="">configure()</code> method in this
584: example.<p>Finally, the worker:<pre>
1.36 ihickson 585: var nextName = 0;
586: function getNextName() {
587: // this could use more friendly names
588: // but for now just return a number
589: return nextName++;
590: }
591:
592: var map = [
593: [0, 0, 0, 0, 0, 0, 0],
594: [1, 1, 0, 1, 0, 1, 1],
595: [0, 1, 0, 1, 0, 0, 0],
596: [0, 1, 0, 1, 0, 1, 1],
597: [0, 0, 0, 1, 0, 0, 0],
598: [1, 0, 0, 1, 1, 1, 1],
599: [1, 1, 0, 1, 1, 0, 1],
600: ];
601:
602: function wrapX(x) {
603: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 604: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 605: return x;
606: }
607:
608: function wrapY(y) {
609: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 610: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 611: return y;
612: }
613:
1.50 ihickson 614: function sendMapData(callback) {
1.36 ihickson 615: var data = '';
616: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
617: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
618: if (data != '')
619: data += ',';
620: data += map[y][x];
621: }
622: }
1.50 ihickson 623: callback('map ' + data);
1.36 ihickson 624: }
625:
626: var viewers = {};
627: onconnect = function (event) {
1.84 ihickson 628: event.ports[0]._name = getNextName();
629: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
630: viewers[event.ports[0]._name] = event.port._data;
631: event.ports[0].postMessage('cfg ' + name);
632: event.ports[0].onmessage = getMessage;
633: sendMapData(event.ports[0].postMessage);
1.36 ihickson 634: };
635:
636: function getMessage(event) {
1.54 ihickson 637: switch (event.data.substr(0, 4)) {
1.36 ihickson 638: case 'mov ':
1.54 ihickson 639: var direction = event.data.substr(4);
1.36 ihickson 640: var dx = 0;
641: var dy = 0;
642: switch (direction) {
643: case 'up': dy = -1; break;
644: case 'down': dy = 1; break;
645: case 'left': dx = -1; break;
646: case 'right': dx = 1; break;
647: }
648: event.target._data.x = wrapX(event.target._data.x + dx);
649: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 650: sendMapData(event.target.postMessage);
1.36 ihickson 651: break;
652: case 'set ':
1.54 ihickson 653: var value = event.data.substr(4);
1.36 ihickson 654: map[event.target._data.y][event.target._data.x] = value;
655: for (var viewer in viewers)
1.50 ihickson 656: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 657: break;
658: case 'txt ':
659: var name = event.target._name;
1.54 ihickson 660: var message = event.data.substr(4);
1.36 ihickson 661: for (var viewer in viewers)
662: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
663: break;
664: case 'msg ':
665: var party1 = event._data;
1.54 ihickson 666: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 667: if (party2) {
668: var channel = new MessageChannel();
1.84 ihickson 669: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
670: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 671: }
672: break;
673: }
1.81 ihickson 674: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
675: the <code title=handler-SharedWorkerGlobalScope-onconnect><a href=#handler-sharedworkerglobalscope-onconnect>onconnect</a></code>
676: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
677: "msg" message from one viewer naming another viewer, it sets up a
678: direct connection between the two, so that the two viewers can
679: communicate directly without the worker having to proxy all the
680: 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
681: performance is to split computationally expensive tasks amongst
682: multiple workers. In this example, a computationally expensive task
683: that is to be performed for every number from 1 to 10,000,000 is
684: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
685: <html>
686: <head>
687: <title>Worker example: One-core computation</title>
688: </head>
689: <body>
690: <p>The highest prime number discovered so far is: <output id="result"></output></p>
691: <script>
1.50 ihickson 692: var worker = new Worker('worker.js');
693: worker.onmessage = function (event) {
1.54 ihickson 694: document.getElementById('result').textContent = event.data;
1.40 ihickson 695: };
1.81 ihickson 696: </script>
697: </body>
698: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 699: var num_workers = 10;
700: var items_per_worker = 1000000;
701:
702: // start the workers
703: var result = 0;
704: var pending_workers = num_workers;
705: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 706: var worker = new Worker('core.js');
707: worker.postMessage(i * items_per_worker);
708: worker.postMessage((i+1) * items_per_worker);
709: worker.onmessage = storeResult;
1.40 ihickson 710: }
711:
712: // handle the results
713: function storeResult(event) {
1.54 ihickson 714: result += 1*event.data;
1.40 ihickson 715: pending_workers -= 1;
716: if (pending_workers <= 0)
1.50 ihickson 717: postMessage(result); // finished!
1.81 ihickson 718: }</pre><p>It consists of a loop to start the subworkers, and then a handler
719: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 720: onmessage = getStart;
1.40 ihickson 721: function getStart(event) {
1.54 ihickson 722: start = 1*event.data;
1.40 ihickson 723: onmessage = getEnd;
724: }
725:
726: var end;
727: function getEnd(event) {
1.54 ihickson 728: end = 1*event.data;
1.40 ihickson 729: onmessage = null;
1.66 ihickson 730: work();
1.40 ihickson 731: }
732:
1.66 ihickson 733: function work() {
1.40 ihickson 734: var result = 0;
735: for (var i = start; i < end; i += 1) {
736: // perform some complex calculation here
737: result += 1;
738: }
1.50 ihickson 739: postMessage(result);
740: close();
1.81 ihickson 741: }</pre><p>They receive two numbers in two events, perform the computation
742: for the range of numbers thus specified, and then report the result
743: 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
744: provides three tasks:<dl><dt>Generate a public/private key pair</dt>
745:
746: <dd>Takes a port, on which it will send two messages, first the
747: public key and then the private key.</dd>
748:
749: <dt>Given a plaintext and a public key, return the corresponding cyphertext</dt>
750:
751: <dd>Takes a port, to which any number of messages can be sent, the
752: first giving the public key, and the remainder giving the
753: plaintext, each of which is encrypted and then sent on that same
754: channel as the cyphertext. The user can close the port when it is
755: done encrypting content.</dd>
756:
757: <dt>Given a cyphertext and a private key, return the corresponding plaintext</dt>
758:
759: <dd>Takes a port, to which any number of messages can be sent, the
760: first giving the private key, and the remainder giving the
761: cyphertext, each of which is decrypted and then sent on that same
762: channel as the plaintext. The user can close the port when it is
763: done decrypting content.</dd>
