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