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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QIODevice Class Reference</h1>
<p>The QIODevice class is the base class of I/O devices.
<a href="#details">More...</a>
<p>All the functions in this class are <a href="threads.html#reentrant">reentrant</a> when Qt is built with thread support.</p>
<p><tt>#include <<a href="qiodevice-h.html">qiodevice.h</a>></tt>
<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>typedef Q_ULONG <a href="#Offset"><b>Offset</b></a></div></li>
<li><div class=fn><a href="#QIODevice"><b>QIODevice</b></a> ()</div></li>
<li><div class=fn>virtual <a href="#~QIODevice"><b>~QIODevice</b></a> ()</div></li>
<li><div class=fn>int <a href="#flags"><b>flags</b></a> () const</div></li>
<li><div class=fn>int <a href="#mode"><b>mode</b></a> () const</div></li>
<li><div class=fn>int <a href="#state"><b>state</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isDirectAccess"><b>isDirectAccess</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isSequentialAccess"><b>isSequentialAccess</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isCombinedAccess"><b>isCombinedAccess</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isBuffered"><b>isBuffered</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isRaw"><b>isRaw</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isSynchronous"><b>isSynchronous</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isAsynchronous"><b>isAsynchronous</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isTranslated"><b>isTranslated</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isReadable"><b>isReadable</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isWritable"><b>isWritable</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isReadWrite"><b>isReadWrite</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isInactive"><b>isInactive</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isOpen"><b>isOpen</b></a> () const</div></li>
<li><div class=fn>int <a href="#status"><b>status</b></a> () const</div></li>
<li><div class=fn>void <a href="#resetStatus"><b>resetStatus</b></a> ()</div></li>
<li><div class=fn>virtual bool <a href="#open"><b>open</b></a> ( int mode ) = 0</div></li>
<li><div class=fn>virtual void <a href="#close"><b>close</b></a> () = 0</div></li>
<li><div class=fn>virtual void <a href="#flush"><b>flush</b></a> () = 0</div></li>
<li><div class=fn>virtual Offset <a href="#size"><b>size</b></a> () const = 0</div></li>
<li><div class=fn>virtual Offset <a href="#at"><b>at</b></a> () const</div></li>
<li><div class=fn>virtual bool <a href="#at-2"><b>at</b></a> ( Offset pos )</div></li>
<li><div class=fn>virtual bool <a href="#atEnd"><b>atEnd</b></a> () const</div></li>
<li><div class=fn>bool <a href="#reset"><b>reset</b></a> ()</div></li>
<li><div class=fn>virtual Q_LONG <a href="#readBlock"><b>readBlock</b></a> ( char * data, Q_ULONG maxlen ) = 0</div></li>
<li><div class=fn>virtual Q_LONG <a href="#writeBlock"><b>writeBlock</b></a> ( const char * data, Q_ULONG len ) = 0</div></li>
<li><div class=fn>virtual Q_LONG <a href="#readLine"><b>readLine</b></a> ( char * data, Q_ULONG maxlen )</div></li>
<li><div class=fn>Q_LONG <a href="#writeBlock-2"><b>writeBlock</b></a> ( const QByteArray & data )</div></li>
<li><div class=fn>virtual QByteArray <a href="#readAll"><b>readAll</b></a> ()</div></li>
<li><div class=fn>virtual int <a href="#getch"><b>getch</b></a> () = 0</div></li>
<li><div class=fn>virtual int <a href="#putch"><b>putch</b></a> ( int ch ) = 0</div></li>
<li><div class=fn>virtual int <a href="#ungetch"><b>ungetch</b></a> ( int ch ) = 0</div></li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
<p> The QIODevice class is the base class of I/O devices.
<p>
<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 such as <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 such as
write() appropriately.
<p> Although applications sometimes use QIODevice directly, it is
usually better to use <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), whereas 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:
<p> <ul>
<p> <li> <a href="#open">open</a>() opens a device for reading and/or writing, depending on
the mode argument.
