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<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01 Transitional//EN' 'http://www.w3.org/TR/html4/loose.dtd'>
<html lang="en" dir="ltr">
<head>
<title>File API: Directories and System</title>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<link href="respec.css" rel="stylesheet" type="text/css" charset="utf-8"><link href="http://www.w3.org/StyleSheets/TR/W3C-WD" rel="stylesheet" type="text/css" charset="utf-8"></head>
<body style="display: inherit; "><div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C"></a></p><h1 class="title" id="title">File API: Directories and System</h1><h2 id="w3c-working-draft-19-april-2011">W3C Working Draft 19 April 2011</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2011/WD-file-system-api-20110419/">http://www.w3.org/TR/2011/WD-file-system-api-20110419/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/file-system-api/">http://www.w3.org/TR/file-system-api/</a></dd><dt>Latest editor's draft:</dt><dd><a href="http://dev.w3.org/2009/dap/file-system/file-dir-sys.html">http://dev.w3.org/2009/dap/file-system/file-dir-sys.html</a></dd>
<dt>Previous version:</dt>
<dd><a href="http://www.w3.org/TR/2010/WD-file-system-api-20101026/">http://www.w3.org/TR/2010/WD-file-system-api-20101026/</a>
</dd><dt>Editor:</dt><dd><a href="http://www.ofb.net/~uranium/">Eric Uhrhane</a>, <a href="http://www.google.com/">Google</a></dd>
</dl><p class="copyright"><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
© 2011 <a href="http://www.w3.org/"><acronym title="World Wide Web
Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p><hr></div>
<div id="abstract" class="introductory section"><h2>Abstract</h2>
This specification defines an <acronym title="Application Programming
Interface">API</acronym> to navigate file system hierarchies, and defines
a means by which a <a href="#dfn-user-agent" class="internalDFN">user agent</a> may expose sandboxed sections of a
user's local filesystem to web applications. It builds on
[<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-WRITER">FILE-WRITER</a></cite>], which in turn built on [<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-API">FILE-API</a></cite>], each adding a
different kind of functionality.
</div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p><p>This document was published by the <a href="http://www.w3.org/2008/webapps/">WebApps Working Group</a> as a Working Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a> (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>). All feedback is welcome.</p><p>Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 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 any patent disclosures</a> made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>.</p></div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">1. </span>Conformance</a></li><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">2. </span>Introduction</a><ul class="toc"><li class="tocline"><a href="#use-cases" class="tocxref"><span class="secno">2.1 </span>Use Cases</a></li><li class="tocline"><a href="#examples" class="tocxref"><span class="secno">2.2 </span>Examples</a></li></ul></li><li class="tocline"><a href="#data-persistence-and-accessing-the-api" class="tocxref"><span class="secno">3. </span>Data Persistence and accessing the API</a><ul class="toc"><li class="tocline"><a href="#temporary-vs.-persistent-storage" class="tocxref"><span class="secno">3.1 </span>Temporary vs. Persistent Storage</a></li><li class="tocline"><a href="#restrictions" class="tocxref"><span class="secno">3.2 </span>Restrictions</a></li><li class="tocline"><a href="#security-considerations" class="tocxref"><span class="secno">3.3 </span>Security Considerations</a></li><li class="tocline"><a href="#obtaining-access-to-file-system-entry-points" class="tocxref"><span class="secno">3.4 </span>Obtaining access to file system entry points</a><ul class="toc"><li class="tocline"><a href="#using-localfilesystem" class="tocxref"><span class="secno">3.4.1 </span>Using <code>LocalFileSystem</code></a><ul class="toc"><li class="tocline"><a href="#methods" class="tocxref"><span class="secno">3.4.1.1 </span>Methods</a></li><li class="tocline"><a href="#constants" class="tocxref"><span class="secno">3.4.1.2 </span>Constants</a></li></ul></li><li class="tocline"><a href="#using-localfilesystemsync" class="tocxref"><span class="secno">3.4.2 </span>Using <code>LocalFileSystemSync</code></a><ul class="toc"><li class="tocline"><a href="#methods-1" class="tocxref"><span class="secno">3.4.2.1 </span>Methods</a></li><li class="tocline"><a href="#constants-1" class="tocxref"><span class="secno">3.4.2.2 </span>Constants</a></li></ul></li></ul></li></ul></li><li class="tocline"><a href="#shared-data-types" class="tocxref"><span class="secno">4. </span>Shared data types</a><ul class="toc"><li class="tocline"><a href="#the-metadata-interface" class="tocxref"><span class="secno">4.1 </span>The <code>Metadata</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes" class="tocxref"><span class="secno">4.1.1 </span>Attributes</a></li></ul></li><li class="tocline"><a href="#the-flags-interface" class="tocxref"><span class="secno">4.2 </span>The <code>Flags</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes-1" class="tocxref"><span class="secno">4.2.1 </span>Attributes</a></li><li class="tocline"><a href="#examples-1" class="tocxref"><span class="secno">4.2.2 </span>Examples</a></li></ul></li></ul></li><li class="tocline"><a href="#the-asynchronous-filesystem-interface" class="tocxref"><span class="secno">5. </span>The asynchronous filesystem interface</a><ul class="toc"><li class="tocline"><a href="#the-filesystem-interface" class="tocxref"><span class="secno">5.1 </span>The <code>FileSystem</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes-2" class="tocxref"><span class="secno">5.1.1 </span>Attributes</a></li></ul></li><li class="tocline"><a href="#the-entry-interface" class="tocxref"><span class="secno">5.2 </span>The <code>Entry</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes-3" class="tocxref"><span class="secno">5.2.1 </span>Attributes</a></li><li class="tocline"><a href="#methods-2" class="tocxref"><span class="secno">5.2.2 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-directoryentry-interface" class="tocxref"><span class="secno">5.3 </span>The <code>DirectoryEntry</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-3" class="tocxref"><span class="secno">5.3.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-directoryreader-interface" class="tocxref"><span class="secno">5.4 </span>The <code>DirectoryReader</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-4" class="tocxref"><span class="secno">5.4.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-fileentry-interface" class="tocxref"><span class="secno">5.5 </span>The <code>FileEntry</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-5" class="tocxref"><span class="secno">5.5.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#callbacks" class="tocxref"><span class="secno">5.6 </span>Callbacks</a><ul class="toc"><li class="tocline"><a href="#the-filesystemcallback-interface" class="tocxref"><span class="secno">5.6.1 </span>The <code>FileSystemCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-6" class="tocxref"><span class="secno">5.6.1.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-entrycallback-interface" class="tocxref"><span class="secno">5.6.2 </span>The <code>EntryCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-7" class="tocxref"><span class="secno">5.6.2.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-entriescallback-interface" class="tocxref"><span class="secno">5.6.3 </span>The <code>EntriesCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-8" class="tocxref"><span class="secno">5.6.3.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-metadatacallback-interface" class="tocxref"><span class="secno">5.6.4 </span>The <code>MetadataCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-9" class="tocxref"><span class="secno">5.6.4.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-filewritercallback-interface" class="tocxref"><span class="secno">5.6.5 </span>The <code>FileWriterCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-10" class="tocxref"><span class="secno">5.6.5.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-filecallback-interface" class="tocxref"><span class="secno">5.6.6 </span>The <code>FileCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-11" class="tocxref"><span class="secno">5.6.6.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-voidcallback-interface" class="tocxref"><span class="secno">5.6.7 </span>The <code>VoidCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-12" class="tocxref"><span class="secno">5.6.7.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-errorcallback-interface" class="tocxref"><span class="secno">5.6.8 </span>The <code>ErrorCallback</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-13" class="tocxref"><span class="secno">5.6.8.1 </span>Methods</a></li></ul></li></ul></li></ul></li><li class="tocline"><a href="#the-synchronous-filesystem-interface" class="tocxref"><span class="secno">6. </span>The synchronous filesystem interface</a><ul class="toc"><li class="tocline"><a href="#the-filesystemsync-interface" class="tocxref"><span class="secno">6.1 </span>The <code>FileSystemSync</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes-4" class="tocxref"><span class="secno">6.1.1 </span>Attributes</a></li></ul></li><li class="tocline"><a href="#the-entrysync-interface" class="tocxref"><span class="secno">6.2 </span>The <code>EntrySync</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes-5" class="tocxref"><span class="secno">6.2.1 </span>Attributes</a></li><li class="tocline"><a href="#methods-14" class="tocxref"><span class="secno">6.2.2 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-directoryentrysync-interface" class="tocxref"><span class="secno">6.3 </span>The <code>DirectoryEntrySync</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-15" class="tocxref"><span class="secno">6.3.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-directoryreadersync-interface" class="tocxref"><span class="secno">6.4 </span>The <code>DirectoryReaderSync</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-16" class="tocxref"><span class="secno">6.4.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#the-fileentrysync-interface" class="tocxref"><span class="secno">6.5 </span>The <code>FileEntrySync</code> interface</a><ul class="toc"><li class="tocline"><a href="#methods-17" class="tocxref"><span class="secno">6.5.1 </span>Methods</a></li></ul></li></ul></li><li class="tocline"><a href="#dealing-with-errors-and-exceptions" class="tocxref"><span class="secno">7. </span>Dealing with errors and exceptions</a><ul class="toc"><li class="tocline"><a href="#the-fileerror-interface" class="tocxref"><span class="secno">7.1 </span>The <code>FileError</code> interface</a><ul class="toc"><li class="tocline"><a href="#attributes-6" class="tocxref"><span class="secno">7.1.1 </span>Attributes</a></li><li class="tocline"><a href="#constants-2" class="tocxref"><span class="secno">7.1.2 </span>Constants</a></li></ul></li><li class="tocline"><a href="#the-fileexception-exception" class="tocxref"><span class="secno">7.2 </span>The FileException exception</a><ul class="toc"><li class="tocline"><a href="#fields" class="tocxref"><span class="secno">7.2.1 </span>Fields</a></li><li class="tocline"><a href="#constants-3" class="tocxref"><span class="secno">7.2.2 </span>Constants</a></li></ul></li><li class="tocline"><a href="#error-code-descriptions" class="tocxref"><span class="secno">7.3 </span>Error Code Descriptions</a></li></ul></li><li class="tocline"><a href="#uniformity-of-interface" class="tocxref"><span class="secno">8. </span>Uniformity of interface</a><ul class="toc"><li class="tocline"><a href="#case-sensitivity" class="tocxref"><span class="secno">8.1 </span>Case-sensitivity</a></li><li class="tocline"><a href="#directories" class="tocxref"><span class="secno">8.2 </span>Directories</a></li><li class="tocline"><a href="#naming-restrictions" class="tocxref"><span class="secno">8.3 </span>Naming restrictions</a></li></ul></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">A. </span>Acknowledgements</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">B. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">B.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">B.2 </span>Informative references</a></li></ul></li></ul></div>
<div id="conformance" class="section"><!--OddPage--><h2><span class="secno">1. </span>Conformance</h2><p>As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.</p>
<p>The key words <em class="rfc2119" title="must">must</em>, <em class="rfc2119" title="must not">must not</em>, <em class="rfc2119" title="required">required</em>, <em class="rfc2119" title="should">should</em>, <em class="rfc2119" title="should not">should not</em>, <em class="rfc2119" title="recommended">recommended</em>, <em class="rfc2119" title="may">may</em>, and <em class="rfc2119" title="optional">optional</em> in this specification are to be interpreted as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC2119">RFC2119</a></cite>].</p>
<p>
This specification defines conformance criteria that apply to a single
product: a <dfn id="dfn-user-agent">user agent</dfn> that implements the interfaces that it
contains.
</p>
</div>
<div class="informative section" id="introduction">
<!--OddPage--><h2><span class="secno">2. </span>Introduction</h2><p><em>This section is non-normative.</em></p>
<p>
This API is intended to satisfy client-side-storage use cases not
well served by databases. These are generally applications that involve
large binary blobs and/or share data with applications outside of the
browser.
