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<td >Qt 5.12</td><td ><a href="qtnetwork-index.html">Qt Network</a></td><td ><a href="qtnetwork-module.html">C++ Classes</a></td><td >QNetworkDiskCache</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right"><a href="qtnetwork-index.html">Qt 5.12.6 Reference Documentation</a></td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#reimplemented-public-functions">Reimplemented Public Functions</a></li>
<li class="level1"><a href="#public-slots">Public Slots</a></li>
<li class="level1"><a href="#static-public-members">Static Public Members</a></li>
<li class="level1"><a href="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QNetworkDiskCache Class</h1>
<!-- $$$QNetworkDiskCache-brief -->
<p>The <a href="qnetworkdiskcache.html">QNetworkDiskCache</a> class provides a very basic disk cache. <a href="#details">More...</a></p>
<!-- @@@QNetworkDiskCache -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QNetworkDiskCache></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += network</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 4.5</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="qabstractnetworkcache.html">QAbstractNetworkCache</a></td></tr></table></div><ul>
<li><a href="qnetworkdiskcache-members.html">List of all members, including inherited members</a></li>
<li><a href="qnetworkdiskcache-obsolete.html">Obsolete members</a></li>
</ul>
<a name="public-functions"></a>
<h2 id="public-functions">Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#QNetworkDiskCache">QNetworkDiskCache</a></b>(QObject *<i>parent</i> = nullptr)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#dtor.QNetworkDiskCache">~QNetworkDiskCache</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QString </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#cacheDirectory">cacheDirectory</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QNetworkCacheMetaData </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#fileMetaData">fileMetaData</a></b>(const QString &<i>fileName</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> qint64 </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#maximumCacheSize">maximumCacheSize</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#setCacheDirectory">setCacheDirectory</a></b>(const QString &<i>cacheDir</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#setMaximumCacheSize">setMaximumCacheSize</a></b>(qint64 <i>size</i>)</td></tr>
</table></div>
<a name="reimplemented-public-functions"></a>
<h2 id="reimplemented-public-functions">Reimplemented Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual qint64 </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#cacheSize">cacheSize</a></b>() const override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual QIODevice *</td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#data">data</a></b>(const QUrl &<i>url</i>) override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#insert">insert</a></b>(QIODevice *<i>device</i>) override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual QNetworkCacheMetaData </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#metaData">metaData</a></b>(const QUrl &<i>url</i>) override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual QIODevice *</td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#prepare">prepare</a></b>(const QNetworkCacheMetaData &<i>metaData</i>) override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual bool </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#remove">remove</a></b>(const QUrl &<i>url</i>) override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#updateMetaData">updateMetaData</a></b>(const QNetworkCacheMetaData &<i>metaData</i>) override</td></tr>
</table></div>
<ul>
<li class="fn">7 public functions inherited from <a href="qabstractnetworkcache.html#public-functions">QAbstractNetworkCache</a></li>
<li class="fn">31 public functions inherited from <a href="../qtcore/qobject.html#public-functions">QObject</a></li>
</ul>
<a name="public-slots"></a>
<h2 id="public-slots">Public Slots</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#clear">clear</a></b>() override</td></tr>
</table></div>
<ul>
<li class="fn">1 public slot inherited from <a href="qabstractnetworkcache.html#public-slots">QAbstractNetworkCache</a></li>
<li class="fn">1 public slot inherited from <a href="../qtcore/qobject.html#public-slots">QObject</a></li>
</ul>
<a name="static-public-members"></a>
<h2 id="static-public-members">Static Public Members</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> const QMetaObject </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#staticMetaObject-var">staticMetaObject</a></b></td></tr>