1.49 ihickson 764:
1.81 ihickson 765: </dl><p>The library itself is as follows:<pre>function handleMessage(e) {
1.54 ihickson 766: if (e.data == "genkeys")
1.84 ihickson 767: genkeys(e.ports[0]);
1.54 ihickson 768: else if (e.data == "encrypt")
1.84 ihickson 769: encrypt(e.ports[0]);
1.54 ihickson 770: else if (e.data == "decrypt")
1.84 ihickson 771: decrypt(e.ports[0]);
1.49 ihickson 772: }
773:
774: function genkeys(p) {
775: var keys = _generateKeyPair();
776: p.postMessage(keys[0]);
777: p.postMessage(keys[1]);
778: }
779:
780: function encrypt(p) {
781: var key, state = 0;
782: p.onmessage = function (e) {
783: if (state == 0) {
1.54 ihickson 784: key = e.data;
1.49 ihickson 785: state = 1;
786: } else {
1.54 ihickson 787: p.postMessage(_encrypt(key, e.data));
1.49 ihickson 788: }
789: };
790: }
791:
792: function decrypt(p) {
793: var key, state = 0;
794: p.onmessage = function (e) {
795: if (state == 0) {
1.54 ihickson 796: key = e.data;
1.49 ihickson 797: state = 1;
798: } else {
1.54 ihickson 799: p.postMessage(_decrypt(key, e.data));
1.49 ihickson 800: }
801: };
802: }
803:
1.50 ihickson 804: // support being used as a shared worker as well as a dedicated worker
805: if (this.onmessage) // dedicated worker
806: onmessage = handleMessage;
807: else // shared worker
808: onconnect = function (e) { e.port.onmessage = handleMessage; }
1.49 ihickson 809:
810:
811: // the "crypto" functions:
812:
813: function _generateKeyPair() {
814: return [Math.random(), Math.random()];
815: }
816:
817: function _encrypt(k, s) {
818: return 'encrypted-' + k + ' ' + s;
819: }
820:
821: function _decrypt(k, s) {
822: return s.substr(s.indexOf(' ')+1);
1.81 ihickson 823: }</pre><p>Note that the crypto functions here are just stubs and don't do
824: real cryptography.<p>This library could be used as follows:<pre><!DOCTYPE HTML>
825: <html>
826: <head>
827: <title>Worker example: Crypto library</title>
828: <script>
1.50 ihickson 829: var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
1.49 ihickson 830: function getKeys() {
831: var state = 0;
1.50 ihickson 832: cryptoLib.startConversation("genkeys").onmessage = function (e) {
1.49 ihickson 833: if (state == 0)
1.54 ihickson 834: document.getElementById('public').value = e.data;
1.49 ihickson 835: else if (state == 1)
1.54 ihickson 836: document.getElementById('private').value = e.data;
1.49 ihickson 837: state += 1;
838: };
839: }
840: function enc() {
1.50 ihickson 841: var port = cryptoLib.startConversation("encrypt");
842: port.postMessage(document.getElementById('public').value);
843: port.postMessage(document.getElementById('input').value);
844: port.onmessage = function (e) {
1.54 ihickson 845: document.getElementById('input').value = e.data;
1.50 ihickson 846: port.close();
1.49 ihickson 847: };
848: }
849: function dec() {
1.50 ihickson 850: var port = cryptoLib.startConversation("decrypt");
851: port.postMessage(document.getElementById('private').value);
852: port.postMessage(document.getElementById('input').value);
853: port.onmessage = function (e) {
1.54 ihickson 854: document.getElementById('input').value = e.data;
1.50 ihickson 855: port.close();
1.49 ihickson 856: };
857: }
1.81 ihickson 858: </script>
859: <style>
1.49 ihickson 860: textarea { display: block; }
1.81 ihickson 861: </style>
862: </head>
863: <body onload="getKeys()">
864: <fieldset>
865: <legend>Keys</legend>
866: <p><label>Public Key: <textarea id="public"></textarea></label></p>
867: <p><label>Private Key: <textarea id="private"></textarea></label></p>
868: </fieldset>
869: <p><label>Input: <textarea id="input"></textarea></label></p>
870: <p><button onclick="enc()">Encrypt</button> <button onclick="dec()">Decrypt</button></p>
871: </body>
872: </html></pre><p>A later version of the API, though, might want to offload all the
873: crypto work onto subworkers. This could be done as follows:<pre>function handleMessage(e) {
1.54 ihickson 874: if (e.data == "genkeys")
1.84 ihickson 875: genkeys(e.ports[0]);
1.54 ihickson 876: else if (e.data == "encrypt")
1.84 ihickson 877: encrypt(e.ports[0]);
1.54 ihickson 878: else if (e.data == "decrypt")
1.84 ihickson 879: decrypt(e.ports[0]);
1.49 ihickson 880: }
881:
882: function genkeys(p) {
1.50 ihickson 883: var generator = new Worker('libcrypto-v2-generator.js');
1.84 ihickson 884: generator.postMessage('', [p]);
1.49 ihickson 885: }
886:
887: function encrypt(p) {
888: p.onmessage = function (e) {
1.54 ihickson 889: var key = e.data;
1.50 ihickson 890: var encryptor = new Worker('libcrypto-v2-encryptor.js');
1.84 ihickson 891: encryptor.postMessage(key, [p]);
1.49 ihickson 892: };
893: }
894:
895: function encrypt(p) {
896: p.onmessage = function (e) {
1.54 ihickson 897: var key = e.data;
1.50 ihickson 898: var decryptor = new Worker('libcrypto-v2-decryptor.js');
1.84 ihickson 899: decryptor.postMessage(key, [p]);
1.49 ihickson 900: };
901: }
902:
1.50 ihickson 903: // support being used as a shared worker as well as a dedicated worker
904: if (this.onmessage) // dedicated worker
905: onmessage = handleMessage;
906: else // shared worker
1.84 ihickson 907: onconnect = function (e) { e.ports[0].onmessage = handleMessage };
1.81 ihickson 908: </pre><p>The little subworkers would then be as follows.<p>For generating key pairs:<pre>onmessage = function (e) {
1.50 ihickson 909: var k = _generateKeyPair();
1.84 ihickson 910: e.ports[0].postMessage(k[0]);
911: e.ports[0].postMessage(k[1]);
1.49 ihickson 912: close();
913: }
1.50 ihickson 914:
915: function _generateKeyPair() {
916: return [Math.random(), Math.random()];
1.81 ihickson 917: }</pre><p>For encrypting:<pre>onmessage = function (e) {
1.54 ihickson 918: var key = e.data;
1.84 ihickson 919: e.ports[0].onmessage = function (e) {
1.54 ihickson 920: var s = e.data;
1.50 ihickson 921: postMessage(_encrypt(key, s));
1.49 ihickson 922: }
1.84 ihickson 923: e.ports[0].onclose = function (e) {
1.49 ihickson 924: close();
925: }
1.50 ihickson 926: }
927:
928: function _encrypt(k, s) {
929: return 'encrypted-' + k + ' ' + s;
1.81 ihickson 930: }</pre><p>For decrypting:<pre>onmessage = function (e) {
1.54 ihickson 931: var key = e.data;
1.84 ihickson 932: e.ports[0].onmessage = function (e) {
1.54 ihickson 933: var s = e.data;
1.50 ihickson 934: postMessage(_decrypt(key, s));
1.49 ihickson 935: }
1.84 ihickson 936: e.ports[0].onclose = function (e) {
1.49 ihickson 937: close();
938: }
1.50 ihickson 939: }
940:
941: function _decrypt(k, s) {
942: return s.substr(s.indexOf(' ')+1);
1.81 ihickson 943: }</pre><p>Notice how the users of the API don't have to even know that this
944: is happening — the API hasn't changed; the library can
945: delegate to subworkers without changing its API, even though it is
1.82 ihickson 946: 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 947: non-normative, as are all sections explicitly marked non-normative.