</p>
<p>
It is intended to be minimal in extent, but sufficiently powerful that
easy-to-use libraries may be built on top of it.
</p>
<div id="use-cases" class="section">
<h3><span class="secno">2.1 </span>Use Cases</h3>
<ol>
<li>Persistent uploader
<ul>
<li>When a file or directory is selected for upload, it copies it
into a local sandbox and uploads a chunk at a time.</li>
<li>It can restart uploads after browser crashes, network
interruptions, etc.</li>
</ul>
</li>
<li>Video game or other app with lots of media assets
<ul>
<li>It downloads one or several large tarballs, and expands them
locally into a directory structure.</li>
<li>The same download should work on any operating system.</li>
<li>It can manage prefetching just the next-to-be-needed assets in
the background, so going to the next game level or activating a new
feature doesn't require waiting for a download.</li>
<li>It uses those assets directly from its local cache, by direct
file reads or by handing local URLs to image or video tags, WebGL
asset loaders, etc.</li>
<li>The files may be of arbitrary binary format.</li>
<li>On the server side, a compressed tarball will often be much
smaller than a collection of separately-compressed files. Also, 1
tarball instead of 1000 little files will involve fewer seeks, all
else being equal.</li>
</ul>
</li>
<li>Audio/Photo editor with offline access or local cache for speed
<ul>
<li>The data blobs are potentially quite large, and are
read-write.</li>
<li>It may want to do partial writes to files (ovewriting just the
ID3/EXIF tags, for example).</li>
<li>The ability to organize project files by creating directories
would be useful.</li>
<li>Edited files should be accessable by client-side applications
[iTunes, Picasa].
</li></ul>
</li>
<li>Offline video viewer
<ul>
<li>It downloads large files (>1GB) for later viewing.</li>
<li>It needs efficient seek + streaming.</li>
<li>It must be able to hand a URL to the video tag.</li>
<li>It should enable access to partly-downloaded files e.g. to let
you watch the first episode of the DVD even if your download didn't
complete before you got on the plane.</li>
<li>It should be able to pull a single episode out of the middle of
a download and give just that to the video tag.</li>
</ul>
</li>
<li>Offline Web Mail Client
<ul>
<li>Downloads attachments and stores them locally.</li>
<li>Caches user-selected attachments for later upload.</li>
<li>Needs to be able to refer to cached attachments and image
thumbnails for display and upload.</li>
<li>Should be able to trigger the UA's download manager just as if
talking to a server.</li>
<li>Should be able to upload an email with attachments as a
multipart post, rather than sending a file at a time in an XHR.</li>
</ul>
</li>
</ol>
</div>
<div id="examples" class="section">
<h3><span class="secno">2.2 </span>Examples</h3>
<pre class="example sh_javascript sh_sourceCode"><span class="sh_comment">// In the DOM or worker context:</span>
<span class="sh_keyword">function</span> <span class="sh_function">useAsyncFS</span><span class="sh_symbol">(</span>fs<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_comment">// see getAsText example in [</span><cite><a class="bibref" rel="biblioentry" href="#bib-FILE-API"><span class="sh_comment">FILE-API</span></a></cite><span class="sh_comment">].</span>
fs<span class="sh_symbol">.</span>root<span class="sh_symbol">.</span><span class="sh_function">getFile</span><span class="sh_symbol">(</span><span class="sh_string">"already_there.txt"</span><span class="sh_symbol">,</span> <span class="sh_keyword">null</span><span class="sh_symbol">,</span> <span class="sh_keyword">function</span> <span class="sh_symbol">(</span>f<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_function">getAsText</span><span class="sh_symbol">(</span>f<span class="sh_symbol">.</span><span class="sh_function">file</span><span class="sh_symbol">());</span>
<span class="sh_cbracket">}</span><span class="sh_symbol">);</span>
<span class="sh_comment">// But now we can also write to the file; see [</span><cite><a class="bibref" rel="biblioentry" href="#bib-FILE-WRITER"><span class="sh_comment">FILE-WRITER</span></a></cite><span class="sh_comment">].</span>
fs<span class="sh_symbol">.</span>root<span class="sh_symbol">.</span><span class="sh_function">getFile</span><span class="sh_symbol">(</span><span class="sh_string">"logFile"</span><span class="sh_symbol">,</span> <span class="sh_cbracket">{</span>create<span class="sh_symbol">:</span> <span class="sh_keyword">true</span><span class="sh_cbracket">}</span><span class="sh_symbol">,</span> <span class="sh_keyword">function</span> <span class="sh_symbol">(</span>f<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
f<span class="sh_symbol">.</span><span class="sh_function">createWriter</span><span class="sh_symbol">(</span>writeDataToLogFile<span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span>
<span class="sh_function">requestFileSystem</span><span class="sh_symbol">(</span>TEMPORARY<span class="sh_symbol">,</span> <span class="sh_number">1024</span> <span class="sh_symbol">*</span> <span class="sh_number">1024</span><span class="sh_symbol">,</span> <span class="sh_keyword">function</span><span class="sh_symbol">(</span>fs<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_function">useAsyncFS</span><span class="sh_symbol">(</span>fs<span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span><span class="sh_symbol">);</span>
<span class="sh_comment">// In a worker:</span>
<span class="sh_keyword">var</span> tempFS <span class="sh_symbol">=</span> <span class="sh_function">requestFileSystem</span><span class="sh_symbol">(</span>TEMPORARY<span class="sh_symbol">,</span> <span class="sh_number">1024</span> <span class="sh_symbol">*</span> <span class="sh_number">1024</span><span class="sh_symbol">);</span>
<span class="sh_keyword">var</span> logFile <span class="sh_symbol">=</span> tempFS<span class="sh_symbol">.</span>root<span class="sh_symbol">.</span><span class="sh_function">getFile</span><span class="sh_symbol">(</span><span class="sh_string">"logFile"</span><span class="sh_symbol">,</span> <span class="sh_cbracket">{</span>create<span class="sh_symbol">:</span> <span class="sh_keyword">true</span><span class="sh_cbracket">}</span><span class="sh_symbol">);</span>
<span class="sh_keyword">var</span> writer <span class="sh_symbol">=</span> logFile<span class="sh_symbol">.</span><span class="sh_function">createWriter</span><span class="sh_symbol">();</span>
writer<span class="sh_symbol">.</span><span class="sh_function">seek</span><span class="sh_symbol">(</span>writer<span class="sh_symbol">.</span>length<span class="sh_symbol">);</span>
<span class="sh_function">writeDataToLogFile</span><span class="sh_symbol">(</span>writer<span class="sh_symbol">);</span></pre>
</div>
</div>
<div id="data-persistence-and-accessing-the-api" class="section">
<!--OddPage--><h2><span class="secno">3. </span>Data Persistence and accessing the API</h2>
<div class="informative section" id="temporary-vs.-persistent-storage">
<h3><span class="secno">3.1 </span>Temporary vs. Persistent Storage</h3><p><em>This section is non-normative.</em></p>
<p>
An application can request <a href="#dfn-temporary" class="internalDFN">temporary</a> or <a href="#dfn-persistent" class="internalDFN">persistent</a>
storage space. Temporary storage may be easier to get, at the UA's
discretion [looser quota restrictions, available without prompting the
user], but the data stored there may be deleted at the UA's
convenience, e.g. to deal with a shortage of disk space.
</p>
<p>
Conversely, once <a href="#dfn-persistent" class="internalDFN">persistent</a> storage has been granted, data
stored there by the application should not be deleted by the UA
without user intervention. The application may of course delete it at
will. The UA should require permission from the user before granting
<a href="#dfn-persistent" class="internalDFN">persistent</a> storage space to the application.
</p>
<p>
This API specifies the standard origin isolation in a filesystem
context, along with persistence of data across invocations.
Applications will likely use <a href="#dfn-temporary" class="internalDFN">temporary</a> storage for caching, and
if it's still around from a previous session, it is often useful.
Persistent data, on the other hand, is useless if you can't access it
again the next time you're invoked. However, even <a href="#dfn-persistent" class="internalDFN">persistent</a>
data may be deleted manually by the user [either through the UA or via
direct filesystem operations].
</p>
</div>
<div id="restrictions" class="section">
<h3><span class="secno">3.2 </span>Restrictions</h3>
<a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a> and <a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a> objects returned by
<code>requestFileSystem</code> <em class="rfc2119" title="must">must</em> have the following properties:
<ul>
<li>The filesystems accessible by any origin <em class="rfc2119" title="must">must</em> be disjoint from
those accessible by any other origin.</li>
<li>Data stored in a <dfn id="dfn-persistent">persistent</dfn> filesystem <em class="rfc2119" title="should not">should not</em> be
deleted by the UA, other than in response to a removal API call,
without explicit authorization from the user.</li>
<li>Data stored in a <dfn id="dfn-temporary">temporary</dfn> filesystem <em class="rfc2119" title="may">may</em> be deleted by
the UA at its discretion, without application or user
intervention.</li>
<li>If
<ol>
<li> an application in a given origin requests a <a href="#dfn-persistent" class="internalDFN">persistent</a>
filesystem on multiple occasions;</li>
<li> each request is granted;</li>
<li> and data from an earlier request still exists in the first
filesystem at the time of a subsequent request.</li>
</ol>
then the <a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a> or <a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a> returned from
the subsequent request <em class="rfc2119" title="must">must</em> refer to the same underlying filesystem
and root directory as the previous request.</li>
<li>If
<ol>
<li> an application in a given origin requests a <a href="#dfn-temporary" class="internalDFN">temporary</a>
filesystem on multiple occasions;</li>
<li> each request is granted;</li>
<li> and data from an earlier request still exists in the first
filesystem at the time of a subsequent request.</li>
</ol>
then the <a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a> or <a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a> returned from
the subsequent request <em class="rfc2119" title="should">should</em> refer to the same underlying
filesystem and root directory as the previous request.</li>
</ul>
<div class="issue">
<p>
Do we need to mandate that the <a href="#dfn-temporary" class="internalDFN">temporary</a> and
<a href="#dfn-persistent" class="internalDFN">persistent</a> filesystems be disjoint?
</p>
</div>
</div>
<div class="informative section" id="security-considerations">
<h3><span class="secno">3.3 </span>Security Considerations</h3><p><em>This section is non-normative.</em></p>
<p>
Because this API may allow untrusted code to read and write parts of a
user's hard drive, there are a number of security and privacy issues
that must be dealt with. Risks to the user include:
</p><ul>
<li>Denial of service by filling a local disk or using up IO
bandwidth. This can be mitigated in part through quota
limitations.</li>
<li>Theft or erasure of private data. This is mitigated by limiting
the scope of access to the local filesystem to a chroot-like,
origin-specific sandbox.</li>
<li>Storing malicious executables or illegal data on a user's
system. This is similar to the risk of any download, and similar
security precautions apply, but is potentially worse in that:
<ul>
<li>It may involve multiple files.</li>
<li>The files may be in a part of the filesystem that's harder
for the user to find than the standard downloads directory.</li>
<li>The malicious writes may happen long enough after granting
of filesystem access that the user doesn't connect the two
events.</li>
</ul>
This may be mitigated by restricting file creation/rename to
non-executable extensions, and by making sure the execute bit is
not set on any file created or modified via the API.
</li>
</ul>
<p></p>
<p>
As with any other client-side storage, filesystem access allows for
cookie-resurrection attacks. UAs will likely wish to present the
option of clearing it when the user clears any other origin-specific
storage, blocking access to it when cookies are blocked, etc. This is
especially important if <a href="#dfn-temporary" class="internalDFN">temporary</a> storage space is permitted by
default without explicit user permission.
