QIODevice Class Reference

The QIODevice class is the base interface class of all I/O devices in Qt. More...

#include <qiodevice.h>

Inheritance diagram for QIODevice:

Public Types
enum	OpenModeFlag {   NotOpen = 0x0000, ReadOnly = 0x0001, WriteOnly = 0x0002, ReadWrite = ReadOnly | WriteOnly,   Append = 0x0004, Truncate = 0x0008, Text = 0x0010, Unbuffered = 0x0020 }
	This enum is used with open() to describe the mode in which a device is opened. More...

Signals
void	aboutToClose ()
	This signal is emitted when the device is about to close. More...
void	bytesWritten (qint64 bytes)
	This signal is emitted every time a payload of data has been written to the device. More...
void	readChannelFinished ()
	This signal is emitted when the input (reading) stream is closed in this device. More...
void	readyRead ()
	This signal is emitted once every time new data is available for reading from the device. More...
Signals inherited from QObject
void	destroyed (QObject *=0)
	This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More...

Public Functions
virtual bool	atEnd () const
	Returns true if the current read and write position is at the end of the device (i.e. More...
virtual qint64	bytesAvailable () const
	Returns the number of bytes that are available for reading. More...
virtual qint64	bytesToWrite () const
	For buffered devices, this function returns the number of bytes waiting to be written. More...
virtual bool	canReadLine () const
	Returns true if a complete line of data can be read from the device; otherwise returns false. More...
virtual void	close ()
	First emits aboutToClose(), then closes the device and sets its OpenMode to NotOpen. More...
QString	errorString () const
	Returns a human-readable description of the last device error that occurred. More...
bool	getChar (char *c)
	Reads one character from the device and stores it in c. More...
bool	isOpen () const
	Returns true if the device is open; otherwise returns false. More...
bool	isReadable () const
	Returns true if data can be read from the device; otherwise returns false. More...
virtual bool	isSequential () const
	Returns true if this device is sequential; otherwise returns false. More...
bool	isTextModeEnabled () const
	Returns true if the Text flag is enabled; otherwise returns false. More...
bool	isWritable () const
	Returns true if data can be written to the device; otherwise returns false. More...
virtual bool	open (OpenMode mode)
	Opens the device and sets its OpenMode to mode. More...
OpenMode	openMode () const
	Returns the mode in which the device has been opened; i.e. More...
qint64	peek (char *data, qint64 maxlen)
	Reads at most maxSize bytes from the device into data, without side effects (i. More...
QByteArray	peek (qint64 maxlen)
	Peeks at most maxSize bytes from the device, returning the data peeked as a QByteArray. More...
virtual qint64	pos () const
	For random-access devices, this function returns the position that data is written to or read from. More...
bool	putChar (char c)
	Writes the character c to the device. More...
	QIODevice ()
	Constructs a QIODevice object. More...
	QIODevice (QObject *parent)
	Constructs a QIODevice object with the given parent. More...
qint64	read (char *data, qint64 maxlen)
	Reads at most maxSize bytes from the device into data, and returns the number of bytes read. More...
QByteArray	read (qint64 maxlen)
	Reads at most maxSize bytes from the device, and returns the data read as a QByteArray. More...
QByteArray	readAll ()
	Reads all available data from the device, and returns it as a QByteArray. More...
qint64	readLine (char *data, qint64 maxlen)
	This function reads a line of ASCII characters from the device, up to a maximum of maxSize - 1 bytes, stores the characters in data, and returns the number of bytes read. More...
QByteArray	readLine (qint64 maxlen=0)
	Reads a line from the device, but no more than maxSize characters, and returns the result as a QByteArray. More...
virtual bool	reset ()
	Seeks to the start of input for random-access devices. More...
virtual bool	seek (qint64 pos)
	For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred. More...
void	setTextModeEnabled (bool enabled)
	If enabled is true, this function sets the Text flag on the device; otherwise the Text flag is removed. More...
virtual qint64	size () const
	For open random-access devices, this function returns the size of the device. More...
void	ungetChar (char c)
	Puts the character c back into the device, and decrements the current position unless the position is 0. More...
virtual bool	waitForBytesWritten (int msecs)
	For buffered devices, this function waits until a payload of buffered written data has been written to the device and the bytesWritten() signal has been emitted, or until msecs milliseconds have passed. More...
virtual bool	waitForReadyRead (int msecs)
	Blocks until new data is available for reading and the readyRead() signal has been emitted, or until msecs milliseconds have passed. More...
qint64	write (const char *data, qint64 len)
	Writes at most maxSize bytes of data from data to the device. More...
qint64	write (const char *data)
	Writes data from a zero-terminated string of 8-bit characters to the device. More...
qint64	write (const QByteArray &data)
	Writes the content of byteArray to the device. More...
virtual	~QIODevice ()
	The destructor is virtual, and QIODevice is an abstract base class. More...
Public Functions inherited from QObject
bool	blockSignals (bool b)
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More...
const QObjectList &	children () const
	Returns a list of child objects. More...
bool	connect (const QObject *sender, const char *signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const
bool	disconnect (const char *signal=0, const QObject *receiver=0, const char *member=0)
bool	disconnect (const QObject *receiver, const char *member=0)
void	dumpObjectInfo ()
	Dumps information about signal connections, etc. More...
void	dumpObjectTree ()
	Dumps a tree of children to the debug output. More...
QList< QByteArray >	dynamicPropertyNames () const
	Returns the names of all properties that were dynamically added to the object using setProperty(). More...
virtual bool	event (QEvent *)
	This virtual function receives events to an object and should return true if the event e was recognized and processed. More...
virtual bool	eventFilter (QObject *, QEvent *)
	Filters events if this object has been installed as an event filter for the watched object. More...
template<typename T >
T	findChild (const QString &aName=QString()) const
	Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More...
template<typename T >
QList< T >	findChildren (const QString &aName=QString()) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. More...
template<typename T >
QList< T >	findChildren (const QRegExp &re) const
bool	inherits (const char *classname) const
	Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false. More...
void	installEventFilter (QObject *)
	Installs an event filter filterObj on this object. More...
bool	isWidgetType () const
	Returns true if the object is a widget; otherwise returns false. More...
void	killTimer (int id)
	Kills the timer with timer identifier, id. More...
virtual const QMetaObject *	metaObject () const
	Returns a pointer to the meta-object of this object. More...
void	moveToThread (QThread *thread)
	Changes the thread affinity for this object and its children. More...
QString	objectName () const
QObject *	parent () const
	Returns a pointer to the parent object. More...
QVariant	property (const char *name) const
	Returns the value of the object's name property. More...
Q_INVOKABLE	QObject (QObject *parent=0)
	Constructs an object with parent object parent. More...
void	removeEventFilter (QObject *)
	Removes an event filter object obj from this object. More...
void	setObjectName (const QString &name)
void	setParent (QObject *)
	Makes the object a child of parent. More...
bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value. More...
void	setUserData (uint id, QObjectUserData *data)
bool	signalsBlocked () const
	Returns true if signals are blocked; otherwise returns false. More...
int	startTimer (int interval)
	Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More...
QThread *	thread () const
	Returns the thread in which the object lives. More...
QObjectUserData *	userData (uint id) const
virtual	~QObject ()
	Destroys the object, deleting all its child objects. More...