<p> <li> <a href="#close">close</a>() closes the device and tidies up (e.g. flushes buffered
data)
<p> <li> <a href="#readBlock">readBlock</a>() reads a block of data from the device.
<p> <li> <a href="#writeBlock">writeBlock</a>() writes a block of data to the device.
<p> <li> <a href="#readLine">readLine</a>() reads a line (of text, usually) from the device.
<p> <li> <a href="#flush">flush</a>() ensures that all buffered data are written to the real device.
<p> </ul>
<p> There are also some other, less used, action functions:
<p> <ul>
<p> <li> <a href="#getch">getch</a>() reads a single character.
<p> <li> <a href="#ungetch">ungetch</a>() forgets the last call to getch(), if possible.
<p> <li> <a href="#putch">putch</a>() writes a single character.
<p> <li> <a href="#size">size</a>() returns the size of the device, if there is one.
<p> <li> <a href="#at">at</a>() returns the current read/write pointer's position, if there
is one for this device, or it moves the pointer if given an offset.
<p> <li> <a href="#atEnd">atEnd</a>() indicates whether there is more to read, if this is
meaningful for this device.
<p> <li> <a href="#reset">reset</a>() moves the read/write pointer to the start of the
device, if that is possible for this device.
<p> </ul>
<p> The state access are all "get" functions. The QIODevice subclass
calls setState() 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:
<p> <ul>
<p> <li> Access type. Some devices are direct access (it is possible
to read/write anywhere), whereas others are sequential. QIODevice
provides the access functions (<a href="#isDirectAccess">isDirectAccess</a>(),
<a href="#isSequentialAccess">isSequentialAccess</a>(), and <a href="#isCombinedAccess">isCombinedAccess</a>()) to tell users what a
given I/O device supports.
<p> <li> Buffering. Some devices are accessed in raw mode, whereas
others are buffered. Buffering usually provides greater
efficiency, particularly for small read/write operations.
<a href="#isBuffered">isBuffered</a>() tells the user whether a given device is buffered.
(This can often be set by the application in the call to <a href="#open">open</a>().)
<p> <li> Synchronicity. Synchronous devices work immediately (for
example, files). When you read from a file, the file delivers its
data straight away. Other kinds of device, such as a socket
connected to a HTTP server, may not deliver the data until seconds
after you ask to read it. <a href="#isSynchronous">isSynchronous</a>() and <a href="#isAsynchronous">isAsynchronous</a>()
tell the user how this device operates.
<p> <li> CR/LF translation. For simplicity, applications often like to
see just a single CR/LF style, and QIODevice subclasses can
provide this. <a href="#isTranslated">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().)
<p> <li> Permissions. Some files cannot be written. For example,
<a href="#isReadable">isReadable</a>(), <a href="#isWritable">isWritable</a>() and <a href="#isReadWrite">isReadWrite</a>() tell 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 <a href="#open">open</a>().)
<p> <li> Finally, <a href="#isOpen">isOpen</a>() returns TRUE if the device is open, i.e.
after an open() call.
<p> </ul>
<p> QIODevice provides numerous pure virtual functions that you need
to implement when subclassing it. Here is a skeleton subclass with
all the members you are sure to need and some that you will
probably need:
<p> <pre>
class MyDevice : public QIODevice
{
public:
MyDevice();
~MyDevice();
bool open( int mode );
void close();
void flush();
uint size() const;
int at() const; // non-pure virtual
bool at( int ); // non-pure virtual
bool atEnd() const; // non-pure virtual
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 need not be reimplemented for
sequential devices.
<p> <p>See also <a href="qdatastream.html">QDataStream</a>, <a href="qtextstream.html">QTextStream</a>, and <a href="io.html">Input/Output and Networking</a>.
<hr><h2>Member Type Documentation</h2>
<h3 class=fn><a name="Offset"></a>QIODevice::Offset</h3>
<p> The offset within the device.
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QIODevice"></a>QIODevice::QIODevice ()
</h3>
Constructs an I/O device.