</p>
</div>
<div id="obtaining-access-to-file-system-entry-points" class="section">
<h3><span class="secno">3.4 </span>Obtaining access to file system entry points</h3>
<p>
There are several ways in which a file system entry point can be
obtained. Not all <a>user agents</a> may in fact implement all of
them. However, in order to avoid blocking UI actions while waiting on
filesystem IO, we define only an asynchronous interface for Window,
and restrict the synchronous API to the Worker context defined in
[<cite><a class="bibref" rel="biblioentry" href="#bib-WEBWORKERS">WEBWORKERS</a></cite>].
</p>
<div id="using-localfilesystem" class="section">
<h4><span class="secno">3.4.1 </span>Using <code>LocalFileSystem</code></h4>
<pre class="idl"><span class="idlImplements"><a>Window</a> implements <a href="#idl-def-LocalFileSystem" class="idlType"><code>LocalFileSystem</code></a>;</span></pre><div class="idlImplementsDesc"><p>All instances of the <code><a>Window</a></code> type are defined to also implement the <a href="#idl-def-LocalFileSystem" class="idlType"><code>LocalFileSystem</code></a> interface.</p></div>
<pre class="idl"><span class="idlImplements"><a>WorkerGlobalScope</a> implements <a href="#idl-def-LocalFileSystem" class="idlType"><code>LocalFileSystem</code></a>;</span></pre><div class="idlImplementsDesc"><p>All instances of the <code><a>WorkerGlobalScope</a></code> type are defined to also implement the <a href="#idl-def-LocalFileSystem" class="idlType"><code>LocalFileSystem</code></a> interface.</p></div> <pre class="idl"><span class="idlInterface" id="idl-def-LocalFileSystem">[<span class="extAttr">Supplemental, NoInterfaceObject</span>]
interface <span class="idlInterfaceID">LocalFileSystem</span> {
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-LocalFileSystem-TEMPORARY">TEMPORARY</a></span> = <span class="idlConstValue">0</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-LocalFileSystem-PERSISTENT">PERSISTENT</a></span> = <span class="idlConstValue">1</span>;</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-LocalFileSystem-requestFileSystem">requestFileSystem</a></span> (<span class="idlParam"><span class="idlParamType"><a>unsigned short</a></span> <span class="idlParamName">type</span></span>, <span class="idlParam"><span class="idlParamType"><a>unsigned long long</a></span> <span class="idlParamName">size</span></span>, <span class="idlParam"><span class="idlParamType"><a href="#idl-def-FileSystemCallback" class="idlType"><code>FileSystemCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-LocalFileSystem-resolveLocalFileSystemURL">resolveLocalFileSystemURL</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">url</span></span>, <span class="idlParam"><span class="idlParamType"><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
};</span>
</pre><div id="methods" class="section"><h5><span class="secno">3.4.1.1 </span>Methods</h5><dl class="methods"><dt id="widl-LocalFileSystem-requestFileSystem"><code>requestFileSystem</code></dt><dd>
<p>
Requests a filesystem in which to store application data.
</p>
<p>
If successful, this function <em class="rfc2119" title="must">must</em> give access to an
origin-private filesystem, as defined above.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">type</td><td class="prmType"><code><a>unsigned short</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Whether the filesystem requested should be <a href="#dfn-persistent" class="internalDFN">persistent</a>,
as defined above. Use one of <code>TEMPORARY</code> or
<code>PERSISTENT</code>.
</td></tr><tr><td class="prmName">size</td><td class="prmType"><code><a>unsigned long long</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
This is an indicator of how much storage space, in bytes, the
application expects to need.
</td></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-FileSystemCallback" class="idlType"><code>FileSystemCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The callback that is called when the <a href="#dfn-user-agent" class="internalDFN">user agent</a> provides
a filesystem.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen, or when the
request to obtain the filesystem is denied.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-LocalFileSystem-resolveLocalFileSystemURL"><code>resolveLocalFileSystemURL</code></dt><dd>
<p>
Allows the user to look up the Entry for a file or directory
referred to by a local URL.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">url</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A URL referring to a local file in a filesystem accessable via
this API.
</td></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called to report the Entry to which the
supplied URL refers.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen, or when the
request to obtain the Entry is denied.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div><div id="constants" class="section"><h5><span class="secno">3.4.1.2 </span>Constants</h5><dl class="constants"><dt id="widl-LocalFileSystem-PERSISTENT"><code>PERSISTENT</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd>
Used for storage that should not be removed by the <a href="#dfn-user-agent" class="internalDFN">user
agent</a> without application or user permission.
</dd><dt id="widl-LocalFileSystem-TEMPORARY"><code>TEMPORARY</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd>
Used for storage with no guarantee of persistence.
</dd></dl></div>
</div>
<div id="using-localfilesystemsync" class="section">
<h4><span class="secno">3.4.2 </span>Using <code>LocalFileSystemSync</code></h4>
<pre class="idl"><span class="idlImplements"><a>WorkerGlobalScope</a> implements <a href="#idl-def-LocalFileSystemSync" class="idlType"><code>LocalFileSystemSync</code></a>;</span></pre><div class="idlImplementsDesc"><p>All instances of the <code><a>WorkerGlobalScope</a></code> type are defined to also implement the <a href="#idl-def-LocalFileSystemSync" class="idlType"><code>LocalFileSystemSync</code></a> interface.</p></div>
<pre class="idl"><span class="idlInterface" id="idl-def-LocalFileSystemSync">[<span class="extAttr">Supplemental, NoInterfaceObject</span>]
interface <span class="idlInterfaceID">LocalFileSystemSync</span> {
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-LocalFileSystemSync-TEMPORARY">TEMPORARY</a></span> = <span class="idlConstValue">0</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-LocalFileSystemSync-PERSISTENT">PERSISTENT</a></span> = <span class="idlConstValue">1</span>;</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a></span> <span class="idlMethName"><a href="#widl-LocalFileSystemSync-requestFileSystemSync">requestFileSystemSync</a></span> (<span class="idlParam"><span class="idlParamType"><a>unsigned short</a></span> <span class="idlParamName">type</span></span>, <span class="idlParam"><span class="idlParamType"><a>unsigned long long</a></span> <span class="idlParamName">size</span></span>) raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></span> <span class="idlMethName"><a href="#widl-LocalFileSystemSync-resolveLocalFileSystemSyncURL">resolveLocalFileSystemSyncURL</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">url</span></span>) raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
};</span>
</pre><div id="methods-1" class="section"><h5><span class="secno">3.4.2.1 </span>Methods</h5><dl class="methods"><dt id="widl-LocalFileSystemSync-requestFileSystemSync"><code>requestFileSystemSync</code></dt><dd>
<p>
Requests a filesystem in which to store application data.
</p>
<p>
If successful, this function <em class="rfc2119" title="must">must</em> give access to an
origin-private filesystem, as defined above.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">type</td><td class="prmType"><code><a>unsigned short</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Whether the filesystem requested should be <a href="#dfn-persistent" class="internalDFN">persistent</a>,
as defined above. Use one of <code>TEMPORARY</code> or
<code>PERSISTENT</code>.
</td></tr><tr><td class="prmName">size</td><td class="prmType"><code><a>unsigned long long</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
This is an indicator of how much storage space, in bytes, the
application expects to need.
</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The application does not have permission to access the
filesystem interface.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a></code></div></dd><dt id="widl-LocalFileSystemSync-resolveLocalFileSystemSyncURL"><code>resolveLocalFileSystemSyncURL</code></dt><dd>
<p>
Allows the user to look up the Entry for a file or directory
referred to by a local URL.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">url</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A URL referring to a local file in a filesystem accessable via
this API.
</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>ENCODING_ERR</code></td><td class="excCodeDesc">The URL was invalid.</td></tr><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The URL was structurally correct, but refers to a resource
that does not exist.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The application does not have permission to access the
filesystem interface or the element referred to by the URL.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></code></div></dd></dl></div><div id="constants-1" class="section"><h5><span class="secno">3.4.2.2 </span>Constants</h5><dl class="constants"><dt id="widl-LocalFileSystemSync-PERSISTENT"><code>PERSISTENT</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd>
Used for storage that should not be removed by the <a href="#dfn-user-agent" class="internalDFN">user
agent</a> without application or user permission.
</dd><dt id="widl-LocalFileSystemSync-TEMPORARY"><code>TEMPORARY</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd>
Used for storage with no guarantee of persistence.
</dd></dl></div>
</div>
</div>
</div>
<div id="shared-data-types" class="section">
<!--OddPage--><h2><span class="secno">4. </span>Shared data types</h2>
<div id="the-metadata-interface" class="section">
<h3><span class="secno">4.1 </span>The <code>Metadata</code> interface</h3>
<p>
This interface supplies information about the state of a file or
directory.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-Metadata">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">Metadata</span> {
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>Date</a></span> <span class="idlAttrName"><a href="#widl-Metadata-modificationTime">modificationTime</a></span>;</span>
};</span>
</pre><div id="attributes" class="section"><h4><span class="secno">4.1.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-Metadata-modificationTime"><code>modificationTime</code> of type <span class="idlAttrType"><a>Date</a></span>, readonly</dt><dd>
This is the time at which the file or directory was last modified.
<div><em>No exceptions.</em></div></dd></dl></div>
</div>
<div id="the-flags-interface" class="section">
<h3><span class="secno">4.2 </span>The <code>Flags</code> interface</h3>
<p>
This interface is used to supply arguments to methods that look up or
create files or directories.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-Flags">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">Flags</span> {
<span class="idlAttribute"> attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-Flags-create">create</a></span>;</span>
<span class="idlAttribute"> attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-Flags-exclusive">exclusive</a></span>;</span>
};</span>
</pre><div id="attributes-1" class="section"><h4><span class="secno">4.2.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-Flags-create"><code>create</code> of type <span class="idlAttrType"><a>boolean</a></span></dt><dd>
Used to indicate that the user wants to create a file or directory
if it was not previously there.
<div><em>No exceptions.</em></div></dd><dt id="widl-Flags-exclusive"><code>exclusive</code> of type <span class="idlAttrType"><a>boolean</a></span></dt><dd>
By itself, <code>exclusive</code> <em class="rfc2119" title="must">must</em> have no effect. Used with
<code>create</code>, it causes getFile and getDirectory to
fail if the target path already exists.
<div><em>No exceptions.</em></div></dd></dl></div>
<div class="informative section" id="examples-1">
<h4><span class="secno">4.2.2 </span>Examples</h4><p><em>This section is non-normative.</em></p>
<pre class="example sh_javascript sh_sourceCode"><span class="sh_comment">// Get the data directory, creating it if it doesn't exist.</span>
dataDir <span class="sh_symbol">=</span> fsSync<span class="sh_symbol">.</span>root<span class="sh_symbol">.</span><span class="sh_function">getDirectory</span><span class="sh_symbol">(</span><span class="sh_string">"data"</span><span class="sh_symbol">,</span> <span class="sh_cbracket">{</span>create<span class="sh_symbol">:</span> <span class="sh_keyword">true</span><span class="sh_cbracket">}</span><span class="sh_symbol">);</span>
<span class="sh_comment">// Create the lock file, if and only if it doesn't exist.</span>
<span class="sh_keyword">try</span> <span class="sh_cbracket">{</span>
lockFile <span class="sh_symbol">=</span> dataDir<span class="sh_symbol">.</span><span class="sh_function">getFile</span><span class="sh_symbol">(</span><span class="sh_string">"lockfile.txt"</span><span class="sh_symbol">,</span>
<span class="sh_cbracket">{</span>create<span class="sh_symbol">:</span> <span class="sh_keyword">true</span><span class="sh_symbol">,</span> exclusive<span class="sh_symbol">:</span> <span class="sh_keyword">true</span><span class="sh_cbracket">}</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span> <span class="sh_keyword">catch</span> <span class="sh_symbol">(</span>ex<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_comment">// It already exists, or something else went wrong.</span>
<span class="sh_symbol">...</span>
<span class="sh_cbracket">}</span></pre>
</div>
</div>
</div>
<div id="the-asynchronous-filesystem-interface" class="section">
<!--OddPage--><h2><span class="secno">5. </span>The asynchronous filesystem interface</h2>
<div id="the-filesystem-interface" class="section">
<h3><span class="secno">5.1 </span>The <code>FileSystem</code> interface</h3>
<p>
This interface represents a file system.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileSystem">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">FileSystem</span> {
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-FileSystem-name">name</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a></span> <span class="idlAttrName"><a href="#widl-FileSystem-root">root</a></span>;</span>
};</span>
</pre><div id="attributes-2" class="section"><h4><span class="secno">5.1.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-FileSystem-name"><code>name</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt><dd>
This is the name of the file system. The specifics of naming
filesystems is unspecified, but a name <em class="rfc2119" title="must">must</em> be unique across the
list of exposed file systems.
