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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<h1 align=center>QIODevice Class Reference</h1><br clear="all">
<p>
The QIODevice class is the base class of I/O devices.
<a href="#details">More...</a>
<p>
<code>#include <<a href="qiodevice-h.html">qiodevice.h</a>></code>
<p>Inherited by <a href="qbuffer.html">QBuffer</a>, <a href="qfile.html">QFile</a>, <a href="qsocket.html">QSocket</a> and <a href="qsocketdevice.html">QSocketDevice</a>.
<p><a href="qiodevice-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li><div class="fn"><a href="#8fa6e5"><b>QIODevice</b></a>()</div>
<li><div class="fn">virtual<a href="#ac6bf9"><b>~QIODevice</b></a>()</div>
<li><div class="fn">int<a href="#6cd02d"><b>flags</b></a>()const</div>
<li><div class="fn">int<a href="#ac5d91"><b>mode</b></a>()const</div>
<li><div class="fn">int<a href="#27e36d"><b>state</b></a>()const</div>
<li><div class="fn">bool<a href="#39a85e"><b>isDirectAccess</b></a>()const</div>
<li><div class="fn">bool<a href="#d264a5"><b>isSequentialAccess</b></a>()const</div>
<li><div class="fn">bool<a href="#663267"><b>isCombinedAccess</b></a>()const</div>
<li><div class="fn">bool<a href="#38dfa5"><b>isBuffered</b></a>()const</div>
<li><div class="fn">bool<a href="#d4dd04"><b>isRaw</b></a>()const</div>
<li><div class="fn">bool<a href="#a5d52b"><b>isSynchronous</b></a>()const</div>
<li><div class="fn">bool<a href="#7d84ac"><b>isAsynchronous</b></a>()const</div>
<li><div class="fn">bool<a href="#8b6c51"><b>isTranslated</b></a>()const</div>
<li><div class="fn">bool<a href="#a109ae"><b>isReadable</b></a>()const</div>
<li><div class="fn">bool<a href="#67abcc"><b>isWritable</b></a>()const</div>
<li><div class="fn">bool<a href="#ed997c"><b>isReadWrite</b></a>()const</div>
<li><div class="fn">bool<a href="#706edf"><b>isInactive</b></a>()const</div>
<li><div class="fn">bool<a href="#1bc7b0"><b>isOpen</b></a>()const</div>
<li><div class="fn">int<a href="#494f6f"><b>status</b></a>()const</div>
<li><div class="fn">void<a href="#0fbc1d"><b>resetStatus</b></a>()</div>
<li><div class="fn">virtualbool<a href="#756b18"><b>open</b></a>(intmode)</div>
<li><div class="fn">virtualvoid<a href="#50fcfd"><b>close</b></a>()</div>
<li><div class="fn">virtualvoid<a href="#dfd9f0"><b>flush</b></a>()</div>
<li><div class="fn">virtualuint<a href="#8ddedd"><b>size</b></a>()const</div>
<li><div class="fn">virtualint<a href="#a8b90e"><b>at</b></a>()const</div>
<li><div class="fn">virtualbool<a href="#90fb01"><b>at</b></a>(int)</div>
<li><div class="fn">virtualbool<a href="#d51a01"><b>atEnd</b></a>()const</div>
<li><div class="fn">bool<a href="#f119f6"><b>reset</b></a>()</div>
<li><div class="fn">virtualint<a href="#c12e6e"><b>readBlock</b></a>(char*data, uintmaxlen)</div>
<li><div class="fn">virtualint<a href="#924d2f"><b>writeBlock</b></a>(constchar*data, uintlen)</div>
<li><div class="fn">virtualint<a href="#0b6051"><b>readLine</b></a>(char*data, uintmaxlen)</div>
<li><div class="fn">int<a href="#ed9d37"><b>writeBlock</b></a>(constQByteArray&data)</div>
<li><div class="fn">QByteArray<a href="#c272a4"><b>readAll</b></a>()</div>
<li><div class="fn">virtualint<a href="#09409b"><b>getch</b></a>()</div>
<li><div class="fn">virtualint<a href="#71cd12"><b>putch</b></a>(int)</div>
<li><div class="fn">virtualint<a href="#05a43c"><b>ungetch</b></a>(int)</div>
</ul>
<h2>Protected Members</h2>
<ul>
<li><div class="fn">void<b>setFlags</b>(intf)(internal)</div>
<li><div class="fn">void<b>setType</b>(int)(internal)</div>
<li><div class="fn">void<b>setMode</b>(int)(internal)</div>
<li><div class="fn">void<b>setState</b>(int)(internal)</div>
<li><div class="fn">void<b>setStatus</b>(int)(internal)</div>
</ul>
<hr><h2><a name="details"></a>Detailed Description</h2>
The QIODevice class is the base class of I/O devices.