948: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
949: NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
950: "OPTIONAL" in the normative parts of this document are to be
951: interpreted as described in RFC2119. For readability, these words do
1.111 ihickson 952: 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 953: (such as "strip any leading space characters" or "return false and
954: abort these steps") are to be interpreted with the meaning of the
955: key word ("must", "should", "may", etc) used in introducing the
956: algorithm.<p>Some conformance requirements are phrased as requirements on
957: attributes, methods or objects. Such requirements are to be
958: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
959: may be implemented in any manner, so long as the end result is
960: equivalent. (In particular, the algorithms defined in this
961: specification are intended to be easy to follow, and not intended to
962: be performant.)<p>The only conformance class defined by this specification is user
963: agents.<p>User agents may impose implementation-specific limits on
964: otherwise unconstrained inputs, e.g. to prevent denial of service
965: attacks, to guard against running out of memory, or to work around
1.82 ihickson 966: 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 967: specifications.<dl><dt>HTML5</dt>
1.49 ihickson 968:
1.81 ihickson 969: <dd>
1.49 ihickson 970:
1.81 ihickson 971: <p>Many fundamental concepts from HTML5 are used by this
1.111 ihickson 972: specification. <a href=#references>[HTML5]</a></p>
1.49 ihickson 973:
1.81 ihickson 974: </dd>
1.1 ihickson 975:
1.81 ihickson 976: <dt>WebIDL</dt>
1.1 ihickson 977:
978: <dd>
979:
1.81 ihickson 980: <p>The IDL blocks in this specification use the semantics of the
1.111 ihickson 981: WebIDL specification. <a href=#references>[WebIDL]</a></p>
1.1 ihickson 982:
1.81 ihickson 983: </dd>
1.1 ihickson 984:
1.82 ihickson 985: </dl><h2 id=terminology><span class=secno>3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 986: <code title="">Foo</code> is actually an interface, is sometimes
987: used instead of the more accurate "an object implementing the
988: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
989: scripts in Web applications, and does not necessarily imply the
990: existence of an actual <code>Document</code> object or of any other
991: <code>Node</code> objects as defined in the DOM Core
1.111 ihickson 992: specifications. <a href=#references>[DOM3CORE]</a><p>A DOM attribute is said to be <em>getting</em> when its value is
1.81 ihickson 993: being retrieved (e.g. by author script), and is said to be
1.103 ihickson 994: <em>setting</em> when a new value is assigned to it.<p>The term "JavaScript" is used to refer to ECMA262, rather than
995: the official term ECMAScript, since the term JavaScript is more
1.111 ihickson 996: 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 997: workers. Dedicated workers, once created, and are linked to their
998: creator; but message ports can be used to communicate from a
999: dedicated worker to multiple other browsing contexts or
1000: workers. Shared workers, on the other hand, are named, and once
1001: created any script running in the same <span>origin</span> can
1.82 ihickson 1002: 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> {
1.81 ihickson 1003: readonly attribute <a href=#workerglobalscope>WorkerGlobalScope</a> <a href=#dom-workerglobalscope-self title=dom-WorkerGlobalScope-self>self</a>;
1004: readonly attribute <a href=#workerlocation>WorkerLocation</a> <a href=#dom-workerglobalscope-location title=dom-WorkerGlobalScope-location>location</a>;
1005: // also implements everything on <a href=#workerutils>WorkerUtils</a>
1006:
1007: void <a href=#dom-workerglobalscope-close title=dom-WorkerGlobalScope-close>close</a>();
1008: attribute <span>EventListener</span> <a href=#handler-workerglobalscope-onclose title=handler-WorkerGlobalScope-onclose>onclose</a>;
1009: attribute <span>EventListener</span> <a href=#handler-workerglobalscope-onerror title=handler-WorkerGlobalScope-onerror>onerror</a>;
1010: };</pre><p>Objects implementing the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> interface
1011: must also implement the <code>EventTarget</code> interface.<p>The <dfn id=dom-workerglobalscope-self title=dom-WorkerGlobalScope-self><code>self</code></dfn> attribute
1012: 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>
1013: attribute must return the <code><a href=#workerlocation>WorkerLocation</a></code> object created
1014: for the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object when the worker was
1015: created. It represents the <span>absolute URL</span> of the script
1016: 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
1017: a <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object, the user agent must run the
1018: following steps:<ol><li><p><span>Queue a task</span> to <span>fire a simple
1019: event</span> called <code title=event-close>close</code> at the
1020: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object.</li>
1021:
1022: <li><p>Set the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object's
1023: <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag to
1024: true.</li>
1025:
1026: <li><p>For each <code>MessagePort</code> object that is entangled
1027: with another port and that has one (but only one) port whose owner
1028: is the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object on which the method
1029: was invoked (this would include, for instance, the implicit port in
1.107 ihickson 1030: used for dedicated workers), disentangle the two ports.</li>
1.81 ihickson 1031:
1.102 ihickson 1032: </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>)
1033: that must be supported, as DOM attributes, by objects implementing
1034: 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>
1035: <tbody><tr><td><dfn id=handler-workerglobalscope-onclose title=handler-WorkerGlobalScope-onclose><code>onclose</code></dfn> <td> <code title=event-close>close</code>
1036: <tr><td><dfn id=handler-workerglobalscope-onerror title=handler-WorkerGlobalScope-onerror><code>onerror</code></dfn> <td> <code title=event-error>error</code>
1037: </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> {
1.84 ihickson 1038: void <a href=#dom-dedicatedworkerglobalscope-postmessage title=dom-DedicatedWorkerGlobalScope-postMessage>postMessage</a>(in any message, [Optional] in <span>MessagePortArray</span> ports);<!--
1.77 ihickson 1039: <span>MessagePort</span> <span title="dom-DedicatedWorkerGlobalScope-startConversation">startConversation</span>(in any message);-->
1.81 ihickson 1040: attribute <span>EventListener</span> <a href=#handler-dedicatedworkerglobalscope-onmessage title=handler-DedicatedWorkerGlobalScope-onmessage>onmessage</a>;
1041: };</pre><p><code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> objects act as if they
1042: had an implicit <code>MessagePort</code> associated with them. This
1043: port is part of a channel that is set up when the worker is created,
1044: but it is not exposed. This object must never be garbage collected
1.107 ihickson 1045: before the <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1046: 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 1047: and <dfn
1048: title="dom-DedicatedWorkerGlobalScope-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1049: method<!--s (startConversation)--> on
1050: <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1051: invoked, it<!--/they (startConversation)--> immediately invoked the
1052: method of the same name on the port, with the same arguments, and
1.102 ihickson 1053: 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>)
1054: that must be supported, as DOM attributes, by objects implementing
1055: 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>
1056: <tbody><tr><td><dfn id=handler-dedicatedworkerglobalscope-onmessage title=handler-DedicatedWorkerGlobalScope-onmessage><code>onmessage</code></dfn> <td> <code title=event-message>message</code>
1057: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1058: networking model, a dedicated worker is an extension of the
1059: <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> {
1.81 ihickson 1060: readonly attribute DOMString <a href=#dom-sharedworkerglobalscope-name title=dom-SharedWorkerGlobalScope-name>name</a>;
1.101 ihickson 1061: readonly attribute <span>ApplicationCache</span> <a href=#dom-sharedworkerglobalscope-applicationcache title=dom-SharedWorkerGlobalScope-applicationCache>applicationCache</a>;
1.81 ihickson 1062: attribute <span>EventListener</span> <a href=#handler-sharedworkerglobalscope-onconnect title=handler-SharedWorkerGlobalScope-onconnect>onconnect</a>;
1063: };</pre><p>Shared workers receive message ports through <code title=event-WorkerGlobalScope-connect>connect</code> events on