<div><em>No exceptions.</em></div></dd><dt id="widl-FileSystem-root"><code>root</code> of type <span class="idlAttrType"><a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a></span>, readonly</dt><dd>
The root directory of the file system.
<div><em>No exceptions.</em></div></dd></dl></div>
</div>
<div id="the-entry-interface" class="section">
<h3><span class="secno">5.2 </span>The <code>Entry</code> interface</h3>
<p>
An abstract interface representing entries in a file system, each of
which may be a <a>File</a> or <a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a>.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-Entry">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">Entry</span> {
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-Entry-isFile">isFile</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-Entry-isDirectory">isDirectory</a></span>;</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-Entry-getMetadata">getMetadata</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-MetadataCallback" class="idlType"><code>MetadataCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-Entry-name">name</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-Entry-fullPath">fullPath</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a></span> <span class="idlAttrName"><a href="#widl-Entry-filesystem">filesystem</a></span>;</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-Entry-moveTo">moveTo</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a></span> <span class="idlParamName">parent</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">newName</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-Entry-copyTo">copyTo</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a></span> <span class="idlParamName">parent</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">newName</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>DOMString</a></span> <span class="idlMethName"><a href="#widl-Entry-toURL">toURL</a></span> (<span class="idlParam">optional <span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">mimeType</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-Entry-remove">remove</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-VoidCallback" class="idlType"><code>VoidCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-Entry-getParent">getParent</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
};</span>
</pre><div id="attributes-3" class="section"><h4><span class="secno">5.2.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-Entry-filesystem"><code>filesystem</code> of type <span class="idlAttrType"><a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a></span>, readonly</dt><dd>
The file system on which the entry resides.
<div><em>No exceptions.</em></div></dd><dt id="widl-Entry-fullPath"><code>fullPath</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt><dd>
The full <a href="#dfn-absolute-path" class="internalDFN">absolute path</a> from the root to the entry.
<div><em>No exceptions.</em></div></dd><dt id="widl-Entry-isDirectory"><code>isDirectory</code> of type <span class="idlAttrType"><a>boolean</a></span>, readonly</dt><dd>
Entry is a directory.
<div><em>No exceptions.</em></div></dd><dt id="widl-Entry-isFile"><code>isFile</code> of type <span class="idlAttrType"><a>boolean</a></span>, readonly</dt><dd>
Entry is a file.
<div><em>No exceptions.</em></div></dd><dt id="widl-Entry-name"><code>name</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt><dd>
The name of the entry, excluding the path leading to it.
<div><em>No exceptions.</em></div></dd></dl></div><div id="methods-2" class="section"><h4><span class="secno">5.2.2 </span>Methods</h4><dl class="methods"><dt id="widl-Entry-copyTo"><code>copyTo</code></dt><dd>
<p>
Copy an entry to a different location on the file system. It is an
error to try to copy an entry inside itself at any depth if it is
a directory, or to copy it into its parent if a name different
from its current one isn't provided. Directory copies are always
recursive--that is, they copy all contents of the directory.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">parent</td><td class="prmType"><code><a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The directory to which to move the entry.
</td></tr><tr><td class="prmName">newName</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
The new name of the entry. Defaults to the Entry's current name
if unspecified.
</td></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called with the Entry for the new object.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-Entry-getMetadata"><code>getMetadata</code></dt><dd>
<p>
Look up metadata about this entry.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-MetadataCallback" class="idlType"><code>MetadataCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called with the time of the last
modification.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-Entry-getParent"><code>getParent</code></dt><dd>
Look up the parent DirectoryEntry containing this Entry. If this
Entry is the root of its filesystem, its parent is itself.
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called to return the parent Entry.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-Entry-moveTo"><code>moveTo</code></dt><dd>
<p>
Move an entry to a different location on the file system.
It is an error to try to:
</p><ul>
<li>move a directory inside itself or to any child at any
depth;</li>
<li>move an entry into its parent if a name different from its
current one isn't provided;</li>
<li>move a file to a path occupied by a directory;</li>
<li>move a directory to a path occupied by a file;</li>
<li>move any element to a path occupied by a directory which is
not empty.</li>
</ul>
A move of a file on top of an existing file <em class="rfc2119" title="must">must</em> attempt to
delete and replace that file.
A move of a directory on top of an existing empty directory <em class="rfc2119" title="must">must</em>
attempt to delete and replace that directory.
<p></p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">parent</td><td class="prmType"><code><a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The directory to which to move the entry.
</td></tr><tr><td class="prmName">newName</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
The new name of the entry. Defaults to the Entry's current name
if unspecified.
</td></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called with the Entry for the new location.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-Entry-remove"><code>remove</code></dt><dd>
<p>
Deletes a file or directory. It is an error to attempt to delete
a directory that is not empty. It is an error to attempt to
delete the root directory of a filesystem.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-VoidCallback" class="idlType"><code>VoidCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called on success.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-Entry-toURL"><code>toURL</code></dt><dd>
<p>
Returns a URL that can be used to identify this entry.
Unlike the URN defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-API">FILE-API</a></cite>], it has no specific
expiration; as it describes a location on disk, it should be valid
at least as long as that location exists.
Users may supply <code>mimeType</code> in order to simulate the
optional mime-type header associated with HTTP downloads.
</p>
<div class="issue">
<p>
Do we want to spec out the URL format/scheme? It would be quite
nice if these could be edited and manipulated easily, as with
normal filesystem paths.
</p>
<p>
How and where can these URLs be used? Can they be interchangeable
with online URLs for the same domain?
</p>
<p>
Proposal currently under discussion:
</p><ul>
<li>Use a format such as
<code>filesystem:http://example.domain/persistent-or-temporary/path/to/file.html
</code>.</li>
<li>URLs should be usable for anything that online URLs can be
used for, whether they appear in online or filesystem-resident
web pages.</li>
<li>However, they can only be used by the origin that owns the
filesystem. No other origin can e.g. reference another origin's
filesystem in an IMG tag.</li>
</ul>
<p></p>
</div>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">mimeType</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
For a FileEntry, the mime type to be used to interpret the file,
when loaded through this URL.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>DOMString</a></code></div></dd></dl></div>
</div>
<div id="the-directoryentry-interface" class="section">
<h3><span class="secno">5.3 </span>The <code>DirectoryEntry</code> interface</h3>
<p>
This interface represents a directory on a file system.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-DirectoryEntry">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">DirectoryEntry</span> : <span class="idlSuperclass"><a href="#idl-def-Entry" class="idlType"><code>Entry</code></a></span> {
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-DirectoryReader" class="idlType"><code>DirectoryReader</code></a></span> <span class="idlMethName"><a href="#widl-DirectoryEntry-createReader">createReader</a></span> ();</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-DirectoryEntry-getFile">getFile</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">path</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></span> <span class="idlParamName">options</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-DirectoryEntry-getDirectory">getDirectory</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">path</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></span> <span class="idlParamName">options</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-DirectoryEntry-removeRecursively">removeRecursively</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-VoidCallback" class="idlType"><code>VoidCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
};</span>
</pre><div id="methods-3" class="section"><h4><span class="secno">5.3.1 </span>Methods</h4><dl class="methods"><dt id="widl-DirectoryEntry-createReader"><code>createReader</code></dt><dd>
<p>
Creates a new DirectoryReader to read Entries from this Directory.
</p>
<div><em>No parameters.</em></div><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a href="#idl-def-DirectoryReader" class="idlType"><code>DirectoryReader</code></a></code></div></dd><dt id="widl-DirectoryEntry-getDirectory"><code>getDirectory</code></dt><dd>
<p>
Creates or looks up a directory.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">path</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Either an <a href="#dfn-absolute-path" class="internalDFN">absolute path</a> or a <a href="#dfn-relative-path" class="internalDFN">relative path</a> from
this DirectoryEntry to the directory to be looked up or created.
It is an error to attempt to create a directory whose immediate
parent does not yet exist.
</td></tr><tr><td class="prmName">options</td><td class="prmType"><code><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
<ul>
<li>If <code>create</code> and <code>exclusive</code> are both
true and the path already exists, getDirectory <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is true, the path doesn't exist,
and no other error occurs, getDirectory <em class="rfc2119" title="must">must</em> create and return
a corresponding DirectoryEntry.</li>
<li>If <code>create</code> is not true and the path doesn't
exist, getDirectory <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is not true and the path exists,
but is a file, getDirectory <em class="rfc2119" title="must">must</em> fail.</li>
<li>Otherwise, if no other error occurs, getDirectory <em class="rfc2119" title="must">must</em>
return a DirectoryEntry corresponding to path.</li>
</ul>
</td></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called to return the DirectoryEntry selected
or created.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-DirectoryEntry-getFile"><code>getFile</code></dt><dd>
<p>
Creates or looks up a file.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">path</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Either an <a href="#dfn-absolute-path" class="internalDFN">absolute path</a> or a <a href="#dfn-relative-path" class="internalDFN">relative path</a> from
this DirectoryEntry to the file to be looked up or created. It
is an error to attempt to create a file whose immediate parent
does not yet exist.
</td></tr><tr><td class="prmName">options</td><td class="prmType"><code><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
<ul>
<li>If <code>create</code> and <code>exclusive</code> are both
true, and the path already exists, getFile <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is true, the path doesn't exist,
and no other error occurs, getFile <em class="rfc2119" title="must">must</em> create it as a
zero-length file and return a corresponding FileEntry.</li>
<li>If <code>create</code> is not true and the path doesn't
exist, getFile <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is not true and the path exists,
but is a directory, getFile <em class="rfc2119" title="must">must</em> fail.</li>
<li>Otherwise, if no other error occurs, getFile <em class="rfc2119" title="must">must</em>
return a FileEntry corresponding to path.</li>
</ul>
</td></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntryCallback" class="idlType"><code>EntryCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called to return the File selected or
created.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-DirectoryEntry-removeRecursively"><code>removeRecursively</code></dt><dd>
<p>
Deletes a directory and all of its contents, if any. In the event
of an error [e.g. trying to delete a directory that contains a
file that cannot be removed], some of the contents of the
directory <em class="rfc2119" title="may">may</em> be deleted. It is an error to attempt to delete the
root directory of a filesystem.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-VoidCallback" class="idlType"><code>VoidCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called on success.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-directoryreader-interface" class="section">
<h3><span class="secno">5.4 </span>The <code>DirectoryReader</code> interface</h3>
<p>
This interface lets a user list files and directories in a directory.