<h3 class=fn><a name="~QIODevice"></a>QIODevice::~QIODevice ()<tt> [virtual]</tt>
</h3>
Destroys the I/O device.
<h3 class=fn><a href="qiodevice.html#Offset">Offset</a> <a name="at"></a>QIODevice::at () const<tt> [virtual]</tt>
</h3>
Virtual function that returns the current I/O device position.
<p> This is the position of the data read/write head of the I/O
device.
<p> <p>See also <a href="#size">size</a>().
<p>Reimplemented in <a href="qsocket.html#at">QSocket</a>.
<h3 class=fn>bool <a name="at-2"></a>QIODevice::at ( <a href="qiodevice.html#Offset">Offset</a> pos )<tt> [virtual]</tt>
</h3>
Virtual function that sets the I/O device position to <em>pos</em>.
Returns TRUE if the position was successfully set, i.e. <em>pos</em> is
within range; otherwise returns FALSE.
<p> <p>See also <a href="#size">size</a>().
<p>Reimplemented in <a href="qsocket.html#at-2">QSocket</a>.
<h3 class=fn>bool <a name="atEnd"></a>QIODevice::atEnd () const<tt> [virtual]</tt>
</h3>
Virtual function that returns TRUE if the I/O device position is
at the end of the input; otherwise returns FALSE.
<p>Reimplemented in <a href="qfile.html#atEnd">QFile</a> and <a href="qsocket.html#atEnd">QSocket</a>.
<h3 class=fn>void <a name="close"></a>QIODevice::close ()<tt> [pure virtual]</tt>
</h3>
<p> Closes the I/O device.
<p> This virtual function must be reimplemented by all subclasses.
<p> <p>See also <a href="#open">open</a>().
<p>Reimplemented in <a href="qfile.html#close">QFile</a> and <a href="qsocket.html#close">QSocket</a>.
<h3 class=fn>int <a name="flags"></a>QIODevice::flags () const
</h3>
<p> Returns the current I/O device flags setting.
<p> Flags consists of mode flags and state flags.
<p> <p>See also <a href="#mode">mode</a>() and <a href="#state">state</a>().
<h3 class=fn>void <a name="flush"></a>QIODevice::flush ()<tt> [pure virtual]</tt>
</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#flush">QFile</a> and <a href="qsocket.html#flush">QSocket</a>.
<h3 class=fn>int <a name="getch"></a>QIODevice::getch ()<tt> [pure virtual]</tt>
</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> <p>See also <a href="#putch">putch</a>() and <a href="#ungetch">ungetch</a>().
<p>Reimplemented in <a href="qfile.html#getch">QFile</a> and <a href="qsocket.html#getch">QSocket</a>.
<h3 class=fn>bool <a name="isAsynchronous"></a>QIODevice::isAsynchronous () const
</h3>
<p> Returns TRUE if the device is an asynchronous device; otherwise
returns FALSE, i.e. if the device is a synchronous device.
<p> This mode is currently not in use.
<p> <p>See also <a href="#isSynchronous">isSynchronous</a>().
<h3 class=fn>bool <a name="isBuffered"></a>QIODevice::isBuffered () const
</h3>
<p> Returns TRUE if the I/O device is a buffered device; otherwise
returns FALSE, i.e. the device is a raw device.
<p> <p>See also <a href="#isRaw">isRaw</a>().
<h3 class=fn>bool <a name="isCombinedAccess"></a>QIODevice::isCombinedAccess () const
</h3>
<p> Returns TRUE if the I/O device is a combined access (both direct
and sequential) device; otherwise returns FALSE.
<p> This access method is currently not in use.
<h3 class=fn>bool <a name="isDirectAccess"></a>QIODevice::isDirectAccess () const
</h3>
<p> Returns TRUE if the I/O device is a direct access device;
otherwise returns FALSE, i.e. if the device is a sequential access
device.
<p> <p>See also <a href="#isSequentialAccess">isSequentialAccess</a>().
<h3 class=fn>bool <a name="isInactive"></a>QIODevice::isInactive () const
</h3>
<p> Returns TRUE if the I/O device state is 0, i.e. the device is not
open; otherwise returns FALSE.