1064: their global object for each connection.<p>The <dfn id=dom-sharedworkerglobalscope-name title=dom-SharedWorkerGlobalScope-name><code>name</code></dfn>
1065: attribute must return the value it was assigned when the
1066: <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object was created by the
1067: "<a href=#run-a-worker>run a worker</a>" algorithm. Its value represents the name
1068: that can be used to obtain a reference to the worker using the
1.102 ihickson 1069: <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>)
1070: that must be supported, as DOM attributes, by objects implementing
1071: 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>
1072: <tbody><tr><td><dfn id=handler-sharedworkerglobalscope-onconnect title=handler-SharedWorkerGlobalScope-onconnect><code>onconnect</code></dfn> <td> <code title=event-connect>connect</code>
1073: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1074: networking model, a shared worker is its own <span>cache
1075: host</span>. The <a href=#run-a-worker>run a worker</a> algorithm takes care of
1076: 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>
1077: returns the <code>ApplicationCache</code> object for the
1078: worker.</p><!-- normative conf criteria is in the appcache section
1079: --><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 1080: origin</span> of scripts running in workers are the
1081: <span>origin</span> of the <span>absolute URL</span> given in that
1082: the worker's <code title=dom-WorkerGlobalScope-location><a href=#dom-workerglobalscope-location>location</a></code> attribute
1.85 ihickson 1083: 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
1084: obtain its source in Unicode, it must run the following steps:<ol><li>
1085:
1086: <p>Let <var title="">character encoding</var> be <i title="">unknown</i>.</p>
1087:
1088: </li>
1089:
1090: <li>
1091:
1092: <p>For each of the rows in the following table, starting with the
1093: first one and going down, if the resource has as many or more
1094: bytes available than the number of bytes in the first column, and
1095: the first bytes of the resource match the bytes given in the first
1096: column, then let <var title="">character encoding</var> be the
1097: encoding given in the cell in the second column of that row:</p>
1098:
1099: <!-- this table is present in several forms in this file; keep them in sync -->
1100: <table><thead><tr><th>Bytes in Hexadecimal
1101: <th>Encoding
1102: <tbody><!-- nobody uses this
1103: <tr>
1104: <td>00 00 FE FF
1105: <td>UTF-32BE
1106: <tr>
1107: <td>FF FE 00 00
1108: <td>UTF-32LE
1109: --><tr><td>FE FF
1110: <td>UTF-16BE
1111: <tr><td>FF FE
1112: <td>UTF-16LE
1113: <tr><td>EF BB BF
1114: <td>UTF-8
1115: <!-- nobody uses this
1116: <tr>
1117: <td>DD 73 66 73
1118: <td>UTF-EBCDIC
1119: -->
1120: </table><p class=note>This step looks for Unicode Byte Order Marks
1121: (BOMs).</p>
1122:
1123: </li>
1124:
1125: <li>
1126:
1127: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, apply the <span>algorithm for extracting an
1128: encoding from a Content-Type</span> to the resource's <span title=Content-Type>Content Type metadata</span>; if this returns
1129: an encoding, and the user agent supports that encoding, then let
1130: <var title="">character encoding</var> be that encoding.</p>
1131:
1132: </li>
1133:
1134: <li>
1135:
1136: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, then let <var title="">character
1137: encoding</var> be UTF-8.</p>
1138:
1139: </li>
1140:
1141: <li>
1142:
1143: <p>Convert the resource to Unicode using the character encoding
1144: given by <var title="">character encoding</var>.</p>
1145:
1146: <p>Return the text that is so obtained.</p>
1147:
1148: </li>
1149:
1150: </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 1151: <span>event loop</span>. This <span>event loop</span> has no
1152: associated <span>browsing context</span>, and its <span title="task
1153: queue">task queues</span> only have events, callbacks, and
1154: networking activity as <span title=concept-task>tasks</span>. The
1155: processing model of these <span title="event loop">event
1156: loops</span> is defined below in the <a href=#run-a-worker>run a worker</a>
1157: 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
1158: initially be false, but which can get set to true by the algorithms
1159: 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
1160: true, the <span>event loop</span>'s <span title="task queue">task
1161: queues</span> must discard any further <span title=concept-task>tasks</span> that would be added to them (tasks
1162: already on the queue are unaffected unless otherwise
1163: specified). Effectively, once the <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is true,
1164: timers stop firing, notifications for all pending asynchronous
1.85 ihickson 1165: 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
1.81 ihickson 1166: <code>MessagePort</code> objects.<p>Each <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> <var title="">worker global
1167: scope</var> has a list of <dfn id=the-worker-s-ports-0>the worker's ports</dfn>, which
1168: consists of all the <code>MessagePort</code> objects that are
1169: entangled with another port and that have one (but only one) port
1170: owned by <var title="">worker global scope</var>. This list includes
1171: <!--all the <code>MessagePort</code> objects that are in events
1.68 ihickson 1172: pending in the <span>event loop</span>, as well as (commented out
1173: because in practice it makes no difference either way as far as I
1174: can tell, and it would be hard to strictly implement since these
1.81 ihickson 1175: ports might not yet be across the thread boundary)--> the implicit
1176: <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
1177: either:<ul><li>at some point past or present a <code>MessagePort</code> owned
1178: by the worker was entangled with a <code>MessagePort</code> <var title="">p</var> whose owner is a <code>Window</code> object whose
1179: <span>active document</span> is the <code>Document</code> that was
1180: that <span>browsing context</span>'s <span>active document</span>
1181: when <var title="">p</var> was created, and that
1182: <code>Document</code> is <span>fully active</span>, or</li>
1183:
1184: <li>at some point past or present a <code>MessagePort</code> owned
1185: by the worker was entangled with a <code>MessagePort</code> owned
1186: by another worker that is currently a <a href=#permissible-worker>permissible
1187: worker</a>.</li>
1188:
1189: </ul><hr><p>A worker is said to be a <dfn id=protected-worker>protected worker</dfn> if
1190: either:<ul><li>it has outstanding timers, database transactions, or network
1191: connections, and is a <a href=#permissible-worker>permissible worker</a>, or</li>
1192:
1193: <li>there is a <a href=#protected-worker>protected worker</a> that at some point
1194: past or present owned a <code>MessagePort</code> that was entangled
1195: with a <code>MessagePort</code> owned by this worker.</li>
1196:
1197: </ul><hr><p>A worker is said to be an <dfn id=active-needed-worker>active needed worker</dfn> if either:
1198:
1199: <ul><li>the worker is a <a href=#protected-worker>protected worker</a>, or</li>
1200:
1201: <li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> is
1202: entangled with a <code>MessagePort</code> <var title="">p</var>
1203: whose owner is a <code>Window</code> object whose <span>active
1204: document</span> is the <code>Document</code> that was that
1205: <span>browsing context</span>'s <span>active document</span> when
1206: that <code>MessagePort</code> <var title="">p</var> was created,
1207: and that <code>Document</code> is <span>fully active</span>,
1208: or</li>
1209:
1210: <li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> has an
1211: entangled <code>MessagePort</code> owned by a
1212: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object that is itself an
1213: <a href=#active-needed-worker>active needed worker</a>.</li>
1214:
1215: </ul><hr><p>A worker is said to be a <dfn id=suspendable-worker>suspendable worker</dfn> if it is
1216: 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
1217: entangled <code>MessagePort</code> owned by a <code>Window</code>
1218: object, or</li>
1219:
1220: <li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> has an
1221: entangled <code>MessagePort</code> owned by a
1222: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object that is itself a <span>needed
1223: worker</span>.</li>
1224:
1.85 ihickson 1225: </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 1226: <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
1227: steps:<ol><li>
1228:
1229: <p>Create a completely separate and parallel execution environment
1230: (i.e. a separate thread or process or equivalent construct), and
1.106 ihickson 1231: run the rest of these steps asynchronously in that context.</p>
1.81 ihickson 1232:
1233: </li>
1.4 ihickson 1234:
1.101 ihickson 1235: <li><p>If <var title="">worker global scope</var> is actually a
1236: <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1237: shared worker), and there are any <span title="relevant application
1238: cache">relevant application caches</span> that are identified by a
1239: manifest URL with the <span>same origin</span> as <var title="">url</var> and that have <var title="">url</var> as one of
1240: their entries, <em>not</em> excluding entries marked as <span title=concept-appcache-foreign>foreign</span>, then associate the
1241: <var title="">worker global scope</var> with the <span title=concept-appcache-selection>most appropriate application
1242: cache</span> of those that match.</li>
1243:
1.4 ihickson 1244: <li>
1.52 ihickson 1245:
1.81 ihickson 1246: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>.</p>
1247:
1248: <p>If the attempt fails, then for each <code><a href=#worker>Worker</a></code> or
1249: <code><a href=#sharedworker>SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1250: <span>fire a simple event</span> called <code title=event-error>error</code> at that object. Abort these
1251: steps.</p>
1.7 ihickson 1252:
1.85 ihickson 1253: <p>If the attempt succeeds, then <a href=#decode-a-script-resource title="decode a script
1254: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1.81 ihickson 1255:
1.68 ihickson 1256: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1257:
1.81 ihickson 1258: <p class=note>As with <code>script</code> elements, the MIME
1259: type of the script is ignored. Unlike with <code>script</code>
1260: elements, there is no way to override the type. It's always
1261: assumed to be JavaScript.</p> <!-- XXX people will complain about
1.7 ihickson 1262: this. I guess we might want to examine the MIME type... -->
1.81 ihickson 1263:
1264: </li>
1.7 ihickson 1265:
1266: <li>
1.68 ihickson 1267:
1.81 ihickson 1268: <p>A new <span title=concept-script>script</span> is now
1269: created, as follows.</p>
1270:
1271: <p>Create a new <span>script execution environment</span>
1272: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1273:
1.68 ihickson 1274: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1275: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1276: entry-points</span>; set the <i>initial code entry-point</i> to
1277: the entry-point for any executable code to be immediately run.</p>
1278:
1279: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1280:
1281: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1282:
1.83 ihickson 1283: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1284: UTF-8. (This is just used for encoding non-ASCII characters in the
1285: query component of URLs.)</p>
1.68 ihickson 1286:
1287: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1288:
1.81 ihickson 1289: <p>Create a new <span>script group</span> and add the <span title=concept-script>script</span> to it.</p>
1290:
1291: </li>
1.4 ihickson 1292:
1293: <li>
1.81 ihickson 1294:
1295: <p><strong>Closing orphan workers</strong>: Start monitoring the
1296: worker such that as soon as it stops being either an <a href=#active-needed-worker>active
1297: 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
1298: to true and <span title="queue a task">a task is queued</span> to
1299: <span>fire a simple event</span> called <code title=event-close>close</code> at <var title="">worker global
1300: scope</var>.</p>
1301:
1302: </li>
1.9 ihickson 1303:
1304: <li>
1.7 ihickson 1305:
1.81 ihickson 1306: <p><strong>Suspending workers</strong>: Start monitoring the
1307: worker, such that whenever <var title="">worker global
1308: scope</var>'s <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is false
1309: and the worker is a <a href=#suspendable-worker>suspendable worker</a>, the user
1310: agent suspends execution of script in that worker until such time
1311: as either the <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag switches
1312: to true or the worker stops being a <a href=#suspendable-worker>suspendable
1313: worker</a>.</p>
1.4 ihickson 1314:
1.81 ihickson 1315: </li>
1.68 ihickson 1316:
1317: <li>
1.4 ihickson 1318:
1.81 ihickson 1319: <p><span title="jump to a code entry-point">Jump</span> to the
1320: <span title=concept-script>script</span>'s <i>initial code
1321: entry-point</i>, and let that run until it either returns, fails
1322: to catch an exception, or gets prematurely aborted by the
1323: "<a href=#kill-a-worker>kill a worker</a>" or "<a href=#terminate-a-worker>terminate a worker</a>"
1324: algorithms defined below.</p>
1325:
1326: <p class=note>If the script gets aborted by the "<a href=#kill-a-worker>kill a
1327: worker</a>" algorithm, then that same algorithm will cause
1328: there to only be a single <span title=concept-task>task</span>
1329: in the <span>event loop</span> at the next step, namely the task
1330: for the <code title=message-close>close</code> event. The
1331: "<a href=#terminate-a-worker>terminate a worker</a>" algorithm removes all the
1332: events.</p>
1.4 ihickson 1333:
1.81 ihickson 1334: </li>
1.4 ihickson 1335:
1.95 ihickson 1336: <li><p>If <var title="">worker global scope</var> is actually a
1337: <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1338: a dedicated worker), then open the <span>port message queue</span>
1339: of the worker's implicit port.</li>
1340:
1.4 ihickson 1341: <li>
1.68 ihickson 1342:
1.81 ihickson 1343: <p><i title="">Event loop</i>: Wait until either there is a <span title=concept-task>task</span> in one of the <span>event
1344: 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
1345: to true.</p>
1.43 ihickson 1346:
1.81 ihickson 1347: </li>
1.4 ihickson 1348:
1349: <li>
1350:
1.81 ihickson 1351: <p>Run the oldest task on one of the <span>event loop</span>'s
1352: <span title="task queue">task queues</span>, if any. The user
1353: agent may pick any <span>task queue</span>.</p>
1354:
1355: <p class=note>The handling of events or the execution of
1356: callbacks might get prematurely aborted by the "<a href=#kill-a-worker>kill a
1357: worker</a>" or "<a href=#terminate-a-worker>terminate a worker</a>" algorithms
1358: defined below.</p>
1.8 ihickson 1359:
1.81 ihickson 1360: </li>
1.4 ihickson 1361:
1362: <li>
1363:
1.81 ihickson 1364: <p>Remove the task run in the previous step, if any, from its
1365: <span>task queue</span>.</p>
1.4 ihickson 1366:
1.81 ihickson 1367: </li>
1.4 ihickson 1368:
1369: <li>
1.8 ihickson 1370:
1.81 ihickson 1371: <p>If there are any more events in the <span>event loop</span>'s
1372: <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
1373: to false, then jump back to the step above labeled <i>event
1374: loop</i>.</p>
1.8 ihickson 1375:
1.81 ihickson 1376: </li>
1.8 ihickson 1377:
1378: <li>
1.71 ihickson 1379:
1.81 ihickson 1380: <p>Freeze the <span>script group</span>.</p>
1.50 ihickson 1381:
1.81 ihickson 1382: <p class=note>This kills timers, database transactions, etc.</p>
1.50 ihickson 1383:
1.81 ihickson 1384: </li>
1.50 ihickson 1385:
1.81 ihickson 1386: <li>
1.50 ihickson 1387:
1.81 ihickson 1388: <p>For each <code><a href=#worker>Worker</a></code> or <code><a href=#sharedworker>SharedWorker</a></code>
1389: object associated with <var title="">worker global scope</var>,
1390: <span>queue a task</span> to <span>fire a simple event</span>
1391: called <code title=event-close>close</code> at that object.</p>
1.5 ihickson 1392:
1.81 ihickson 1393: </li>
1.50 ihickson 1394:
1.81 ihickson 1395: </ol><hr><p>When a user agent is to <dfn id=kill-a-worker>kill a worker</dfn> it must
1396: run the following steps in parallel with the worker's main loop (the
1397: "<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
1398: <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is
1399: false, <span>queue a task</span> to <span>fire a simple
1400: event</span> called <code title=event-close>close</code> at the
1401: worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object.</li>
1402:
1403: <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
1404: true.</li>
1405:
1406: <li><p>Wait a user-agent-defined amount of time. If the "<a href=#run-a-worker>run
1407: a worker</a>" processing model defined above immediately starts
1408: running event listeners registered for the <code title=event-close>close</code> event, this time should not be
1409: zero — the idea is that the <code title=event-close>close</code> event can be used to clean up
1410: when shutting down unexpectedly.</li>
1411:
1412: <li><p>If there are any <span title=concept-task>tasks</span>
1413: queued in the <span>event loop</span>'s <span title="task
1414: queue">task queues</span> other than the <code title=event-close>close</code> event that this algorithm just
1415: added, discard them without processing them.</li>
1416:
1417: <li><p>If the <code title=event-close>close</code> event that
1418: this algorithm just queued hasn't yet been dispatched, then abort