If there are no additions to or deletions from a directory between the
first and last call to readEntries, and no errors occur, then:
</p><ul>
<li>A series of calls to readEntries <em class="rfc2119" title="must">must</em> return each entry in the
directory exactly once.</li>
<li>Once all entries have been returned, the next call to
readEntries <em class="rfc2119" title="must">must</em> produce an empty array.</li>
<li>If not all entries have been returned, the array produced by
readEntries <em class="rfc2119" title="must not">must not</em> be empty.</li>
<li>The entries produced by readEntries <em class="rfc2119" title="must not">must not</em> include the
directory itself ["."] or its parent [".."].</li>
</ul>
<p></p>
<pre class="idl"><span class="idlInterface" id="idl-def-DirectoryReader">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">DirectoryReader</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-DirectoryReader-readEntries">readEntries</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-EntriesCallback" class="idlType"><code>EntriesCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
};</span>
</pre><div id="methods-4" class="section"><h4><span class="secno">5.4.1 </span>Methods</h4><dl class="methods"><dt id="widl-DirectoryReader-readEntries"><code>readEntries</code></dt><dd>
<p>
Read the next block of entries from this directory.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-EntriesCallback" class="idlType"><code>EntriesCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Called once per successful call to readEntries to deliver the
next previously-unreported set of Entries in the associated
Directory. If all Entries have already been returned from
previous invocations of readEntries, successCallback <em class="rfc2119" title="must">must</em> be
called with a zero-length array as an argument.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback indicating that there was an error reading from the
Directory.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-fileentry-interface" class="section">
<h3><span class="secno">5.5 </span>The <code>FileEntry</code> interface</h3>
<p>
This interface represents a file on a file system.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileEntry">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">FileEntry</span> : <span class="idlSuperclass"><a href="#idl-def-Entry" class="idlType"><code>Entry</code></a></span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-FileEntry-createWriter">createWriter</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-FileWriterCallback" class="idlType"><code>FileWriterCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-FileEntry-file">file</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-FileCallback" class="idlType"><code>FileCallback</code></a></span> <span class="idlParamName">successCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></span> <span class="idlParamName">errorCallback</span></span>);</span>
};</span>
</pre><div id="methods-5" class="section"><h4><span class="secno">5.5.1 </span>Methods</h4><dl class="methods"><dt id="widl-FileEntry-createWriter"><code>createWriter</code></dt><dd>
<p>
Creates a new <code>FileWriter</code> associated with the file
that this <code>FileEntry</code> represents.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-FileWriterCallback" class="idlType"><code>FileWriterCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called with the new <a>FileWriter</a>.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-FileEntry-file"><code>file</code></dt><dd>
<p>
Returns a <code>File</code> that represents the current state of
the file that this <code>FileEntry</code> represents.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">successCallback</td><td class="prmType"><code><a href="#idl-def-FileCallback" class="idlType"><code>FileCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
A callback that is called with the new <a>FileWriter</a>.
</td></tr><tr><td class="prmName">errorCallback</td><td class="prmType"><code><a href="#idl-def-ErrorCallback" class="idlType"><code>ErrorCallback</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
A callback that is called when errors happen.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="callbacks" class="section">
<h3><span class="secno">5.6 </span>Callbacks</h3>
<p>
Several calls in this API are asynchronous, and use callbacks.
</p>
<div id="the-filesystemcallback-interface" class="section">
<h4><span class="secno">5.6.1 </span>The <code>FileSystemCallback</code> interface</h4>
<p>
When <code>requestFileSystem()</code> succeeds, the following
callback is made:
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileSystemCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">FileSystemCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-FileSystemCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a></span> <span class="idlParamName">filesystem</span></span>);</span>
};</span>
</pre><div id="methods-6" class="section"><h5><span class="secno">5.6.1.1 </span>Methods</h5><dl class="methods"><dt id="widl-FileSystemCallback-handleEvent"><code>handleEvent</code></dt><dd>
<p>
The file system was successfully obtained.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">filesystem</td><td class="prmType"><code><a href="#idl-def-FileSystem" class="idlType"><code>FileSystem</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The file systems to which the app is granted access.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-entrycallback-interface" class="section">
<h4><span class="secno">5.6.2 </span>The <code>EntryCallback</code> interface</h4>
<p>
This interface is the callback used to look up Entry objects.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-EntryCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">EntryCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-EntryCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-Entry" class="idlType"><code>Entry</code></a></span> <span class="idlParamName">entry</span></span>);</span>
};</span>
</pre><div id="methods-7" class="section"><h5><span class="secno">5.6.2.1 </span>Methods</h5><dl class="methods"><dt id="widl-EntryCallback-handleEvent"><code>handleEvent</code></dt><dd>
Used to supply an Entry as a response to a user query.
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">entry</td><td class="prmType"><code><a href="#idl-def-Entry" class="idlType"><code>Entry</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc"></td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-entriescallback-interface" class="section">
<h4><span class="secno">5.6.3 </span>The <code>EntriesCallback</code> interface</h4>
<p>
When <code>readEntries()</code> succeeds, the following callback is
made.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-EntriesCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">EntriesCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-EntriesCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-Entry" class="idlType"><code>Entry</code></a>[]</span> <span class="idlParamName">entries</span></span>);</span>
};</span>
</pre><div id="methods-8" class="section"><h5><span class="secno">5.6.3.1 </span>Methods</h5><dl class="methods"><dt id="widl-EntriesCallback-handleEvent"><code>handleEvent</code></dt><dd>
Used to supply an array of Entries as a response to a user query.
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">entries</td><td class="prmType"><code><a href="#idl-def-Entry" class="idlType"><code>Entry</code></a>[]</code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc"></td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-metadatacallback-interface" class="section">
<h4><span class="secno">5.6.4 </span>The <code>MetadataCallback</code> interface</h4>
<p>
This interface is the callback used to look up file and directory
metadata.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-MetadataCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">MetadataCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-MetadataCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-Metadata" class="idlType"><code>Metadata</code></a></span> <span class="idlParamName">metadata</span></span>);</span>
};</span>
</pre><div id="methods-9" class="section"><h5><span class="secno">5.6.4.1 </span>Methods</h5><dl class="methods"><dt id="widl-MetadataCallback-handleEvent"><code>handleEvent</code></dt><dd>
<p>
Used to supply file or directory metadata as a response to a
user query.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">metadata</td><td class="prmType"><code><a href="#idl-def-Metadata" class="idlType"><code>Metadata</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc"></td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-filewritercallback-interface" class="section">
<h4><span class="secno">5.6.5 </span>The <code>FileWriterCallback</code> interface</h4>
<p>
This interface is the callback used to create a
<code>FileWriter</code>.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileWriterCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">FileWriterCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-FileWriterCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a>FileWriter</a></span> <span class="idlParamName">fileWriter</span></span>);</span>
};</span>
</pre><div id="methods-10" class="section"><h5><span class="secno">5.6.5.1 </span>Methods</h5><dl class="methods"><dt id="widl-FileWriterCallback-handleEvent"><code>handleEvent</code></dt><dd>
<p>
Used to supply a <code>FileWriter</code> as a response to a user
query.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">fileWriter</td><td class="prmType"><code><a>FileWriter</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc"></td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-filecallback-interface" class="section">
<h4><span class="secno">5.6.6 </span>The <code>FileCallback</code> interface</h4>
<p>
This interface is the callback used to obtain a <code>File</code>.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">FileCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-FileCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a>File</a></span> <span class="idlParamName">file</span></span>);</span>
};</span>
</pre><div id="methods-11" class="section"><h5><span class="secno">5.6.6.1 </span>Methods</h5><dl class="methods"><dt id="widl-FileCallback-handleEvent"><code>handleEvent</code></dt><dd>
<p>
Used to supply a <code>File</code> as a response to a user query.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">file</td><td class="prmType"><code><a>File</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc"></td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-voidcallback-interface" class="section">
<h4><span class="secno">5.6.7 </span>The <code>VoidCallback</code> interface</h4>
<p>
This interface is the generic callback used to indicate success of
an asynchronous method.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-VoidCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">VoidCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-VoidCallback-handleEvent">handleEvent</a></span> ();</span>
};</span>
</pre><div id="methods-12" class="section"><h5><span class="secno">5.6.7.1 </span>Methods</h5><dl class="methods"><dt id="widl-VoidCallback-handleEvent"><code>handleEvent</code></dt><dd>
<div><em>No parameters.</em></div><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-errorcallback-interface" class="section">
<h4><span class="secno">5.6.8 </span>The <code>ErrorCallback</code> interface</h4>
<p>
When an error occurs, the following callback is made:
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-ErrorCallback">[<span class="extAttr">NoInterfaceObject, Callback=FunctionOnly</span>]
interface <span class="idlInterfaceID">ErrorCallback</span> {
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-ErrorCallback-handleEvent">handleEvent</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-FileError" class="idlType"><code>FileError</code></a></span> <span class="idlParamName">err</span></span>);</span>
};</span>
</pre><div id="methods-13" class="section"><h5><span class="secno">5.6.8.1 </span>Methods</h5><dl class="methods"><dt id="widl-ErrorCallback-handleEvent"><code>handleEvent</code></dt><dd>
<p>
There was an error with the request. Details are provided by the
<a href="#idl-def-FileError" class="idlType"><code>FileError</code></a> parameter.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">err</td><td class="prmType"><code><a href="#idl-def-FileError" class="idlType"><code>FileError</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The error that was generated.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
</div>
</div>
<div id="the-synchronous-filesystem-interface" class="section">
<!--OddPage--><h2><span class="secno">6. </span>The synchronous filesystem interface</h2>
<div id="the-filesystemsync-interface" class="section">
<h3><span class="secno">6.1 </span>The <code>FileSystemSync</code> interface</h3>
<p>
This interface represents a file system.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileSystemSync">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">FileSystemSync</span> {
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-FileSystemSync-name">name</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></span> <span class="idlAttrName"><a href="#widl-FileSystemSync-root">root</a></span>;</span>
};</span>
</pre><div id="attributes-4" class="section"><h4><span class="secno">6.1.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-FileSystemSync-name"><code>name</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt><dd>
This is the name of the file system. The specifics of naming
filesystems is unspecified, but a name <em class="rfc2119" title="must">must</em> be unique across the
list of exposed file systems.
<div><em>No exceptions.</em></div></dd><dt id="widl-FileSystemSync-root"><code>root</code> of type <span class="idlAttrType"><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></span>, readonly</dt><dd>
The root directory of the file system.
<div><em>No exceptions.</em></div></dd></dl></div>
</div>
<div id="the-entrysync-interface" class="section">
<h3><span class="secno">6.2 </span>The <code>EntrySync</code> interface</h3>
<p>
An abstract interface representing entries in a file system, each of
which may be a <a href="#idl-def-FileEntrySync" class="idlType"><code>FileEntrySync</code></a> or <a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a>.
</p><div class="issue">
Some have requested support for archive files. I've not required
that, but I've left space for it by not ruling out having both
isFile and isDirectory be true. I welcome comments on this
approach.
</div>
<p></p>
<pre class="idl"><span class="idlInterface" id="idl-def-EntrySync">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">EntrySync</span> {
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-EntrySync-isFile">isFile</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-EntrySync-isDirectory">isDirectory</a></span>;</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-Metadata" class="idlType"><code>Metadata</code></a></span> <span class="idlMethName"><a href="#widl-EntrySync-getMetadata">getMetadata</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-EntrySync-name">name</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-EntrySync-fullPath">fullPath</a></span>;</span>
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a></span> <span class="idlAttrName"><a href="#widl-EntrySync-filesystem">filesystem</a></span>;</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></span> <span class="idlMethName"><a href="#widl-EntrySync-moveTo">moveTo</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></span> <span class="idlParamName">parent</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">newName</span></span>) raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></span> <span class="idlMethName"><a href="#widl-EntrySync-copyTo">copyTo</a></span> (<span class="idlParam"><span class="idlParamType"><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></span> <span class="idlParamName">parent</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">newName</span></span>) raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>DOMString</a></span> <span class="idlMethName"><a href="#widl-EntrySync-toURL">toURL</a></span> (<span class="idlParam">optional <span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">mimeType</span></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-EntrySync-remove">remove</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></span> <span class="idlMethName"><a href="#widl-EntrySync-getParent">getParent</a></span> ();</span>
};</span>
</pre><div id="attributes-5" class="section"><h4><span class="secno">6.2.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-EntrySync-filesystem"><code>filesystem</code> of type <span class="idlAttrType"><a href="#idl-def-FileSystemSync" class="idlType"><code>FileSystemSync</code></a></span>, readonly</dt><dd>
The file system on which the entry resides.