<p> <p>See also <a href="#isOpen">isOpen</a>().
<h3 class=fn>bool <a name="isOpen"></a>QIODevice::isOpen () const
</h3>
<p> Returns TRUE if the I/O device has been opened; otherwise returns
FALSE.
<p> <p>See also <a href="#isInactive">isInactive</a>().
<p>Example: <a href="networkprotocol-example.html#x601">network/networkprotocol/nntp.cpp</a>.
<h3 class=fn>bool <a name="isRaw"></a>QIODevice::isRaw () const
</h3>
<p> Returns TRUE if the device is a raw device; otherwise returns
FALSE, i.e. if the device is a buffered device.
<p> <p>See also <a href="#isBuffered">isBuffered</a>().
<h3 class=fn>bool <a name="isReadWrite"></a>QIODevice::isReadWrite () const
</h3>
<p> Returns TRUE if the I/O device was opened using <a href="qfile.html#open">IO_ReadWrite</a>
mode; otherwise returns FALSE.
<p> <p>See also <a href="#isReadable">isReadable</a>() and <a href="#isWritable">isWritable</a>().
<h3 class=fn>bool <a name="isReadable"></a>QIODevice::isReadable () const
</h3>
<p> Returns TRUE if the I/O device was opened using <a href="qfile.html#open">IO_ReadOnly</a> or
<a href="qfile.html#open">IO_ReadWrite</a> mode; otherwise returns FALSE.
<p> <p>See also <a href="#isWritable">isWritable</a>() and <a href="#isReadWrite">isReadWrite</a>().
<h3 class=fn>bool <a name="isSequentialAccess"></a>QIODevice::isSequentialAccess () const
</h3>
<p> Returns TRUE if the device is a sequential access device;
otherwise returns FALSE, i.e. if the device is a direct access
device.
<p> Operations involving <a href="#size">size</a>() and <a href="#at">at</a>(int) are not valid on
sequential devices.
<p> <p>See also <a href="#isDirectAccess">isDirectAccess</a>().
<h3 class=fn>bool <a name="isSynchronous"></a>QIODevice::isSynchronous () const
</h3>
<p> Returns TRUE if the I/O device is a synchronous device; otherwise
returns FALSE, i.e. the device is an asynchronous device.
<p> <p>See also <a href="#isAsynchronous">isAsynchronous</a>().
<h3 class=fn>bool <a name="isTranslated"></a>QIODevice::isTranslated () const
</h3>
<p> Returns TRUE if the I/O device translates carriage-return and
linefeed characters; otherwise returns FALSE.
<p> A <a href="qfile.html">QFile</a> is translated if it is opened with the <a href="qfile.html#open">IO_Translate</a>
mode flag.
<h3 class=fn>bool <a name="isWritable"></a>QIODevice::isWritable () const
</h3>
<p> Returns TRUE if the I/O device was opened using <a href="qfile.html#open">IO_WriteOnly</a> or
<a href="qfile.html#open">IO_ReadWrite</a> mode; otherwise returns FALSE.
<p> <p>See also <a href="#isReadable">isReadable</a>() and <a href="#isReadWrite">isReadWrite</a>().
<h3 class=fn>int <a name="mode"></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="#open">open</a>() function.
<p> The flags are <a href="qfile.html#open">IO_ReadOnly</a>, <a href="qfile.html#open">IO_WriteOnly</a>, <a href="qfile.html#open">IO_ReadWrite</a>,
<a href="qfile.html#open">IO_Append</a>, <a href="qfile.html#open">IO_Truncate</a> and <a href="qfile.html#open">IO_Translate</a>.
<h3 class=fn>bool <a name="open"></a>QIODevice::open ( int mode )<tt> [pure virtual]</tt>
</h3>
<p> Opens the I/O device using the specified <em>mode</em>. Returns TRUE if
the device was successfully opened; otherwise returns FALSE.