Protected Functions
	QIODevice (QIODevicePrivate &dd, QObject *parent=0)
virtual qint64	readData (char *data, qint64 maxlen)=0
	Reads up to maxSize bytes from the device into data, and returns the number of bytes read or -1 if an error occurred. More...
virtual qint64	readLineData (char *data, qint64 maxlen)
	Reads up to maxSize characters into data and returns the number of characters read. More...
void	setErrorString (const QString &errorString)
	Sets the human readable description of the last device error that occurred to str. More...
void	setOpenMode (OpenMode openMode)
	Sets the OpenMode of the device to openMode. More...
virtual qint64	writeData (const char *data, qint64 len)=0
	Writes up to maxSize bytes from data to the device. More...
Protected Functions inherited from QObject
virtual void	childEvent (QChildEvent *)
	This event handler can be reimplemented in a subclass to receive child events. More...
virtual void	connectNotify (const char *signal)
	This virtual function is called when something has been connected to signal in this object. More...
virtual void	customEvent (QEvent *)
	This event handler can be reimplemented in a subclass to receive custom events. More...
virtual void	disconnectNotify (const char *signal)
	This virtual function is called when something has been disconnected from signal in this object. More...
	QObject (QObjectPrivate &dd, QObject *parent=0)
int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal. More...
QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0. More...
int	senderSignalIndex () const
virtual void	timerEvent (QTimerEvent *)
	This event handler can be reimplemented in a subclass to receive timer events for the object. More...

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	Schedules this object for deletion. More...
Static Public Functions inherited from QObject
static bool	connect (const QObject *sender, const char *signal, const QObject *receiver, const char *member, Qt::ConnectionType=Qt::AutoConnection)
	Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More...
static bool	connect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)
static bool	disconnect (const QObject *sender, const char *signal, const QObject *receiver, const char *member)
	Disconnects signal in object sender from method in object receiver. More...
static bool	disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &member)
static uint	registerUserData ()
static QString	tr (const char *sourceText, const char *comment=0, int n=-1)
static QString	trUtf8 (const char *sourceText, const char *comment=0, int n=-1)
Static Public Variables inherited from QObject
static const QMetaObject	staticMetaObject
	This variable stores the meta-object for the class. More...
Protected Variables inherited from QObject
QScopedPointer< QObjectData >	d_ptr
Static Protected Variables inherited from QObject
static const QMetaObject	staticQtMetaObject
Related Functions inherited from QObject
T	qFindChildqFindChildren (const QObject *obj, const QString &name)()
QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()
QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QRegExp &regExp)()
T *	qobject_cast (QObject *object)
	QObjectList
void *	qt_find_obj_child (QObject *parent, const char *type, const QString &name)
	Returns a pointer to the object named name that inherits type and with a given parent. More...

Detailed Description

The QIODevice class is the base interface class of all I/O devices in Qt.

Note

This class or function is reentrant.

QIODevice provides both a common implementation and an abstract interface for devices that support reading and writing of blocks of data, such as QFile, QBuffer and QTcpSocket. QIODevice is abstract and can not be instantiated, but it is common to use the interface it defines to provide device-independent I/O features. For example, Qt's XML classes operate on a QIODevice pointer, allowing them to be used with various devices (such as files and buffers).

Before accessing the device, open() must be called to set the correct OpenMode (such as ReadOnly or ReadWrite). You can then write to the device with write() or putChar(), and read by calling either read(), readLine(), or readAll(). Call close() when you are done with the device.

QIODevice distinguishes between two types of devices: random-access devices and sequential devices.

• Random-access devices support seeking to arbitrary positions using seek(). The current position in the file is available by calling pos(). QFile and QBuffer are examples of random-access devices.

• Sequential devices don't support seeking to arbitrary positions. The data must be read in one pass. The functions pos() and size() don't work for sequential devices. QTcpSocket and QProcess are examples of sequential devices.

You can use isSequential() to determine the type of device.

QIODevice emits readyRead() when new data is available for reading; for example, if new data has arrived on the network or if additional data is appended to a file that you are reading from. You can call bytesAvailable() to determine the number of bytes that are currently available for reading. It's common to use bytesAvailable() together with the readyRead() signal when programming with asynchronous devices such as QTcpSocket, where fragments of data can arrive at arbitrary points in time. QIODevice emits the bytesWritten() signal every time a payload of data has been written to the device. Use bytesToWrite() to determine the current amount of data waiting to be written.

Certain subclasses of QIODevice, such as QTcpSocket and QProcess, are asynchronous. This means that I/O functions such as write() or read() always return immediately, while communication with the device itself may happen when control goes back to the event loop. QIODevice provides functions that allow you to force these operations to be performed immediately, while blocking the calling thread and without entering the event loop. This allows QIODevice subclasses to be used without an event loop, or in a separate thread:

• waitForReadyRead() - This function suspends operation in the calling thread until new data is available for reading.

• waitForBytesWritten() - This function suspends operation in the calling thread until one payload of data has been written to the device.

• waitFor....() - Subclasses of QIODevice implement blocking functions for device-specific operations. For example, QProcess has a function called waitForStarted() which suspends operation in the calling thread until the process has started.

Calling these functions from the main, GUI thread, may cause your user interface to freeze. Example:

QProcess gzip;
gzip.start("gzip", QStringList() << "-c");
if (!gzip.waitForStarted())
    return false;

gzip.write("uncompressed data");

QByteArray compressed;
while (gzip.waitForReadyRead())
    compressed += gzip.readAll();

By subclassing QIODevice, you can provide the same interface to your own I/O devices. Subclasses of QIODevice are only required to implement the protected readData() and writeData() functions. QIODevice uses these functions to implement all its convenience functions, such as getChar(), readLine() and write(). QIODevice also handles access control for you, so you can safely assume that the device is opened in write mode if writeData() is called.

Some subclasses, such as QFile and QTcpSocket, are implemented using a memory buffer for intermediate storing of data. This reduces the number of required device accessing calls, which are often very slow. Buffering makes functions like getChar() and putChar() fast, as they can operate on the memory buffer instead of directly on the device itself. Certain I/O operations, however, don't work well with a buffer. For example, if several users open the same device and read it character by character, they may end up reading the same data when they meant to read a separate chunk each. For this reason, QIODevice allows you to bypass any buffering by passing the Unbuffered flag to open(). When subclassing QIODevice, remember to bypass any buffer you may use when the device is open in Unbuffered mode.

See also

QBuffer QFile QTcpSocket

Definition at line 66 of file qiodevice.h.

Enumerations

OpenModeFlag

enum QIODevice::OpenModeFlag

This enum is used with open() to describe the mode in which a device is opened.

It is also returned by openMode().

• NotOpen The device is not open.
• ReadOnly The device is open for reading.
• WriteOnly The device is open for writing.
• ReadWrite The device is open for reading and writing.
• Append The device is opened in append mode, so that all data is written to the end of the file.
• Truncate If possible, the device is truncated before it is opened. All earlier contents of the device are lost.
• Text When reading, the end-of-line terminators are translated to '
  '. When writing, the end-of-line terminators are translated to the local encoding, for example '
  ' for Win32.
• Unbuffered Any buffer in the device is bypassed.

Certain flags, such as Unbuffered and Truncate, are meaningless when used with some subclasses. Some of these restrictions are implied by the type of device that is represented by a subclass. In other cases, the restriction may be due to the implementation, or may be imposed by the underlying platform; for example, QTcpSocket does not support Unbuffered mode, and limitations in the native API prevent QFile from supporting Unbuffered on Windows.

Enumerator
NotOpen
ReadOnly
WriteOnly
ReadWrite
Append
Truncate
Text
Unbuffered

Definition at line 75 of file qiodevice.h.