<div><em>No exceptions.</em></div></dd><dt id="widl-EntrySync-fullPath"><code>fullPath</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt><dd>
The full <a href="#dfn-absolute-path" class="internalDFN">absolute path</a> from the root to the entry.
<div><em>No exceptions.</em></div></dd><dt id="widl-EntrySync-isDirectory"><code>isDirectory</code> of type <span class="idlAttrType"><a>boolean</a></span>, readonly</dt><dd>
EntrySync is a directory.
<div><em>No exceptions.</em></div></dd><dt id="widl-EntrySync-isFile"><code>isFile</code> of type <span class="idlAttrType"><a>boolean</a></span>, readonly</dt><dd>
EntrySync is a file.
<div><em>No exceptions.</em></div></dd><dt id="widl-EntrySync-name"><code>name</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt><dd>
The name of the entry, excluding the path leading to it.
<div><em>No exceptions.</em></div></dd></dl></div><div id="methods-14" class="section"><h4><span class="secno">6.2.2 </span>Methods</h4><dl class="methods"><dt id="widl-EntrySync-copyTo"><code>copyTo</code></dt><dd>
<p>
Copy an entry to a different location on the file system. It is an
error to try to copy an entry inside itself at any depth if it is
a directory, or to copy it into its parent if a name different
from its current one isn't provided.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">parent</td><td class="prmType"><code><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The directory to which to move the entry.
</td></tr><tr><td class="prmName">newName</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
The new name of the entry. Defaults to the EntrySync's current
name if unspecified.
</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>ENCODING_ERR</code></td><td class="excCodeDesc">The name supplied was invalid.</td></tr><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The target directory does not exist.</td></tr><tr><td class="excCodeName"><code>INVALID_MODIFICATION_ERR</code></td><td class="excCodeDesc">The user attempted to copy an entry into its parent without
changing its name, or attempted to copy a directory into a
directory that it contains directly or indirectly.</td></tr><tr><td class="excCodeName"><code>NO_MODIFICATION_ALLOWED_ERR</code></td><td class="excCodeDesc">The target directory is not writable.</td></tr><tr><td class="excCodeName"><code>QUOTA_EXCEEDED_ERR</code></td><td class="excCodeDesc">The operation would cause the application to exceed its
storage quota.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></code></div></dd><dt id="widl-EntrySync-getMetadata"><code>getMetadata</code></dt><dd>
<p>
Look up metadata about this entry.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The entry no longer exists.</td></tr><tr><td class="excCodeName"><code>INVALID_STATE_ERR</code></td><td class="excCodeDesc">This FileSystemSync is no longer valid for some reason other
than it having been deleted.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-Metadata" class="idlType"><code>Metadata</code></a></code></div></dd><dt id="widl-EntrySync-getParent"><code>getParent</code></dt><dd>
Look up the parent DirectoryEntrySync containing this Entry. If
this EntrySync is the root of its filesystem, its parent is itself.
<div><em>No parameters.</em></div><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></code></div></dd><dt id="widl-EntrySync-moveTo"><code>moveTo</code></dt><dd>
<p>
Move an entry to a different location on the file system.
It is an error to try to:
</p><ul>
<li>move a directory inside itself or to any child at any
depth;</li>
<li>move an entry into its parent if a name different from its
current one isn't provided;</li>
<li>move a file to a path occupied by a directory;</li>
<li>move a directory to a path occupied by a file;</li>
<li>move any element to a path occupied by a directory which is
not empty.</li>
</ul>
A move of a file on top of an existing file <em class="rfc2119" title="must">must</em> attempt to
delete and replace that file.
A move of a directory on top of an existing empty directory <em class="rfc2119" title="must">must</em>
attempt to delete and replace that directory.
<p></p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">parent</td><td class="prmType"><code><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
The directory to which to move the entry.
</td></tr><tr><td class="prmName">newName</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
The new name of the entry. Defaults to the EntrySync's current
name if unspecified.
</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>ENCODING_ERR</code></td><td class="excCodeDesc">The name supplied was invalid.</td></tr><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The target directory does not exist.</td></tr><tr><td class="excCodeName"><code>INVALID_MODIFICATION_ERR</code></td><td class="excCodeDesc">The user attempted to move an entry into its parent without
changing its name, or attempted to move a directory into a
directory that it contains directly or indirectly.</td></tr><tr><td class="excCodeName"><code>NO_MODIFICATION_ALLOWED_ERR</code></td><td class="excCodeDesc">The either the source entry, its parent directory, or the
target directory is not writable.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></code></div></dd><dt id="widl-EntrySync-remove"><code>remove</code></dt><dd>
<p>
Deletes a file or directory. It is an error to attempt to delete
a directory that is not empty. It is an error to attempt to
delete the root directory of a filesystem.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The target directory does not exist.</td></tr><tr><td class="excCodeName"><code>INVALID_MODIFICATION_ERR</code></td><td class="excCodeDesc">The user attempted to remove a directory that was not
empty.</td></tr><tr><td class="excCodeName"><code>NO_MODIFICATION_ALLOWED_ERR</code></td><td class="excCodeDesc">The target or its containing directory is not writable.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>void</a></code></div></dd><dt id="widl-EntrySync-toURL"><code>toURL</code></dt><dd>
<p>
Returns a URL that can be used to identify this entry.
Unlike the URN defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-API">FILE-API</a></cite>], it has no specific
expiration; as it describes a location on disk, it should be valid
at least as long as that location exists.
Users may supply <code>mimeType</code> in order to simulate the
optional mime-type header associated with HTTP downloads.
</p>
<div class="issue">
<p>
If we use the same opaque URL scheme as in [<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-API">FILE-API</a></cite>], users
won't be able to edit and generate URLs themselves. On the other
hand, it would prevent us from having to go to all the trouble of
designing a new scheme, and it would simplify the use of the two
APIs together.
</p>
</div>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">mimeType</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
For a FileEntry, the mime type to be used to interpret the file,
when loaded through this URL.
</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>DOMString</a></code></div></dd></dl></div>
</div>
<div id="the-directoryentrysync-interface" class="section">
<h3><span class="secno">6.3 </span>The <code>DirectoryEntrySync</code> interface</h3>
<p>
This interface represents a directory on a file system.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-DirectoryEntrySync">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">DirectoryEntrySync</span> : <span class="idlSuperclass"><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></span> {
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-DirectoryReaderSync" class="idlType"><code>DirectoryReaderSync</code></a></span> <span class="idlMethName"><a href="#widl-DirectoryEntrySync-createReader">createReader</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-FileEntrySync" class="idlType"><code>FileEntrySync</code></a></span> <span class="idlMethName"><a href="#widl-DirectoryEntrySync-getFile">getFile</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">path</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></span> <span class="idlParamName">options</span></span>) raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></span> <span class="idlMethName"><a href="#widl-DirectoryEntrySync-getDirectory">getDirectory</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">path</span></span>, <span class="idlParam">optional <span class="idlParamType"><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></span> <span class="idlParamName">options</span></span>) raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-DirectoryEntrySync-removeRecursively">removeRecursively</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
};</span>
</pre><div id="methods-15" class="section"><h4><span class="secno">6.3.1 </span>Methods</h4><dl class="methods"><dt id="widl-DirectoryEntrySync-createReader"><code>createReader</code></dt><dd>
<p>
Creates a new DirectoryReaderSync to read EntrySyncs from this
DirectorySync.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The directory no longer exists.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-DirectoryReaderSync" class="idlType"><code>DirectoryReaderSync</code></a></code></div></dd><dt id="widl-DirectoryEntrySync-getDirectory"><code>getDirectory</code></dt><dd>
<p>
Creates or looks up a directory.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">path</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Either an <a href="#dfn-absolute-path" class="internalDFN">absolute path</a> or a <a href="#dfn-relative-path" class="internalDFN">relative path</a> from
this DirectoryEntrySync to the directory to be looked up or
created. It is an error to attempt to create a directory whose
immediate parent does not yet exist.
</td></tr><tr><td class="prmName">options</td><td class="prmType"><code><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
<ul>
<li>If <code>create</code> and <code>exclusive</code> are both
true and the path already exists, getDirectory <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is true, the path doesn't exist,
and no other error occurs, getDirectory <em class="rfc2119" title="must">must</em> create and return
a corresponding DirectoryEntry.</li>
<li>If <code>create</code> is not true and the path doesn't
exist, getDirectory <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is not true and the path exists,
but is a file, getDirectory <em class="rfc2119" title="must">must</em> fail.</li>
<li>Otherwise, if no other error occurs, getDirectory <em class="rfc2119" title="must">must</em>
return a DirectoryEntrySync corresponding to path.</li>
</ul>
</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>ENCODING_ERR</code></td><td class="excCodeDesc">The path was invalid.</td></tr><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The path was structurally correct, but refers to a resource
that does not exist.</td></tr><tr><td class="excCodeName"><code>NO_MODIFICATION_ALLOWED_ERR</code></td><td class="excCodeDesc">The target directory is not writable.</td></tr><tr><td class="excCodeName"><code>PATH_EXISTS_ERR</code></td><td class="excCodeDesc">The user attempted to create a directory where an element
already exists.
</td></tr><tr><td class="excCodeName"><code>QUOTA_EXCEEDED_ERR</code></td><td class="excCodeDesc">The operation would cause the application to exceed its
storage quota.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The application does not have permission to access the
element referred to by path.</td></tr><tr><td class="excCodeName"><code>TYPE_MISMATCH_ERR</code></td><td class="excCodeDesc">The path supplied exists, but is not a directory.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a></code></div></dd><dt id="widl-DirectoryEntrySync-getFile"><code>getFile</code></dt><dd>
<p>
Creates or looks up a file.
</p>
<table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">path</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">?</td><td class="prmOptFalse">?</td><td class="prmDesc">
Either an <a href="#dfn-absolute-path" class="internalDFN">absolute path</a> or a <a href="#dfn-relative-path" class="internalDFN">relative path</a> from
this DirectoryEntrySync to the file to be looked up or created.
It is an error to attempt to create a file whose immediate
parent does not yet exist.
</td></tr><tr><td class="prmName">options</td><td class="prmType"><code><a href="#idl-def-Flags" class="idlType"><code>Flags</code></a></code></td><td class="prmNullFalse">?</td><td class="prmOptTrue">?</td><td class="prmDesc">
<ul>
<li>If <code>create</code> and <code>exclusive</code> are both
true and the path already exists, getFile <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is true, the path doesn't exist,
and no other error occurs, getFile <em class="rfc2119" title="must">must</em> create it as a
zero-length file and return a corresponding FileEntry.</li>
<li>If <code>create</code> is not true and the path doesn't
exist, getFile <em class="rfc2119" title="must">must</em> fail.</li>
<li>If <code>create</code> is not true and the path exists,
but is a directory, getFile <em class="rfc2119" title="must">must</em> fail.</li>
<li>Otherwise, if no other error occurs, getFile <em class="rfc2119" title="must">must</em>
return a FileEntrySync corresponding to path.</li>
</ul>
</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>ENCODING_ERR</code></td><td class="excCodeDesc">The path was invalid.</td></tr><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The path was structurally correct, but refers to a resource
that does not exist.</td></tr><tr><td class="excCodeName"><code>NO_MODIFICATION_ALLOWED_ERR</code></td><td class="excCodeDesc">The target directory or file is not writable.</td></tr><tr><td class="excCodeName"><code>PATH_EXISTS_ERR</code></td><td class="excCodeDesc">The user attempted to create a file where an element already
exists.
