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| 31 | </td>
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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QDataSource Class Reference<br><small>[obsolete]</small></h1>
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| 33 |
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| 34 | <p>The QDataSource class is an asynchronous producer of data.
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| 35 | <a href="#details">More...</a>
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| 36 | <p><tt>#include <<a href="qasyncio-h.html">qasyncio.h</a>></tt>
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| 37 | <p>Inherits <a href="qasyncio.html">QAsyncIO</a>.
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| 38 | <p>Inherited by <a href="qiodevicesource.html">QIODeviceSource</a>.
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| 39 | <p><a href="qdatasource-members.html">List of all member functions.</a>
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| 40 | <h2>Public Members</h2>
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| 41 | <ul>
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| 42 | <li class=fn>virtual int <a href="#readyToSend"><b>readyToSend</b></a> () = 0</li>
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| 43 | <li class=fn>virtual void <a href="#sendTo"><b>sendTo</b></a> ( QDataSink *, int count ) = 0</li>
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| 44 | <li class=fn>void <a href="#maybeReady"><b>maybeReady</b></a> ()</li>
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| 45 | <li class=fn>virtual bool <a href="#rewindable"><b>rewindable</b></a> () const</li>
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| 46 | <li class=fn>virtual void <a href="#enableRewind"><b>enableRewind</b></a> ( bool on )</li>
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| 47 | <li class=fn>virtual void <a href="#rewind"><b>rewind</b></a> ()</li>
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| 48 | </ul>
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| 49 | <hr><a name="details"></a><h2>Detailed Description</h2>
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| 50 |
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| 51 |
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| 52 | <b>This class is obsolete.</b> It is provided to keep old source working. We strongly advise against using it in new code.
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| 53 | <p> The QDataSource class is an asynchronous producer of data.
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| 54 | <p> A data source is an object which provides data from some source in an
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| 55 | asynchronous manner. This means that at some time not determined by
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| 56 | the data source, blocks of data will be taken from it for processing.
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| 57 | The data source is able to limit the maximum size of such blocks which
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| 58 | it is currently able to provide.
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| 59 | <p> <p>See also <a href="qasyncio.html">QAsyncIO</a>, <a href="qdatasink.html">QDataSink</a>, and <a href="qdatapump.html">QDataPump</a>.
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| 60 |
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| 61 | <hr><h2>Member Function Documentation</h2>
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| 62 | <h3 class=fn>void <a name="enableRewind"></a>QDataSource::enableRewind ( bool on )<tt> [virtual]</tt>
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| 63 | </h3>
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| 64 | If this function is called with <em>on</em> set to TRUE, and <a href="#rewindable">rewindable</a>()
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| 65 | is TRUE, then the data source must take measures to allow the <a href="#rewind">rewind</a>()
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| 66 | function to subsequently operate as described. If rewindable() is FALSE,
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| 67 | the function should call <a href="#enableRewind">QDataSource::enableRewind</a>(), which aborts with
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| 68 | a <a href="qapplication.html#qFatal">qFatal</a>() error.
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| 69 | <p> For example, a network connection may choose to use a disk cache
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| 70 | of input only if rewinding is enabled before the first buffer-full of
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| 71 | data is discarded, returning FALSE in rewindable() if that first buffer
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| 72 | is discarded.
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| 73 |
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| 74 | <p>Reimplemented in <a href="qiodevicesource.html#enableRewind">QIODeviceSource</a>.
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| 75 | <h3 class=fn>void <a name="maybeReady"></a>QDataSource::maybeReady ()
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| 76 | </h3>
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| 77 | This should be called whenever <a href="#readyToSend">readyToSend</a>() might have become non-zero.
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| 78 | It is merely calls <a href="qasyncio.html#ready">QAsyncIO::ready</a>() if readyToSend() is non-zero.
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| 79 |
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| 80 | <h3 class=fn>int <a name="readyToSend"></a>QDataSource::readyToSend ()<tt> [pure virtual]</tt>
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| 81 | </h3>
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| 82 |
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| 83 | <p> The data source should return a value indicating how much data it is ready
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| 84 | to provide. This may be 0. If the data source knows it will never be
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| 85 | able to provide any more data (until after a <a href="#rewind">rewind</a>()), it may return -1.
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| 86 |
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| 87 | <p>Reimplemented in <a href="qiodevicesource.html#readyToSend">QIODeviceSource</a>.
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| 88 | <h3 class=fn>void <a name="rewind"></a>QDataSource::rewind ()<tt> [virtual]</tt>
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| 89 | </h3>
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| 90 | This function rewinds the data source. This may only be called if
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| 91 | <a href="#enableRewind">enableRewind</a>(TRUE) has been previously called.
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| 92 |
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| 93 | <p>Reimplemented in <a href="qiodevicesource.html#rewind">QIODeviceSource</a>.
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| 94 | <h3 class=fn>bool <a name="rewindable"></a>QDataSource::rewindable () const<tt> [virtual]</tt>
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| 95 | </h3>
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| 96 | This function should return TRUE if the data source can be rewound.
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| 97 | <p> The default returns FALSE.
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| 98 |
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| 99 | <p>Reimplemented in <a href="qiodevicesource.html#rewindable">QIODeviceSource</a>.
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| 100 | <h3 class=fn>void <a name="sendTo"></a>QDataSource::sendTo ( <a href="qdatasink.html">QDataSink</a> *, int count )<tt> [pure virtual]</tt>
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| 101 | </h3>
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| 102 |
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| 103 | <p> This function is called to extract data from the source, by sending
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| 104 | it to the given data sink. The <em>count</em> will be no more than the amount
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| 105 | indicated by the most recent call to <a href="#readyToSend">readyToSend</a>(). The source must
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| 106 | use all the provided data, and the sink will be prepared to accept at
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| 107 | least this much data.
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| 108 |
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| 109 | <p>Reimplemented in <a href="qiodevicesource.html#sendTo">QIODeviceSource</a>.
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| 110 | <!-- eof -->
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| 111 | <hr><p>
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| 112 | This file is part of the <a href="index.html">Qt toolkit</a>.
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| 113 | Copyright © 1995-2007
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| 114 | <a href="http://www.trolltech.com/">Trolltech</a>. All Rights Reserved.<p><address><hr><div align=center>
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| 116 | <td>Copyright © 2007
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| 117 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 118 | <td align=right><div align=right>Qt 3.3.8</div>
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| 119 | </table></div></address></body>
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