                      {
        NotOpen = 0x0000,
        ReadOnly = 0x0001,
        WriteOnly = 0x0002,
        ReadWrite = ReadOnly | WriteOnly,
        Append = 0x0004,
        Truncate = 0x0008,
        Text = 0x0010,
        Unbuffered = 0x0020
    };

Constructors and Destructors

QIODevice() [1/3]

QIODevice::QIODevice

(

)

Constructs a QIODevice object.

Definition at line 390 of file qiodevice.cpp.

Referenced by QIODevicePrivate::~QIODevicePrivate().

    : QObject(*new QIODevicePrivate, 0)
{
#if defined QIODEVICE_DEBUG
    QFile *file = qobject_cast<QFile *>(this);
    printf("%p QIODevice::QIODevice(\"%s\") %s\n", this, metaObject()->className(),
           qPrintable(file ? file->fileName() : QString()));
#endif
}

QIODevice() [2/3]

QIODevice::QIODevice ( QObject *  parent )

explicit

Constructs a QIODevice object with the given parent.

Definition at line 404 of file qiodevice.cpp.

    : QObject(*new QIODevicePrivate, parent)
{
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::QIODevice(%p \"%s\")\n", this, parent, metaObject()->className());
#endif
}

~QIODevice()

QIODevice::~QIODevice ( )

virtual

The destructor is virtual, and QIODevice is an abstract base class.

This destructor does not call close(), but the subclass destructor might. If you are in doubt, call close() before destroying the QIODevice.

Definition at line 427 of file qiodevice.cpp.

{
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::~QIODevice()\n", this);
#endif
}

QIODevice() [3/3]

QIODevice::QIODevice ( QIODevicePrivate &  dd, QObject *  parent = 0  )

protected

Warning

This function is not part of the public interface.

Definition at line 414 of file qiodevice.cpp.

    : QObject(dd, parent)
{
}

Functions

aboutToClose

QIODevice::aboutToClose ( )

signal

This signal is emitted when the device is about to close.

Connect this signal if you have operations that need to be performed before the device closes (e.g., if you have data in a separate buffer that needs to be written to the device).

Referenced by close(), QProcess::close(), and QPatternist::QIODeviceDelegate::QIODeviceDelegate().

atEnd()

bool QIODevice::atEnd ( ) const

virtual

Returns true if the current read and write position is at the end of the device (i.e.

there is no more data available for reading on the device); otherwise returns false.

For some devices, atEnd() can return true even though there is more data to read. This special case only applies to devices that generate data in direct response to you calling read() (e.g., /dev or /proc files on Unix and Mac OS X, or console input / stdin on all platforms).

See also

bytesAvailable(), read(), isSequential()

Reimplemented in QAuthDevice, QProcess, QByteDeviceWrappingIoDevice, QAbstractSocket, QFile, QHttpMultiPartIODevice, QSslSocket, QBuffer, and QPatternist::QIODeviceDelegate.

Definition at line 711 of file qiodevice.cpp.

Referenced by QNetworkReplyImplPrivate::_q_copyReadyRead(), QPatternist::QIODeviceDelegate::atEnd(), QBuffer::atEnd(), QSslSocket::atEnd(), QDataStream::atEnd(), QAbstractSocket::atEnd(), QProcess::atEnd(), QPSPrintEnginePrivate::emitPages(), QPdf::ByteStream::operator<<(), QHttpPrivate::postMoreData(), QPdf::ByteStream::prepareBuffer(), qt_read_dibv5(), read_dib_body(), QNonContiguousByteDeviceIoDeviceImpl::readPointer(), QTextStreamPrivate::scan(), QFile::symLinkTarget(), QNetworkDiskCache::updateMetaData(), and QPdfEnginePrivate::writeCompressed().

{
    Q_D(const QIODevice);
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::atEnd() returns %s, d->openMode == %d, d->pos == %d\n", this, (d->openMode == NotOpen || d->pos == size()) ? "true" : "false",
           int(d->openMode), int(d->pos));
#endif
    return d->openMode == NotOpen || (d->buffer.isEmpty() && bytesAvailable() == 0);
}

bytesAvailable()

qint64 QIODevice::bytesAvailable ( ) const

virtual

Returns the number of bytes that are available for reading.

This function is commonly used with sequential devices to determine the number of bytes to allocate in a buffer before reading.

Subclasses that reimplement this function must call the base implementation in order to include the size of QIODevices' buffer. Example:

qint64 CustomDevice::bytesAvailable() const
{
    return buffer.size() + QIODevice::bytesAvailable();
}

See also

bytesToWrite(), readyRead(), isSequential()

Reimplemented in QAuthDevice, QProcess, QUnixSocket, QAbstractSocket, QHttpMultiPartIODevice, QSslSocket, QLocalSocket, QNetworkReplyImpl, QNetworkReplyFileImpl, QNetworkReplyDataImpl, QPatternist::QIODeviceDelegate, and QOstDevice.

Definition at line 752 of file qiodevice.cpp.

Referenced by QNetworkReplyImplPrivate::_q_bufferOutgoingData(), QNetworkReplyImplPrivate::_q_copyReadyRead(), QLocalSocketPrivate::_q_pipeClosed(), atEnd(), QFile::atEnd(), QPatternist::QIODeviceDelegate::bytesAvailable(), QNetworkReplyDataImpl::bytesAvailable(), QNetworkReplyFileImpl::bytesAvailable(), QNetworkReplyImpl::bytesAvailable(), QLocalSocket::bytesAvailable(), QSslSocket::bytesAvailable(), QAbstractSocket::bytesAvailable(), QUnixSocket::bytesAvailable(), QProcess::bytesAvailable(), qws_read_command(), qws_read_uint(), QWSClient::readMoreCommand(), QPacketProtocolPrivate::readyToRead(), QAuthDevice::recvReadyRead(), and size().

{
    Q_D(const QIODevice);
    if (!d->isSequential())
        return qMax(size() - d->pos, qint64(0));
    return d->buffer.size();
}

bytesToWrite()

qint64 QIODevice::bytesToWrite ( ) const

virtual

For buffered devices, this function returns the number of bytes waiting to be written.

For devices with no buffer, this function returns 0.

See also

bytesAvailable(), bytesWritten(), isSequential()

Reimplemented in QAuthDevice, QProcess, QUnixSocket, QHttpMultiPartIODevice, QAbstractSocket, QSslSocket, QLocalSocket, and QPatternist::QIODeviceDelegate.

Definition at line 767 of file qiodevice.cpp.

Referenced by QPatternist::QIODeviceDelegate::bytesToWrite().

{
    return qint64(0);
}

bytesWritten

QIODevice::bytesWritten ( qint64  bytes )

signal

This signal is emitted every time a payload of data has been written to the device.

The bytes argument is set to the number of bytes that were written in this payload.

bytesWritten() is not emitted recursively; if you reenter the event loop or call waitForBytesWritten() inside a slot connected to the bytesWritten() signal, the signal will not be reemitted (although waitForBytesWritten() may still return true).

See also

readyRead()

Referenced by QAuthDevice::QAuthDevice(), QPatternist::QIODeviceDelegate::QIODeviceDelegate(), QAuthDevice::targetBytesWritten(), QUnixSocket::waitForBytesWritten(), QUnixSocketPrivate::writeActivated(), QOstDevice::writeData(), QAbstractSocket::writeData(), and QUdpSocket::writeDatagram().

canReadLine()

bool QIODevice::canReadLine ( ) const

virtual

Returns true if a complete line of data can be read from the device; otherwise returns false.

Note that unbuffered devices, which have no way of determining what can be read, always return false.

This function is often called in conjunction with the readyRead() signal.