<p>
An I/O device represents a medium that one can read bytes from
and/or write bytes to. The QIODevice class is the abstract
superclass of all such devices; classes like <a href="qfile.html">QFile</a>, <a href="qbuffer.html">QBuffer</a> and
<a href="qsocket.html">QSocket</a> inherit QIODevice and implement virtual functions like
write() appropriately.
<p>While applications sometimes use QIODevice directly, mostly it is
better to go through <a href="qtextstream.html">QTextStream</a> and <a href="qdatastream.html">QDataStream</a>, which provide
stream operations on any QIODevice subclass. QTextStream provides
text-oriented stream functionality (for human-readable ASCII files,
for example), while QDataStream deals with binary data in a totally
platform-independent manner.
<p>The public member functions in QIODevice roughly fall into two
groups: The action functions and the state access functions. The
most important action functions are: <ul>
<li> <a href="#756b18">open</a>() opens a device for reading and/or writing, depending on
the argument to open().
<li> <a href="#50fcfd">close</a>() closes the device and tidies up.
<li> <a href="#c12e6e">readBlock</a>() reads a block of data from the device.
<li> <a href="#924d2f">writeBlock</a>() writes a block of data to the device.
<li> <a href="#0b6051">readLine</a>() reads a line (of text, usually) from the device.
<li> <a href="#dfd9f0">flush</a>() ensures that all buffered data are written to the real device.
<p></ul>There are also some other, less used, action functions: <ul>
<li> <a href="#09409b">getch</a>() reads a single character.
<li> <a href="#05a43c">ungetch</a>() forgets the last call to getch(), if possible.
<li> <a href="#71cd12">putch</a>() writes a single character.
<li> <a href="#8ddedd">size</a>() returns the size of the device, if there is one.
<li> <a href="#90fb01">at</a>() returns the current read/write pointer, if there is one
for this device, or it moves the pointer.
<li> <a href="#d51a01">atEnd</a>() says whether there is more to read, if that is a
meaningful question for this device.
<li> <a href="#f119f6">reset</a>() moves the read/write pointer to the start of the
device, if that is possible for this device.
<p></ul>The state access are all "get" functions. The QIODevice subclass
calls <a href="#5af6f9">setState</a>() to update the state, and simple access functions
tell the user of the device what the device's state is. Here are
the settings, and their associated access functions: <ul>
<li> Access type. Some devices are direct access (it is possible to
read/write anywhere) while others are sequential. QIODevice
provides the access functions <a href="#39a85e">isDirectAccess</a>(), <a href="#d264a5">isSequentialAccess</a>()
and <a href="#663267">isCombinedAccess</a>() to tell users what a given I/O device
supports.
<li> Buffering. Some devices are accessed in raw mode while others
are buffered. Buffering usually provides greater efficiency,
particularly for small read/write operations. <a href="#38dfa5">isBuffered</a>() tells
the user whether a given device is buffered. (This can often be set
by the application in the call to open().)
<li> Synchronicity. Synchronous devices work there and then, for
example files. When you read from a file, the file delivers its
data right away. Others, such as a socket connected to a HTTP
server, may not deliver the data until seconds after you ask to read
it. <a href="#a5d52b">isSynchronous</a>() and <a href="#7d84ac">isAsynchronous</a>() tells the user how this
device operates.
<li> CR/LF translation. For simplicity, applications often like to
see just a single CR/LF style, and QIODevice subclasses can provide
that. <a href="#8b6c51">isTranslated</a>() returns TRUE if this object translates CR/LF
to just LF. (This can often be set by the application in the call
to open().)
<li> Accessibility. Some files cannot be written, for example.
<a href="#a109ae">isReadable</a>(), isWritable and <a href="#ed997c">isReadWrite</a>() tells the application
whether it can read from and write to a given device. (This can
often be set by the application in the call to open().)