<p> The mode parameter <em>mode</em> must be an OR'ed combination of the
following flags.
<center><table cellpadding="4" cellspacing="2" border="0">
<tr bgcolor="#a2c511"> <th valign="top">Mode flags <th valign="top">Meaning
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qfile.html#open">IO_Raw</a> <td valign="top">specifies raw (unbuffered) file access.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qfile.html#open">IO_ReadOnly</a> <td valign="top">opens a file in read-only mode.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qfile.html#open">IO_WriteOnly</a> <td valign="top">opens a file in write-only mode.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qfile.html#open">IO_ReadWrite</a> <td valign="top">opens a file in read/write mode.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qfile.html#open">IO_Append</a> <td valign="top">sets the file index to the end of the file.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qfile.html#open">IO_Truncate</a> <td valign="top">truncates the file.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qfile.html#open">IO_Translate</a> <td valign="top">enables carriage returns and linefeed
translation for text files under MS-DOS, Windows 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 if you write write
binary data. Cannot be combined with <a href="qfile.html#open">IO_Raw</a>.
</table></center>
<p> This virtual function must be reimplemented by all subclasses.
<p> <p>See also <a href="#close">close</a>().
<p>Reimplemented in <a href="qfile.html#open">QFile</a> and <a href="qsocket.html#open">QSocket</a>.
<h3 class=fn>int <a name="putch"></a>QIODevice::putch ( int ch )<tt> [pure virtual]</tt>
</h3>
<p> Writes the character <em>ch</em> to the I/O device.
<p> Returns <em>ch</em>, or -1 if an error occurred.
<p> This virtual function must be reimplemented by all subclasses.
<p> <p>See also <a href="#getch">getch</a>() and <a href="#ungetch">ungetch</a>().
<p>Reimplemented in <a href="qfile.html#putch">QFile</a> and <a href="qsocket.html#putch">QSocket</a>.
<h3 class=fn><a href="qbytearray.html">QByteArray</a> <a name="readAll"></a>QIODevice::readAll ()<tt> [virtual]</tt>
</h3>
This convenience function returns all of the remaining data in the
device.
<h3 class=fn>Q_LONG <a name="readBlock"></a>QIODevice::readBlock ( char * data, Q_ULONG maxlen )<tt> [pure virtual]</tt>
</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 function should return -1 if a fatal error occurs and should
return 0 if there are no bytes to read.
<p> The device must be opened for reading, and <em>data</em> must not be 0.
<p> This virtual function must be reimplemented by all subclasses.
<p> <p>See also <a href="#writeBlock">writeBlock</a>(), <a href="#isOpen">isOpen</a>(), and <a href="#isReadable">isReadable</a>().
<p>Reimplemented in <a href="qsocket.html#readBlock">QSocket</a> and <a href="qsocketdevice.html#readBlock">QSocketDevice</a>.
<h3 class=fn>Q_LONG <a name="readLine"></a>QIODevice::readLine ( char * data, Q_ULONG maxlen )<tt> [virtual]</tt>
</h3>
Reads a line of text, (or up to <em>maxlen</em> bytes if a newline isn't
encountered) plus a terminating '\0' into <em>data</em>. 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 if an error occurred.
<p> This virtual function can be reimplemented much more efficiently
by the most subclasses.
<p> <p>See also <a href="#readBlock">readBlock</a>() and <a href="qtextstream.html#readLine">QTextStream::readLine</a>().
<p>Reimplemented in <a href="qfile.html#readLine">QFile</a>.
<h3 class=fn>bool <a name="reset"></a>QIODevice::reset ()
</h3>
<p> Sets the device index position to 0.
<p> <p>See also <a href="#at">at</a>().
<h3 class=fn>void <a name="resetStatus"></a>QIODevice::resetStatus ()
</h3>
<p> Sets the I/O device status to <a href="qiodevice.html#status">IO_Ok</a>.
<p> <p>See also <a href="#status">status</a>().
