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6<title>QBuffer Class</title>
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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>QBuffer Class Reference</h1>
33
34<p>The QBuffer class is an I/O device that operates on a QByteArray.
35<a href="#details">More...</a>
36<p>All the functions in this class are <a href="threads.html#reentrant">reentrant</a> when Qt is built with thread support.</p>
37<p><tt>#include &lt;<a href="qbuffer-h.html">qbuffer.h</a>&gt;</tt>
38<p>Inherits <a href="qiodevice.html">QIODevice</a>.
39<p><a href="qbuffer-members.html">List of all member functions.</a>
40<h2>Public Members</h2>
41<ul>
42<li class=fn><a href="#QBuffer"><b>QBuffer</b></a> ()</li>
43<li class=fn><a href="#QBuffer-2"><b>QBuffer</b></a> ( QByteArray&nbsp;buf )</li>
44<li class=fn><a href="#~QBuffer"><b>~QBuffer</b></a> ()</li>
45<li class=fn>QByteArray <a href="#buffer"><b>buffer</b></a> () const</li>
46<li class=fn>bool <a href="#setBuffer"><b>setBuffer</b></a> ( QByteArray&nbsp;buf )</li>
47<li class=fn>virtual Q_LONG <a href="#writeBlock"><b>writeBlock</b></a> ( const&nbsp;char&nbsp;*&nbsp;p, Q_ULONG&nbsp;len )</li>
48<li class=fn>Q_LONG <a href="#writeBlock-2"><b>writeBlock</b></a> ( const&nbsp;QByteArray&nbsp;&amp;&nbsp;data )</li>
49</ul>
50<hr><a name="details"></a><h2>Detailed Description</h2>
51
52
53
54The QBuffer class is an I/O device that operates on a <a href="qbytearray.html">QByteArray</a>.
55<p>
56
57<p> QBuffer is used to read and write to a memory buffer. It is
58normally used with a <a href="qtextstream.html">QTextStream</a> or a <a href="qdatastream.html">QDataStream</a>. QBuffer has an
59associated QByteArray which holds the buffer data. The <a href="qiodevice.html#size">size</a>() of
60the buffer is automatically adjusted as data is written.
61<p> The constructor <tt>QBuffer(QByteArray)</tt> creates a QBuffer using an
62existing byte array. The byte array can also be set with
63<a href="#setBuffer">setBuffer</a>(). Writing to the QBuffer will modify the original byte
64array because QByteArray is <a href="shclass.html">explicitly
65 shared.</a>
66<p> Use <a href="qiodevice.html#open">open</a>() to open the buffer before use and to set the mode
67(read-only, write-only, etc.). <a href="qiodevice.html#close">close</a>() closes the buffer. The
68buffer must be closed before reopening or calling setBuffer().
69<p> A common way to use QBuffer is through <a href="qdatastream.html">QDataStream</a> or <a href="qtextstream.html">QTextStream</a>, which have constructors that take a QBuffer
70parameter. For convenience, there are also QDataStream and
71<a href="qtextstream.html">QTextStream</a> constructors that take a <a href="qbytearray.html">QByteArray</a> parameter. These
72constructors create and open an internal QBuffer.
73<p> Note that QTextStream can also operate on a <a href="qstring.html">QString</a> (a Unicode
74string); a QBuffer cannot.
75<p> You can also use QBuffer directly through the standard <a href="qiodevice.html">QIODevice</a>
76functions <a href="qiodevice.html#readBlock">readBlock</a>(), <a href="#writeBlock">writeBlock</a>() <a href="qiodevice.html#readLine">readLine</a>(), <a href="qiodevice.html#at">at</a>(), <a href="qiodevice.html#getch">getch</a>(),
77<a href="qiodevice.html#putch">putch</a>() and <a href="qiodevice.html#ungetch">ungetch</a>().