<li> Finally, <a href="#1bc7b0">isOpen</a>() returns TRUE if the device is open. This can
quite obviously be set using open() :)
<p></ul>
<p>QIODevice provides numerous pure virtual functions you need to
implement when subclassing it. Here is a skeleton subclass with all
the members you are certain to need, and some it's likely that you
will need:
<p><pre> class YourDevice : public QIODevice
{
public:
YourDevice();
~YourDevice();
bool open( int mode );
void close();
void flush();
uint size() const;
int at() const; // not a pure virtual function
bool at( int ); // not a pure virtual function
bool atEnd() const; // not a pure virtual function
int readBlock( char *data, uint maxlen );
int writeBlock( const char *data, uint len );
int readLine( char *data, uint maxlen );
int getch();
int putch( int );
int ungetch( int );
};
</pre>
<p>The three non-pure virtual functions can be ignored if your device
is sequential (e.g. an RS-232 port).
<p>See also <a href="qdatastream.html">QDataStream</a> and <a href="qtextstream.html">QTextStream</a>.
<hr><h2>Member Function Documentation</h2>
<h3 class="fn"><a name="8fa6e5"></a>QIODevice::QIODevice()</h3>
<p>Constructs an I/O device.
<h3 class="fn"><a name="ac6bf9"></a>QIODevice::~QIODevice() <code>[virtual]</code></h3>
<p>Destructs the I/O device.
<h3 class="fn">bool<a name="90fb01"></a>QIODevice::at(intpos) <code>[virtual]</code></h3>
<p>Virtual function that sets the I/O device index to <em>pos.</em>
<p>See also <a href="#8ddedd">size</a>().
<p>Reimplemented in <a href="qsocketdevice.html#aaa87c">QSocketDevice</a>, <a href="qfile.html#858d0b">QFile</a>, <a href="qsocket.html#b852fb">QSocket</a> and <a href="qbuffer.html#491c1f">QBuffer</a>.
<h3 class="fn">int<a name="a8b90e"></a>QIODevice::at()const <code>[virtual]</code></h3>
<p>Virtual function that returns the current I/O device index.
<p>This index is the data read/write head of the I/O device.
<p>See also <a href="#8ddedd">size</a>().
<p>Reimplemented in <a href="qbuffer.html#3c9864">QBuffer</a>, <a href="qsocketdevice.html#00088b">QSocketDevice</a>, <a href="qfile.html#8218c0">QFile</a> and <a href="qsocket.html#d13990">QSocket</a>.
<h3 class="fn">bool<a name="d51a01"></a>QIODevice::atEnd()const <code>[virtual]</code></h3>
<p>Virtual function that returns TRUE if the I/O device index is at the
end of the input.
<p>Reimplemented in <a href="qsocket.html#78c453">QSocket</a>, <a href="qfile.html#b08f02">QFile</a> and <a href="qsocketdevice.html#394a25">QSocketDevice</a>.
<h3 class="fn">void<a name="50fcfd"></a>QIODevice::close() <code>[virtual]</code></h3>
<p>Closes the I/O device.
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#756b18">open</a>().
<p>Reimplemented in <a href="qfile.html#64e640">QFile</a>, <a href="qbuffer.html#bcf8f3">QBuffer</a>, <a href="qsocketdevice.html#dfe8ce">QSocketDevice</a> and <a href="qsocket.html#9e4421">QSocket</a>.
<h3 class="fn">int<a name="6cd02d"></a>QIODevice::flags()const</h3>
<p>Returns the current I/O device flags setting.
<p>Flags consists of mode flags and state flags.
<p>See also <a href="#ac5d91">mode</a>() and <a href="#27e36d">state</a>().
<h3 class="fn">void<a name="dfd9f0"></a>QIODevice::flush() <code>[virtual]</code></h3>
<p>Flushes an open I/O device.
<p>This virtual function must be reimplemented by all subclasses.
<p>Reimplemented in <a href="qfile.html#cb0092">QFile</a>, <a href="qsocket.html#a0a8a9">QSocket</a>, <a href="qbuffer.html#c73504">QBuffer</a> and <a href="qsocketdevice.html#951a6c">QSocketDevice</a>.
<h3 class="fn">int<a name="09409b"></a>QIODevice::getch() <code>[virtual]</code></h3>
<p>Reads a single byte/character from the I/O device.
<p>Returns the byte/character read, or -1 if the end of the I/O device has been
reached.
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#71cd12">putch</a>() and <a href="#05a43c">ungetch</a>().