</table></div>
<ul>
<li class="fn">9 static public members inherited from <a href="../qtcore/qobject.html#static-public-members">QObject</a></li>
</ul>
<a name="protected-functions"></a>
<h2 id="protected-functions">Protected Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual qint64 </td><td class="memItemRight bottomAlign"><b><a href="qnetworkdiskcache.html#expire">expire</a></b>()</td></tr>
</table></div>
<ul>
<li class="fn">9 protected functions inherited from <a href="../qtcore/qobject.html#protected-functions">QObject</a></li>
</ul>
<h3>Additional Inherited Members</h3>
<ul>
<li class="fn">1 property inherited from <a href="../qtcore/qobject.html#properties">QObject</a></li>
<li class="fn">2 signals inherited from <a href="../qtcore/qobject.html#signals">QObject</a></li>
</ul>
<a name="details"></a>
<!-- $$$QNetworkDiskCache-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qnetworkdiskcache.html">QNetworkDiskCache</a> class provides a very basic disk cache.</p>
<p><a href="qnetworkdiskcache.html">QNetworkDiskCache</a> stores each url in its own file inside of the <a href="qnetworkdiskcache.html#cacheDirectory">cacheDirectory</a> using <a href="../qtcore/qdatastream.html">QDataStream</a>. Files with a text MimeType are compressed using <a href="../qtcore/qbytearray.html#qCompress">qCompress</a>. Data is written to disk only in <a href="qnetworkdiskcache.html#insert">insert</a>() and <a href="qnetworkdiskcache.html#updateMetaData">updateMetaData</a>().</p>
<p>Currently you cannot share the same cache files with more than one disk cache.</p>
<p><a href="qnetworkdiskcache.html">QNetworkDiskCache</a> by default limits the amount of space that the cache will use on the system to 50MB.</p>
<p>Note you have to set the cache directory before it will work.</p>
<p>A network disk cache can be enabled by:</p>
<pre class="cpp">
<span class="type"><a href="qnetworkaccessmanager.html">QNetworkAccessManager</a></span> <span class="operator">*</span>manager <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qnetworkaccessmanager.html">QNetworkAccessManager</a></span>(<span class="keyword">this</span>);
<span class="type"><a href="qnetworkdiskcache.html#QNetworkDiskCache">QNetworkDiskCache</a></span> <span class="operator">*</span>diskCache <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qnetworkdiskcache.html#QNetworkDiskCache">QNetworkDiskCache</a></span>(<span class="keyword">this</span>);
diskCache<span class="operator">-</span><span class="operator">></span>setCacheDirectory(<span class="string">"cacheDir"</span>);
manager<span class="operator">-</span><span class="operator">></span>setCache(diskCache);
</pre>
<p>When sending requests, to control the preference of when to use the cache and when to use the network, consider the following:</p>
<pre class="cpp">
<span class="comment">// do a normal request (preferred from network, as this is the default)</span>
<span class="type"><a href="qnetworkrequest.html">QNetworkRequest</a></span> request(<span class="type"><a href="../qtcore/qurl.html">QUrl</a></span>(<span class="type"><a href="../qtcore/qstring.html">QString</a></span>(<span class="string">"http://qt-project.org"</span>)));
manager<span class="operator">-</span><span class="operator">></span>get(request);
<span class="comment">// do a request preferred from cache</span>
<span class="type"><a href="qnetworkrequest.html">QNetworkRequest</a></span> request2(<span class="type"><a href="../qtcore/qurl.html">QUrl</a></span>(<span class="type"><a href="../qtcore/qstring.html">QString</a></span>(<span class="string">"http://qt-project.org"</span>)));
request2<span class="operator">.</span>setAttribute(<span class="type"><a href="qnetworkrequest.html">QNetworkRequest</a></span><span class="operator">::</span>CacheLoadControlAttribute<span class="operator">,</span> <span class="type"><a href="qnetworkrequest.html">QNetworkRequest</a></span><span class="operator">::</span>PreferCache);
manager<span class="operator">-</span><span class="operator">></span>get(request2);
</pre>
<p>To check whether the response came from the cache or from the network, the following can be applied:</p>
<pre class="cpp">
<span class="type">void</span> replyFinished(<span class="type"><a href="qnetworkreply.html">QNetworkReply</a></span> <span class="operator">*</span>reply) {
<span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span> fromCache <span class="operator">=</span> reply<span class="operator">-</span><span class="operator">></span>attribute(<span class="type"><a href="qnetworkrequest.html">QNetworkRequest</a></span><span class="operator">::</span>SourceIsFromCacheAttribute);