Subclasses that reimplement this function must call the base implementation in order to include the contents of the QIODevice's buffer. Example:

bool CustomDevice::canReadLine() const
{
    return buffer.contains('\n') || QIODevice::canReadLine();
}

See also

readyRead(), readLine()

Reimplemented in QProcess, QUnixSocket, QAbstractSocket, QSslSocket, QLocalSocket, QBuffer, QNetworkReplyImpl, and QPatternist::QIODeviceDelegate.

Definition at line 1330 of file qiodevice.cpp.

Referenced by QLocalSocketPrivate::_q_pipeClosed(), QPatternist::QIODeviceDelegate::canReadLine(), QNetworkReplyImpl::canReadLine(), QBuffer::canReadLine(), QLocalSocket::canReadLine(), QSslSocket::canReadLine(), QAbstractSocket::canReadLine(), and QProcess::canReadLine().

{
    return d_func()->buffer.canReadLine();
}

close()

void QIODevice::close ( )

virtual

First emits aboutToClose(), then closes the device and sets its OpenMode to NotOpen.

The error string is also reset.

See also

setOpenMode() OpenMode

Reimplemented in QProcess, QAbstractSocket, QFile, QUnixSocket, QHttpMultiPartIODevice, QSslSocket, QNetworkReply, QLocalSocket, QBuffer, QNetworkReplyImpl, QPatternist::QIODeviceDelegate, QNetworkReplyFileImpl, QNetworkReplyDataImpl, and QOstDevice.

Definition at line 590 of file qiodevice.cpp.

Referenced by QLocalSocketPrivate::_q_pipeClosed(), QZipWriter::addFile(), QOstDevice::close(), QPatternist::QIODeviceDelegate::close(), QBuffer::close(), QLocalSocket::close(), QZipWriter::close(), QNetworkReply::close(), QZipReader::close(), QHttpMultiPartIODevice::close(), QFile::close(), QAbstractSocket::close(), QProcess::close(), QNetworkAccessCacheBackend::closeDownstreamChannel(), QPdfBaseEnginePrivate::closePrintDevice(), QAbstractSocket::disconnectFromHostImplementation(), qws_read_command(), QFile::symLinkTarget(), QTextDocumentWriter::write(), and QXmlStreamStrategy::~QXmlStreamStrategy().

{
    Q_D(QIODevice);
    if (d->openMode == NotOpen)
        return;

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::close()\n", this);
#endif

#ifndef QT_NO_QOBJECT
    emit aboutToClose();
#endif
    d->openMode = NotOpen;
    d->errorString.clear();
    d->pos = 0;
    d->seqDumpPos = 0;
    d->buffer.clear();
    d->firstRead = true;
}

errorString()

QString QIODevice::errorString

(

)

const

Returns a human-readable description of the last device error that occurred.

See also

setErrorString()

Definition at line 1671 of file qiodevice.cpp.

Referenced by QHttpNetworkConnectionChannel::_q_error(), QSslSocketPrivate::_q_errorSlot(), QHttpPrivate::_q_slotError(), QSocks5SocketEngine::bind(), QSvgTinyDocument::load(), QPatternist::AccelTreeResourceLoader::load(), QDeclarativePixmapReader::networkRequestDone(), QNetworkAccessFileBackend::open(), QNetworkReplyFileImpl::QNetworkReplyFileImpl(), qt_parse_pattern(), QNetworkAccessFileBackend::readMoreFromFile(), QFile::rename(), QSocks5SocketEnginePrivate::setErrorState(), QSslSocketBackendPrivate::transmit(), QNetworkAccessFileBackend::uploadReadyReadSlot(), QAbstractSocket::waitForBytesWritten(), QAbstractSocket::waitForDisconnected(), and QAbstractSocket::waitForReadyRead().

{
    Q_D(const QIODevice);
    if (d->errorString.isEmpty()) {
#ifdef QT_NO_QOBJECT
        return QLatin1String(QT_TRANSLATE_NOOP(QIODevice, "Unknown error"));
#else
        return tr("Unknown error");
#endif
    }
    return d->errorString;
}

getChar()

bool QIODevice::getChar

(

char *

c

)

Reads one character from the device and stores it in c.

If c is 0, the character is discarded. Returns true on success; otherwise returns false.

See also

read() putChar() ungetChar()

Definition at line 1536 of file qiodevice.cpp.

Referenced by QNonContiguousByteDeviceIoDeviceImpl::advanceReadPointer(), Tga16Reader::operator()(), Tga24Reader::operator()(), Tga32Reader::operator()(), QDataStream::operator>>(), read_dib_body(), read_pbm_int(), read_xpm_body(), QTgaFile::readImage(), and runningUnderDebugger().

{
    // readability checked in read()
    char ch;
    return (1 == read(c ? c : &ch, 1));
}

isOpen()

bool QIODevice::isOpen

(

)

const

Returns true if the device is open; otherwise returns false.

A device is open if it can be read from and/or written to. By default, this function returns false if openMode() returns NotOpen.

See also

openMode() OpenMode

Definition at line 530 of file qiodevice.cpp.

Referenced by QNetworkReplyImplPrivate::_q_copyReadyRead(), QFtpPrivate::_q_startNextCommand(), QZipWriterPrivate::addEntry(), QFile::atEnd(), QAbstractSocket::atEnd(), QProcess::atEnd(), QBuffer::canReadLine(), QImageWriter::canWrite(), QTiffPlugin::capabilities(), QICOPlugin::capabilities(), QJpegPlugin::capabilities(), QTgaPlugin::capabilities(), QMngPlugin::capabilities(), QPicturePrivate::checkFormat(), QFile::close(), QHttpPrivate::closeConn(), QTemporaryFile::createLocalFile(), QUuid::createUuid(), errorString(), QXmlInputSource::fetchData(), QTransportAuthPrivate::getClientKey(), QFile::handle(), QNetworkReplyImplPrivate::initCacheSaveDevice(), QImageReaderPrivate::initHandler(), QAbstractSocket::isValid(), QOstDevice::open(), QFile::open(), QPatternist::XsdStateMachine< XsdSchemaToken::NodeName >::outputGraph(), QNetworkAccessManagerPrivate::prepareMultipart(), QPicturePrivate::QPicturePrivate(), qt_inflateGZipDataFrom(), QXmlInputSource::QXmlInputSource(), QPictureIO::read(), QFile::rename(), QFile::resize(), QZipReaderPrivate::scanFiles(), QFile::seek(), QBuffer::setBuffer(), QBuffer::setData(), QFile::setFileName(), setTextModeEnabled(), QNetworkDiskCachePrivate::storeItem(), QConfFileSettingsPrivate::syncConfFile(), and QPictureIO::write().

{
    return d_func()->openMode != NotOpen;
}

isReadable()

bool QIODevice::isReadable

(

)

const

Returns true if data can be read from the device; otherwise returns false.

Use bytesAvailable() to determine how many bytes can be read.

This is a convenience function which checks if the OpenMode of the device contains the ReadOnly flag.

See also

openMode() OpenMode

Definition at line 544 of file qiodevice.cpp.

Referenced by QXmlQuery::bindVariable(), QTiffPlugin::capabilities(), QJpegPlugin::capabilities(), QTgaPlugin::capabilities(), QICOPlugin::capabilities(), QSvgPlugin::capabilities(), QMngPlugin::capabilities(), QGifPlugin::capabilities(), QPatternist::ExpressionFactory::createExpression(), QZipReader::isReadable(), QXmlSchemaPrivate::load(), QNetworkAccessManagerPrivate::prepareMultipart(), qt_inflateGZipDataFrom(), QTgaFile::QTgaFile(), qtiffReadProc(), QPatternist::AccelTreeResourceLoader::retrieveDocument(), QXmlQuery::setFocus(), setOpenMode(), QXmlQuery::setQuery(), QConfFileSettingsPrivate::syncConfFile(), and QXmlSchemaValidator::validate().