<p>Reimplemented in <a href="qfile.html#596f05">QFile</a>, <a href="qsocket.html#42465c">QSocket</a>, <a href="qbuffer.html#9769c6">QBuffer</a> and <a href="qsocketdevice.html#6bb6e4">QSocketDevice</a>.
<h3 class="fn">bool<a name="7d84ac"></a>QIODevice::isAsynchronous()const</h3>
<p>Returns TRUE if the I/O device is a asynchronous device, otherwise
FALSE.
<p>This mode is currently not in use.
<p>See also <a href="#a5d52b">isSynchronous</a>().
<h3 class="fn">bool<a name="38dfa5"></a>QIODevice::isBuffered()const</h3>
<p>Returns TRUE if the I/O device is a buffered (not raw) device, otherwise
FALSE.
<p>See also <a href="#d4dd04">isRaw</a>().
<h3 class="fn">bool<a name="663267"></a>QIODevice::isCombinedAccess()const</h3>
<p>Returns TRUE if the I/O device is a combined access (both direct and
sequential) device, otherwise FALSE.
<p>This access method is currently not in use.
<h3 class="fn">bool<a name="39a85e"></a>QIODevice::isDirectAccess()const</h3>
<p>Returns TRUE if the I/O device is a direct access (not sequential) device,
otherwise FALSE.
<p>See also <a href="#d264a5">isSequentialAccess</a>().
<h3 class="fn">bool<a name="706edf"></a>QIODevice::isInactive()const</h3>
<p>Returns TRUE if the I/O device state is 0, i.e. the device is not open.
<p>See also <a href="#1bc7b0">isOpen</a>().
<h3 class="fn">bool<a name="1bc7b0"></a>QIODevice::isOpen()const</h3>
<p>Returns TRUE if the I/O device state has been opened, otherwise FALSE.
<p>See also <a href="#706edf">isInactive</a>().
<h3 class="fn">bool<a name="d4dd04"></a>QIODevice::isRaw()const</h3>
<p>Returns TRUE if the I/O device is a raw (not buffered) device, otherwise
FALSE.
<p>See also <a href="#38dfa5">isBuffered</a>().
<h3 class="fn">bool<a name="ed997c"></a>QIODevice::isReadWrite()const</h3>
<p>Returns TRUE if the I/O device was opened using <code>IO_ReadWrite</code> mode.
<p>See also <a href="#a109ae">isReadable</a>() and <a href="#67abcc">isWritable</a>().
<h3 class="fn">bool<a name="a109ae"></a>QIODevice::isReadable()const</h3>
<p>Returns TRUE if the I/O device was opened using <code>IO_ReadOnly</code> or
<code>IO_ReadWrite</code> mode.
<p>See also <a href="#67abcc">isWritable</a>() and <a href="#ed997c">isReadWrite</a>().
<h3 class="fn">bool<a name="d264a5"></a>QIODevice::isSequentialAccess()const</h3>
<p>Returns TRUE if the I/O device is a sequential access (not direct) device,
otherwise FALSE. Operations involving <a href="#8ddedd">size</a>() and <a href="#90fb01">at</a>(int) are not valid
on sequential devices.
<p>See also <a href="#39a85e">isDirectAccess</a>().
<h3 class="fn">bool<a name="a5d52b"></a>QIODevice::isSynchronous()const</h3>
<p>Returns TRUE if the I/O device is a synchronous device, otherwise
FALSE.
<p>See also <a href="#7d84ac">isAsynchronous</a>().
<h3 class="fn">bool<a name="8b6c51"></a>QIODevice::isTranslated()const</h3>
<p>Returns TRUE if the I/O device translates carriage-return and linefeed
characters.
<p>A <a href="qfile.html">QFile</a> is translated if it is opened with the <code>IO_Translate</code> mode
flag.
<h3 class="fn">bool<a name="67abcc"></a>QIODevice::isWritable()const</h3>
<p>Returns TRUE if the I/O device was opened using <code>IO_WriteOnly</code> or
<code>IO_ReadWrite</code> mode.
<p>See also <a href="#a109ae">isReadable</a>() and <a href="#ed997c">isReadWrite</a>().
<h3 class="fn">int<a name="ac5d91"></a>QIODevice::mode()const</h3>
<p>Returns bits OR'ed together that specify the current operation mode.
<p>These are the flags that were given to the <a href="#756b18">open</a>() function.
