Annotation of html5/workers/Overview.html, revision 1.184
1.155 ihickson 1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!-- when publishing, change bits marked ZZZ --><html lang="en-US-x-Hixie"><title>Web Workers</title><style type="text/css">
1.82 ihickson 2: pre { margin-left: 2em; white-space: pre-wrap; }
3: h2 { margin: 3em 0 1em 0; }
4: h3 { margin: 2.5em 0 1em 0; }
5: h4 { margin: 2.5em 0 0.75em 0; }
6: h5, h6 { margin: 2.5em 0 1em; }
7: h1 + h2, h1 + h2 + h2 { margin: 0.75em 0 0.75em; }
8: h2 + h3, h3 + h4, h4 + h5, h5 + h6 { margin-top: 0.5em; }
9: p { margin: 1em 0; }
10: hr:not(.top) { display: block; background: none; border: none; padding: 0; margin: 2em 0; height: auto; }
11: dl, dd { margin-top: 0; margin-bottom: 0; }
12: dt { margin-top: 0.75em; margin-bottom: 0.25em; clear: left; }
13: dt + dt { margin-top: 0; }
14: dd dt { margin-top: 0.25em; margin-bottom: 0; }
15: dd p { margin-top: 0; }
16: dd dl + p { margin-top: 1em; }
17: dd table + p { margin-top: 1em; }
18: p + * > li, dd li { margin: 1em 0; }
19: dt, dfn { font-weight: bold; font-style: normal; }
20: dt dfn { font-style: italic; }
21: pre, code { font-size: inherit; font-family: monospace; font-variant: normal; }
22: pre strong { color: black; font: inherit; font-weight: bold; background: yellow; }
23: pre em { font-weight: bolder; font-style: normal; }
1.89 ihickson 24: @media screen { code { color: orangered; } code :link, code :visited { color: inherit; } }
1.82 ihickson 25: var sub { vertical-align: bottom; font-size: smaller; position: relative; top: 0.1em; }
26: table { border-collapse: collapse; border-style: hidden hidden none hidden; }
27: table thead { border-bottom: solid; }
28: table tbody th:first-child { border-left: solid; }
1.180 ihickson 29: table tbody th { text-align: left; }
1.82 ihickson 30: table td, table th { border-left: solid; border-right: solid; border-bottom: solid thin; vertical-align: top; padding: 0.2em; }
31: blockquote { margin: 0 0 0 2em; border: 0; padding: 0; font-style: italic; }
32:
33: .bad, .bad *:not(.XXX) { color: gray; border-color: gray; background: transparent; }
34: .matrix, .matrix td { border: none; text-align: right; }
35: .matrix { margin-left: 2em; }
36: .dice-example { border-collapse: collapse; border-style: hidden solid solid hidden; border-width: thin; margin-left: 3em; }
37: .dice-example caption { width: 30em; font-size: smaller; font-style: italic; padding: 0.75em 0; text-align: left; }
38: .dice-example td, .dice-example th { border: solid thin; width: 1.35em; height: 1.05em; text-align: center; padding: 0; }
39:
40: .toc dfn, h1 dfn, h2 dfn, h3 dfn, h4 dfn, h5 dfn, h6 dfn { font: inherit; }
41: img.extra { float: right; }
42: pre.idl { border: solid thin; background: #EEEEEE; color: black; padding: 0.5em 1em; }
43: pre.idl :link, pre.idl :visited { color: inherit; background: transparent; }
44: pre.css { border: solid thin; background: #FFFFEE; color: black; padding: 0.5em 1em; }
45: pre.css:first-line { color: #AAAA50; }
46: dl.domintro { color: green; margin: 2em 0 2em 2em; padding: 0.5em 1em; border: none; background: #EEFFEE; }
47: hr + dl.domintro, div.impl + dl.domintro { margin-top: 2.5em; margin-bottom: 1.5em; }
48: dl.domintro dt, dl.domintro dt * { color: black; text-decoration: none; }
49: dl.domintro dd { margin: 0.5em 0 1em 2em; padding: 0; }
50: dl.domintro dd p { margin: 0.5em 0; }
51: dl.switch { padding-left: 2em; }
52: dl.switch > dt { text-indent: -1.5em; }
53: dl.switch > dt:before { content: '\21AA'; padding: 0 0.5em 0 0; display: inline-block; width: 1em; text-align: right; line-height: 0.5em; }
1.121 ihickson 54: dl.triple { padding: 0 0 0 1em; }
55: dl.triple dt, dl.triple dd { margin: 0; display: inline }
56: dl.triple dt:after { content: ':'; }
57: dl.triple dd:after { content: '\A'; white-space: pre; }
1.82 ihickson 58: .diff-old { text-decoration: line-through; color: silver; background: transparent; }
59: .diff-chg, .diff-new { text-decoration: underline; color: green; background: transparent; }
60: a .diff-new { border-bottom: 1px blue solid; }
61:
62: h2 { page-break-before: always; }
1.139 ihickson 63: h1, h2, h3, h4, h5, h6 { page-break-after: avoid; }
1.82 ihickson 64: h1 + h2, hr + h2.no-toc { page-break-before: auto; }
65:
1.87 ihickson 66: p > span:not([title=""]):not([class="XXX"]):not([class="impl"]), li > span:not([title=""]):not([class="XXX"]):not([class="impl"]) { border-bottom: solid #9999CC; }
1.82 ihickson 67:
68: div.head { margin: 0 0 1em; padding: 1em 0 0 0; }
69: div.head p { margin: 0; }
70: div.head h1 { margin: 0; }
71: div.head .logo { float: right; margin: 0 1em; }
72: div.head .logo img { border: none } /* remove border from top image */
73: div.head dl { margin: 1em 0; }
74: p.copyright { font-size: x-small; font-style: oblique; margin: 0; }
75:
76: body > .toc > li { margin-top: 1em; margin-bottom: 1em; }
77: body > .toc.brief > li { margin-top: 0.35em; margin-bottom: 0.35em; }
78: body > .toc > li > * { margin-bottom: 0.5em; }
79: body > .toc > li > * > li > * { margin-bottom: 0.25em; }
80: .toc, .toc li { list-style: none; }
81:
82: .brief { margin-top: 1em; margin-bottom: 1em; line-height: 1.1; }
83: .brief li { margin: 0; padding: 0; }
84: .brief li p { margin: 0; padding: 0; }
85:
1.137 ihickson 86: .category-list { margin-top: -0.75em; margin-bottom: 1em; line-height: 1.5; }
87: .category-list::before { content: '\21D2\A0'; font-size: 1.2em; font-weight: 900; }
88: .category-list li { display: inline; }
89: .category-list li:not(:last-child)::after { content: ', '; }
90: .category-list li > span, .category-list li > a { text-transform: lowercase; }
91: .category-list li * { text-transform: none; } /* don't affect <code> nested in <a> */
92:
1.82 ihickson 93: .XXX { color: #E50000; background: white; border: solid red; padding: 0.5em; margin: 1em 0; }
94: .XXX > :first-child { margin-top: 0; }
95: p .XXX { line-height: 3em; }
1.158 ihickson 96: .annotation { border: solid thin black; background: #0C479D; color: white; position: relative; margin: 8px 0 20px 0; }
97: .annotation:before { position: absolute; left: 0; top: 0; width: 100%; height: 100%; margin: 6px -6px -6px 6px; background: #333333; z-index: -1; content: ''; }
98: .annotation :link, .annotation :visited { color: inherit; }
99: .annotation :link:hover, .annotation :visited:hover { background: transparent; }
100: .annotation span { border: none ! important; }
1.82 ihickson 101: .note { color: green; background: transparent; font-family: sans-serif; }
102: .warning { color: red; background: transparent; }
103: .note, .warning { font-weight: bolder; font-style: italic; }
104: p.note, div.note { padding: 0.5em 2em; }
105: span.note { padding: 0 2em; }
106: .note p:first-child, .warning p:first-child { margin-top: 0; }
107: .note p:last-child, .warning p:last-child { margin-bottom: 0; }
108: .warning:before { font-style: normal; }
109: p.note:before { content: 'Note: '; }
110: p.warning:before { content: '\26A0 Warning! '; }
111:
112: .bookkeeping:before { display: block; content: 'Bookkeeping details'; font-weight: bolder; font-style: italic; }
113: .bookkeeping { font-size: 0.8em; margin: 2em 0; }
114: .bookkeeping p { margin: 0.5em 2em; display: list-item; list-style: square; }
115:
116: h4 { position: relative; z-index: 3; }
117: h4 + .element, h4 + div + .element { margin-top: -2.5em; padding-top: 2em; }
118: .element {
1.88 ihickson 119: background: #EEEEFF;
1.82 ihickson 120: color: black;
121: margin: 0 0 1em 0.15em;
122: padding: 0 1em 0.25em 0.75em;
1.88 ihickson 123: border-left: solid #9999FF 0.25em;
1.82 ihickson 124: position: relative;
125: z-index: 1;
126: }
127: .element:before {
128: position: absolute;
129: z-index: 2;
130: top: 0;
131: left: -1.15em;
132: height: 2em;
133: width: 0.9em;
1.88 ihickson 134: background: #EEEEFF;
1.82 ihickson 135: content: ' ';
136: border-style: none none solid solid;
1.88 ihickson 137: border-color: #9999FF;
1.82 ihickson 138: border-width: 0.25em;
139: }
140:
1.156 ihickson 141: .example { display: block; color: #222222; background: #FCFCFC; border-left: double; margin-left: 2em; padding-left: 1em; }
142: td > .example:only-child { margin: 0 0 0 0.1em; }
1.82 ihickson 143:
144: .tall-and-narrow {
145: font-size: 0.6em;
146: column-width: 25em;
147: column-gap: 1em;
148: -moz-column-width: 25em;
149: -moz-column-gap: 1em;
150: -webkit-column-width: 25em;
151: -webkit-column-gap: 1em;
152: }
1.131 ihickson 153:
154: ul.domTree, ul.domTree ul { padding: 0 0 0 1em; margin: 0; }
155: ul.domTree li { padding: 0; margin: 0; list-style: none; position: relative; }
156: ul.domTree li li { list-style: none; }
157: ul.domTree li:first-child::before { position: absolute; top: 0; height: 0.6em; left: -0.75em; width: 0.5em; border-style: none none solid solid; content: ''; border-width: 0.1em; }
158: ul.domTree li:not(:last-child)::after { position: absolute; top: 0; bottom: -0.6em; left: -0.75em; width: 0.5em; border-style: none none solid solid; content: ''; border-width: 0.1em; }
159: ul.domTree span { font-style: italic; font-family: serif; }
160: ul.domTree .t1 code { color: purple; font-weight: bold; }
161: ul.domTree .t2 { font-style: normal; font-family: monospace; }
162: ul.domTree .t2 .name { color: black; font-weight: bold; }
163: ul.domTree .t2 .value { color: blue; font-weight: normal; }
164: ul.domTree .t3 code, .domTree .t4 code, .domTree .t5 code { color: gray; }
165: ul.domTree .t7 code, .domTree .t8 code { color: green; }
166: ul.domTree .t10 code { color: teal; }
167:
1.155 ihickson 168: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><!-- ZZZ ED vs WD --><div class="head">
1.115 ihickson 169: <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 170: <h1>Web Workers</h1>
1.109 ihickson 171: <!--ZZZ:-->
1.117 ihickson 172: <!--<h2 class="no-num no-toc">W3C Working Draft 23 April 2009</h2>-->
1.182 ihickson 173: <h2 class="no-num no-toc" id="editor-s-draft-14-october-2009">Editor's Draft 14 October 2009</h2>
1.109 ihickson 174: <!--:ZZZ-->
1.155 ihickson 175: <dl><!-- ZZZ: update the month/day (twice), (un)comment out
1.117 ihickson 176: <dt>This Version:</dt>
1.115 ihickson 177: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a></dd>
1.155 ihickson 178: :ZZZ --><dt>Latest Published Version:</dt>
1.115 ihickson 179: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 180: <dt>Latest Editor's Draft:</dt>
1.115 ihickson 181: <dd><a href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.117 ihickson 182: <!-- ZZZ: add the new version after it has shipped-->
1.2 ihickson 183: <dt>Previous Versions:</dt>
1.113 ihickson 184: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a>
1.117 ihickson 185: <!-- :ZZZ -->
1.81 ihickson 186: <dt>Editors:</dt>
1.115 ihickson 187: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 188: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
189: © 2009 <a href="http://www.w3.org/"><abbr title="World Wide
190: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.115 ihickson 191: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.org/"><abbr title="European Research
192: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
193: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
194: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
195: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 196: use</a> rules apply.</p>
1.155 ihickson 197: </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 198: authors to spawn background workers running scripts in parallel to
199: their main page. This allows for thread-like operation with
1.155 ihickson 200: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id="status-of-this-document">Status of this document</h2><!-- intro boilerplate (required) --><p><em>This section describes the status of this document at the
1.81 ihickson 201: time of its publication. Other documents may supersede this
202: document. A list of current W3C publications and the most recently
203: formally published revision of this technical report can be found in
1.115 ihickson 204: the <a href="http://www.w3.org/TR/">W3C technical reports index</a>
1.155 ihickson 205: at http://www.w3.org/TR/.</em></p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- XXX this section will be moved back to just below the copyright
1.116 ihickson 206: notice in the header by October 2009 unless the spec as a whole has
1.155 ihickson 207: been transitioned to a more permissive license by that time. --><!-- XXX when moving this text, add: class="alt copyright" --><p>The <a href="http://www.whatwg.org/specs/web-workers/current-work/">WHATWG
1.116 ihickson 208: version</a> of this specification is available under a license that
1.155 ihickson 209: permits reuse of the specification text.</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- where to send feedback (required) --><p>If you wish to make comments regarding this document, please send
1.115 ihickson 210: them to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a>
1.90 ihickson 211: (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
1.115 ihickson 212: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>)
1.81 ihickson 213:
214: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.115 ihickson 215: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
216: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.110 ihickson 217: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.1 ihickson 218:
1.155 ihickson 219: All feedback is welcome.</p><!-- stability (required) --><p>Implementors should be aware that this specification is not
1.81 ihickson 220: stable. <strong>Implementors who are not taking part in the
221: discussions are likely to find the specification changing out from
222: under them in incompatible ways.</strong> Vendors interested in
223: implementing this specification before it eventually reaches the
224: Candidate Recommendation stage should join the aforementioned
1.155 ihickson 225: mailing lists and take part in the discussions.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) --><p>The latest stable version of the editor's draft of this
1.115 ihickson 226: specification is always available on <a href="http://dev.w3.org/html5/workers/Overview.html">the W3C CVS
227: server</a> and in the <a href="http://svn.whatwg.org/webworkers/">WHATWG Subversion
1.81 ihickson 228: repository</a>. The latest editor's working copy (which may contain
1.115 ihickson 229: unfinished text in the process of being prepared) is available <a href="http://www.whatwg.org/specs/web-workers/current-work/">on the
1.81 ihickson 230: WHATWG site</a>. Detailed change history can be obtained from the
1.155 ihickson 231: 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>
1.115 ihickson 232: <li>Interactive Web interface: <a href="http://html5.org/tools/web-workers-tracker">http://html5.org/tools/web-workers-tracker</a></li>
233: <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>
234: <li>Subversion interface: <a href="http://svn.whatwg.org/webworkers/">http://svn.whatwg.org/webworkers/</a></li>
235: <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>
1.155 ihickson 236: </ul><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) --><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Apps
1.81 ihickson 237: Working Group</a> is the W3C working group responsible for this
238: specification's progress along the W3C Recommendation track.