<h3 class=fn><a href="qiodevice.html#Offset">Offset</a> <a name="size"></a>QIODevice::size () const<tt> [pure virtual]</tt>
</h3>
<p> Virtual function that returns the size of the I/O device.
<p> <p>See also <a href="#at">at</a>().
<p>Reimplemented in <a href="qfile.html#size">QFile</a> and <a href="qsocket.html#size">QSocket</a>.
<h3 class=fn>int <a name="state"></a>QIODevice::state () const
</h3>
<p> Returns bits OR'ed together that specify the current state.
<p> The flags are: <tt>IO_Open</tt>.
<p> Subclasses may define additional flags.
<h3 class=fn>int <a name="status"></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="#open">open</a>() returns
FALSE or <a href="#readBlock">readBlock</a>() or <a href="#writeBlock">writeBlock</a>() return -1, this function can
be called to find out the reason why the operation failed.
<p> <!-- index IO_Ok --><!-- index IO_ReadError --><!-- index IO_WriteError --><!-- index IO_FatalError --><!-- index IO_OpenError --><!-- index IO_ConnectError --><!-- index IO_AbortError --><!-- index IO_TimeOutError --><!-- index IO_UnspecifiedError -->
<p> The status codes are:
<center><table cellpadding="4" cellspacing="2" border="0">
<tr bgcolor="#a2c511"> <th valign="top">Status code <th valign="top">Meaning
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qiodevice.html#status">IO_Ok</a> <td valign="top">The operation was successful.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qiodevice.html#status">IO_ReadError</a> <td valign="top">Could not read from the device.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qiodevice.html#status">IO_WriteError</a> <td valign="top">Could not write to the device.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qiodevice.html#status">IO_FatalError</a> <td valign="top">A fatal unrecoverable error occurred.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qiodevice.html#status">IO_OpenError</a> <td valign="top">Could not open the device.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qiodevice.html#status">IO_ConnectError</a> <td valign="top">Could not connect to the device.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qiodevice.html#status">IO_AbortError</a> <td valign="top">The operation was unexpectedly aborted.
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="qiodevice.html#status">IO_TimeOutError</a> <td valign="top">The operation timed out.
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="qiodevice.html#status">IO_UnspecifiedError</a> <td valign="top">An unspecified error happened on close.
</table></center>
<p> <p>See also <a href="#resetStatus">resetStatus</a>().
<h3 class=fn>int <a name="ungetch"></a>QIODevice::ungetch ( int ch )<tt> [pure virtual]</tt>
</h3>
<p> Puts the character <em>ch</em> back into the I/O device and decrements
the index position if it is not zero.
<p> This function is normally called to "undo" a <a href="#getch">getch</a>() operation.
<p> Returns <em>ch</em>, or -1 if an error occurred.
<p> This virtual function must be reimplemented by all subclasses.
<p> <p>See also <a href="#getch">getch</a>() and <a href="#putch">putch</a>().
<p>Reimplemented in <a href="qfile.html#ungetch">QFile</a> and <a href="qsocket.html#ungetch">QSocket</a>.
<h3 class=fn>Q_LONG <a name="writeBlock"></a>QIODevice::writeBlock ( const char * data, Q_ULONG len )<tt> [pure virtual]</tt>
</h3>
<p> Writes <em>len</em> bytes from <em>data</em> to the I/O device and returns the
number of bytes actually written.
<p> This function should return -1 if a fatal error occurs.
<p> This virtual function must be reimplemented by all subclasses.
<p> <p>See also <a href="#readBlock">readBlock</a>().
<p>Reimplemented in <a href="qbuffer.html#writeBlock">QBuffer</a>, <a href="qsocket.html#writeBlock">QSocket</a>, and <a href="qsocketdevice.html#writeBlock">QSocketDevice</a>.
<h3 class=fn>Q_LONG <a name="writeBlock-2"></a>QIODevice::writeBlock ( const <a href="qbytearray.html">QByteArray</a> & data )
</h3>
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
<p> This convenience function is the same as calling <a href="#writeBlock">writeBlock</a>(
data.data(), data.<a href="#size">size</a>() ).
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