<p>The flags are: <code>IO_ReadOnly, IO_WriteOnly, IO_ReadWrite, IO_Append, IO_Truncate</code> and <code>IO_Translate.</code>
<h3 class="fn">bool<a name="756b18"></a>QIODevice::open(intmode) <code>[virtual]</code></h3>
<p>Opens the I/O device using the specified <em>mode.</em>
Returns TRUE if successful, or FALSE if the device could not be opened.
<p>The mode parameter <em>m</em> must be a combination of the following flags.
<ul>
<li><code>IO_Raw</code> specified raw (unbuffered) file access.
<li><code>IO_ReadOnly</code> opens a file in read-only mode.
<li><code>IO_WriteOnly</code> opens a file in write-only mode.
<li><code>IO_ReadWrite</code> opens a file in read/write mode.
<li><code>IO_Append</code> sets the file index to the end of the file.
<li><code>IO_Truncate</code> truncates the file.
<li><code>IO_Translate</code> enables carriage returns and linefeed translation
for text files under MS-DOS, Window, OS/2 and Macintosh. On Unix systems
this flag has no effect. Use with caution as it will also transform every linefeed
written to the file into a CRLF pair. This is likely to corrupt your file when
writing binary data to it. Cannot be combined with <code>IO_Raw.</code>
</ul>
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#50fcfd">close</a>().
<p>Reimplemented in <a href="qsocket.html#45f735">QSocket</a>, <a href="qbuffer.html#53d514">QBuffer</a>, <a href="qfile.html#84dd8e">QFile</a> and <a href="qsocketdevice.html#32c3be">QSocketDevice</a>.
<h3 class="fn">int<a name="71cd12"></a>QIODevice::putch(intch) <code>[virtual]</code></h3>
<p>Writes the character <em>ch</em> to the I/O device.
<p>Returns <em>ch,</em> or -1 if some error occurred.
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#09409b">getch</a>() and <a href="#05a43c">ungetch</a>().
<p>Reimplemented in <a href="qsocketdevice.html#89d3fd">QSocketDevice</a>, <a href="qfile.html#d70b87">QFile</a>, <a href="qsocket.html#64bd57">QSocket</a> and <a href="qbuffer.html#434945">QBuffer</a>.
<h3 class="fn"><a href="qbytearray.html">QByteArray</a><a name="c272a4"></a>QIODevice::readAll()</h3>
<p>This convenience function returns all of the remaining data in the
device. Note that this only works for direct access devices, such
as <a href="qfile.html">QFile</a>.
<p>See also <a href="#39a85e">isDirectAccess</a>().
<h3 class="fn">int<a name="c12e6e"></a>QIODevice::readBlock(char*data, uintmaxlen) <code>[virtual]</code></h3>
<p>Reads at most <em>maxlen</em> bytes from the I/O device into <em>data</em> and
returns the number of bytes actually read.
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#924d2f">writeBlock</a>().
<p>Reimplemented in <a href="qbuffer.html#9062f3">QBuffer</a>, <a href="qsocket.html#d942f7">QSocket</a>, <a href="qfile.html#8c8ccc">QFile</a> and <a href="qsocketdevice.html#f51391">QSocketDevice</a>.
<h3 class="fn">int<a name="0b6051"></a>QIODevice::readLine(char*data, uintmaxlen) <code>[virtual]</code></h3>
<p>Reads a line of text, up to <em>maxlen</em> bytes including a terminating
\0. If there is a newline at the end if the line, it is not stripped.
<p>Returns the number of bytes read including the terminating \0, or -1 in case
of error.
<p>This virtual function can be reimplemented much more efficiently by
the most subclasses.
<p>See also <a href="#c12e6e">readBlock</a>() and <a href="qtextstream.html#ae4af4">QTextStream::readLine</a>().
<p>Reimplemented in <a href="qfile.html#0a06c2">QFile</a>, <a href="qsocket.html#068c90">QSocket</a> and <a href="qbuffer.html#07bef1">QBuffer</a>.
<h3 class="fn">bool<a name="f119f6"></a>QIODevice::reset()</h3>
<p>Sets the device index to 0.
<p>See also <a href="#90fb01">at</a>().
<h3 class="fn">void<a name="0fbc1d"></a>QIODevice::resetStatus()</h3>
<p>Sets the I/O device status to <code>IO_Ok.</code>
<p>See also <a href="#494f6f">status</a>().