</td></tr><tr><td class="excCodeName"><code>QUOTA_EXCEEDED_ERR</code></td><td class="excCodeDesc">The operation would cause the application to exceed its
storage quota.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The application does not have permission to access the
element referred to by path.</td></tr><tr><td class="excCodeName"><code>TYPE_MISMATCH_ERR</code></td><td class="excCodeDesc">The path supplied exists, but is not a directory.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-FileEntrySync" class="idlType"><code>FileEntrySync</code></a></code></div></dd><dt id="widl-DirectoryEntrySync-removeRecursively"><code>removeRecursively</code></dt><dd>
<p>
Deletes a directory and all of its contents, if any. In the event
of an error [e.g. trying to delete a directory that contains a
file that cannot be removed], some of the contents of the
directory <em class="rfc2119" title="may">may</em> be deleted. It is an error to attempt to delete the
root directory of a filesystem.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">This DirectoryEntrySync refers to a resource that does not
exist.</td></tr><tr><td class="excCodeName"><code>INVALID_STATE_ERR</code></td><td class="excCodeDesc">This DirectoryEntrySync is no longer valid for some reason
other than it having been deleted.</td></tr><tr><td class="excCodeName"><code>NO_MODIFICATION_ALLOWED_ERR</code></td><td class="excCodeDesc">At least one of the target directory, its parent, or some of
its contents, is not writable.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The application does not have permission to access the target
directory, its parent, or some of its contents.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
</div>
<div id="the-directoryreadersync-interface" class="section">
<h3><span class="secno">6.4 </span>The <code>DirectoryReaderSync</code> interface</h3>
<p>
This interface lets a user list files and directories in a directory.
If there are no additions to or deletions from a directory between the
first and last call to readEntries, and no errors occur, then:
</p><ul>
<li>A series of calls to readEntries <em class="rfc2119" title="must">must</em> return each entry in the
directory exactly once.</li>
<li>Once all entries have been returned, the next call to
readEntries <em class="rfc2119" title="must">must</em> produce an empty array.</li>
<li>If not all entries have been returned, the array produced by
readEntries <em class="rfc2119" title="must not">must not</em> be empty.</li>
<li>The entries produced by readEntries <em class="rfc2119" title="must not">must not</em> include the
directory itself ["."] or its parent [".."].</li>
</ul>
<p></p>
<pre class="idl"><span class="idlInterface" id="idl-def-DirectoryReaderSync">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">DirectoryReaderSync</span> {
<span class="idlMethod"> <span class="idlMethType"><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a>[]</span> <span class="idlMethName"><a href="#widl-DirectoryReaderSync-readEntries">readEntries</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
};</span>
</pre><div id="methods-16" class="section"><h4><span class="secno">6.4.1 </span>Methods</h4><dl class="methods"><dt id="widl-DirectoryReaderSync-readEntries"><code>readEntries</code></dt><dd>
<p>
Read the next block of entries from this directory.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The directory no longer exists.</td></tr><tr><td class="excCodeName"><code>INVALID_STATE_ERR</code></td><td class="excCodeDesc">The directory has been modified since the first call to
readEntries began to be processed.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a>[]</code></div></dd></dl></div>
</div>
<div id="the-fileentrysync-interface" class="section">
<h3><span class="secno">6.5 </span>The <code>FileEntrySync</code> interface</h3>
<p>
This interface represents a file on a file system.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileEntrySync">[<span class="extAttr">NoInterfaceObject</span>]
interface <span class="idlInterfaceID">FileEntrySync</span> : <span class="idlSuperclass"><a href="#idl-def-EntrySync" class="idlType"><code>EntrySync</code></a></span> {
<span class="idlMethod"> <span class="idlMethType"><a>FileWriterSync</a></span> <span class="idlMethName"><a href="#widl-FileEntrySync-createWriter">createWriter</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
<span class="idlMethod"> <span class="idlMethType"><a>File</a></span> <span class="idlMethName"><a href="#widl-FileEntrySync-file">file</a></span> () raises (<span class="idlRaises"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></span>);</span>
};</span>
</pre><div id="methods-17" class="section"><h4><span class="secno">6.5.1 </span>Methods</h4><dl class="methods"><dt id="widl-FileEntrySync-createWriter"><code>createWriter</code></dt><dd>
<p>
Creates a new <code>FileWriterSync</code> associated with the file
that this <code>FileEntrySync</code> represents.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The entry no longer exists.</td></tr><tr><td class="excCodeName"><code>INVALID_STATE_ERR</code></td><td class="excCodeDesc">This FileEntrySync is no longer valid for some reason other
than it having been deleted.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>FileWriterSync</a></code></div></dd><dt id="widl-FileEntrySync-file"><code>file</code></dt><dd>
<p>
Returns a <code>File</code> that represents the current state of
the file that this <code>FileEntrySync</code> represents.
</p>
<div><em>No parameters.</em></div><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a href="#idl-def-FileException" class="idlType"><code>FileException</code></a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>NOT_FOUND_ERR</code></td><td class="excCodeDesc">The entry no longer exists.</td></tr><tr><td class="excCodeName"><code>INVALID_STATE_ERR</code></td><td class="excCodeDesc">This FileEntrySync is no longer valid for some reason other
than it having been deleted.</td></tr><tr><td class="excCodeName"><code>SECURITY_ERR</code></td><td class="excCodeDesc">The <a href="#dfn-user-agent" class="internalDFN">user agent</a> determined that it was not safe to carry
out this action.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>File</a></code></div></dd></dl></div>
</div>
</div>
<div id="dealing-with-errors-and-exceptions" class="section">
<!--OddPage--><h2><span class="secno">7. </span>Dealing with errors and exceptions</h2>
<div id="the-fileerror-interface" class="section">
<h3><span class="secno">7.1 </span>The <code>FileError</code> interface</h3>
<p>
This interface extends the <a href="#idl-def-FileError" class="idlType"><code>FileError</code></a> interface described in
[<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-WRITER">FILE-WRITER</a></cite>] to add several new error codes.
It is used to report errors asynchronously.
</p>
<pre class="idl"><span class="idlInterface" id="idl-def-FileError">interface <span class="idlInterfaceID">FileError</span> {
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-NOT_FOUND_ERR">NOT_FOUND_ERR</a></span> = <span class="idlConstValue">1</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-SECURITY_ERR">SECURITY_ERR</a></span> = <span class="idlConstValue">2</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-ABORT_ERR">ABORT_ERR</a></span> = <span class="idlConstValue">3</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-NOT_READABLE_ERR">NOT_READABLE_ERR</a></span> = <span class="idlConstValue">4</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-ENCODING_ERR">ENCODING_ERR</a></span> = <span class="idlConstValue">5</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-NO_MODIFICATION_ALLOWED_ERR">NO_MODIFICATION_ALLOWED_ERR</a></span> = <span class="idlConstValue">6</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-INVALID_STATE_ERR">INVALID_STATE_ERR</a></span> = <span class="idlConstValue">7</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-SYNTAX_ERR">SYNTAX_ERR</a></span> = <span class="idlConstValue">8</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-INVALID_MODIFICATION_ERR">INVALID_MODIFICATION_ERR</a></span> = <span class="idlConstValue">9</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-QUOTA_EXCEEDED_ERR">QUOTA_EXCEEDED_ERR</a></span> = <span class="idlConstValue">10</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-TYPE_MISMATCH_ERR">TYPE_MISMATCH_ERR</a></span> = <span class="idlConstValue">11</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileError-PATH_EXISTS_ERR">PATH_EXISTS_ERR</a></span> = <span class="idlConstValue">12</span>;</span>
<span class="idlAttribute"> attribute <span class="idlAttrType"><a>unsigned short</a></span> <span class="idlAttrName"><a href="#widl-FileError-code">code</a></span>;</span>
};</span>
</pre><div id="attributes-6" class="section"><h4><span class="secno">7.1.1 </span>Attributes</h4><dl class="attributes"><dt id="widl-FileError-code"><code>code</code> of type <span class="idlAttrType"><a>unsigned short</a></span></dt><dd>
The <a>code</a> attribute, on getting, <em class="rfc2119" title="must">must</em> return one of the
constants of the <a href="#idl-def-FileError" class="idlType"><code>FileError</code></a> error, which <em class="rfc2119" title="must">must</em> be the most
appropriate code from the table below.
<div><em>No exceptions.</em></div></dd></dl></div><div id="constants-2" class="section"><h4><span class="secno">7.1.2 </span>Constants</h4><dl class="constants"><dt id="widl-FileError-ABORT_ERR"><code>ABORT_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-ENCODING_ERR"><code>ENCODING_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-INVALID_MODIFICATION_ERR"><code>INVALID_MODIFICATION_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-INVALID_STATE_ERR"><code>INVALID_STATE_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-NOT_FOUND_ERR"><code>NOT_FOUND_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-NOT_READABLE_ERR"><code>NOT_READABLE_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-NO_MODIFICATION_ALLOWED_ERR"><code>NO_MODIFICATION_ALLOWED_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-PATH_EXISTS_ERR"><code>PATH_EXISTS_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-QUOTA_EXCEEDED_ERR"><code>QUOTA_EXCEEDED_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-SECURITY_ERR"><code>SECURITY_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-SYNTAX_ERR"><code>SYNTAX_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileError-TYPE_MISMATCH_ERR"><code>TYPE_MISMATCH_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd></dl></div>
</div>
<div id="the-fileexception-exception" class="section">
<h3><span class="secno">7.2 </span>The FileException exception</h3>
This interface extends the <a href="#idl-def-FileException" class="idlType"><code>FileException</code></a> interface described in
[<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-WRITER">FILE-WRITER</a></cite>] to add several new error codes. Any errors that need
to be reported synchronously, including all that occur during use of
the synchronous filesystem methods, are reported using the
FileException exception.
<pre class="idl"><span class="idlException" id="idl-def-FileException">exception <span class="idlExceptionID">FileException</span> {
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-NOT_FOUND_ERR">NOT_FOUND_ERR</a></span> = <span class="idlConstValue">1</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-SECURITY_ERR">SECURITY_ERR</a></span> = <span class="idlConstValue">2</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-ABORT_ERR">ABORT_ERR</a></span> = <span class="idlConstValue">3</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-NOT_READABLE_ERR">NOT_READABLE_ERR</a></span> = <span class="idlConstValue">4</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-ENCODING_ERR">ENCODING_ERR</a></span> = <span class="idlConstValue">5</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-NO_MODIFICATION_ALLOWED_ERR">NO_MODIFICATION_ALLOWED_ERR</a></span> = <span class="idlConstValue">6</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-INVALID_STATE_ERR">INVALID_STATE_ERR</a></span> = <span class="idlConstValue">7</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-SYNTAX_ERR">SYNTAX_ERR</a></span> = <span class="idlConstValue">8</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-INVALID_MODIFICATION_ERR">INVALID_MODIFICATION_ERR</a></span> = <span class="idlConstValue">9</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-QUOTA_EXCEEDED_ERR">QUOTA_EXCEEDED_ERR</a></span> = <span class="idlConstValue">10</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-TYPE_MISMATCH_ERR">TYPE_MISMATCH_ERR</a></span> = <span class="idlConstValue">11</span>;</span>
<span class="idlConst"> const <span class="idlConstType"><a>unsigned short</a></span> <span class="idlConstName"><a href="#widl-FileException-PATH_EXISTS_ERR">PATH_EXISTS_ERR</a></span> = <span class="idlConstValue">12</span>;</span>
<span class="idlField"> <span class="idlFieldType"><a>readonly attribute unsigned short</a></span> <span class="idlFieldName"><a href="#widl-FileException-code">code</a></span>;</span>
};</span>
</pre><div id="fields" class="section"><h4><span class="secno">7.2.1 </span>Fields</h4><dl class="fields"><dt id="widl-FileException-code"><code>code</code> of type <span class="idlFieldType"><a>readonly attribute unsigned short</a></span></dt><dd>
The <a>code</a> attribute, on getting, <em class="rfc2119" title="must">must</em> return one of the
constants of the <a href="#idl-def-FileException" class="idlType"><code>FileException</code></a> exception, which <em class="rfc2119" title="must">must</em> be the
most appropriate code from the table below.