<a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator"><</span><span class="operator"><</span> <span class="string">"page from cache?"</span> <span class="operator"><</span><span class="operator"><</span> fromCache<span class="operator">.</span>toBool();
}
</pre>
</div>
<!-- @@@QNetworkDiskCache -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QNetworkDiskCache[overload1]$$$QNetworkDiskCacheQObject* -->
<h3 class="fn" id="QNetworkDiskCache"><a name="QNetworkDiskCache"></a>QNetworkDiskCache::<span class="name">QNetworkDiskCache</span>(<span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> *<i>parent</i> = nullptr)</h3>
<p>Creates a new disk cache. The <i>parent</i> argument is passed to <a href="qabstractnetworkcache.html">QAbstractNetworkCache</a>'s constructor.</p>
<!-- @@@QNetworkDiskCache -->
<!-- $$$~QNetworkDiskCache[overload1]$$$~QNetworkDiskCache -->
<h3 class="fn" id="dtor.QNetworkDiskCache"><a name="dtor.QNetworkDiskCache"></a><code>[virtual] </code>QNetworkDiskCache::<span class="name">~QNetworkDiskCache</span>()</h3>
<p>Destroys the cache object. This does not clear the disk cache.</p>
<!-- @@@~QNetworkDiskCache -->
<!-- $$$cacheDirectory[overload1]$$$cacheDirectory -->
<h3 class="fn" id="cacheDirectory"><a name="cacheDirectory"></a><span class="type"><a href="../qtcore/qstring.html">QString</a></span> QNetworkDiskCache::<span class="name">cacheDirectory</span>() const</h3>
<p>Returns the location where cached files will be stored.</p>
<p><b>See also </b><a href="qnetworkdiskcache.html#setCacheDirectory">setCacheDirectory</a>().</p>
<!-- @@@cacheDirectory -->
<!-- $$$cacheSize[overload1]$$$cacheSize -->
<h3 class="fn" id="cacheSize"><a name="cacheSize"></a><code>[override virtual] </code><span class="type"><a href="../qtcore/qtglobal.html#qint64-typedef">qint64</a></span> QNetworkDiskCache::<span class="name">cacheSize</span>() const</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#cacheSize">QAbstractNetworkCache::cacheSize</a>().</p>
<!-- @@@cacheSize -->
<!-- $$$clear[overload1]$$$clear -->
<h3 class="fn" id="clear"><a name="clear"></a><code>[override virtual slot] </code><span class="type">void</span> QNetworkDiskCache::<span class="name">clear</span>()</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#clear">QAbstractNetworkCache::clear</a>().</p>
<!-- @@@clear -->
<!-- $$$data[overload1]$$$dataconstQUrl& -->
<h3 class="fn" id="data"><a name="data"></a><code>[override virtual] </code><span class="type"><a href="../qtcore/qiodevice.html">QIODevice</a></span> *QNetworkDiskCache::<span class="name">data</span>(const <span class="type"><a href="../qtcore/qurl.html">QUrl</a></span> &<i>url</i>)</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#data">QAbstractNetworkCache::data</a>().</p>
<!-- @@@data -->
<!-- $$$expire[overload1]$$$expire -->
<h3 class="fn" id="expire"><a name="expire"></a><code>[virtual protected] </code><span class="type"><a href="../qtcore/qtglobal.html#qint64-typedef">qint64</a></span> QNetworkDiskCache::<span class="name">expire</span>()</h3>
<p>Cleans the cache so that its size is under the maximum cache size. Returns the current size of the cache.</p>
<p>When the current size of the cache is greater than the <a href="qnetworkdiskcache.html#maximumCacheSize">maximumCacheSize</a>() older cache files are removed until the total size is less then 90% of <a href="qnetworkdiskcache.html#maximumCacheSize">maximumCacheSize</a>() starting with the oldest ones first using the file creation date to determine how old a cache file is.</p>
<p>Subclasses can reimplement this function to change the order that cache files are removed taking into account information in the application knows about that <a href="qnetworkdiskcache.html">QNetworkDiskCache</a> does not, for example the number of times a cache is accessed.</p>
<p><b>Note: </b><a href="qnetworkdiskcache.html#cacheSize">cacheSize</a>() calls expire if the current cache size is unknown.</p><p><b>See also </b><a href="qnetworkdiskcache.html#maximumCacheSize">maximumCacheSize</a>() and <a href="qnetworkdiskcache.html#fileMetaData">fileMetaData</a>().</p>
<!-- @@@expire -->
<!-- $$$fileMetaData[overload1]$$$fileMetaDataconstQString& -->
<h3 class="fn" id="fileMetaData"><a name="fileMetaData"></a><span class="type"><a href="qnetworkcachemetadata.html">QNetworkCacheMetaData</a></span> QNetworkDiskCache::<span class="name">fileMetaData</span>(const <span class="type"><a href="../qtcore/qstring.html">QString</a></span> &<i>fileName</i>) const</h3>
<p>Returns the <a href="qnetworkcachemetadata.html">QNetworkCacheMetaData</a> for the cache file <i>fileName</i>.</p>
<p>If <i>fileName</i> is not a cache file <a href="qnetworkcachemetadata.html">QNetworkCacheMetaData</a> will be invalid.</p>
<!-- @@@fileMetaData -->
<!-- $$$insert[overload1]$$$insertQIODevice* -->