{
    return (openMode() & ReadOnly) != 0;
}

isSequential()

bool QIODevice::isSequential ( ) const

virtual

Returns true if this device is sequential; otherwise returns false.

Sequential devices, as opposed to a random-access devices, have no concept of a start, an end, a size, or a current position, and they do not support seeking. You can only read from the device when it reports that data is available. The most common example of a sequential device is a network socket. On Unix, special files such as /dev/zero and fifo pipes are sequential.

Regular files, on the other hand, do support random access. They have both a size and a current position, and they also support seeking backwards and forwards in the data stream. Regular files are non-sequential.

The QIODevice implementation returns false.

See also

bytesAvailable()

Reimplemented in QtMultimediaInternal::MacInputDevice, MacOutputDevice, QAuthDevice, QProcess, QUnixSocket, QByteDeviceWrappingIoDevice, QAbstractSocket, QFile, QHttpMultiPartIODevice, QNetworkReply, QLocalSocket, QPatternist::QIODeviceDelegate, QNetworkReplyFileImpl, and QNetworkReplyDataImpl.

Definition at line 454 of file qiodevice.cpp.

Referenced by QNetworkReplyImplPrivate::_q_copyReadyRead(), QFtpPrivate::_q_startNextCommand(), QXbmHandler::canRead(), ICOReader::canRead(), createReadHandlerHelper(), QNetworkAccessManager::createRequest(), QTextStreamPrivate::fillReadBuffer(), QMoviePrivate::infoForFrame(), iod_read_fn(), QPatternist::QIODeviceDelegate::isSequential(), QHttpMultiPartIODevice::isSequential(), QPdf::ByteStream::operator<<(), QtIcoHandler::option(), QPdf::ByteStream::prepareBuffer(), QFtp::put(), QPatternist::QIODeviceDelegate::QIODeviceDelegate(), qt_term_source(), QTgaFile::QTgaFile(), QUnixSocket::read(), read_dib_body(), readLineData(), QNonContiguousByteDeviceIoDeviceImpl::readPointer(), QNetworkReplyImplPrivate::setup(), QNonContiguousByteDeviceIoDeviceImpl::size(), QDataStream::skipRawData(), and QFile::symLinkTarget().

{
    return false;
}

isTextModeEnabled()

bool QIODevice::isTextModeEnabled

(

)

const

Returns true if the Text flag is enabled; otherwise returns false.

See also

setTextModeEnabled()

Definition at line 517 of file qiodevice.cpp.

Referenced by QTextStreamPrivate::fillReadBuffer(), and QTextStreamPrivate::flushWriteBuffer().

{
    return d_func()->openMode & Text;
}

isWritable()

bool QIODevice::isWritable

(

)

const

Returns true if data can be written to the device; otherwise returns false.

This is a convenience function which checks if the OpenMode of the device contains the WriteOnly flag.

See also

openMode() OpenMode

Definition at line 558 of file qiodevice.cpp.

Referenced by QImageWriter::canWrite(), QTiffPlugin::capabilities(), QICOPlugin::capabilities(), QJpegPlugin::capabilities(), QXmlQuery::evaluateTo(), QZipWriter::isWritable(), qt_write_dib(), qt_write_dibv5(), QXmlSerializer::QXmlSerializer(), QBuffer::seek(), QConfFileSettingsPrivate::syncConfFile(), QTextDocumentWriter::write(), write_xpm_image(), and QTextOdfWriter::writeAll().

{
    return (openMode() & WriteOnly) != 0;
}

open()

bool QIODevice::open ( OpenMode  mode )

virtual

Opens the device and sets its OpenMode to mode.

Returns true if successful; otherwise returns false. This function should be called from any reimplementations of open() or other functions that open the device.

See also

openMode() OpenMode

Reimplemented in QFile, QTemporaryFile, QBuffer, and QPatternist::QIODeviceDelegate.

Definition at line 570 of file qiodevice.cpp.

Referenced by QLocalSocketPrivate::_q_pipeClosed(), QFtpPrivate::_q_startNextCommand(), QZipWriterPrivate::addEntry(), QZipWriter::addFile(), QPdf::ByteStream::ByteStream(), QImageWriter::canWrite(), QPdf::ByteStream::clear(), QSslSocket::connectToHostImplementation(), QAbstractSocket::connectToHostImplementation(), QLocalSocket::connectToServer(), QPdf::ByteStream::constructor_helper(), QXmlInputSource::fetchData(), QAudioOutputPrivate::freeBlocks(), QAudioInputPrivate::freeBlocks(), QImageReaderPrivate::initHandler(), QOstDevice::open(), QPatternist::QIODeviceDelegate::open(), QBuffer::open(), QFile::open(), QNetworkAccessManagerPrivate::prepareMultipart(), QAuthDevice::QAuthDevice(), QByteDeviceWrappingIoDevice::QByteDeviceWrappingIoDevice(), QNetworkReplyDataImpl::QNetworkReplyDataImpl(), QNetworkReplyFileImpl::QNetworkReplyFileImpl(), qt_inflateGZipDataFrom(), QZipStreamStrategy::QZipStreamStrategy(), QCacheItem::read(), QAuthDevice::recvReadyRead(), QZipReaderPrivate::scanFiles(), QLocalSocket::setSocketDescriptor(), QAbstractSocket::setSocketDescriptor(), QAudioOutputPrivate::start(), QAudioInputPrivate::start(), QProcess::start(), QFile::symLinkTarget(), QTextDocumentWriter::write(), and QTextOdfWriter::writeAll().

{
    Q_D(QIODevice);
    d->openMode = mode;
    d->pos = (mode & Append) ? size() : qint64(0);
    d->buffer.clear();
    d->accessMode = QIODevicePrivate::Unset;
    d->firstRead = true;
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::open(0x%x)\n", this, quint32(mode));
#endif
    return true;
}

openMode()

QIODevice::OpenMode QIODevice::openMode

(

)

const

Returns the mode in which the device has been opened; i.e.

ReadOnly or WriteOnly.

See also

OpenMode

Definition at line 465 of file qiodevice.cpp.

Referenced by QZipWriter::addFile(), QPacket::clear(), QZipWriter::close(), QAbstractSocket::connectToHost(), isReadable(), isWritable(), QPatternist::QIODeviceDelegate::open(), QFilePrivate::putCharHelper(), QPacket::QPacket(), QPicturePrivate::QPicturePrivate(), QZipReaderPrivate::scanFiles(), and setOpenMode().

{
    return d_func()->openMode;
}

peek() [1/2]

qint64 QIODevice::peek	(	char *	data,
		qint64	maxSize
	)

Reads at most maxSize bytes from the device into data, without side effects (i.

Since

4.1

e., if you call read() after peek(), you will get the same data). Returns the number of bytes read. If an error occurs, such as when attempting to peek a device opened in WriteOnly mode, this function returns -1.

0 is returned when no more data is available for reading.

Example:

bool isExeFile(QFile *file)
{
    char buf[2];
    if (file->peek(buf, sizeof(buf)) == sizeof(buf))
        return (buf[0] == 'M' && buf[1] == 'Z');
    return false;
}

See also

read()

Definition at line 1563 of file qiodevice.cpp.