239: <!--ZZZ:-->
1.117 ihickson 240: <!--This specification is the 23 April 2009 Working Draft.-->
1.182 ihickson 241: This specification is the 14 October 2009 Editor's Draft.
1.81 ihickson 242: <!--:ZZZ-->
1.155 ihickson 243: </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
244: 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
1.81 ihickson 245: platform closely related to HTML5. It is defined in a separate
1.155 ihickson 246: 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
1.115 ihickson 247: February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of
1.81 ihickson 248: any patent disclosures</a> made in connection with the deliverables
249: of the group; that page also includes instructions for disclosing a
250: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 251: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
252: Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
1.155 ihickson 253: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of contents</h2>
1.81 ihickson 254: <!--begin-toc-->
1.115 ihickson 255: <ol class="toc">
256: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 257: <ol>
1.115 ihickson 258: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
259: <li><a href="#tutorial"><span class="secno">1.2 </span>Tutorial</a>
1.81 ihickson 260: <ol>
1.115 ihickson 261: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
262: <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>
263: <li><a href="#worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</a></li>
264: <li><a href="#shared-workers"><span class="secno">1.2.4 </span>Shared workers</a></li>
265: <li><a href="#delegation"><span class="secno">1.2.5 </span>Delegation</a></li>
266: <li><a href="#providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</a></ol></ol></li>
1.148 ihickson 267: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 268: <ol>
1.148 ihickson 269: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
270: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
271: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
272: <ol>
273: <li><a href="#the-global-scope"><span class="secno">4.1 </span>The global scope</a>
1.81 ihickson 274: <ol>
1.148 ihickson 275: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
276: <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>
277: <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>
1.160 ihickson 278: <li><a href="#origins-of-workers"><span class="secno">4.2 </span>Origins of workers</a></li>
1.148 ihickson 279: <li><a href="#decoding-scripts"><span class="secno">4.3 </span>Decoding scripts</a></li>
280: <li><a href="#the-event-loop"><span class="secno">4.4 </span>The event loop</a></li>
281: <li><a href="#the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</a></li>
282: <li><a href="#processing-model"><span class="secno">4.6 </span>Processing model</a></li>
283: <li><a href="#runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</a></li>
284: <li><a href="#creating-workers"><span class="secno">4.8 </span>Creating workers</a>
1.81 ihickson 285: <ol>
1.148 ihickson 286: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
287: <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>
288: <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>
289: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 290: <ol>
1.148 ihickson 291: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
292: <li><a href="#the-navigator-object"><span class="secno">5.2 </span>The <code title="worker-Navigator">Navigator</code> object</a></li>
293: <li><a href="#apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</a></li>
294: <li><a href="#interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</a></li>
295: <li><a href="#worker-locations"><span class="secno">5.5 </span>Worker locations</a></ol></li>
1.115 ihickson 296: <li><a class="no-num" href="#references">References</a></li>
297: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.155 ihickson 298: <!--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><i>This section is non-normative.</i><p>This specification defines an API for running scripts in the
299: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 300: scripts that respond to clicks or other user interactions, and
301: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 302: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 303: relatively heavy-weight, and are not intended to be used in large
304: numbers. For example, it would be inappropriate to launch one worker
305: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 306: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
307: start-up performance cost, and a high per-instance memory cost.<h3 id="tutorial"><span class="secno">1.2 </span>Tutorial</h3><p><i>This section is non-normative.</i><p>There are a variety of uses that workers can be put to. The
308: 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><i>This section is non-normative.</i><p>The simplest use of workers is for performing a computationally
309: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
310: (naïvely) compute prime numbers, and progressively displays the
311: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 312: <html>
313: <head>
314: <title>Worker example: One-core computation</title>
315: </head>
316: <body>
317: <p>The highest prime number discovered so far is: <output id="result"></output></p>
318: <script>
1.50 ihickson 319: var worker = new Worker('worker.js');
320: worker.onmessage = function (event) {
1.54 ihickson 321: document.getElementById('result').textContent = event.data;
1.29 ihickson 322: };
1.81 ihickson 323: </script>
324: </body>
1.155 ihickson 325: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 326: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 327: representing that worker, which is used to communicate with the
1.177 ihickson 328: worker. That object's <code title="handler-Worker-onmessage"><a href="#handler-worker-onmessage">onmessage</a></code> event handler allows the code to receive messages from the worker.<p>The worker itself is as follows:<pre>var n = 1;
1.29 ihickson 329: search: while (true) {
330: n += 1;
331: for (var i = 2; i <= Math.sqrt(n); i += 1)
332: if (n % i == 0)
333: continue search;
334: // found a prime!
1.50 ihickson 335: postMessage(n);
1.155 ihickson 336: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.115 ihickson 337: number. To send a message back to the page, the <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
1.155 ihickson 338: 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><i>This section is non-normative.</i><p>In this example, the main document spawns a worker whose only
1.81 ihickson 339: task is to listen for notifications from the server, and, when
340: appropriate, either add or remove data from the client-side
1.155 ihickson 341: database.<p>Since no communication occurs between the worker and the main
342: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 343: new Worker('worker.js');
1.155 ihickson 344: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 345: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 346: server.onmessage = function (event) {
347: // data is in the format "command key value"
1.54 ihickson 348: var data = event.data.split(' ');
1.31 ihickson 349: switch (data[0]) {
350: case '+':
351: database.transaction(function(tx) {
352: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
353: });
354: case '-':
355: database.transaction(function(tx) {
356: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
357: });
358: }
1.155 ihickson 359: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 360: mechanism and opens the local database (which, we presume, has been
361: created earlier). The worker then just listens for messages from the
362: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 363: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 364: this example online</a>. (This example will not actually function,
365: since the server does not actually exist and the database is not
1.155 ihickson 366: 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><i>This section is non-normative.</i><p>In this example, the main document uses two workers, one for
1.81 ihickson 367: fetching stock updates for at regular intervals, and one for
1.155 ihickson 368: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 369: <html>
370: <head>
371: <title>Worker example: Stock ticker</title>
372: <script>
1.33 ihickson 373: // TICKER
374: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 375: var ticker = new Worker('ticker.js');
1.33 ihickson 376:
377: // SEARCHER
1.50 ihickson 378: var searcher = new Worker('searcher.js');
1.33 ihickson 379: function search(query) {
1.50 ihickson 380: searcher.postMessage(query);
1.33 ihickson 381: }
382:
383: // SYMBOL SELECTION UI
384: function select(newSymbol) {
385: symbol = newSymbol;
1.50 ihickson 386: ticker.postMessage(symbol);
1.33 ihickson 387: }
1.81 ihickson 388: </script>
389: </head>
1.122 ihickson 390: <body onload="search('')">
1.81 ihickson 391: <p><output id="symbol"></output> <output id="value"></output></p>
392: <script>
1.50 ihickson 393: ticker.onmessage = function (event) {
1.54 ihickson 394: var data = event.data.split(' ');
1.33 ihickson 395: document.getElementById('symbol').textContent = data[0];
396: document.getElementById('value').textContent = data[1];
397: };
1.50 ihickson 398: ticker.postMessage(symbol);
1.81 ihickson 399: </script>
1.122 ihickson 400: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 401: <ul id="results"></ul>
402: <script>
1.50 ihickson 403: searcher.onmessage = function (event) {
1.54 ihickson 404: var data = event.data.split(' ');
1.33 ihickson 405: var results = document.getElementById('results');
406: while (results.hasChildNodes()) // clear previous results
407: results.removeChild(results.firstChild);
408: for (var i = 0; i < data.length; i += 1) {
409: // add a list item with a button for each result
410: var li = document.createElement('li');
411: var button = document.createElement('button');
412: button.value = data[i];
413: button.type = 'button';
414: button.onclick = function () { select(this.value); };
415: button.textContent = data[i];
416: li.appendChild(button);
417: results.appendChild(li);
418: }
419: };
1.81 ihickson 420: </script>
421: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
422: </body>
1.155 ihickson 423: </html></pre><p>The two workers use a common library for performing the actual
424: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 425: try {
426: var xhr = new XMLHttpRequest();
427: xhr.open('GET', url, false);
428: xhr.send();
429: return xhr.responseText;
430: } catch (e) {
431: return ''; // turn all errors into empty results
432: }
1.155 ihickson 433: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 434: var timer;
435: var symbol;
436: function update() {
1.50 ihickson 437: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 438: timer = setTimeout(update, 10000);
439: }
1.50 ihickson 440: onmessage = function (event) {
1.33 ihickson 441: if (timer)
442: clearTimeout(timer);
1.54 ihickson 443: symbol = event.data;
1.33 ihickson 444: update();
1.155 ihickson 445: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 446: onmessage = function (event) {