1419: the script currently running in the worker.</li>
1420:
1421: <li><p>Wait a user-agent-defined amount of time.</li>
1422:
1423: <li><p>Abort the script currently running in the worker (if any
1424: script is running, then it will be a handler for the <code title=event-close>close</code> event).</li>
1425:
1426: </ol><p>User agents may invoke the "<a href=#kill-a-worker>kill a worker</a>"
1427: processing model on a worker at any time, e.g. in response to user
1428: requests, in response to CPU quota management, or when a worker
1429: stops being an <a href=#active-needed-worker>active needed worker</a> if the worker
1430: continues executing even after its <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag was
1431: set to true.<hr><p>When a user agent is to <dfn id=terminate-a-worker>terminate a worker</dfn> it must run
1432: the following steps in parallel with the worker's main loop (the
1433: "<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
1434: <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag to
1435: true.</li>
1436:
1437: <li><p>If there are any <span title=concept-task>tasks</span>
1438: queued in the <span>event loop</span>'s <span title="task
1439: queue">task queues</span>, discard them without processing
1440: them.</li>
1441:
1442: <li><p>Abort the script currently running in the worker.</li>
1443:
1444: <li><p>If the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object is
1445: actually a <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> object (i.e. the
1446: worker is a dedicated worker), then empty the <span>port message
1447: queue</span> of the port that the worker's implicit port is
1448: entangled with.</li>
1449:
1.99 ihickson 1450: </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 1451: scripts, if the error did not occur while handling a previous script
1452: error, the user agent must <span>queue a task</span> to <a href=#fire-an-error-event>fire
1.108 ihickson 1453: an error event</a> at the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code>
1.81 ihickson 1454: object.<p>For shared workers, if the error is still <i title="">not
1455: handled</i> afterwards, or if the error occured while handling a
1456: previous script error, the error should be reported to the user.<p>For dedicated workers, if the error is still <i title="">not
1457: handled</i> afterwards, or if the error occured while handling a
1458: previous script error, the user agent must further <span>queue a
1459: task</span> to <a href=#fire-an-error-event>fire an error event</a> at the
1460: <code><a href=#worker>Worker</a></code> object associated with the worker.<p>When the user agent is to <dfn id=fire-an-error-event>fire an error event</dfn> at a
1461: <code><a href=#worker>Worker</a></code> object, it must dispatch an event that uses the
1462: <code><a href=#errorevent>ErrorEvent</a></code> interface, with the name <code title=event-error>error</code>, that doesn't bubble and is
1463: 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
1464: appropriately. The default action of this event depends on whether
1465: the <code><a href=#worker>Worker</a></code> object is itself in a worker. If it is, and
1466: that worker is also a dedicated worker, then the user agent must
1467: again <span>queue a task</span> to <a href=#fire-an-error-event>fire an error event</a>
1468: at the <code><a href=#worker>Worker</a></code> object associated with <em>that</em>
1469: worker. Otherwise, then the error should be reported to the
1470: user.<hr><pre class=idl>interface <dfn id=errorevent>ErrorEvent</dfn> : Event {
1471: readonly attribute DOMObject <a href=#dom-errorevent-message title=dom-ErrorEvent-message>message</a>;
1472: readonly attribute DOMObject <a href=#dom-errorevent-filename title=dom-ErrorEvent-filename>filename</a>;
1473: readonly attribute unsigned long <a href=#dom-errorevent-lineno title=dom-ErrorEvent-lineno>lineno</a>;
1474: 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);
1475: 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);
1476: };</pre><p>The <dfn id=dom-errorevent-initerrorevent title=dom-ErrorEvent-initErrorEvent><code>initErrorEvent()</code></dfn>
1477: and <dfn id=dom-errorevent-initerroreventns title=dom-ErrorEvent-initErrorEventNS><code>initErrorEventNS()</code></dfn>
1478: methods must initialize the event in a manner analogous to the
1.111 ihickson 1479: 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>
1.81 ihickson 1480: attribute represents the error message.<p>The <dfn id=dom-errorevent-filename title=dom-ErrorEvent-filename><code>filename</code></dfn>
1481: attribute represents the <span>absolute URL</span> of the script in
1482: which the error originally occured.<p>The <dfn id=dom-errorevent-lineno title=dom-ErrorEvent-lineno><code>lineno</code></dfn>
1483: attribute represents the line number where the error occured in the
1.99 ihickson 1484: 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> {
1.81 ihickson 1485: attribute <span>EventListener</span> <a href=#handler-abstractworker-onerror title=handler-AbstractWorker-onerror>onerror</a>;
1486: attribute <span>EventListener</span> <a href=#handler-abstractworker-onclose title=handler-AbstractWorker-onclose>onclose</a>;
1487: };</pre><p>Objects implementing the <code><a href=#abstractworker>AbstractWorker</a></code> interface
1.102 ihickson 1488: 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>)
1489: that must be supported, as DOM attributes, by objects implementing
1490: 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>
1491: <tbody><tr><td><dfn id=handler-abstractworker-onerror title=handler-AbstractWorker-onerror><code>onerror</code></dfn> <td> <code title=event-error>error</code>
1492: <tr><td><dfn id=handler-abstractworker-onclose title=handler-AbstractWorker-onclose><code>onclose</code></dfn> <td> <code title=event-close>close</code>
1493: </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)]
1.81 ihickson 1494: interface <dfn id=worker>Worker</dfn> : <a href=#abstractworker>AbstractWorker</a> {
1495: void <a href=#dom-worker-terminate title=dom-Worker-terminate>terminate</a>();
1.50 ihickson 1496:
1.84 ihickson 1497: void <a href=#dom-worker-postmessage title=dom-Worker-postMessage>postMessage</a>(in any message, [Optional] in <span>MessagePortArray</span> ports);<!--
1.81 ihickson 1498: <span>MessagePort</span> <span title="dom-Worker-startConversation">startConversation</span>(in any message);-->
1499: attribute <span>EventListener</span> <a href=#handler-worker-onmessage title=handler-Worker-onmessage>onmessage</a>;
1500: };</pre><p>The <dfn id=dom-worker-terminate title=dom-Worker-terminate><code>terminate()</code></dfn> method,
1501: when invoked, must cause the "<a href=#terminate-a-worker>terminate a worker</a>"
1502: algorithm to be run on the worker with with the object is
1503: associated.<p><code><a href=#worker>Worker</a></code> objects act as if they had an implicit
1504: <code>MessagePort</code> associated with them. This port is part of
1505: a channel that is set up when the worker is created, but it is not
1506: exposed. This object must never be garbage collected before the
1.107 ihickson 1507: <code><a href=#worker>Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1508: 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 1509: and <dfn
1510: title="dom-Worker-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1511: method<!--s (startConversation)--> on <code><a href=#worker>Worker</a></code> objects
1512: must act as if, when invoked, it<!--/they (startConversation)-->
1513: immediately invoked the method of the same name on the port, with
1.102 ihickson 1514: 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>)
1515: that must be supported, as DOM attributes, by objects implementing
1516: 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>
1517: <tbody><tr><td><dfn id=handler-worker-onmessage title=handler-Worker-onmessage><code>onmessage</code></dfn> <td> <code title=event-message>message</code>
1518: </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 1519: 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 1520:
1.81 ihickson 1521: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1522: exception.</li>
1.9 ihickson 1523:
1.81 ihickson 1524: <li><p>If the <span>origin</span> of the resulting <span>absolute
1525: URL</span> is not the <span title="same origin">same</span> as the
1526: origin of the script that invoked the constructor, then throw a
1527: <span>security exception</span>.</li>
1.9 ihickson 1528:
1.81 ihickson 1529: <li><p><span>Create a new <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code>
1530: object</span>. Let <var title="">worker global scope</var> be this
1531: new object.</li>
1.9 ihickson 1532:
1.81 ihickson 1533: <li><p>Create a new <code><a href=#worker>Worker</a></code> object, associated with
1534: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1535:
1.81 ihickson 1536: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1537: by the <span>script execution context</span> of the script that
1538: invoked the method. Let this be the <var title="">outside
1539: port</var>.</li>
1.9 ihickson 1540:
1.81 ihickson 1541: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1542:
1.81 ihickson 1543: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1544: by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1545:
1.81 ihickson 1546: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1547:
1.81 ihickson 1548: <li><p><span>Entangle</span> <var title="">outside port</var> and
1549: <var title="">inside port</var>.</li>
1.50 ihickson 1550:
1.81 ihickson 1551: <li><p>Return <var title="">worker</var>, and run the following
1552: steps asynchronously.</li>
1.50 ihickson 1553:
1.81 ihickson 1554: <li><p>Open <var title="">inside port</var>'s <span>port message
1555: queue</span>.</li>
1.50 ihickson 1556:
1.81 ihickson 1557: <li><p>Open <var title="">outside port</var>'s <span>port message
1558: queue</span>.</li>
1.50 ihickson 1559:
1560: <li>
1.51 ihickson 1561:
1.81 ihickson 1562: <p><a href=#run-a-worker>Run a worker</a> for the resulting <span>absolute
1563: URL</span>, with the <span>script browsing context</span> of the
1564: script that invoked the method as the <var title="">owner browsing
1565: context</var>, and with <var title="">worker global scope</var> as
1566: the global scope.</p>
1.9 ihickson 1567:
1.81 ihickson 1568: </li>
1.4 ihickson 1569:
1.99 ihickson 1570: </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)]
1.81 ihickson 1571: interface <dfn id=sharedworker>SharedWorker</dfn> : <a href=#abstractworker>AbstractWorker</a> {
1572: readonly attribute <span>MessagePort</span> <a href=#dom-sharedworker-port title=dom-SharedWorker-port>port</a>;
1573: };</pre><p>The <dfn id=dom-sharedworker-port title=dom-SharedWorker-port><code>port</code></dfn>
1574: attribute must return the value it was assigned by the object's
1575: constructor. It represents the <code>MessagePort</code> for
1576: 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>
1577: constructor is invoked, the user agent must run the following
1578: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1579:
1580: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1581: exception.</li>
1582:
1583: <li><p>If the <span>origin</span> of the resulting <span>absolute
1584: URL</span> is not the <span title="same origin">same</span> as the
1585: origin of the script that invoked the constructor, then throw a
1586: <span>security exception</span>.</li>
1.9 ihickson 1587:
1588: <li>
1589:
1.50 ihickson 1590: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1591:
1.81 ihickson 1592: <ol><li><p>Create a new <code><a href=#sharedworker>SharedWorker</a></code> object, which will
1593: shortly be associated with a <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code>
1594: object. Let this <code><a href=#sharedworker>SharedWorker</a></code> object be <var title="">worker</var>.</li>
1595:
1596: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1597: by the <span>script execution context</span> of the script that
1598: invoked the method. Let this be the <var title="">outside
1599: port</var>.</li>
1600:
1601: <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>
1602:
1.9 ihickson 1603: <li>
1604:
1.81 ihickson 1605: <p>If there exists a <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object
1606: whose <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a>
1607: flag is false, whose <code title=dom-WorkerGlobalScope-name>name</code> attribute is
1608: exactly equal to the <var title="">name</var> argument, and
1609: whose <code title=dom-WorkerGlobalScope-location><a href=#dom-workerglobalscope-location>location</a></code> attribute
1610: represents an <span>absolute URL</span> that has the <span>same
1611: origin</span> as the resulting <span>absolute URL</span>, then
1612: run these substeps:</p>
1613:
1614: <ol><li><p>Let <var title="">worker global scope</var> be that
1615: <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object.</li>
1616:
1617: <li><p>If <var title="">worker global scope</var>'s <code title=dom-WorkerGlobalScope-location><a href=#dom-workerglobalscope-location>location</a></code>
1618: attribute represents an <span>absolute URL</span> that is not
1619: exactly equal to the resulting <span>absolute URL</span>, then
1620: throw a <code>URL_MISMATCH_ERR</code> exception and abort all
1.82 ihickson 1621: these steps. <span class=XXX>code 21</span></li>
1.81 ihickson 1622:
1623: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1624:
1625: <li><p><span>Create a <code>MessagePort</code> object</span>
1626: owned by <var title="">worker global scope</var>. Let this
1627: be the <var title="">inside port</var>.</li>
1628:
1629: <li><p><span>Entangle</span> <var title="">outside port</var>
1630: and <var title="">inside port</var>.</li>
1631:
1632: <li><p>Return <var title="">worker</var> and perform the next
1633: step asynchronously.</li>
1.9 ihickson 1634:
1.81 ihickson 1635: <li><p>Create an event that uses the <code>MessageEvent</code>
1636: interface, with the name <code title=event-connect>connect</code>, which does not bubble, is
1637: cancelable, has no default action, has a <code title=dom-MessageEvent-data>data</code> attribute whose value
1.84 ihickson 1638: is the empty string and has a <code title=dom-MessageEvent-ports>ports</code>
1639: attribute whose value is an array containing only the newly
1640: created port, and <span>queue a task</span> to dispatch the
1641: event at <var title="">worker global scope</var>.</li>
1.43 ihickson 1642:
1.81 ihickson 1643: <li><p>Abort all these steps.</li>
1.9 ihickson 1644:
1.81 ihickson 1645: </ol></li>
1.9 ihickson 1646:
1.81 ihickson 1647: <li><p><span>Create a new <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code>
1648: object</span>. Let <var title="">worker global scope</var> be
1649: this new object.</li>
1.9 ihickson 1650:
1.81 ihickson 1651: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1652:
1.81 ihickson 1653: <li><p>Set the <code title=dom-SharedWorkerGlobalScope-name><a href=#dom-sharedworkerglobalscope-name>name</a></code> attribute of
1654: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1655:
1.81 ihickson 1656: <li><p><span>Create a <code>MessagePort</code> object</span>
1657: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1658:
1.81 ihickson 1659: <li><p><span>Entangle</span> <var title="">outside port</var> and
1660: <var title="">inside port</var>.</li>
1.9 ihickson 1661:
1.81 ihickson 1662: </ol></li>
1.28 ihickson 1663:
1.81 ihickson 1664: <li><p>Return <var title="">worker</var> and perform the next step
1665: asynchronously.</li>
1.18 ihickson 1666:
1.81 ihickson 1667: <li><p>Create an event that uses the <code>MessageEvent</code>
1668: interface, with the name <code title=event-connect>connect</code>, which does not bubble, is
1669: cancelable, has no default action, has a <code title=dom-MessageEvent-data>data</code> attribute whose value is
1.84 ihickson 1670: the empty string and has a <code title=dom-MessageEvent-ports>ports</code> attribute
1671: whose value is an array containing only the newly created port, and
1672: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.26 ihickson 1673:
1674: <li>
1.46 ihickson 1675:
1.81 ihickson 1676: <p><a href=#run-a-worker>Run a worker</a> for the resulting <span>absolute
1677: URL</span>, with the <span>script browsing context</span> of the
1678: script that invoked the method as the <var title="">owner browsing
1679: context</var>, and with <var title="">worker global scope</var> as
1680: the global scope.</p>
1.26 ihickson 1681:
1.60 ihickson 1682: </li>
1.81 ihickson 1683:
1.82 ihickson 1684: </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> {
1.81 ihickson 1685: void <a href=#dom-workerglobalscope-importscripts title=dom-WorkerGlobalScope-importScripts>importScripts</a>([Variadic] in DOMString urls);
1.93 ihickson 1686: readonly attribute <a href=#worker-navigator title=worker-Navigator>Navigator</a> <a href=#dom-worker-navigator title=dom-worker-navigator>navigator</a>;
1.104 ihickson 1687: <span>Database</span> <span title=dom-opendatabase>openDatabase</span>(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize);
1688: <span>DatabaseSync</span> <span title=dom-opendatabase-sync>openDatabaseSync</span>(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize);
1.81 ihickson 1689: };</pre><p>Objects that implement the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code>
1690: interface must also implement the <code><a href=#workerutils>WorkerUtils</a></code>
1691: interface.<p>Objects that implement the <code><a href=#workerutils>WorkerUtils</a></code> interface
1692: must also implement the <code>WindowTimers</code> interface. (This
1693: interface provides the <code title="">setTimeout()</code> method and