Referenced by QHttpNetworkConnectionChannel::_q_readyRead(), QTiffHandler::canRead(), QSvgIOHandler::canRead(), QJpegHandler::canRead(), QGifHandler::canRead(), QXpmHandler::canRead(), QMngHandler::canRead(), QPpmHandler::canRead(), QPngHandler::canRead(), QBmpHandler::canRead(), QGLPixmapData::fromFile(), QHttpNetworkReplyPrivate::getChunkSize(), QSslSocketPrivate::peek(), and QSslSocketBackendPrivate::transmit().

{
    return d_func()->peek(data, maxSize);
}

peek() [2/2]

QByteArray QIODevice::peek

(

qint64

maxSize

)

Peeks at most maxSize bytes from the device, returning the data peeked as a QByteArray.

Since

4.1 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Example:

bool isExeFile(QFile *file)
{
    return file->peek(2) == "MZ";
}

This function has no way of reporting errors; returning an empty QByteArray() can mean either that no data was currently available for peeking, or that an error occurred.

See also

read()

Definition at line 1588 of file qiodevice.cpp.

{
    return d_func()->peek(maxSize);
}

pos()

qint64 QIODevice::pos ( ) const

virtual

For random-access devices, this function returns the position that data is written to or read from.

For sequential devices or closed devices, where there is no concept of a "current position", 0 is returned.

The current read/write position of the device is maintained internally by QIODevice, so reimplementing this function is not necessary. When subclassing QIODevice, use QIODevice::seek() to notify QIODevice about changes in the device position.

See also

isSequential(), seek()

Reimplemented in QFile, QBuffer, and QPatternist::QIODeviceDelegate.

Definition at line 624 of file qiodevice.cpp.

Referenced by QZipWriterPrivate::addEntry(), QTiffHandler::canRead(), QXbmHandler::canRead(), ICOReader::canRead(), QZipWriter::close(), QTextStreamPrivate::consume(), createReadHandlerHelper(), QAudioOutputPrivate::deviceReady(), QPicture::exec(), QZipReader::fileData(), QAudioOutputPrivate::freeBlocks(), iod_read_fn(), QPdf::ByteStream::operator<<(), QTiffHandler::option(), QtIcoHandler::option(), QPictureIO::pictureFormat(), QPatternist::QIODeviceDelegate::pos(), QBuffer::pos(), QFile::pos(), QHttpPrivate::postMoreData(), QPdf::ByteStream::prepareBuffer(), QMovie::QMovie(), QNonContiguousByteDeviceIoDeviceImpl::QNonContiguousByteDeviceIoDeviceImpl(), qt_term_source(), qtiffSeekProc(), read_dib_body(), QBmpHandler::readHeader(), ICOReader::readHeader(), QMoviePrivate::reset(), QTextStreamPrivate::resetReadBuffer(), QGIFFormat::scan(), seek(), QDataStream::skipRawData(), QFile::symLinkTarget(), and ICOReader::write().

{
    Q_D(const QIODevice);
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::pos() == %d\n", this, int(d->pos));
#endif
    return d->pos;
}

putChar()

bool QIODevice::putChar

(

char

c

)

Writes the character c to the device.

Returns true on success; otherwise returns false.

See also

write() getChar() ungetChar()

Definition at line 1486 of file qiodevice.cpp.

Referenced by QDataStream::operator<<(), and QXmlSerializerPrivate::write().

{
    return d_func()->putCharHelper(c);
}

read() [1/2]

qint64 QIODevice::read	(	char *	data,
		qint64	maxSize
	)

Reads at most maxSize bytes from the device into data, and returns the number of bytes read.

If an error occurs, such as when attempting to read from a device opened in WriteOnly mode, this function returns -1.

0 is returned when no more data is available for reading. However, reading past the end of the stream is considered an error, so this function returns -1 in those cases (that is, reading on a closed socket or after a process has died).

See also

readData() readLine() write()

Definition at line 791 of file qiodevice.cpp.

Referenced by QNetworkReplyImplPrivate::_q_bufferOutgoingData(), QNetworkReplyImplPrivate::_q_copyReadyRead(), QHttpPrivate::_q_slotReadyRead(), QVNCServer::clientCutText(), QSocks5PasswordAuthenticator::continueAuthenticate(), QFile::copy(), QTemporaryFile::createLocalFile(), QUuid::createUuid(), QAudioOutputPrivate::deviceReady(), QTranslatorPrivate::do_load(), QPSPrintEnginePrivate::emitPages(), QXmlInputSource::fetchData(), QZipReader::fileData(), QtMultimediaInternal::QAudioOutputBuffer::fillBuffer(), QTextStreamPrivate::fillReadBuffer(), QAudioOutputPrivate::freeBlocks(), getChar(), QXmlStreamReaderPrivate::getChar_helper(), QHttpNetworkReplyPrivate::getChunkSize(), QTransportAuthPrivate::getClientKey(), ICOReader::iconAt(), iod_read_fn(), QPdf::ByteStream::operator<<(), QDataStream::operator>>(), QSocks5SocketEnginePrivate::parseAuthenticationMethodReply(), QPictureIO::pictureFormat(), QHttpPrivate::postMoreData(), QPdf::ByteStream::prepareBuffer(), qt_fill_input_buffer(), qt_inflateGZipDataFrom(), qt_read_dibv5(), QTgaFile::QTgaFile(), qtiffReadProc(), qws_read_command(), qws_read_uint(), QFtpDTP::read(), read(), QRfbRect::read(), QRfbPixelFormat::read(), QUnixSocket::read(), QRfbServerInit::read(), QRfbSetEncodings::read(), QRfbFrameBufferUpdateRequest::read(), QRfbKeyEvent::read(), QRfbPointerEvent::read(), QRfbClientCutText::read(), ICOReader::read16_24_32BMP(), ICOReader::read1BitBMP(), ICOReader::read4BitBMP(), ICOReader::read8BitBMP(), read_dib_body(), read_pbm_body(), read_pbm_header(), read_xpm_string(), readAll(), readBMPInfoHeader(), QHttpNetworkReplyPrivate::readBodyFast(), QHttpNetworkReplyPrivate::readBodyVeryFast(), QDataStream::readBytes(), QVNCServer::readClient(), ICOReader::readColorTable(), QPatternist::QIODeviceDelegate::readData(), QFile::readData(), QAuthDevice::readData(), QHttpNetworkReplyPrivate::readHeader(), readIconDir(), readIconDirEntry(), readLineData(), QFile::readLineData(), QNetworkAccessFileBackend::readMoreFromFile(), QNonContiguousByteDeviceIoDeviceImpl::readPointer(), QDataStream::readRawData(), QHttpNetworkReplyPrivate::readReplyBodyChunked(), QHttpNetworkReplyPrivate::readReplyBodyRaw(), QHttpNetworkReplyPrivate::readStatus(), QPacketProtocolPrivate::readyToRead(), QDynamicFileResourceRoot::registerSelf(), QFile::rename(), QGIFFormat::scan(), QZipReaderPrivate::scanFiles(), QVNCServer::setEncodings(), QVNCServer::setPixelFormat(), QTransportAuth::setProcessKey(), QDataStream::skipRawData(), QFtpDTP::socketReadyRead(), QSslSocketBackendPrivate::transmit(), ungetChar(), QNetworkDiskCache::updateMetaData(), and QPdfEnginePrivate::writeCompressed().