1.54 ihickson 447: postMessage(get('search.cgi?' + event.data));
1.155 ihickson 448: };</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><i>This section is non-normative.</i><p>In this example, multiple windows (viewers) can be opened that
1.81 ihickson 449: are all viewing the same map. All the windows share the same map
450: information, with a single worker coordinating all the viewers. Each
451: viewer can move around independently, but if they set any data on
1.155 ihickson 452: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
453: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 454: <html>
455: <head>
456: <title>Workers example: Multiviewer</title>
457: <script>
1.36 ihickson 458: function openViewer() {
459: window.open('viewer.html');
460: }
1.81 ihickson 461: </script>
462: </head>
463: <body>
464: <p><button type=button onclick="openViewer()">Open a new
465: viewer</button></p>
466: <p>Each viewer opens in a new window. You can have as many viewers
467: as you like, they all view the same data.</p>
468: </body>
1.155 ihickson 469: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 470: <html>
471: <head>
472: <title>Workers example: Multiviewer viewer</title>
473: <script>
1.50 ihickson 474: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 475:
476: // CONFIGURATION
477: function configure(event) {
1.54 ihickson 478: if (event.data.substr(0, 4) != 'cfg ') return;
479: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 480: // update display to mention our name is name
481: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
482: // no longer need this listener
1.43 ihickson 483: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 484: }
1.53 ihickson 485: worker.port.addEventListener('message', configure, false);
1.36 ihickson 486:
487: // MAP
488: function paintMap(event) {
1.54 ihickson 489: if (event.data.substr(0, 4) != 'map ') return;
490: var data = event.data.substr(4).split(',');
1.36 ihickson 491: // display tiles data[0] .. data[8]
492: var canvas = document.getElementById('map');
493: var context = canvas.getContext('2d');
494: for (var y = 0; y < 3; y += 1) {
495: for (var x = 0; x < 3; x += 1) {
496: var tile = data[y * 3 + x];
497: if (tile == '0')
498: context.fillStyle = 'green';
499: else
500: context.fillStyle = 'maroon';
501: fillRect(x * 50, y * 50, 50, 50);
502: }
503: }
504: }
1.53 ihickson 505: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 506:
507: // PUBLIC CHAT
508: function updatePublicChat(event) {
1.54 ihickson 509: if (event.data.substr(0, 4) != 'txt ') return;
510: var name = event.data.substr(4).split(' ', 1);
511: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 512: // display "<name> message" in public chat
1.36 ihickson 513: var dialog = document.getElementById('public');
514: var dt = document.createElement('dt');
515: dt.textContent = name;
516: dialog.appendChild(dt);
517: var dd = document.createElement('dd');
518: dd.textContent = message;
519: dialog.appendChild(dd);
520: }
1.53 ihickson 521: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 522:
523: // PRIVATE CHAT
524: function startPrivateChat(event) {
1.54 ihickson 525: if (event.data.substr(0, 4) != 'msg ') return;
526: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 527: var port = event.ports[0];
1.36 ihickson 528: // display a private chat UI
529: var ul = document.getElementById('private');
530: var li = document.createElement('li');
531: var h3 = document.createElement('h3');
532: h3.textContent = 'Private chat with ' + name;
533: li.appendChild(h3);
534: var dialog = document.createElement('dialog');
535: var addMessage = function(name, message) {
536: var dt = document.createElement('dt');
537: dt.textContent = name;
538: dialog.appendChild(dt);
539: var dd = document.createElement('dd');
540: dd.textContent = message;
541: dialog.appendChild(dd);
542: };
543: port.onmessage = function (event) {
1.54 ihickson 544: addMessage(name, event.data);
1.36 ihickson 545: };
546: li.appendChild(dialog);
547: var form = document.createElement('form');
548: var p = document.createElement('p');
549: var input = document.createElement('input');
550: input.size = 50;
551: p.appendChild(input);
552: p.appendChild(document.createTextNode(' '));
553: var button = document.createElement('button');
554: button.textContent = 'Post';
555: p.appendChild(button);
556: form.onsubmit = function () {
557: port.postMessage(input.value);
558: addMessage('me', input.value);
559: input.value = '';
560: return false;
561: };
562: form.appendChild(p);
563: li.appendChild(form);
564: }
1.53 ihickson 565: worker.port.addEventListener('message', startPrivateChat, false);
1.81 ihickson 566: </script>
567: </head>
568: <body>
569: <h1>Viewer</h1>
570: <h2>Map</h2>
571: <p><canvas id="map" height=150 width=150></canvas></p>
572: <p>
573: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
574: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
575: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
576: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
577: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
578: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
579: </p>
580: <h2>Public Chat</h2>
581: <dialog id="public"></dialog>
582: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
583: <p>
584: <input type="text" name="message" size="50">
585: <button>Post</button>
586: </p>
587: </form>
588: <h2>Private Chat</h2>
589: <ul id="private"></ul>
590: </body>
591: </html>
1.155 ihickson 592: </pre><p>There are several key things worth noting about the way the
593: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 594: processing function, the code here attaches multiple event
595: listeners, each one performing a quick check to see if it is
596: relevant for the message. In this example it doesn't make much
597: difference, but if multiple authors wanted to collaborate using a
598: single port to communicate with a worker, it would allow for
599: independent code instead of changes having to all be made to a
1.155 ihickson 600: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 601: unregister specific listeners when you are done with them, as is
602: done with the <code title="">configure()</code> method in this
1.155 ihickson 603: example.<p>Finally, the worker:<pre>
604: var nextName = 0;
1.36 ihickson 605: function getNextName() {
606: // this could use more friendly names
607: // but for now just return a number
608: return nextName++;
609: }
610:
611: var map = [
612: [0, 0, 0, 0, 0, 0, 0],
613: [1, 1, 0, 1, 0, 1, 1],
614: [0, 1, 0, 1, 0, 0, 0],
615: [0, 1, 0, 1, 0, 1, 1],
616: [0, 0, 0, 1, 0, 0, 0],
617: [1, 0, 0, 1, 1, 1, 1],
618: [1, 1, 0, 1, 1, 0, 1],
619: ];
620:
621: function wrapX(x) {
622: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 623: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 624: return x;
625: }
626:
627: function wrapY(y) {
628: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 629: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 630: return y;
631: }
632:
1.50 ihickson 633: function sendMapData(callback) {
1.36 ihickson 634: var data = '';
635: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
636: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
637: if (data != '')
638: data += ',';
639: data += map[y][x];
640: }
641: }
1.50 ihickson 642: callback('map ' + data);
1.36 ihickson 643: }
644:
645: var viewers = {};
646: onconnect = function (event) {
1.84 ihickson 647: event.ports[0]._name = getNextName();
648: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
649: viewers[event.ports[0]._name] = event.port._data;
650: event.ports[0].postMessage('cfg ' + name);
651: event.ports[0].onmessage = getMessage;
652: sendMapData(event.ports[0].postMessage);
1.36 ihickson 653: };
654:
655: function getMessage(event) {
1.54 ihickson 656: switch (event.data.substr(0, 4)) {
1.36 ihickson 657: case 'mov ':
1.54 ihickson 658: var direction = event.data.substr(4);
1.36 ihickson 659: var dx = 0;
660: var dy = 0;
661: switch (direction) {
662: case 'up': dy = -1; break;
663: case 'down': dy = 1; break;
664: case 'left': dx = -1; break;
665: case 'right': dx = 1; break;
666: }
667: event.target._data.x = wrapX(event.target._data.x + dx);
668: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 669: sendMapData(event.target.postMessage);
1.36 ihickson 670: break;
671: case 'set ':
1.54 ihickson 672: var value = event.data.substr(4);
1.36 ihickson 673: map[event.target._data.y][event.target._data.x] = value;
674: for (var viewer in viewers)
1.50 ihickson 675: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 676: break;
677: case 'txt ':
678: var name = event.target._name;
1.54 ihickson 679: var message = event.data.substr(4);
1.36 ihickson 680: for (var viewer in viewers)
681: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
682: break;
683: case 'msg ':
684: var party1 = event._data;
1.54 ihickson 685: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 686: if (party2) {
687: var channel = new MessageChannel();
1.84 ihickson 688: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
689: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 690: }
691: break;
692: }
1.155 ihickson 693: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 694: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 695: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 696: "msg" message from one viewer naming another viewer, it sets up a
697: direct connection between the two, so that the two viewers can
698: communicate directly without the worker having to proxy all the
1.155 ihickson 699: 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><i>This section is non-normative.</i><p>With multicore CPUs becoming prevalent, one way to obtain better
1.81 ihickson 700: performance is to split computationally expensive tasks amongst
701: multiple workers. In this example, a computationally expensive task
702: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 703: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 704: <html>
705: <head>
706: <title>Worker example: One-core computation</title>
707: </head>
708: <body>
709: <p>The highest prime number discovered so far is: <output id="result"></output></p>
710: <script>
1.50 ihickson 711: var worker = new Worker('worker.js');
712: worker.onmessage = function (event) {
1.54 ihickson 713: document.getElementById('result').textContent = event.data;
1.40 ihickson 714: };
1.81 ihickson 715: </script>
716: </body>
1.155 ihickson 717: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 718: var num_workers = 10;
719: var items_per_worker = 1000000;
720:
721: // start the workers
722: var result = 0;
723: var pending_workers = num_workers;
724: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 725: var worker = new Worker('core.js');
726: worker.postMessage(i * items_per_worker);
727: worker.postMessage((i+1) * items_per_worker);
728: worker.onmessage = storeResult;
1.40 ihickson 729: }
730:
731: // handle the results
732: function storeResult(event) {
1.54 ihickson 733: result += 1*event.data;
1.40 ihickson 734: pending_workers -= 1;
735: if (pending_workers <= 0)
1.50 ihickson 736: postMessage(result); // finished!