1.104 ihickson 1694: 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 1695: objects, etc) are not available to workers in this version of this
1.82 ihickson 1696: 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
1.81 ihickson 1697: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object, the user agent must run the
1698: following steps:<ol><li><p>If there are no arguments, return without doing
1699: anything. Abort these steps.</li>
1700:
1701: <li><p><span title="resolve a url">Resolve</span> each
1702: argument.</li>
1703:
1704: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1705: exception.</li>
1706:
1707: <!--
1.67 ihickson 1708: <li><p>If any of the resulting <span title="absolute URL">absolute
1709: URLs</span> have an <span>origin</span> that is not the <span
1710: title="same origin">same</span> as the origin of the script that
1711: invoked the method, then throw a <span>security
1712: exception</span>.</p></li>
1713: -->
1.26 ihickson 1714:
1715: <li>
1.81 ihickson 1716:
1.45 ihickson 1717: <p>Attempt to <span>fetch</span> each resource identified by the
1.81 ihickson 1718: resulting <span title="absolute URLs">absolute URL</span>.</p>
1719:
1720: </li>
1.26 ihickson 1721:
1722: <li>
1723:
1.81 ihickson 1724: <p>For each argument in turn, in the order given, starting with
1725: the first one, run these substeps:</p>
1.26 ihickson 1726:
1.81 ihickson 1727: <ol><li>
1.26 ihickson 1728:
1.81 ihickson 1729: <p>Wait for the fetching attempt for the corresponding resource
1730: to complete.</p>
1.60 ihickson 1731:
1.81 ihickson 1732: <p>If the fetching attempt failed, throw a
1733: <code>NETWORK_ERR</code> exception and abort all these
1734: steps.</p>
1.45 ihickson 1735:
1.85 ihickson 1736: <p>If the attempt succeeds, then <a href=#decode-a-script-resource title="decode a script
1737: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1738:
1739: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1740:
1.81 ihickson 1741: <p class=note>As with the worker's script, the script here is
1742: always assumed to be JavaScript, regardless of the MIME
1743: type.</p> <!-- XXX -->
1.61 ihickson 1744:
1.81 ihickson 1745: </li>
1.26 ihickson 1746:
1.81 ihickson 1747: <li>
1.26 ihickson 1748:
1.81 ihickson 1749: <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
1750: same global object, browsing context, character encoding, base
1751: URL, and script group as the <span title=concept-script>script</span> that was created by the
1752: worker's <a href=#run-a-worker>run a worker</a> algorithm.</p>
1753:
1754: <p>Let the newly created <span title=concept-script>script</span> run until it either
1755: returns, fails to parse, fails to catch an exception, or gets
1756: prematurely aborted by the "<a href=#kill-a-worker>kill a worker</a>" or
1757: "<a href=#terminate-a-worker>terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1758:
1.81 ihickson 1759: <p>If it failed to parse, then throw a
1760: <code>SyntaxError</code><!-- XXX ref? --> exception and abort
1761: all these steps.</p>
1.63 ihickson 1762:
1.81 ihickson 1763: <p>If an exception was raised or if the script was prematurely
1764: aborted, then abort all these steps, letting the exception or
1765: aborting continue to be processed by the script that called the
1766: <code title=dom-WorkerGlobalScope-importScripts><a href=#dom-workerglobalscope-importscripts>importScripts()</a></code>
1767: method.</p>
1768:
1769: <p>If the "<a href=#kill-a-worker>kill a worker</a>" or "<a href=#terminate-a-worker>terminate a
1770: worker</a>" algorithms abort the script then abort all these
1771: steps.</p>
1772:
1773: </li>
1774:
1775: </ol></li>
1776:
1.93 ihickson 1777: </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
1778: of the <code><a href=#workerutils>WorkerUtils</a></code> interface must return an instance of
1779: the <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code> interface, which
1780: represents the identity and state of the user agent (the
1781: client):<pre class=idl>interface <dfn id=worker-navigator title=worker-Navigator>Navigator</dfn> {
1.81 ihickson 1782: // objects implementing this interface also implement the interfaces listed below
1.93 ihickson 1783: };</pre><p>Objects implementing the <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code> interface must also
1784: implement the <span>NavigatorID</span> and
1.81 ihickson 1785: <span>NavigatorOnLine</span> interfaces specified in the HTML5
1.111 ihickson 1786: specification. <a href=#references>[HTML5]</a><p class=note>The <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code>
1.93 ihickson 1787: interface defined in this specification is different than the one
1.104 ihickson 1788: 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
1789: <code title=dom-opendatabase-sync>openDatabaseSync()</code>
1.111 ihickson 1790: 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 1791: the global scope of scripts whose <span>script execution
1792: context</span> is a <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object except for
1793: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1794: constructors defined by the XMLHttpRequest specifications, except
1795: that the <span>document response entity body</span> must always be
1.111 ihickson 1796: null. <a href=#references>[XHR]</a></li>
1.81 ihickson 1797:
1798: <li><p>The <code>WebSocket</code> interface object and
1.111 ihickson 1799: constructor. <a href=#references>[WEBSOCKET]</a></li>
1.81 ihickson 1800:
1801: <li><p>The <code>MessageChannel</code> interface object and
1.111 ihickson 1802: constructor. <a href=#references>[HTML5]</a></li>
1.81 ihickson 1803:
1804: <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>
1805:
1.82 ihickson 1806: </ul><h3 id=worker-locations><span class=secno>5.5 </span>Worker locations</h3><pre class=idl>interface <dfn id=workerlocation>WorkerLocation</dfn> {
1.81 ihickson 1807: readonly attribute DOMString <a href=#dom-workerlocation-href title=dom-WorkerLocation-href>href</a>;
1808: readonly attribute DOMString <a href=#dom-workerlocation-protocol title=dom-WorkerLocation-protocol>protocol</a>;
1809: readonly attribute DOMString <a href=#dom-workerlocation-host title=dom-WorkerLocation-host>host</a>;
1810: readonly attribute DOMString <a href=#dom-workerlocation-hostname title=dom-WorkerLocation-hostname>hostname</a>;
1811: readonly attribute DOMString <a href=#dom-workerlocation-port title=dom-WorkerLocation-port>port</a>;
1812: readonly attribute DOMString <a href=#dom-workerlocation-pathname title=dom-WorkerLocation-pathname>pathname</a>;
1813: readonly attribute DOMString <a href=#dom-workerlocation-search title=dom-WorkerLocation-search>search</a>;
1814: readonly attribute DOMString <a href=#dom-workerlocation-hash title=dom-WorkerLocation-hash>hash</a>;
1815: };</pre><p>A <code><a href=#workerlocation>WorkerLocation</a></code> object represents an <span>absolute
1816: URL</span> set at its creation.<p>The <dfn id=dom-workerlocation-href title=dom-WorkerLocation-href><code>href</code></dfn>
1817: attribute must return the <span>absolute URL</span> that the object
1818: represents.<p>The <code><a href=#workerlocation>WorkerLocation</a></code> interface also has the complement
1819: of <span>URL decomposition attributes</span>, <dfn id=dom-workerlocation-protocol title=dom-WorkerLocation-protocol><code>protocol</code></dfn>,
1820: <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>,
1821: <dfn id=dom-workerlocation-pathname title=dom-WorkerLocation-pathname><code>pathname</code></dfn>,
1822: <dfn id=dom-workerlocation-search title=dom-WorkerLocation-search><code>search</code></dfn>,
1823: and <dfn id=dom-workerlocation-hash title=dom-WorkerLocation-hash><code>hash</code></dfn>. These must
1824: follow the rules given for URL decomposition attributes, with the
1825: <span title=concept-uda-input>input</span> being the
1826: <span>absolute URL</span> that the object represents (same as the
1827: <code title=dom-WorkerLocation-href><a href=#dom-workerlocation-href>href</a></code> attribute), and
1828: the <span title=concept-uda-setter>common setter action</span>
1.111 ihickson 1829: 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
1.81 ihickson 1830: draft.<!--XXX--><h2 class=no-num id=acknowledgements>Acknowledgements</h2><!-- ACKS --><p>Thanks to
1831:
1832: Aaron Boodman,
1833: Алексей Проскуряков (Alexey Proskuryakov),
1834: Anne van Kesteren,
1835: Ben Turner,
1836: Dmitry Titov,
1.96 ihickson 1837: Drew Wilson,
1.97 ihickson 1838: Jeremy Orlow,
1.81 ihickson 1839: Jonas Sicking,
1840: Justin James,
1841: Kevin Hakanson,
1842: Maciej Stachowiak,
1843: Michael Nordman,
1844: Mike Smith,
1845:
1846: and
1847:
1848: Philip Taylor
1849:
1850: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1851: technology and whose experience has been a huge influence on this
1852: specification.
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