{
    Q_D(QIODevice);

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::read(%p, %d), d->pos = %d, d->buffer.size() = %d\n",
           this, data, int(maxSize), int(d->pos), int(d->buffer.size()));
#endif

    // Short circuit for getChar()
    if (maxSize == 1) {
        int chint;
        while ((chint = d->buffer.getChar()) != -1) {
            ++(*d->pPos);

            char c = char(uchar(chint));
            if (c == '\r' && (d->openMode & Text))
                continue;
            *data = c;
#if defined QIODEVICE_DEBUG
            printf("%p \tread 0x%hhx (%c) returning 1 (shortcut)\n", this,
                   int(c), isprint(c) ? c : '?');
#endif
            return qint64(1);
        }
    }

    CHECK_MAXLEN(read, qint64(-1));
    qint64 readSoFar = 0;
    bool moreToRead = true;
    do {
        // Try reading from the buffer.
        int lastReadChunkSize = d->buffer.read(data, maxSize);
        if (lastReadChunkSize > 0) {
            *d->pPos += lastReadChunkSize;
            readSoFar += lastReadChunkSize;
            // fast exit when satisfied by buffer
            if (lastReadChunkSize == maxSize && !(d->openMode & Text))
                return readSoFar;

            data += lastReadChunkSize;
            maxSize -= lastReadChunkSize;
#if defined QIODEVICE_DEBUG
            printf("%p \treading %d bytes from buffer into position %d\n", this, lastReadChunkSize,
                   int(readSoFar) - lastReadChunkSize);
#endif
        } else {
            if (d->firstRead) {
                // this is the first time the file has been read, check it's valid and set up pos pointers
                // for fast pos updates.
                CHECK_READABLE(read, qint64(-1));
                d->firstRead = false;
                if (d->isSequential()) {
                    d->pPos = &d->seqDumpPos;
                    d->pDevicePos = &d->seqDumpPos;
                }
            }

            if (!maxSize)
                return readSoFar;

            if ((d->openMode & Unbuffered) == 0 && maxSize < QIODEVICE_BUFFERSIZE) {
                // In buffered mode, we try to fill up the QIODevice buffer before
                // we do anything else.
                // buffer is empty at this point, try to fill it
                int bytesToBuffer = QIODEVICE_BUFFERSIZE;
                char *writePointer = d->buffer.reserve(bytesToBuffer);

                // Make sure the device is positioned correctly.
                if (d->pos != d->devicePos && !d->isSequential() && !seek(d->pos))
                    return readSoFar ? readSoFar : qint64(-1);
                qint64 readFromDevice = readData(writePointer, bytesToBuffer);
                d->buffer.chop(bytesToBuffer - (readFromDevice < 0 ? 0 : int(readFromDevice)));

                if (readFromDevice > 0) {
                    *d->pDevicePos += readFromDevice;
#if defined QIODEVICE_DEBUG
                    printf("%p \treading %d from device into buffer\n", this, int(readFromDevice));
#endif

                    if (!d->buffer.isEmpty()) {
                        lastReadChunkSize = d->buffer.read(data, maxSize);
                        readSoFar += lastReadChunkSize;
                        data += lastReadChunkSize;
                        maxSize -= lastReadChunkSize;
                        *d->pPos += lastReadChunkSize;
#if defined QIODEVICE_DEBUG
                        printf("%p \treading %d bytes from buffer at position %d\n", this,
                               lastReadChunkSize, int(readSoFar));
#endif
                    }
                }
            }
        }

        // If we need more, try reading from the device.
        if (maxSize > 0) {
            // Make sure the device is positioned correctly.
            if (d->pos != d->devicePos && !d->isSequential() && !seek(d->pos))
                return readSoFar ? readSoFar : qint64(-1);
            qint64 readFromDevice = readData(data, maxSize);
#if defined QIODEVICE_DEBUG
            printf("%p \treading %d bytes from device (total %d)\n", this, int(readFromDevice), int(readSoFar));
#endif
            if (readFromDevice == -1 && readSoFar == 0) {
                // error and we haven't read anything: return immediately
                return -1;
            }
            if (readFromDevice > 0) {
                lastReadChunkSize += int(readFromDevice);
                readSoFar += readFromDevice;
                data += readFromDevice;
                maxSize -= readFromDevice;
                *d->pPos += readFromDevice;
                *d->pDevicePos += readFromDevice;
            }
        }
        // Best attempt has been made to read data, don't try again except for text mode adjustment below
        moreToRead = false;

        if (readSoFar && d->openMode & Text) {
            char *readPtr = data - lastReadChunkSize;
            const char *endPtr = data;

            if (readPtr < endPtr) {
                // optimization to avoid initial self-assignment
                while (*readPtr != '\r') {
                    if (++readPtr == endPtr)
                        return readSoFar;
                }

                char *writePtr = readPtr;

                while (readPtr < endPtr) {
                    char ch = *readPtr++;
                    if (ch != '\r')
                        *writePtr++ = ch;
                    else {
                        --readSoFar;
                        --data;
                        ++maxSize;
                    }
                }

                // Make sure we get more data if there is room for more. This
                // is very important for when someone seeks to the start of a
                // '\r\n' and reads one character - they should get the '\n'.
                moreToRead = (readPtr != writePtr);
            }
        }
    } while (moreToRead);

#if defined QIODEVICE_DEBUG
    printf("%p \treturning %d, d->pos == %d, d->buffer.size() == %d\n", this,
           int(readSoFar), int(d->pos), d->buffer.size());
    debugBinaryString(data - readSoFar, readSoFar);
#endif
    return readSoFar;
}

read() [2/2]

QByteArray QIODevice::read

(

qint64

maxSize

)

Reads at most maxSize bytes from the device, and returns the data read as a QByteArray.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

This function has no way of reporting errors; returning an empty QByteArray() can mean either that no data was currently available for reading, or that an error occurred.

Definition at line 968 of file qiodevice.cpp.

{
    Q_D(QIODevice);
    QByteArray result;

    CHECK_MAXLEN(read, result);

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::read(%d), d->pos = %d, d->buffer.size() = %d\n",
           this, int(maxSize), int(d->pos), int(d->buffer.size()));
#else
    Q_UNUSED(d);
#endif

    if (maxSize != qint64(int(maxSize))) {
        qWarning("QIODevice::read: maxSize argument exceeds QByteArray size limit");
        maxSize = INT_MAX;
    }

    qint64 readBytes = 0;
    if (maxSize) {
        result.resize(int(maxSize));
        if (!result.size()) {
            // If resize fails, read incrementally.
            qint64 readResult;
            do {
                result.resize(int(qMin(maxSize, result.size() + QIODEVICE_BUFFERSIZE)));
                readResult = read(result.data() + readBytes, result.size() - readBytes);
                if (readResult > 0 || readBytes == 0)
                    readBytes += readResult;
            } while (readResult == QIODEVICE_BUFFERSIZE);
        } else {
            readBytes = read(result.data(), result.size());
        }
    }

    if (readBytes <= 0)
        result.clear();
    else
        result.resize(int(readBytes));

    return result;
}

readAll()

QByteArray QIODevice::readAll

(

)

Reads all available data from the device, and returns it as a QByteArray.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

This function has no way of reporting errors; returning an empty QByteArray() can mean either that no data was currently available for reading, or that an error occurred.

Definition at line 1025 of file qiodevice.cpp.