1.155 ihickson 737: }</pre><p>It consists of a loop to start the subworkers, and then a handler
738: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 739: onmessage = getStart;
1.40 ihickson 740: function getStart(event) {
1.54 ihickson 741: start = 1*event.data;
1.40 ihickson 742: onmessage = getEnd;
743: }
744:
745: var end;
746: function getEnd(event) {
1.54 ihickson 747: end = 1*event.data;
1.40 ihickson 748: onmessage = null;
1.66 ihickson 749: work();
1.40 ihickson 750: }
751:
1.66 ihickson 752: function work() {
1.40 ihickson 753: var result = 0;
754: for (var i = start; i < end; i += 1) {
755: // perform some complex calculation here
756: result += 1;
757: }
1.50 ihickson 758: postMessage(result);
759: close();
1.155 ihickson 760: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 761: for the range of numbers thus specified, and then report the result
1.155 ihickson 762: 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><i>This section is non-normative.</i><p>Suppose that a cryptography library is made available that
763: provides three tasks:<dl><dt>Generate a public/private key pair</dt>
1.81 ihickson 764:
765: <dd>Takes a port, on which it will send two messages, first the
766: public key and then the private key.</dd>
767:
768: <dt>Given a plaintext and a public key, return the corresponding cyphertext</dt>
769:
770: <dd>Takes a port, to which any number of messages can be sent, the
771: first giving the public key, and the remainder giving the
772: plaintext, each of which is encrypted and then sent on that same
773: channel as the cyphertext. The user can close the port when it is
774: done encrypting content.</dd>
775:
776: <dt>Given a cyphertext and a private key, return the corresponding plaintext</dt>
777:
778: <dd>Takes a port, to which any number of messages can be sent, the
779: first giving the private key, and the remainder giving the
780: cyphertext, each of which is decrypted and then sent on that same
781: channel as the plaintext. The user can close the port when it is
782: done decrypting content.</dd>
1.49 ihickson 783:
1.155 ihickson 784: </dl><p>The library itself is as follows:<pre>function handleMessage(e) {
1.54 ihickson 785: if (e.data == "genkeys")
1.84 ihickson 786: genkeys(e.ports[0]);
1.54 ihickson 787: else if (e.data == "encrypt")
1.84 ihickson 788: encrypt(e.ports[0]);
1.54 ihickson 789: else if (e.data == "decrypt")
1.84 ihickson 790: decrypt(e.ports[0]);
1.49 ihickson 791: }
792:
793: function genkeys(p) {
794: var keys = _generateKeyPair();
795: p.postMessage(keys[0]);
796: p.postMessage(keys[1]);
797: }
798:
799: function encrypt(p) {
800: var key, state = 0;
801: p.onmessage = function (e) {
802: if (state == 0) {
1.54 ihickson 803: key = e.data;
1.49 ihickson 804: state = 1;
805: } else {
1.54 ihickson 806: p.postMessage(_encrypt(key, e.data));
1.49 ihickson 807: }
808: };
809: }
810:
811: function decrypt(p) {
812: var key, state = 0;
813: p.onmessage = function (e) {
814: if (state == 0) {
1.54 ihickson 815: key = e.data;
1.49 ihickson 816: state = 1;
817: } else {
1.54 ihickson 818: p.postMessage(_decrypt(key, e.data));
1.49 ihickson 819: }
820: };
821: }
822:
1.50 ihickson 823: // support being used as a shared worker as well as a dedicated worker
824: if (this.onmessage) // dedicated worker
825: onmessage = handleMessage;
826: else // shared worker
827: onconnect = function (e) { e.port.onmessage = handleMessage; }
1.49 ihickson 828:
829:
830: // the "crypto" functions:
831:
832: function _generateKeyPair() {
833: return [Math.random(), Math.random()];
834: }
835:
836: function _encrypt(k, s) {
837: return 'encrypted-' + k + ' ' + s;
838: }
839:
840: function _decrypt(k, s) {
841: return s.substr(s.indexOf(' ')+1);
1.155 ihickson 842: }</pre><p>Note that the crypto functions here are just stubs and don't do
843: real cryptography.<p>This library could be used as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 844: <html>
845: <head>
846: <title>Worker example: Crypto library</title>
847: <script>
1.50 ihickson 848: var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
1.49 ihickson 849: function getKeys() {
850: var state = 0;
1.50 ihickson 851: cryptoLib.startConversation("genkeys").onmessage = function (e) {
1.49 ihickson 852: if (state == 0)
1.54 ihickson 853: document.getElementById('public').value = e.data;
1.49 ihickson 854: else if (state == 1)
1.54 ihickson 855: document.getElementById('private').value = e.data;
1.49 ihickson 856: state += 1;
857: };
858: }
859: function enc() {
1.50 ihickson 860: var port = cryptoLib.startConversation("encrypt");
861: port.postMessage(document.getElementById('public').value);
862: port.postMessage(document.getElementById('input').value);
863: port.onmessage = function (e) {
1.54 ihickson 864: document.getElementById('input').value = e.data;
1.50 ihickson 865: port.close();
1.49 ihickson 866: };
867: }
868: function dec() {
1.50 ihickson 869: var port = cryptoLib.startConversation("decrypt");
870: port.postMessage(document.getElementById('private').value);
871: port.postMessage(document.getElementById('input').value);
872: port.onmessage = function (e) {
1.54 ihickson 873: document.getElementById('input').value = e.data;
1.50 ihickson 874: port.close();
1.49 ihickson 875: };
876: }
1.81 ihickson 877: </script>
878: <style>
1.49 ihickson 879: textarea { display: block; }
1.81 ihickson 880: </style>
881: </head>
882: <body onload="getKeys()">
883: <fieldset>
884: <legend>Keys</legend>
885: <p><label>Public Key: <textarea id="public"></textarea></label></p>
886: <p><label>Private Key: <textarea id="private"></textarea></label></p>
887: </fieldset>
888: <p><label>Input: <textarea id="input"></textarea></label></p>
889: <p><button onclick="enc()">Encrypt</button> <button onclick="dec()">Decrypt</button></p>
890: </body>
1.155 ihickson 891: </html></pre><p>A later version of the API, though, might want to offload all the
892: crypto work onto subworkers. This could be done as follows:<pre>function handleMessage(e) {
1.54 ihickson 893: if (e.data == "genkeys")
1.84 ihickson 894: genkeys(e.ports[0]);
1.54 ihickson 895: else if (e.data == "encrypt")
1.84 ihickson 896: encrypt(e.ports[0]);
1.54 ihickson 897: else if (e.data == "decrypt")
1.84 ihickson 898: decrypt(e.ports[0]);
1.49 ihickson 899: }
900:
901: function genkeys(p) {
1.50 ihickson 902: var generator = new Worker('libcrypto-v2-generator.js');
1.84 ihickson 903: generator.postMessage('', [p]);
1.49 ihickson 904: }
905:
906: function encrypt(p) {
907: p.onmessage = function (e) {
1.54 ihickson 908: var key = e.data;
1.50 ihickson 909: var encryptor = new Worker('libcrypto-v2-encryptor.js');
1.84 ihickson 910: encryptor.postMessage(key, [p]);
1.49 ihickson 911: };
912: }
913:
914: function encrypt(p) {
915: p.onmessage = function (e) {
1.54 ihickson 916: var key = e.data;
1.50 ihickson 917: var decryptor = new Worker('libcrypto-v2-decryptor.js');
1.84 ihickson 918: decryptor.postMessage(key, [p]);
1.49 ihickson 919: };
920: }
921:
1.50 ihickson 922: // support being used as a shared worker as well as a dedicated worker
923: if (this.onmessage) // dedicated worker
924: onmessage = handleMessage;
925: else // shared worker
1.84 ihickson 926: onconnect = function (e) { e.ports[0].onmessage = handleMessage };
1.155 ihickson 927: </pre><p>The little subworkers would then be as follows.<p>For generating key pairs:<pre>onmessage = function (e) {
1.50 ihickson 928: var k = _generateKeyPair();
1.84 ihickson 929: e.ports[0].postMessage(k[0]);
930: e.ports[0].postMessage(k[1]);
1.49 ihickson 931: close();
932: }
1.50 ihickson 933:
934: function _generateKeyPair() {
935: return [Math.random(), Math.random()];
1.155 ihickson 936: }</pre><p>For encrypting:<pre>onmessage = function (e) {
1.54 ihickson 937: var key = e.data;
1.84 ihickson 938: e.ports[0].onmessage = function (e) {
1.54 ihickson 939: var s = e.data;
1.50 ihickson 940: postMessage(_encrypt(key, s));
1.49 ihickson 941: }
1.50 ihickson 942: }
943:
944: function _encrypt(k, s) {
945: return 'encrypted-' + k + ' ' + s;
1.155 ihickson 946: }</pre><p>For decrypting:<pre>onmessage = function (e) {
1.54 ihickson 947: var key = e.data;
1.84 ihickson 948: e.ports[0].onmessage = function (e) {
1.54 ihickson 949: var s = e.data;
1.50 ihickson 950: postMessage(_decrypt(key, s));
1.49 ihickson 951: }
1.50 ihickson 952: }
953:
954: function _decrypt(k, s) {
955: return s.substr(s.indexOf(' ')+1);
1.155 ihickson 956: }</pre><p>Notice how the users of the API don't have to even know that this
957: is happening — the API hasn't changed; the library can
1.81 ihickson 958: delegate to subworkers without changing its API, even though it is
1.155 ihickson 959: 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 960: non-normative, as are all sections explicitly marked non-normative.
1.155 ihickson 961: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
1.81 ihickson 962: NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
963: "OPTIONAL" in the normative parts of this document are to be
964: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 965: not appear in all uppercase letters in this specification. <a href="#refsRFC2119">[RFC2119]</a><p>Requirements phrased in the imperative as part of algorithms
1.81 ihickson 966: (such as "strip any leading space characters" or "return false and
967: abort these steps") are to be interpreted with the meaning of the
968: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 969: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 970: attributes, methods or objects. Such requirements are to be
1.155 ihickson 971: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 972: may be implemented in any manner, so long as the end result is
973: equivalent. (In particular, the algorithms defined in this
974: specification are intended to be easy to follow, and not intended to
1.155 ihickson 975: be performant.)<p>The only conformance class defined by this specification is user
976: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 977: otherwise unconstrained inputs, e.g. to prevent denial of service
978: attacks, to guard against running out of memory, or to work around
1.155 ihickson 979: platform-specific limitations.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
980: specifications.<dl><dt>HTML5</dt>
1.49 ihickson 981:
1.81 ihickson 982: <dd>
1.49 ihickson 983:
1.81 ihickson 984: <p>Many fundamental concepts from HTML5 are used by this
1.152 ihickson 985: specification. <a href="#refsHTML5">[HTML5]</a></p>
1.49 ihickson 986:
1.81 ihickson 987: </dd>
1.1 ihickson 988:
1.81 ihickson 989: <dt>WebIDL</dt>
1.1 ihickson 990:
991: <dd>
992:
1.81 ihickson 993: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 994: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 995:
1.81 ihickson 996: </dd>
1.1 ihickson 997:
1.155 ihickson 998: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 999: <code title="">Foo</code> is actually an interface, is sometimes
1000: used instead of the more accurate "an object implementing the
1.155 ihickson 1001: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 1002: scripts in Web applications, and does not necessarily imply the
1003: existence of an actual <code>Document</code> object or of any other
1004: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 1005: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 1006: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 1007: <em>setting</em> when a new value is assigned to it.<p>The term "JavaScript" is used to refer to ECMA262, rather than
1.103 ihickson 1008: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 1009: widely known. <a href="#refsECMA262">[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 1010: workers. Dedicated workers, once created, and are linked to their
1011: creator; but message ports can be used to communicate from a
1012: dedicated worker to multiple other browsing contexts or
1013: workers. Shared workers, on the other hand, are named, and once
1014: created any script running in the same <span>origin</span> can
1.155 ihickson 1015: 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> {
1.115 ihickson 1016: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1017: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1018:
1019: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.144 ihickson 1020: <!-- v2-onclose attribute <span>Function</span> <span title="handler-WorkerGlobalScope-onclose">onclose</span>;
1021: --> attribute <span>Function</span> <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1.150 ihickson 1022: };
1.172 ihickson 1023: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <a href="#workerutils">WorkerUtils</a>;
1024: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <span>EventTarget</span>;</pre><p>The <dfn id="dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self"><code>self</code></dfn> attribute
1.155 ihickson 1025: 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>
1.115 ihickson 1026: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1027: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1028: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 1029: that was used to initialize the worker, after any redirects.<hr><p>When a script invokes the <dfn id="dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close"><code>close()</code></dfn>
1.123 ihickson 1030: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 1031: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 1032: have been added to the <span>event loop</span>'s <span title="task
1033: queue">task queues</span>.</p>
1034:
1035: <!-- v2-onclose
1036: <li><p><span>Queue a task</span> to <span>fire a simple
1.179 ihickson 1037: event</span> named <code title="event-close">close</code> at the
1.123 ihickson 1038: <code>WorkerGlobalScope</code> object.</p></li>
1039: -->
1.81 ihickson 1040:
1.115 ihickson 1041: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1042: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 1043: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1044:
1.124 ihickson 1045: <li><p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1.123 ihickson 1046: ports</a>.</li>
1.81 ihickson 1047:
1.177 ihickson 1048: </ol><p>The following are the <span>event handlers</span> (and their
1049: corresponding <span title="event handler event type">event handler
1050: event types</span>) that must be supported, as IDL attributes, by
1051: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1052: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1053: <tbody><!-- v2-onclose <tr><td><dfn title="handler-WorkerGlobalScope-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code> --><tr><td><dfn id="handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1054: </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><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1055: interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.174 ihickson 1056: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(in any message, in optional <span>MessagePortArray</span> ports);<!--