<h3 class="fn" id="insert"><a name="insert"></a><code>[override virtual] </code><span class="type">void</span> QNetworkDiskCache::<span class="name">insert</span>(<span class="type"><a href="../qtcore/qiodevice.html">QIODevice</a></span> *<i>device</i>)</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#insert">QAbstractNetworkCache::insert</a>().</p>
<!-- @@@insert -->
<!-- $$$maximumCacheSize[overload1]$$$maximumCacheSize -->
<h3 class="fn" id="maximumCacheSize"><a name="maximumCacheSize"></a><span class="type"><a href="../qtcore/qtglobal.html#qint64-typedef">qint64</a></span> QNetworkDiskCache::<span class="name">maximumCacheSize</span>() const</h3>
<p>Returns the current maximum size for the disk cache.</p>
<p><b>See also </b><a href="qnetworkdiskcache.html#setMaximumCacheSize">setMaximumCacheSize</a>().</p>
<!-- @@@maximumCacheSize -->
<!-- $$$metaData[overload1]$$$metaDataconstQUrl& -->
<h3 class="fn" id="metaData"><a name="metaData"></a><code>[override virtual] </code><span class="type"><a href="qnetworkcachemetadata.html">QNetworkCacheMetaData</a></span> QNetworkDiskCache::<span class="name">metaData</span>(const <span class="type"><a href="../qtcore/qurl.html">QUrl</a></span> &<i>url</i>)</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#metaData">QAbstractNetworkCache::metaData</a>().</p>
<!-- @@@metaData -->
<!-- $$$prepare[overload1]$$$prepareconstQNetworkCacheMetaData& -->
<h3 class="fn" id="prepare"><a name="prepare"></a><code>[override virtual] </code><span class="type"><a href="../qtcore/qiodevice.html">QIODevice</a></span> *QNetworkDiskCache::<span class="name">prepare</span>(const <span class="type"><a href="qnetworkcachemetadata.html">QNetworkCacheMetaData</a></span> &<i>metaData</i>)</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#prepare">QAbstractNetworkCache::prepare</a>().</p>
<!-- @@@prepare -->
<!-- $$$remove[overload1]$$$removeconstQUrl& -->
<h3 class="fn" id="remove"><a name="remove"></a><code>[override virtual] </code><span class="type">bool</span> QNetworkDiskCache::<span class="name">remove</span>(const <span class="type"><a href="../qtcore/qurl.html">QUrl</a></span> &<i>url</i>)</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#remove">QAbstractNetworkCache::remove</a>().</p>
<!-- @@@remove -->
<!-- $$$setCacheDirectory[overload1]$$$setCacheDirectoryconstQString& -->
<h3 class="fn" id="setCacheDirectory"><a name="setCacheDirectory"></a><span class="type">void</span> QNetworkDiskCache::<span class="name">setCacheDirectory</span>(const <span class="type"><a href="../qtcore/qstring.html">QString</a></span> &<i>cacheDir</i>)</h3>
<p>Sets the directory where cached files will be stored to <i>cacheDir</i></p>
<p><a href="qnetworkdiskcache.html">QNetworkDiskCache</a> will create this directory if it does not exists.</p>
<p>Prepared cache items will be stored in the new cache directory when they are inserted.</p>
<p><b>See also </b><a href="qnetworkdiskcache.html#cacheDirectory">cacheDirectory</a>() and <a href="../qtgui/qdesktopservices-obsolete.html#StandardLocation-enum">QDesktopServices::CacheLocation</a>.</p>
<!-- @@@setCacheDirectory -->
<!-- $$$setMaximumCacheSize[overload1]$$$setMaximumCacheSizeqint64 -->
<h3 class="fn" id="setMaximumCacheSize"><a name="setMaximumCacheSize"></a><span class="type">void</span> QNetworkDiskCache::<span class="name">setMaximumCacheSize</span>(<span class="type"><a href="../qtcore/qtglobal.html#qint64-typedef">qint64</a></span> <i>size</i>)</h3>
<p>Sets the maximum size of the disk cache to be <i>size</i>.</p>
<p>If the new size is smaller then the current cache size then the cache will call <a href="qnetworkdiskcache.html#expire">expire</a>().</p>
<p><b>See also </b><a href="qnetworkdiskcache.html#maximumCacheSize">maximumCacheSize</a>().</p>
<!-- @@@setMaximumCacheSize -->
<!-- $$$updateMetaData[overload1]$$$updateMetaDataconstQNetworkCacheMetaData& -->
<h3 class="fn" id="updateMetaData"><a name="updateMetaData"></a><code>[override virtual] </code><span class="type">void</span> QNetworkDiskCache::<span class="name">updateMetaData</span>(const <span class="type"><a href="qnetworkcachemetadata.html">QNetworkCacheMetaData</a></span> &<i>metaData</i>)</h3>
<p>Reimplemented from <a href="qabstractnetworkcache.html#updateMetaData">QAbstractNetworkCache::updateMetaData</a>().</p>
<!-- @@@updateMetaData -->
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<acronym title="Copyright">©</acronym> 2019 The Qt Company Ltd.
Documentation contributions included herein are the copyrights of
their respective owners.<br/> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br/> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property
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