</dd></dl></div><div id="constants-3" class="section"><h4><span class="secno">7.2.2 </span>Constants</h4><dl class="constants"><dt id="widl-FileException-ABORT_ERR"><code>ABORT_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-ENCODING_ERR"><code>ENCODING_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-INVALID_MODIFICATION_ERR"><code>INVALID_MODIFICATION_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-INVALID_STATE_ERR"><code>INVALID_STATE_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-NOT_FOUND_ERR"><code>NOT_FOUND_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-NOT_READABLE_ERR"><code>NOT_READABLE_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-NO_MODIFICATION_ALLOWED_ERR"><code>NO_MODIFICATION_ALLOWED_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-PATH_EXISTS_ERR"><code>PATH_EXISTS_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-QUOTA_EXCEEDED_ERR"><code>QUOTA_EXCEEDED_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-SECURITY_ERR"><code>SECURITY_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-SYNTAX_ERR"><code>SYNTAX_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd><dt id="widl-FileException-TYPE_MISMATCH_ERR"><code>TYPE_MISMATCH_ERR</code> of type <span class="idlConstType"><a>unsigned short</a></span></dt><dd> </dd></dl></div>
</div>
<div id="error-code-descriptions" class="section">
<h3><span class="secno">7.3 </span>Error Code Descriptions</h3>
<table class="simple">
<thead>
<tr><th>Name</th><th>Value</th><th>Description</th></tr>
</thead>
<tbody>
<tr><td>ABORT_ERR</td><td>3</td>
<td>
This value <em class="rfc2119" title="must not">must not</em> be used in this API.
</td>
</tr>
<tr>
<td>ENCODING_ERR</td><td>5</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code when a URL supplied to
the API is malformed.
</td>
</tr>
<tr>
<td>INVALID_MODIFICATION_ERR</td><td>9</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="may">may</em> use this code if the modification
requested is illegal. Examples of invalid modifications
include moving a directory into its own child or moving a file
into its parent directory without changing its name.
</td>
</tr>
<tr>
<td>INVALID_STATE_ERR</td><td>7</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="may">may</em> use this code if an operation depends on
state cached in an interface object that has changed since it
was read from disk.
<div class="issue">
Which values will actually go stale? Modification
time, name, more rarely type. If an atomic save [replacing
a file with a new one of the same name] happens underneath,
should we even be required to notice?
</div>
</td>
</tr>
<tr>
<td>NOT_FOUND_ERR</td><td>1</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code if a required file or
directory could not be found at the time an operation was
processed.
</td>
</tr>
<tr>
<td>NOT_READABLE_ERR</td><td>4</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code if a file or directory
cannot be read, typically due due to permission problems that
occur after a reference to a file has been acquired (e.g.
concurrent lock with another application).
</td>
</tr>
<tr>
<td>NO_MODIFICATION_ALLOWED_ERR</td><td>6</td>
<td><a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code when attempting to
write to a file or directory which cannot be modified due to
the state of the underlying filesystem.
</td>
</tr>
<tr>
<td>PATH_EXISTS_ERR</td><td>12</td>
<td><a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code when failing to
create a file or directory due to the existence of a file or
directory with the same path.
</td>
</tr>
<tr>
<td>QUOTA_EXCEEDED_ERR</td><td>10</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code if the operation failed
because it would cause the application to exceed its storage
quota.
</td>
</tr>
<tr>
<td>SECURITY_ERR</td><td>2</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="may">may</em> use this code if:
<ul>
<li> it is determined that certain files are unsafe for
access within a Web application</li>
<li>it is determined that too many calls are being made on
file resources</li>
</ul>
This is a security error code to be used in situations not
covered by any other error codes.
</td>
</tr>
<tr>
<td>SYNTAX_ERR</td><td>8</td>
<td>
This error code is not used in this specification; it is
included here only for completeness, as it is used in
[<cite><a class="bibref" rel="biblioentry" href="#bib-FILE-WRITER">FILE-WRITER</a></cite>].
</td>
</tr>
<tr>
<td>TYPE_MISMATCH_ERR</td><td>11</td>
<td>
<a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="must">must</em> use this code when the user has
attempted to look up a file or directory, but the Entry
found is of the wrong type [e.g. is a DirectoryEntry when the
user requested a FileEntry].
</td>
</tr>
</tbody>
</table>
</div>
</div>
<div id="uniformity-of-interface" class="section">
<!--OddPage--><h2><span class="secno">8. </span>Uniformity of interface</h2>
<div class="informative section">
<p>
In order to make it easy for web app developers to write portable
applications that work on all platforms, we enforce certain restrictions
and make certain guarantees with respect to paths used in this API.
</p><p><em>This section is non-normative.</em></p>
<p>
These restrictions are intended to prevent developers from accidentally
requiring the creation of paths that can only be created on a subset of
platforms. They are not intended to prevent access to files created
outside of this API.
</p>
</div>
The implementation <em class="rfc2119" title="must">must</em> refuse to create any file or directory whose name
or existence would violate these rules. The implementation <em class="rfc2119" title="may">may</em> accept a
noncompliant path where it is used to look up an Entry or EntrySync for an
existing file or directory. The implementation <em class="rfc2119" title="must not">must not</em> accept a
noncompliant path where it designates the new name of a file or directory
to be moved, copied, or created.
<p></p>
<div class="issue">
<p>
What about path and path segment lengths? For portability we should
probably clip segments at 255 bytes of UTF-8 in normalization form D,
and clip paths at 4095 bytes, but users can't easily check the byte
length of strings, or renormalize, so that makes for an annoying API.
It's also hard to control the true length of a path, due to renames of
parent directories, so we really just want to reject the
obviously-too-long; they won't often really come up anyway.
</p>
<p>
What about normalization? Are two different normalizations of the
same string equivalent as filenames? We don't want to let any
underlying platform behaviors leak through. This could be solved for
in-API paths by supplying a "filenames are equal" function and
normalizing everything inside the API, but we'd have to do it in both
directions, since paths created outside the API might not be
normalized.
</p>
</div>
<div id="case-sensitivity" class="section">
<h3><span class="secno">8.1 </span>Case-sensitivity</h3>
<p>
Paths in this filesystem are case-insensitive and case-preserving,
regardless of the rules of the underlying filesystem, if any.
</p>
<p>
Case-insensitivity <em class="rfc2119" title="should">should</em> respect the locale of the user.
</p>
<div class="issue">
We could choose the user or the author; I think the user's probably
the better way to go. There are still situations in which you can get
into trouble, but matching the locale of the user's computer should
avoid many of the most common conflicts.
</div>
</div>
<div id="directories" class="section">
<h3><span class="secno">8.2 </span>Directories</h3>
<p>
The directory separator is '/', regardless of the directory separator
used by the underlying system, if any.
</p>
<p>
The character '/', when it is the first character in a path, refers to
the root directory.
</p>
<p>
All absolute paths begin with '/'; no relative paths begin with '/'.
</p>
<p>
A <dfn id="dfn-relative-path">relative path</dfn> describes how to get from a particular
directory to a file or directory. All methods that accept paths are on
<a href="#idl-def-DirectoryEntry" class="idlType"><code>DirectoryEntry</code></a> or <a href="#idl-def-DirectoryEntrySync" class="idlType"><code>DirectoryEntrySync</code></a> objects; the paths,
if relative, are interpreted as being relative to the directories
represented by these objects.
</p>
<p>
An <dfn id="dfn-absolute-path">absolute path</dfn> is a <a href="#dfn-relative-path" class="internalDFN">relative path</a> from the root
directory, prepended with a '/'.
</p>
<p>
'.', when used where it is legal to use a directory name, refers to the
currently-referenced directory. Thus 'foo/./bar' is equivalent to
'foo/bar', and './foo' is equivalent to 'foo'.
</p>
<p>
'..', when used where it is legal to use a directory name, refers to the
parent of the currently-referenced directory. Thus, 'foo/..' refers to
the directory containing 'foo', and '../foo' refers to an element named
'foo' in the parent of the directory on whose DirectoryEntry or
DirectoryEntrySync the method receiving the path is being called.
</p>
<p>
Directories <em class="rfc2119" title="must not">must not</em> be made to contain more than 5000 entries.
</p>
</div>
<div id="naming-restrictions" class="section">
<h3><span class="secno">8.3 </span>Naming restrictions</h3>
<p>
Files and directories <em class="rfc2119" title="must not">must not</em> be named any of the following, and <em class="rfc2119" title="must
not">must
not</em> begin with any of the following followed by a period.
</p><ul>
<li>CON</li>
<li>PRN</li>
<li>AUX</li>
<li>NUL</li>
<li>COM1</li>
<li>COM2</li>
<li>COM3</li>
<li>COM4</li>
<li>COM5</li>
<li>COM6</li>
<li>COM7</li>
<li>COM8</li>
<li>COM9</li>
<li>LPT1</li>
<li>LPT2</li>
<li>LPT3</li>
<li>LPT4</li>
<li>LPT5</li>
<li>LPT6</li>
<li>LPT7</li>
<li>LPT8</li>
<li>LPT9</li>
</ul>
These restrictions hold regardless of case, i.e. "con", "PrN" are also
illegal.
<p></p>
<p>File and directory names <em class="rfc2119" title="must not">must not</em> end in period or space.
</p>
<p>File and directory names <em class="rfc2119" title="must not">must not</em> contain any of the following
characters:
</p><ul>
<li>/</li>
<li>\</li>
<li><</li>
<li>></li>
<li>:</li>
<li>?</li>
<li>*</li>
<li>"</li>
<li>|</li>
</ul>
<p></p>
<p>File and directory names <em class="rfc2119" title="must not">must not</em> contain any character whose
representation in UTF-8 is between 0 and 31, inclusive.
</p>
</div>
</div>
<div class="appendix section" id="acknowledgements">
<!--OddPage--><h2><span class="secno">A. </span>Acknowledgements</h2>
<p>
Thanks to Arun Ranganathan for his File API, Opera for theirs, and Robin
Berjon both for his work on various file APIs and for ReSpec.
</p>
</div>
<div id="references" class="appendix section"><!--OddPage--><h2><span class="secno">B. </span>References</h2><div id="normative-references" class="section"><h3><span class="secno">B.1 </span>Normative references</h3><dl class="bibliography"><dt id="bib-FILE-API">[FILE-API]</dt><dd>Arun Ranganathan. <a href="http://www.w3.org/TR/2009/WD-FileAPI-20091117/"><cite>File API.</cite></a> 17 November 2009. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2009/WD-FileAPI-20091117/">http://www.w3.org/TR/2009/WD-FileAPI-20091117/</a>
</dd><dt id="bib-FILE-WRITER">[FILE-WRITER]</dt><dd>Eric Uhrhane. <a href="http://dev.w3.org/2009/dap/file-system/file-writer.html"><cite>File Writer API.</cite></a> W3C Working Draft. (Work in progress.) URL: <a href="http://dev.w3.org/2009/dap/file-system/file-writer.html">http://dev.w3.org/2009/dap/file-system/file-writer.html</a>
</dd><dt id="bib-RFC2119">[RFC2119]</dt><dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key words for use in RFCs to Indicate Requirement Levels.</cite></a> March 1997. Internet RFC 2119. URL: <a href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
</dd><dt id="bib-WEBWORKERS">[WEBWORKERS]</dt><dd>Ian Hickson. <a href="http://www.w3.org/TR/2009/WD-workers-20091222/"><cite>Web Workers.</cite></a> 22 December 2009. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2009/WD-workers-20091222/">http://www.w3.org/TR/2009/WD-workers-20091222/</a>
</dd></dl></div><div id="informative-references" class="section"><h3><span class="secno">B.2 </span>Informative references</h3><p>No informative references.</p></div></div></body></html>