1.77 ihickson 1057: <span>MessagePort</span> <span title="dom-DedicatedWorkerGlobalScope-startConversation">startConversation</span>(in any message);-->
1.144 ihickson 1058: attribute <span>Function</span> <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.155 ihickson 1059: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.81 ihickson 1060: had an implicit <code>MessagePort</code> associated with them. This
1061: port is part of a channel that is set up when the worker is created,
1062: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1063: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1064: 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 1065: and <dfn
1066: title="dom-DedicatedWorkerGlobalScope-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1067: method<!--s (startConversation)--> on
1.115 ihickson 1068: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.81 ihickson 1069: invoked, it<!--/they (startConversation)--> immediately invoked the
1070: method of the same name on the port, with the same arguments, and
1.177 ihickson 1071: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1072: corresponding <span title="event handler event type">event handler
1073: event types</span>) that must be supported, as IDL attributes, by
1074: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1075: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1076: <tbody><tr><td><dfn id="handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1077: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1078: networking model, a dedicated worker is an extension of the
1.155 ihickson 1079: <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><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1080: interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1081: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1.181 ihickson 1082: readonly attribute <span>ApplicationCache</span> <span title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</span>;
1.144 ihickson 1083: attribute <span>Function</span> <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.155 ihickson 1084: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1085: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1086: attribute must return the value it was assigned when the
1.115 ihickson 1087: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1088: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1089: that can be used to obtain a reference to the worker using the
1.177 ihickson 1090: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1091: corresponding <span title="event handler event type">event handler
1092: event types</span>) that must be supported, as IDL attributes, by
1093: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1094: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1095: <tbody><tr><td><dfn id="handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect"><code>onconnect</code></dfn> <td> <code title="event-connect">connect</code>
1096: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1097: networking model, a shared worker is its own <span>cache
1.115 ihickson 1098: host</span>. The <a href="#run-a-worker">run a worker</a> algorithm takes care of
1.181 ihickson 1099: associating the worker with an <span>application cache</span>.<p class="note">The <code title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</code>
1.123 ihickson 1100: attribute returns the <code>ApplicationCache</code> object for the
1.101 ihickson 1101: worker.</p><!-- normative conf criteria is in the appcache section
1.160 ihickson 1102: --><h3 id="origins-of-workers"><span class="secno">4.2 </span>Origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1103: origin</span> of scripts running in workers are the
1104: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1105: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.155 ihickson 1106: 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
1107: obtain its source in Unicode, it must run the following steps:<ol><li>
1.85 ihickson 1108:
1109: <p>Let <var title="">character encoding</var> be <i title="">unknown</i>.</p>
1110:
1111: </li>
1112:
1113: <li>
1114:
1115: <p>For each of the rows in the following table, starting with the
1116: first one and going down, if the resource has as many or more
1117: bytes available than the number of bytes in the first column, and
1118: the first bytes of the resource match the bytes given in the first
1119: column, then let <var title="">character encoding</var> be the
1120: encoding given in the cell in the second column of that row:</p>
1121:
1122: <!-- this table is present in several forms in this file; keep them in sync -->
1.155 ihickson 1123: <table><thead><tr><th>Bytes in Hexadecimal
1.85 ihickson 1124: <th>Encoding
1.155 ihickson 1125: <tbody><!-- nobody uses this
1.85 ihickson 1126: <tr>
1127: <td>00 00 FE FF
1128: <td>UTF-32BE
1129: <tr>
1130: <td>FF FE 00 00
1131: <td>UTF-32LE
1.155 ihickson 1132: --><tr><td>FE FF
1.85 ihickson 1133: <td>UTF-16BE
1.155 ihickson 1134: <tr><td>FF FE
1.85 ihickson 1135: <td>UTF-16LE
1.155 ihickson 1136: <tr><td>EF BB BF
1.85 ihickson 1137: <td>UTF-8
1138: <!-- nobody uses this
1139: <tr>
1140: <td>DD 73 66 73
1141: <td>UTF-EBCDIC
1142: -->
1.155 ihickson 1143: </table><p class="note">This step looks for Unicode Byte Order Marks
1.85 ihickson 1144: (BOMs).</p>
1145:
1146: </li>
1147:
1148: <li>
1149:
1150: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, apply the <span>algorithm for extracting an
1.115 ihickson 1151: encoding from a Content-Type</span> to the resource's <span title="Content-Type">Content Type metadata</span>; if this returns
1.85 ihickson 1152: an encoding, and the user agent supports that encoding, then let
1153: <var title="">character encoding</var> be that encoding.</p>
1154:
1155: </li>
1156:
1157: <li>
1158:
1159: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, then let <var title="">character
1160: encoding</var> be UTF-8.</p>
1161:
1162: </li>
1163:
1164: <li>
1165:
1166: <p>Convert the resource to Unicode using the character encoding
1167: given by <var title="">character encoding</var>.</p>
1168:
1169: <p>Return the text that is so obtained.</p>
1170:
1171: </li>
1172:
1.155 ihickson 1173: </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 has an <span>event
1.128 ihickson 1174: loop</span> distinct from those defined for <span title="unit of
1175: related similar-origin browsing contexts">units of related
1176: similar-origin browsing contexts</span>. This <span>event
1177: loop</span> has no associated <span>browsing context</span>, and its
1178: <span title="task queue">task queues</span> only have events,
1179: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1180: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1181: <a href="#run-a-worker">run a worker</a> algorithm.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object also has a <dfn id="dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</dfn> flag, which must
1.81 ihickson 1182: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1183: in the processing model section below.<p>Once the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set to
1.81 ihickson 1184: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1185: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1186: already on the queue are unaffected except where otherwise
1.115 ihickson 1187: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1188: timers stop firing, notifications for all pending asynchronous
1.155 ihickson 1189: operations are dropped, etc.<h3 id="the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</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
1190: <code>MessagePort</code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1191: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.81 ihickson 1192: consists of all the <code>MessagePort</code> objects that are
1193: entangled with another port and that have one (but only one) port
1194: owned by <var title="">worker global scope</var>. This list includes
1195: <!--all the <code>MessagePort</code> objects that are in events
1.68 ihickson 1196: pending in the <span>event loop</span>, as well as (commented out
1197: because in practice it makes no difference either way as far as I
1198: can tell, and it would be hard to strictly implement since these
1.81 ihickson 1199: ports might not yet be across the thread boundary)--> the implicit
1.155 ihickson 1200: <code>MessagePort</code> in the case of <a href="#dedicatedworkerglobalscope" title="DedicatedWorkerGlobalScope">dedicated workers</a>.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> also has a list of <dfn id="the-worker-s-workers">the
1.124 ihickson 1201: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1202: populated when the worker creates or obtains further workers.<p>Finally, each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> also has a list of
1.124 ihickson 1203: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1204: is empty; it is populated when the worker is created.<p>Whenever a <code>Document</code> <var title="">d</var> is <dfn id="add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">added to the
1.123 ihickson 1205: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1206: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1207: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1208: <var title="">d</var>, <a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's
1.123 ihickson 1209: documents">add <var title="">d</var> to <var title="">q</var>'s
1210: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.155 ihickson 1211: <code>Document</code>s</span></a>.</p><!-- suggestions welcome
1212: on making this sentence into understandable English --><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1213: Document">discarded</span>, it must be removed from the list of
1214: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.155 ihickson 1215: whose list contains that <code>Document</code>.<p>Given a <span>script's global scope</span> <var title="">o</var>
1.123 ihickson 1216: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1217: <code>Document</code> objects to add</dfn> depends on the type of
1218: <var title="">o</var>. If <var title="">o</var> is a
1219: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1220: nested worker), then the relevant <code>Document</code>s are the
1221: <code>Document</code>s that are in <var title="">o</var>'s own list
1222: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a>. Otherwise, <var title="">o</var> is a <code>Window</code> object, and the relevant
1223: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1224: <span>active document</span> of the <code>Window</code> object <var title="">o</var>.<hr><p>A worker is said to be a <dfn id="permissible-worker">permissible worker</dfn> if its
1.123 ihickson 1225: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1226: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1227: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1228: timers, database transactions, or network connections, or its list
1.124 ihickson 1229: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1230: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1231: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1232: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1233: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1234: <code>Document</code>s</a> are <span>fully active</span>.<p>A worker is said to be a <dfn id="suspendable-worker">suspendable worker</dfn> if it is
1.123 ihickson 1235: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.155 ihickson 1236: <a href="#permissible-worker">permissible worker</a>.<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
1.176 ihickson 1237: <span>URL</span> <var title="">url</var>, a browsing context <var title="">owner browsing context</var>, an origin <var title="">owner
1238: origin</var>, and with global scope <var title="">worker global
1239: scope</var>, it must run the following steps:<ol><li>
1.81 ihickson 1240:
1241: <p>Create a completely separate and parallel execution environment
1242: (i.e. a separate thread or process or equivalent construct), and
1.106 ihickson 1243: run the rest of these steps asynchronously in that context.</p>
1.81 ihickson 1244:
1245: </li>
1.4 ihickson 1246:
1.101 ihickson 1247: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1248: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1249: shared worker), and there are any <span title="relevant application
1250: cache">relevant application caches</span> that are identified by a
1251: manifest URL with the <span>same origin</span> as <var title="">url</var> and that have <var title="">url</var> as one of
1.115 ihickson 1252: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1253: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1254: cache</span> of those that match.</li>
1255:
1.4 ihickson 1256: <li>
1.52 ihickson 1257:
1.176 ihickson 1258: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>.</p>
1259: <!-- not http-origin privacy sensitive -->
1.81 ihickson 1260:
1.129 ihickson 1261: <p>If the attempt fails, or if the attempt involves any redirects
1262: to URIs that do not have the <span>same origin</span> as <var title="">url</var> (even if the final URI is at the <span>same
1263: origin</span> as the original <var title="">url</var>), then for
1264: each <code><a href="#worker">Worker</a></code> or <code><a href="#sharedworker">SharedWorker</a></code> object
1265: associated with <var title="">worker global scope</var>,
1266: <span>queue a task</span> to <span>fire a simple event</span>
1.179 ihickson 1267: named <code title="event-error">error</code> at that
1.129 ihickson 1268: object. Abort these steps.</p>
1.7 ihickson 1269:
1.115 ihickson 1270: <p>If the attempt succeeds, then <a href="#decode-a-script-resource" title="decode a script
1.85 ihickson 1271: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1.81 ihickson 1272:
1.68 ihickson 1273: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1274:
1.115 ihickson 1275: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1276: type of the script is ignored. Unlike with <code>script</code>
1277: elements, there is no way to override the type. It's always
1.170 ihickson 1278: assumed to be JavaScript.</p>
1.81 ihickson 1279:
1280: </li>
1.7 ihickson 1281:
1282: <li>
1.68 ihickson 1283:
1.115 ihickson 1284: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1285: created, as follows.</p>
1286:
1287: <p>Create a new <span>script execution environment</span>
1288: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1289:
1.68 ihickson 1290: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1291: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1292: entry-points</span>; set the <i>initial code entry-point</i> to
1293: the entry-point for any executable code to be immediately run.</p>
1294:
1295: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1296:
1297: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1298:
1.83 ihickson 1299: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1300: UTF-8. (This is just used for encoding non-ASCII characters in the
1301: query component of URLs.)</p>
1.68 ihickson 1302:
1303: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1304:
1.81 ihickson 1305: </li>
1.4 ihickson 1306:
1307: <li>
1.81 ihickson 1308:
1309: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1310: worker such that no sooner than it stops being either a
1311: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1312: worker</a>, and no later than it stops being a
1313: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1314: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1315: to true<!-- v2-onclose and <span title="queue a task">a task is
1.179 ihickson 1316: queued</span> to <span>fire a simple event</span> named <code
1.123 ihickson 1317: title="event-close">close</code> at <var title="">worker global
1318: scope</var>-->.</p>
1.81 ihickson 1319:
1320: </li>
1.9 ihickson 1321:
1322: <li>
1.7 ihickson 1323:
1.81 ihickson 1324: <p><strong>Suspending workers</strong>: Start monitoring the
1325: worker, such that whenever <var title="">worker global
1.115 ihickson 1326: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1327: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1328: agent suspends execution of script in that worker until such time
1.115 ihickson 1329: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1330: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1331: worker</a>.</p>
1.4 ihickson 1332:
1.81 ihickson 1333: </li>
1.68 ihickson 1334:
1335: <li>
1.4 ihickson 1336:
1.81 ihickson 1337: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1338: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1339: entry-point</i>, and let that run until it either returns, fails
1340: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1341: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1342: algorithms defined below.</p>
1343:
1.149 ihickson 1344: <!-- v2-onclose
1345: <p class="note">If the script gets aborted by the "<span>kill a
1346: worker</span>" algorithm, then that same algorithm will cause
1.115 ihickson 1347: there to only be a single <span title="concept-task">task</span>
1.81 ihickson 1348: in the <span>event loop</span> at the next step, namely the task
1.115 ihickson 1349: for the <code title="message-close">close</code> event. The
1.149 ihickson 1350: "<span>terminate a worker</span>" algorithm removes all the
1.81 ihickson 1351: events.</p>
1.149 ihickson 1352: -->
1.4 ihickson 1353:
1.81 ihickson 1354: </li>
1.4 ihickson 1355:
1.95 ihickson 1356: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1357: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1358: a dedicated worker), then enable the <span>port message
1359: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1360:
1.4 ihickson 1361: <li>
1.68 ihickson 1362:
1.115 ihickson 1363: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1364: loop</span>'s <span title="task queue">task queues</span> or <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1365: to true.</p>
1.43 ihickson 1366:
1.81 ihickson 1367: </li>
1.4 ihickson 1368:
1369: <li>
1370:
1.81 ihickson 1371: <p>Run the oldest task on one of the <span>event loop</span>'s
1372: <span title="task queue">task queues</span>, if any. The user
1373: agent may pick any <span>task queue</span>.</p>
1374:
1.115 ihickson 1375: <p class="note">The handling of events or the execution of
1376: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1377: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1378: defined below.</p>
1.8 ihickson 1379:
1.81 ihickson 1380: </li>
1.4 ihickson 1381:
1382: <li>
1383:
1.81 ihickson 1384: <p>Remove the task run in the previous step, if any, from its
1385: <span>task queue</span>.</p>
1.4 ihickson 1386:
1.81 ihickson 1387: </li>
1.4 ihickson 1388:
1389: <li>
1.8 ihickson 1390:
1.81 ihickson 1391: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1392: <span title="task queue">task queues</span> or if <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1393: to false, then jump back to the step above labeled <i>event
1394: loop</i>.</p>
1.8 ihickson 1395:
1.81 ihickson 1396: </li>
1.8 ihickson 1397:
1398: <li>
1.71 ihickson 1399:
1.123 ihickson 1400: <p>If there are any outstanding transactions that have callbacks
1401: that involve <span title="concept-script">scripts</span> whose
1402: <span title="script's global object">global object</span> is the
1403: <var title="">worker global scope</var>, roll them back (without
1404: invoking any of the callbacks).</p>
1.50 ihickson 1405:
1.123 ihickson 1406: </li>
1407:
1408: <li>
1409:
1410: <p>Empty the <var title="">worker global scope</var>'s <span>list
1411: of active timeouts</span> and its <span>list of active
1412: intervals</span>.</p>
1.50 ihickson 1413:
1.81 ihickson 1414: </li>
1.50 ihickson 1415:
1.123 ihickson 1416: <!-- v2-onclose
1.81 ihickson 1417: <li>
1.50 ihickson 1418:
1.123 ihickson 1419: <p>For each <code>Worker</code> or <code>SharedWorker</code>
1.81 ihickson 1420: object associated with <var title="">worker global scope</var>,
1421: <span>queue a task</span> to <span>fire a simple event</span>
1.179 ihickson 1422: named <code title="event-close">close</code> at that object.</p>
1.5 ihickson 1423:
1.81 ihickson 1424: </li>
1.123 ihickson 1425: -->
1.155 ihickson 1426: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1427: run the following steps in parallel with the worker's main loop (the
1.155 ihickson 1428: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><!-- v2-onclose
1.123 ihickson 1429: <li><p>If the worker's <code>WorkerGlobalScope</code> object's
1430: <span title="dom-WorkerGlobalScope-closing">closing</span> flag is
1.81 ihickson 1431: false, <span>queue a task</span> to <span>fire a simple
1.179 ihickson 1432: event</span> named <code title="event-close">close</code> at the
1.123 ihickson 1433: worker's <code>WorkerGlobalScope</code> object.</p></li>
1.155 ihickson 1434: --><li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1435: true.</li>
1436:
1.123 ihickson 1437: <!-- v2-onclose
1438: <li><p>Wait a user-agent-defined amount of time. If the "<span>run
1439: a worker</span>" processing model defined above immediately starts
1440: running event listeners registered for the <code
1441: title="event-close">close</code> event, this time should not be
1442: zero — the idea is that the <code
1443: title="event-close">close</code> event can be used to clean up
1444: when shutting down unexpectedly.</p></li>
1445: -->
1.81 ihickson 1446:
1.115 ihickson 1447: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1448: queued in the <span>event loop</span>'s <span title="task
1.123 ihickson 1449: queue">task queues</span><!-- v2-onclose other than the <code
1450: title="event-close">close</code> event that this algorithm just
1451: added-->, discard them without processing them.</li>
1.81 ihickson 1452:
1.123 ihickson 1453: <!-- v2-onclose
1.115 ihickson 1454: <li><p>If the <code title="event-close">close</code> event that
1.81 ihickson 1455: this algorithm just queued hasn't yet been dispatched, then abort
1.123 ihickson 1456: the script currently running in the worker.</p></li>
1457: -->
1.81 ihickson 1458:
1459: <li><p>Wait a user-agent-defined amount of time.</li>
1460:
1.123 ihickson 1461: <li><p>Abort the script currently running in the worker<!--
1462: v2-onclose (if any script is running, then it will be a handler for
1463: the <code title="event-close">close</code> event)-->.</li>
1.81 ihickson 1464:
1.155 ihickson 1465: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1466: processing model on a worker at any time, e.g. in response to user
1467: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1468: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1469: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1470: set to true.<hr><p>When a user agent is to <dfn id="terminate-a-worker">terminate a worker</dfn> it must run
1.81 ihickson 1471: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1472: "<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
1.115 ihickson 1473: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1474: true.</li>
1475:
1.115 ihickson 1476: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1477: queued in the <span>event loop</span>'s <span title="task
1478: queue">task queues</span>, discard them without processing
1479: them.</li>
1480:
1481: <li><p>Abort the script currently running in the worker.</li>
1482:
1.115 ihickson 1483: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1484: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1485: worker is a dedicated worker), then empty the <span>port message
1486: queue</span> of the port that the worker's implicit port is
1487: entangled with.</li>
1488:
1.155 ihickson 1489: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1490: <span>DOM manipulation task source</span>.<h3 id="runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</h3><p>Whenever an uncaught runtime script error occurs in one of the
1.143 ihickson 1491: worker's scripts, if the error did not occur while handling a
1492: previous script error, the user agent must <span>report the
1493: error</span> using the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code>
1.155 ihickson 1494: attribute. <a href="#refsHTML5">[HTML5]</a><p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1495: the error occurred while handling a previous script error, the error
1.155 ihickson 1496: should be reported to the user. <a href="#refsHTML5">[HTML5]</a><p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1497: the error occurred while handling a previous script error, the user
1.123 ihickson 1498: agent must <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1499: event</a> at the <code><a href="#worker">Worker</a></code> object associated with the
1.155 ihickson 1500: worker.<p>When the user agent is to <dfn id="fire-a-worker-error-event">fire a worker error event</dfn> at
1.118 ihickson 1501: a <code><a href="#worker">Worker</a></code> object, it must dispatch an event that uses
1502: the <code><a href="#errorevent">ErrorEvent</a></code> interface, with the name <code title="event-error">error</code>, that doesn't bubble and is
1.115 ihickson 1503: cancelable, with its <code title="dom-ErrorEvent-message"><a href="#dom-errorevent-message">message</a></code>, <code title="dom-ErrorEvent-filename"><a href="#dom-errorevent-filename">filename</a></code>, and <code title="dom-ErrorEvent-lineno"><a href="#dom-errorevent-lineno">lineno</a></code> attributes set
1.81 ihickson 1504: appropriately. The default action of this event depends on whether
1.115 ihickson 1505: the <code><a href="#worker">Worker</a></code> object is itself in a worker. If it is, and
1.81 ihickson 1506: that worker is also a dedicated worker, then the user agent must
1.118 ihickson 1507: again <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1508: event</a> at the <code><a href="#worker">Worker</a></code> object associated with
1509: <em>that</em> worker. Otherwise, then the error should be reported
1.155 ihickson 1510: to the user.<p>The <span>task source</span> for the tasks mentioned above is the
1511: <span>DOM manipulation task source</span>.<hr><pre class="idl">interface <dfn id="errorevent">ErrorEvent</dfn> : Event {
1.147 ihickson 1512: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1513: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1514: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.147 ihickson 1515: void <a href="#dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent">initErrorEvent</a>(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString messageArg, in DOMString filenameArg, in unsigned long linenoArg);
1516: 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 DOMString messageArg, in DOMString filenameArg, in unsigned long linenoArg);
1.155 ihickson 1517: };</pre><p>The <dfn id="dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent"><code>initErrorEvent()</code></dfn>
1.115 ihickson 1518: and <dfn id="dom-errorevent-initerroreventns" title="dom-ErrorEvent-initErrorEventNS"><code>initErrorEventNS()</code></dfn>
1.81 ihickson 1519: methods must initialize the event in a manner analogous to the
1.155 ihickson 1520: similarly-named methods in the DOM Events interfaces. <a href="#refsDOMEVENTS">[DOMEVENTS]</a><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn>
1521: attribute represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1.81 ihickson 1522: attribute represents the <span>absolute URL</span> of the script in
1.155 ihickson 1523: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.132 ihickson 1524: attribute represents the line number where the error occurred in the
1.155 ihickson 1525: 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> {
1.144 ihickson 1526: attribute <span>Function</span> <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1527: <!-- v2-onclose attribute <span>Function</span> <span title="handler-AbstractWorker-onclose">onclose</span>; -->
1.172 ihickson 1528: };
1.177 ihickson 1529: <a href="#abstractworker">AbstractWorker</a> implements <span>EventTarget</span>;</pre><p>The following are the <span>event handlers</span> (and their
1530: corresponding <span title="event handler event type">event handler
1531: event types</span>) that must be supported, as IDL attributes, by
1532: objects implementing the <code><a href="#abstractworker">AbstractWorker</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1533: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.123 ihickson 1534: <!-- v2-onclose <tr><td><dfn title="handler-AbstractWorker-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code> -->
1.155 ihickson 1535: </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)]
1.115 ihickson 1536: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1537: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1538:
1.174 ihickson 1539: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(in any message, in optional <span>MessagePortArray</span> ports);<!--
1.81 ihickson 1540: <span>MessagePort</span> <span title="dom-Worker-startConversation">startConversation</span>(in any message);-->
1.144 ihickson 1541: attribute <span>Function</span> <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.155 ihickson 1542: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1543: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1544: algorithm to be run on the worker with with the object is
1.155 ihickson 1545: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.81 ihickson 1546: <code>MessagePort</code> associated with them. This port is part of
1547: a channel that is set up when the worker is created, but it is not
1548: exposed. This object must never be garbage collected before the
1.155 ihickson 1549: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1550: 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 1551: and <dfn
1552: title="dom-Worker-startConversation"><code>startConversation()</code></dfn>-->
1.115 ihickson 1553: method<!--s (startConversation)--> on <code><a href="#worker">Worker</a></code> objects
1.81 ihickson 1554: must act as if, when invoked, it<!--/they (startConversation)-->
1555: immediately invoked the method of the same name on the port, with
1.177 ihickson 1556: the same arguments, and returned the same return value.<p>The following are the <span>event handlers</span> (and their
1557: corresponding <span title="event handler event type">event handler
1558: event types</span>) that must be supported, as IDL attributes, by
1559: objects implementing the <code><a href="#worker">Worker</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1560: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1561: </table><hr><p>When the <dfn id="dom-worker" title="dom-Worker"><code>Worker(<var title="">scriptURL</var>)</code></dfn> constructor is invoked, the
1562: user agent must run the following steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument relative to the <span>first
1.133 ihickson 1563: script</span>'s <span title="script's base URL">base URL</span>,
1564: when the method is invoked.</li>
1.9 ihickson 1565:
1.81 ihickson 1566: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1567: exception.</li>
1.9 ihickson 1568:
1.167 ihickson 1569: <li>
1570:
1571: <p>If the <span>origin</span> of the resulting <span>absolute
1572: URL</span> is not the <span title="same origin">same</span> as the
1.176 ihickson 1573: origin of the <span>first script</span>, then throw a
1.182 ihickson 1574: <code>SECURITY_ERR</code> exception.</p>
1.167 ihickson 1575:
1576: <p class="note">Thus, scripts must be external files with the same
1577: scheme as the original page: you can't load a script from a <code title="">data:</code> URL or <code title="">javascript:</code>
1578: URL, and a <code>http:</code> page couldn't start workers using
1579: scripts with <code>http:</code> URLs.</p>
1580:
1581: </li>
1.9 ihickson 1582:
1.115 ihickson 1583: <li><p><span>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1.81 ihickson 1584: object</span>. Let <var title="">worker global scope</var> be this
1585: new object.</li>
1.9 ihickson 1586:
1.115 ihickson 1587: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1588: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1589:
1.81 ihickson 1590: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1.123 ihickson 1591: by the <span title="script's global scope">global scope</span> of
1592: the <span title="concept-script">script</span> that invoked the
1593: constructor. Let this be the <var title="">outside
1.81 ihickson 1594: port</var>.</li>
1.9 ihickson 1595:
1.81 ihickson 1596: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1597:
1.81 ihickson 1598: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1599: by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1600:
1.81 ihickson 1601: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1602:
1.81 ihickson 1603: <li><p><span>Entangle</span> <var title="">outside port</var> and
1604: <var title="">inside port</var>.</li>
1.50 ihickson 1605:
1.81 ihickson 1606: <li><p>Return <var title="">worker</var>, and run the following
1607: steps asynchronously.</li>
1.50 ihickson 1608:
1.126 ihickson 1609: <li><p>Enable <var title="">inside port</var>'s <span>port message
1.81 ihickson 1610: queue</span>.</li>
1.50 ihickson 1611:
1.126 ihickson 1612: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1613: queue</span>.</li>
1.50 ihickson 1614:
1615: <li>
1.51 ihickson 1616:
1.123 ihickson 1617: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1618: <code>Document</code> objects to add</a> given the <span title="script's global scope">global scope</span> of the <span title="concept-script">script</span> that invoked the
1619: constructor.</p>
1620:
1621: </li>
1622:
1623: <li>
1624:
1625: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1626: <var title="">worker global scope</var>'s list of <span>the
1627: worker's <code>Document</code>s</span></a> the
1628: <code>Document</code> objects in <var title="">docs</var>.</p>
1629:
1630: </li>
1631:
1632: <li>
1633:
1.124 ihickson 1634: <p>If the <span title="script's global scope">global scope</span>
1635: of the <span title="concept-script">script</span> that invoked the
1636: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1637: are creating a nested worker), add <var title="">worker global
1638: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1639: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object that is the <span title="script's global scope">global scope</span> of the <span title="concept-script">script</span> that invoked the
1640: constructor.</p>
1641:
1642: </li>
1643:
1644: <li>
1645:
1.115 ihickson 1646: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.81 ihickson 1647: URL</span>, with the <span>script browsing context</span> of the
1648: script that invoked the method as the <var title="">owner browsing
1.176 ihickson 1649: context</var>, with the <span>origin</span> of the <span>first
1650: script</span> as the <var title="">owner origin</var>, and with
1651: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1652:
1.81 ihickson 1653: </li>
1.4 ihickson 1654:
1.155 ihickson 1655: </ol><p>This constructor must be visible when the <span>script's global
1.135 ihickson 1656: scope</span> is either a <code>Window</code> object or an object
1.174 ihickson 1657: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<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 optional DOMString name)]
1.115 ihickson 1658: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1659: readonly attribute <span>MessagePort</span> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.155 ihickson 1660: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1661: attribute must return the value it was assigned by the object's
1662: constructor. It represents the <code>MessagePort</code> for
1.155 ihickson 1663: communicating with the shared worker.<p>When the <dfn id="dom-sharedworker" title="dom-SharedWorker"><code>SharedWorker(<var title="">scriptURL</var>, <var title="">name</var>)</code></dfn>
1.81 ihickson 1664: constructor is invoked, the user agent must run the following
1.155 ihickson 1665: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1666:
1667: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1668: exception.</li>
1669:
1.159 ihickson 1670: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1671: resulting <span>absolute URL</span>.</li>
1672:
1673: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1674: argument, or the empty string if the second argument was
1675: omitted.</li>
1.159 ihickson 1676:
1.167 ihickson 1677: <li>
1678:
1679: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1680: not the <span title="same origin">same</span> as the origin of the
1.182 ihickson 1681: <span>first script</span>, then throw a <code>SECURITY_ERR</code>
1682: exception.</p>
1.167 ihickson 1683:
1684: <p class="note">Thus, scripts must be external files with the same
1685: scheme as the original page: you can't load a script from a <code title="">data:</code> URL or <code title="">javascript:</code>
1686: URL, and a <code>http:</code> page couldn't start workers using
1687: scripts with <code>http:</code> URLs.</p>
1688:
1689: </li>
1.9 ihickson 1690:
1691: <li>
1692:
1.123 ihickson 1693: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1694: <code>Document</code> objects to add</a> given the <span title="script's global scope">global scope</span> of the <span title="concept-script">script</span> that invoked the
1695: constructor.</p>
1696:
1697: </li>
1698:
1699: <li>
1700:
1.50 ihickson 1701: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1702:
1.155 ihickson 1703: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1704: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1705: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1706:
1.123 ihickson 1707: <li><p><span>Create a <code>MessagePort</code> object</span>
1708: owned by the <span title="script's global scope">global
1709: scope</span> of the script that invoked the method. Let this be
1710: the <var title="">outside port</var>.</li>
1.81 ihickson 1711:
1.115 ihickson 1712: <li><p>Assign <var title="">outside port</var> to the <code title="dom-SharedWorker-port"><a href="#dom-sharedworker-port">port</a></code> attribute of <var title="">worker</var>.</li>
1.81 ihickson 1713:
1.164 ihickson 1714: <li><p>Let <var title="">worker global scope</var> be
1715: null.</li>
1716:
1717: <li><p>If <var title="">name</var> is not the empty string and
1718: there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose
1719: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag
1720: is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1721: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1722: represents an <span>absolute URL</span> with the <span>same
1723: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1724: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1725:
1726: <li><p>Otherwise, if <var title="">name</var> is the empty string
1727: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1728: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1729: flag is false, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1730: is exactly equal to <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1731: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1732:
1.9 ihickson 1733: <li>
1734:
1.164 ihickson 1735: <p>If <var title="">worker global scope</var> is not null, then
1736: run these steps:</p>
1.81 ihickson 1737:
1.164 ihickson 1738: <ol><li><p>If <var title="">worker global scope</var>'s <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code>
1.81 ihickson 1739: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1740: exactly equal to <var title="">scriptURL</var>, then throw a
1741: <code>URL_MISMATCH_ERR</code> exception and abort all these
1742: steps.</li>
1.81 ihickson 1743:
1744: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1745:
1746: <li><p><span>Create a <code>MessagePort</code> object</span>
1747: owned by <var title="">worker global scope</var>. Let this
1748: be the <var title="">inside port</var>.</li>
1749:
1750: <li><p><span>Entangle</span> <var title="">outside port</var>
1751: and <var title="">inside port</var>.</li>
1752:
1753: <li><p>Return <var title="">worker</var> and perform the next
1754: step asynchronously.</li>
1.9 ihickson 1755:
1.81 ihickson 1756: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1757: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1758: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1759: is the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1760: value is an array containing only the newly created port, and
1761: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.43 ihickson 1762:
1.123 ihickson 1763: <li>
1764:
1765: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1766: <var title="">worker global scope</var>'s list of <span>the
1767: worker's <code>Document</code>s</span></a> the
1768: <code>Document</code> objects in <var title="">docs</var>.</p>
1769:
1770: </li>
1771:
1.124 ihickson 1772: <li>
1773:
1774: <p>If the <span title="script's global scope">global
1775: scope</span> of the <span title="concept-script">script</span>
1776: that invoked the constructor is a
1777: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, add <var title="">worker global scope</var> to the list of <a href="#the-worker-s-workers">the
1778: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1779: object that is the <span title="script's global scope">global
1780: scope</span> of the <span title="concept-script">script</span>
1781: that invoked the constructor.</p>
1782:
1783: </li>
1784:
1.81 ihickson 1785: <li><p>Abort all these steps.</li>
1.9 ihickson 1786:
1.155 ihickson 1787: </ol></li>
1.9 ihickson 1788:
1.115 ihickson 1789: <li><p><span>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1.81 ihickson 1790: object</span>. Let <var title="">worker global scope</var> be
1791: this new object.</li>
1.9 ihickson 1792:
1.81 ihickson 1793: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1794:
1.115 ihickson 1795: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1796: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1797:
1.81 ihickson 1798: <li><p><span>Create a <code>MessagePort</code> object</span>
1799: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1800:
1.81 ihickson 1801: <li><p><span>Entangle</span> <var title="">outside port</var> and
1802: <var title="">inside port</var>.</li>
1.9 ihickson 1803:
1.155 ihickson 1804: </ol></li>
1.28 ihickson 1805:
1.123 ihickson 1806: <li><p>Return <var title="">worker</var> and perform the remaining
1807: steps asynchronously.</li>
1.18 ihickson 1808:
1.81 ihickson 1809: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1810: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1811: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.118 ihickson 1812: the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1813: is an array containing only the newly created port, and <span>queue
1814: a task</span> to dispatch the event at <var title="">worker global
1815: scope</var>.</li>
1.26 ihickson 1816:
1817: <li>
1.46 ihickson 1818:
1.123 ihickson 1819: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1820: <var title="">worker global scope</var>'s list of <span>the
1821: worker's <code>Document</code>s</span></a> the
1822: <code>Document</code> objects in <var title="">docs</var>.</p>
1823:
1824: </li>
1825:
1826: <li>
1827:
1.124 ihickson 1828: <p>If the <span title="script's global scope">global scope</span>