78<p> <p>See also <a href="qfile.html">QFile</a>, <a href="qdatastream.html">QDataStream</a>, <a href="qtextstream.html">QTextStream</a>, <a href="qbytearray.html">QByteArray</a>, <a href="shclass.html">Shared Classes</a>, <a href="collection.html">Collection Classes</a>, and <a href="io.html">Input/Output and Networking</a>.
79
80<hr><h2>Member Function Documentation</h2>
81<h3 class=fn><a name="QBuffer"></a>QBuffer::QBuffer ()
82</h3>
83Constructs an empty buffer.
84
85<h3 class=fn><a name="QBuffer-2"></a>QBuffer::QBuffer ( <a href="qbytearray.html">QByteArray</a>&nbsp;buf )
86</h3>
87Constructs a buffer that operates on <em>buf</em>.
88<p> If you open the buffer in write mode (<a href="qfile.html#open"><a href="qfile.html#open">IO_WriteOnly</a></a> or
89<a href="qfile.html#open">IO_ReadWrite</a>) and write something into the buffer, <em>buf</em>
90will be modified.
91<p> Example:
92<pre>
93 <a href="qcstring.html">QCString</a> str = "abc";
94 QBuffer b( str );
95 b.<a href="qiodevice.html#open">open</a>( IO_WriteOnly );
96 b.<a href="qiodevice.html#at">at</a>( 3 ); // position at the 4th character (the terminating \0)
97 b.<a href="#writeBlock">writeBlock</a>( "def", 4 ); // write "def" including the terminating \0
98 b.<a href="qiodevice.html#close">close</a>();
99 // Now, str == "abcdef" with a terminating \0
100 </pre>
101
102<p> <p>See also <a href="#setBuffer">setBuffer</a>().
103
104<h3 class=fn><a name="~QBuffer"></a>QBuffer::~QBuffer ()
105</h3>
106Destroys the buffer.
107
108<h3 class=fn><a href="qbytearray.html">QByteArray</a> <a name="buffer"></a>QBuffer::buffer () const
109</h3>
110
111<p> Returns this buffer's byte array.
112<p> <p>See also <a href="#setBuffer">setBuffer</a>().
113
114<h3 class=fn>bool <a name="setBuffer"></a>QBuffer::setBuffer ( <a href="qbytearray.html">QByteArray</a>&nbsp;buf )
115</h3>
116Replaces the buffer's contents with <em>buf</em> and returns TRUE.
117<p> Does nothing (and returns FALSE) if <a href="qiodevice.html#isOpen">isOpen</a>() is TRUE.
118<p> Note that if you open the buffer in write mode (<a href="qfile.html#open"><a href="qfile.html#open">IO_WriteOnly</a></a> or
119<a href="qfile.html#open">IO_ReadWrite</a>) and write something into the buffer, <em>buf</em> is also
120modified because <a href="qbytearray.html">QByteArray</a> is an <a href="shclass.html#explicitly-shared">explicitly shared</a> class.
121<p> <p>See also <a href="#buffer">buffer</a>(), <a href="qiodevice.html#open">open</a>(), and <a href="qiodevice.html#close">close</a>().
122
123<h3 class=fn>Q_LONG <a name="writeBlock"></a>QBuffer::writeBlock ( const&nbsp;char&nbsp;*&nbsp;p, Q_ULONG&nbsp;len )<tt> [virtual]</tt>
124</h3>
125Writes <em>len</em> bytes from <em>p</em> into the buffer at the current
126index position, overwriting any characters there and extending the
127buffer if necessary. Returns the number of bytes actually written.
128<p> Returns -1 if an error occurred.
129<p> <p>See also <a href="qiodevice.html#readBlock">readBlock</a>().
130
131<p>Reimplemented from <a href="qiodevice.html#writeBlock">QIODevice</a>.
132<h3 class=fn>Q_LONG <a name="writeBlock-2"></a>QBuffer::writeBlock ( const&nbsp;<a href="qbytearray.html">QByteArray</a>&nbsp;&amp;&nbsp;data )
133</h3>
134This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
135<p> This convenience function is the same as calling
136<tt>writeBlock( data.data(), data.size() )</tt> with <em>data</em>.
137
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