<h3 class="fn">uint<a name="8ddedd"></a>QIODevice::size()const <code>[virtual]</code></h3>
<p>Virtual function that returns the size of the I/O device.
<p>See also <a href="#90fb01">at</a>().
<p>Reimplemented in <a href="qsocket.html#abe4ea">QSocket</a>, <a href="qfile.html#1e3b5e">QFile</a>, <a href="qbuffer.html#c4d405">QBuffer</a> and <a href="qsocketdevice.html#a126c7">QSocketDevice</a>.
<h3 class="fn">int<a name="27e36d"></a>QIODevice::state()const</h3>
<p>Returns bits OR'ed together that specify the current state.
<p>The flags are: <code>IO_Open.</code>
<p>Subclasses may define more flags.
<h3 class="fn">int<a name="494f6f"></a>QIODevice::status()const</h3>
<p>Returns the I/O device status.
<p>The I/O device status returns an error code. If <a href="#756b18">open</a>() returns FALSE
or <a href="#c12e6e">readBlock</a>() or <a href="#924d2f">writeBlock</a>() return -1, this function can be called to
get the reason why the operation did not succeed.
<p>The status codes are:
<ul>
<li><code>IO_Ok</code> The operation was successful.
<li><code>IO_ReadError</code> Could not read from the device.
<li><code>IO_WriteError</code> Could not write to the device.
<li><code>IO_FatalError</code> A fatal unrecoverable error occurred.
<li><code>IO_OpenError</code> Could not open the device.
<li><code>IO_ConnectError</code> Could not connect to the device.
<li><code>IO_AbortError</code> The operation was unexpectedly aborted.
<li><code>IO_TimeOutError</code> The operation timed out.
<li><code>IO_UnspecifiedError</code> An unspecified error happened on close.
</ul>
<p>See also <a href="#0fbc1d">resetStatus</a>().
<h3 class="fn">int<a name="05a43c"></a>QIODevice::ungetch(intch) <code>[virtual]</code></h3>
<p>Puts the character <em>ch</em> back into the I/O device and decrements the
index if it is not zero.
<p>This function is normally called to "undo" a <a href="#09409b">getch</a>() operation.
<p>Returns <em>ch,</em> or -1 if some error occurred.
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#09409b">getch</a>() and <a href="#71cd12">putch</a>().
<p>Reimplemented in <a href="qsocket.html#a6be3e">QSocket</a>, <a href="qbuffer.html#4788e0">QBuffer</a>, <a href="qfile.html#471cf3">QFile</a> and <a href="qsocketdevice.html#68f6c9">QSocketDevice</a>.
<h3 class="fn">int<a name="ed9d37"></a>QIODevice::writeBlock(const<a href="qbytearray.html">QByteArray</a>&data)</h3>
<p>This convenience function is the same as calling
<a href="#924d2f">writeBlock</a>( data.data(), data.<a href="#8ddedd">size</a>() ).
<h3 class="fn">int<a name="924d2f"></a>QIODevice::writeBlock(constchar*data, uintlen) <code>[virtual]</code></h3>
<p>Writes <em>len</em> bytes from <em>p</em> to the I/O device and returns the number of
bytes actually written.
<p>This virtual function must be reimplemented by all subclasses.
<p>See also <a href="#c12e6e">readBlock</a>().
<p>Reimplemented in <a href="qsocketdevice.html#61dc32">QSocketDevice</a>, <a href="qfile.html#a44b6a">QFile</a>, <a href="qbuffer.html#d0ec2c">QBuffer</a> and <a href="qsocket.html#3cd3d6">QSocket</a>.
<h3 class="fn">void<a name="3975e7"></a>QIODevice::setFlags(intf) <code>[protected]</code></h3>
<p>For internal use only.
<h3 class="fn">void<a name="fff4ec"></a>QIODevice::setMode(intm) <code>[protected]</code></h3>
<p>For internal use only.
<h3 class="fn">void<a name="5af6f9"></a>QIODevice::setState(ints) <code>[protected]</code></h3>
<p>For internal use only.
<h3 class="fn">void<a name="b7a5e7"></a>QIODevice::setStatus(ints) <code>[protected]</code></h3>
<p>For internal use only.
<h3 class="fn">void<a name="4915ca"></a>QIODevice::setType(intt) <code>[protected]</code></h3>
<p>For internal use only.
<hr><p>
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