1829: of the <span title="concept-script">script</span> that invoked the
1830: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, add <var title="">worker global scope</var> to the list of <a href="#the-worker-s-workers">the
1831: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1832: object that is the <span title="script's global scope">global
1833: scope</span> of the <span title="concept-script">script</span>
1834: that invoked the constructor.</p>
1835:
1836: </li>
1837:
1838: <li>
1839:
1.159 ihickson 1840: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1841: with the <span>script browsing context</span> of the script that
1842: invoked the method as the <var title="">owner browsing
1.176 ihickson 1843: context</var>, with the <span>origin</span> of the <span>first
1844: script</span> as the <var title="">owner origin</var>, and with
1845: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1846:
1.60 ihickson 1847: </li>
1.81 ihickson 1848:
1.155 ihickson 1849: </ol><p>This constructor must be visible when the <span>script's global
1.135 ihickson 1850: scope</span> is either a <code>Window</code> object or an object
1.155 ihickson 1851: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<p>The <span>task source</span> for the tasks mentioned above is the
1852: <span>DOM manipulation task source</span>.<h2 id="apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</h2><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1853: interface <dfn id="workerutils">WorkerUtils</dfn> {
1854: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(in DOMString... urls);
1.115 ihickson 1855: readonly attribute <a href="#worker-navigator" title="worker-Navigator">Navigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1856: };
1.184 ! ihickson 1857: <a href="#workerutils">WorkerUtils</a> implements <span>WindowTimers</span>;</pre><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1858: objects, etc) are not available to workers in this version of this
1.155 ihickson 1859: 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
1.115 ihickson 1860: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1861: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1862: anything. Abort these steps.</li>
1863:
1864: <li><p><span title="resolve a url">Resolve</span> each
1865: argument.</li>
1866:
1867: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1868: exception.</li>
1869:
1870: <!--
1.67 ihickson 1871: <li><p>If any of the resulting <span title="absolute URL">absolute
1872: URLs</span> have an <span>origin</span> that is not the <span
1873: title="same origin">same</span> as the origin of the script that
1.182 ihickson 1874: invoked the method, then throw a <code>SECURITY_ERR</code>
1875: exception.</p></li>
1.67 ihickson 1876: -->
1.26 ihickson 1877:
1878: <li>
1.81 ihickson 1879:
1.45 ihickson 1880: <p>Attempt to <span>fetch</span> each resource identified by the
1.176 ihickson 1881: resulting <span title="absolute URLs">absolute URL</span>, from
1882: the <span>first script</span>'s <span>origin</span>.</p> <!-- not
1883: http-origin privacy sensitive -->
1.81 ihickson 1884:
1885: </li>
1.26 ihickson 1886:
1887: <li>
1888:
1.81 ihickson 1889: <p>For each argument in turn, in the order given, starting with
1890: the first one, run these substeps:</p>
1.26 ihickson 1891:
1.155 ihickson 1892: <ol><li>
1.26 ihickson 1893:
1.81 ihickson 1894: <p>Wait for the fetching attempt for the corresponding resource
1895: to complete.</p>
1.60 ihickson 1896:
1.81 ihickson 1897: <p>If the fetching attempt failed, throw a
1898: <code>NETWORK_ERR</code> exception and abort all these
1899: steps.</p>
1.45 ihickson 1900:
1.115 ihickson 1901: <p>If the attempt succeeds, then <a href="#decode-a-script-resource" title="decode a script
1.85 ihickson 1902: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1903:
1904: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1905:
1.115 ihickson 1906: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1907: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1908: type.</p>
1.61 ihickson 1909:
1.81 ihickson 1910: </li>
1.26 ihickson 1911:
1.81 ihickson 1912: <li>
1.26 ihickson 1913:
1.81 ihickson 1914: <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
1915: same global object, browsing context, character encoding, base
1.115 ihickson 1916: URL, and script group as the <span title="concept-script">script</span> that was created by the
1917: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1918:
1.115 ihickson 1919: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1920: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1921: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1922: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1923:
1.170 ihickson 1924: <p>If it failed to parse, then throw a <code>SyntaxError</code>
1925: exception and abort all these steps.</p>
1.63 ihickson 1926:
1.81 ihickson 1927: <p>If an exception was raised or if the script was prematurely
1928: aborted, then abort all these steps, letting the exception or
1929: aborting continue to be processed by the script that called the
1.115 ihickson 1930: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1931: method.</p>
1932:
1.115 ihickson 1933: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1934: worker</a>" algorithms abort the script then abort all these
1935: steps.</p>
1936:
1937: </li>
1938:
1.155 ihickson 1939: </ol></li>
1.152 ihickson 1940:
1.155 ihickson 1941: </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
1.115 ihickson 1942: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1943: the <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> interface, which
1.93 ihickson 1944: represents the identity and state of the user agent (the
1.155 ihickson 1945: client):<pre class="idl">interface <dfn id="worker-navigator" title="worker-Navigator">Navigator</dfn> {};
1.150 ihickson 1946: <a href="#worker-navigator" title="worker-Navigator">Navigator</a> implements <span>NavigatorID</span>;
1.155 ihickson 1947: <a href="#worker-navigator" title="worker-Navigator">Navigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> interface also implement
1.150 ihickson 1948: the <code>NavigatorID</code> and <code>NavigatorOnLine</code>
1.155 ihickson 1949: interfaces. <a href="#refsHTML5">[HTML5]</a><p class="note">The <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code>
1.93 ihickson 1950: interface defined in this specification is different than the one
1.155 ihickson 1951: defined in the HTML 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
1.115 ihickson 1952: <code title="dom-opendatabase-sync">openDatabaseSync()</code>
1.155 ihickson 1953: methods are defined in the Web Database specification. <a href="#refsWEBDATABASE">[WEBDATABASE]</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 1954: the global scope of scripts whose <span>script execution
1.115 ihickson 1955: context</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1956: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1957: constructors defined by the XMLHttpRequest specifications, except
1958: that the <span>document response entity body</span> must always be
1.160 ihickson 1959: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1960: <span>script's base URL</span>; the
1961: <span><code>XMLHttpRequest</code> origin</span> is the script's
1962: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1963:
1964: <li><p>The <code>WebSocket</code> interface object and
1.152 ihickson 1965: constructor. <a href="#refsWEBSOCKET">[WEBSOCKET]</a></li>
1.81 ihickson 1966:
1.119 ihickson 1967: <li><p>The <code>EventSource</code> interface object and
1.152 ihickson 1968: constructor. <a href="#refsEVENTSOURCE">[EVENTSOURCE]</a></li>
1.119 ihickson 1969:
1.81 ihickson 1970: <li><p>The <code>MessageChannel</code> interface object and
1.152 ihickson 1971: constructor. <a href="#refsHTML5">[HTML5]</a></li>
1.81 ihickson 1972:
1.183 ihickson 1973: <li><p>The <code title="dom-Worker"><a href="#dom-worker">Worker</a></code> and <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker</a></code> interface objects and
1974: constructors.</li>
1.81 ihickson 1975:
1.155 ihickson 1976: </ul><h3 id="worker-locations"><span class="secno">5.5 </span>Worker locations</h3><pre class="idl">interface <dfn id="workerlocation">WorkerLocation</dfn> {
1.115 ihickson 1977: readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1978: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1979: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1980: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1981: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1982: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1983: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1984: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1985: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1986: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1987: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1988: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1989: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1990: <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>,
1991: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1992: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1993: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>. These must
1.163 ihickson 1994: follow the rules given for URL decomposition IDL attributes, with the
1.115 ihickson 1995: <span title="concept-uda-input">input</span> being the
1.81 ihickson 1996: <span>absolute URL</span> that the object represents (same as the
1.115 ihickson 1997: <code title="dom-WorkerLocation-href"><a href="#dom-workerlocation-href">href</a></code> attribute), and
1998: the <span title="concept-uda-setter">common setter action</span>
1.178 ihickson 1999: being a no-op, since the attributes are defined to be readonly. <a href="#refsHTML5">[HTML5]</a></p><!--START vCard--><!--START vEvent--><h2 class="no-num" id="references">References</h2><!--REFS--><!--END vCard--><!--END vEvent--><p>All references are normative unless marked "Non-normative".</p><!--START vCard--><!--START vEvent--><dl><dt id="refsDOMCORE">[DOMCORE]</dt>
1.153 ihickson 2000: <dd><cite><a href="http://www.w3.org/TR/DOM-Level-3-Core/">Document
2001: Object Model (DOM) Level 3 Core Specification</a></cite>, A. Le
2002: Hors, P. Le Hegaret, L. Wood, G. Nicol, J. Robie, M. Champion,
2003: S. Byrnes. W3C, April 2004.</dd>
2004: <!--
2005: <dd><cite><a href="http://simon.html5.org/specs/web-dom-core">Web
2006: DOM Core</a></cite>, S. Pieters. W3C, June 2009.</dd>
2007: -->
2008:
1.152 ihickson 2009: <dt id="refsDOMEVENTS">[DOMEVENTS]</dt>
2010: <!--
2011: <dd><cite><a
2012: href="http://www.w3.org/TR/DOM-Level-3-Events/">Document Object
2013: Model (DOM) Level 3 Events Specification</a></cite>,
2014: B. Höhrmann, P. Le Hegaret, T. Pixley. W3C, December
2015: 2007.</dd>
2016: -->
2017: <dd><cite><a href="http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html">Document
2018: Object Model (DOM) Level 3 Events Specification</a></cite>,
2019: D. Schepers. W3C, July 2009.</dd>
2020:
2021: <dt id="refsECMA262">[ECMA262]</dt>
2022: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
2023: Language Specification</a></cite>. ECMA, December 1999.</dd>
2024:
2025: <dt id="refsEVENTSOURCE">[EVENTSOURCE]</dt>
2026: <!--
2027: <dd><cite><a href="http://www.w3.org/TR/eventsource/">Server-Sent
2028: Events</a></cite>, I. Hickson. W3C, April 2009.</dd>
2029: -->
2030: <dd><cite><a href="http://dev.w3.org/html5/eventsource/">Server-Sent
2031: Events</a></cite>, I. Hickson. W3C, July 2009.</dd>
2032:
2033: <dt id="refsHTML5">[HTML5]</dt>
2034: <!--
1.161 ihickson 2035: <dd><cite><a href="http://www.w3.org/TR/html5/">HTML5</a></cite>,
1.152 ihickson 2036: I. Hickson, D. Hyatt. W3C, April 2009.</dd>
1.161 ihickson 2037: <dd><cite><a
2038: href="http://www.w3.org/html/wg/html5/">HTML5</a></cite>,
2039: I. Hickson, D. Hyatt. W3C, August 2009.</dd>
1.152 ihickson 2040: -->
1.161 ihickson 2041: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML5</a></cite>,
2042: I. Hickson. WHATWG, August 2009.</dd>
1.152 ihickson 2043:
1.154 ihickson 2044: <dt id="refsRFC2119">[RFC2119]</dt>
2045: <dd><cite><a href="http://www.ietf.org/rfc/rfc2119.txt">Key words for use in
2046: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF, March
2047: 1997.</dd>
2048:
1.152 ihickson 2049: <dt id="refsWEBDATABASE">[WEBDATABASE]</dt>
2050: <dd><cite><a href="http://dev.w3.org/html5/webdatabase/">Web
2051: Database</a></cite>, I. Hickson. W3C, July
2052: 2009.</dd>
2053:
1.154 ihickson 2054: <dt id="refsWEBIDL">[WEBIDL]</dt>
2055: <!--
2056: <dd><cite><a href="http://www.w3.org/TR/WebIDL/">Web
2057: IDL</a></cite>, C. McCormack. W3C, December 2008.</dd>
2058: -->
2059: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
2060: IDL</a></cite>, C. McCormack. W3C, July 2009.</dd>
2061:
1.152 ihickson 2062: <dt id="refsWEBSOCKET">[WEBSOCKET]</dt>
2063: <!--
2064: <dd><cite><a href="http://www.w3.org/TR/websockets/">The Web Sockets
2065: API</a></cite>, I. Hickson. W3C, April
2066: 2009.</dd>
2067: -->
2068: <dd><cite><a href="http://dev.w3.org/html5/websockets/">The Web Sockets
2069: API</a></cite>, I. Hickson. W3C, August
2070: 2009.</dd>
2071:
2072: <dt id="refsXHR">[XHR]</dt>
2073: <!--
2074: <dd><cite><a href="http://www.w3.org/TR/XMLHttpRequest/">The XMLHttpRequest
2075: Object</a></cite>, A. van Kesteren. W3C, April
2076: 2008.</dd>
2077: -->
1.160 ihickson 2078: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.152 ihickson 2079: A. van Kesteren. W3C, June 2009.</dd>
2080:
1.178 ihickson 2081: </dl><!--END vCard--><!--END vEvent--><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 2082:
2083: Aaron Boodman,
1.155 ihickson 2084: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 2085: Anne van Kesteren,
2086: Ben Turner,
2087: Dmitry Titov,
1.96 ihickson 2088: Drew Wilson,
1.97 ihickson 2089: Jeremy Orlow,
1.81 ihickson 2090: Jonas Sicking,
2091: Justin James,
2092: Kevin Hakanson,
2093: Maciej Stachowiak,
2094: Michael Nordman,
2095: Mike Smith,
2096:
2097: and
2098:
2099: Philip Taylor
2100:
1.155 ihickson 2101: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 2102: technology and whose experience has been a huge influence on this
1.155 ihickson 2103: specification.
Webmaster
![[BACK]](/http/77726476706e69737468656265737421f4f257d23063265f6c0f/cvsweb/icons/back.gif?vpn-1){kind=icon}
Return to Overview.html CVS log ![[TXT]](/http/77726476706e69737468656265737421f4f257d23063265f6c0f/cvsweb/icons/text.gif?vpn-1){kind=icon}
![[DIR]](/http/77726476706e69737468656265737421f4f257d23063265f6c0f/cvsweb/icons/dir.gif?vpn-1){kind=icon}
Up to [Public] / html5 / workers