Referenced by QHttpPrivate::_q_slotReadyRead(), QFontDatabase::addApplicationFont(), QZipWriter::addFile(), QGLShader::compileSourceFile(), QPatternist::ExpressionFactory::createExpression(), QNetworkDiskCache::data(), QDeclarativeXMLHttpRequest::downloadProgress(), QDeclarativeInclude::finished(), QDeclarativeXMLHttpRequest::finished(), QSslCertificate::fromDevice(), QDirectFBPixmapData::fromFile(), QGLPixmapData::fromFile(), QSslCertificate::fromPath(), QFreetypeFace::getFace(), QDeclarativeInclude::include(), QSvgIOHandlerPrivate::load(), QPicture::load(), QDeclarativeDataLoader::load(), QAxScriptManager::load(), QRawFont::loadFromFile(), QTextBrowser::loadResource(), QTextDocument::loadResource(), QDeclarativeDataLoader::networkReplyFinished(), QDeclarativePixmapReader::networkRequestDone(), operator<<(), QDeclarativeDirParser::parse(), QDeclarativeWorkerScriptEnginePrivate::processLoad(), QSslCertificate::QSslCertificate(), QSslKey::QSslKey(), qt_getDefaultFromHomePrinters(), qt_parse_pattern(), QFtpDTP::readAll(), QProcess::readAllStandardError(), QProcess::readAllStandardOutput(), registerFont(), QDeclarativeFontObject::replyFinished(), QPatternist::AccelTreeResourceLoader::retrieveUnparsedText(), QSslSocket::setLocalCertificate(), QSslSocket::setPrivateKey(), QNetworkReplyImplPrivate::setup(), QFtpDTP::socketConnectionClosed(), QFtpDTP::socketReadyRead(), QConfFileSettingsPrivate::syncConfFile(), QSocks5Authenticator::unSeal(), QDeclarativeInclude::worker_include(), and QSvgIconEngine::write().

{
    Q_D(QIODevice);
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::readAll(), d->pos = %d, d->buffer.size() = %d\n",
           this, int(d->pos), int(d->buffer.size()));
#endif

    QByteArray result;
    qint64 readBytes = 0;

    // flush internal read buffer
    if (!(d->openMode & Text) && !d->buffer.isEmpty()) {
        result = d->buffer.readAll();
        readBytes = result.size();
        d->pos += readBytes;
    }

    qint64 theSize;
    if (d->isSequential() || (theSize = size()) == 0) {
        // Size is unknown, read incrementally.
        qint64 readResult;
        do {
            result.resize(result.size() + QIODEVICE_BUFFERSIZE);
            readResult = read(result.data() + readBytes, result.size() - readBytes);
            if (readResult > 0 || readBytes == 0)
                readBytes += readResult;
        } while (readResult > 0);
    } else {
        // Read it all in one go.
        // If resize fails, don't read anything.
        result.resize(int(readBytes + theSize - d->pos));
        readBytes += read(result.data() + readBytes, result.size() - readBytes);
    }

    if (readBytes <= 0)
        result.clear();
    else
        result.resize(int(readBytes));

    return result;
}

readChannelFinished

QIODevice::readChannelFinished ( )

signal

This signal is emitted when the input (reading) stream is closed in this device.

Since

4.4

It is emitted as soon as the closing is detected, which means that there might still be data available for reading with read().

See also

atEnd(), read()

Referenced by QAbstractSocket::disconnectFromHostImplementation(), and QPatternist::QIODeviceDelegate::QIODeviceDelegate().

readData()

qint64 QIODevice::readData ( char *  data, qint64  maxSize  )

protectedpure virtual

Reads up to maxSize bytes from the device into data, and returns the number of bytes read or -1 if an error occurred.

If there are no bytes to be read and there can never be more bytes available (examples include socket closed, pipe closed, sub-process finished), this function returns -1.

This function is called by QIODevice. Reimplement this function when creating a subclass of QIODevice.

When reimplementing this function it is important that this function reads all the required data before returning. This is required in order for QDataStream to be able to operate on the class. QDataStream assumes all the requested information was read and therefore does not retry reading if there was a problem.

See also

read() readLine() writeData()

Implemented in QtMultimediaInternal::MacInputDevice, MacOutputDevice, QDisabledNetworkReply, QAuthDevice, QProcess, QFile, QAbstractSocket, QSslSocket, QUnixSocket, QByteDeviceWrappingIoDevice, OutputPrivate, InputPrivate, QHttpMultiPartIODevice, InputPrivate, OutputPrivate, QLocalSocket, QBuffer, QPatternist::QIODeviceDelegate, QNetworkReplyImpl, QNetworkReplyFileImpl, QNetworkReplyDataImpl, and QOstDevice.

Referenced by read(), and QUnixSocket::read().

readLine() [1/2]

qint64 QIODevice::readLine	(	char *	data,
		qint64	maxSize
	)

This function reads a line of ASCII characters from the device, up to a maximum of maxSize - 1 bytes, stores the characters in data, and returns the number of bytes read.

If a line could not be read but no error ocurred, this function returns 0. If an error occurs, this function returns the length of what could be read, or -1 if nothing was read.

A terminating '\0' byte is always appended to data, so maxSize must be larger than 1.

Data is read until either of the following conditions are met:

• The first '
  ' character is read.
• maxSize - 1 bytes are read.
• The end of the device data is detected.

For example, the following code reads a line of characters from a file:

QFile file("box.txt");
if (file.open(QFile::ReadOnly)) {
    char buf[1024];
    qint64 lineLength = file.readLine(buf, sizeof(buf));
    if (lineLength != -1) {
        // the line is available in buf
    }
}

The newline character ('
') is included in the buffer. If a newline is not encountered before maxSize - 1 bytes are read, a newline will not be inserted into the buffer. On windows newline characters are replaced with '
'.

This function calls readLineData(), which is implemented using repeated calls to getChar(). You can provide a more efficient implementation by reimplementing readLineData() in your own subclass.

See also

getChar(), read(), write()

Definition at line 1110 of file qiodevice.cpp.

Referenced by QHttpPrivate::_q_slotReadyRead(), QBenchmarkValgrindUtils::extractResult(), QTextStreamPrivate::fillReadBuffer(), fontFile(), fontPath(), QHostInfo::localDomainName(), QDeclarativeGridScaledImage::QDeclarativeGridScaledImage(), qt_getLprPrinters(), qt_parseEtcLpPrinters(), qt_parseNsswitchConf(), qt_parsePrintcap(), qt_parsePrintersConf(), qt_read_xpm_image_or_array(), read_pbm_int(), read_xbm_body(), read_xbm_header(), readLine(), QFtpPI::readyRead(), QFtpDTP::socketReadyRead(), and QCoreApplicationData::~QCoreApplicationData().

{
    Q_D(QIODevice);
    if (maxSize < 2) {
        qWarning("QIODevice::readLine: Called with maxSize < 2");
        return qint64(-1);
    }

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::readLine(%p, %d), d->pos = %d, d->buffer.size() = %d\n",
           this, data, int(maxSize), int(d->pos), int(d->buffer.size()));
#endif

    // Leave room for a '\0'
    --maxSize;

    const bool sequential = d->isSequential();

    qint64 readSoFar = 0;
    if (!d->buffer.isEmpty()) {
        readSoFar = d->buffer.readLine(data, maxSize);
        if (!sequential)
            d->pos += readSoFar;
#if defined QIODEVICE_DEBUG
        printf("%p \tread from buffer: %d bytes, last character read: %hhx\n", this,
               int(readSoFar), data[int(readSoFar) - 1]);
        if (readSoFar)
            debugBinaryString(data, int(readSoFar));
#endif
#if defined(Q_OS_SYMBIAN)
        // Open C fgets strips '\r' but readSoFar gets returned as if it was still there
        if ((d->openMode & Text) &&
            readSoFar > 1 &&
            data[readSoFar - 1] == '\0' &&
            data[readSoFar - 2] == '\n') {
            --readSoFar;
        }
#endif
        if (readSoFar && data[readSoFar - 1] == '\n') {
            if (d->openMode & Text) {
                // QRingBuffer::readLine() isn't Text aware.
                if (readSoFar > 1 && data[readSoFar - 2] == '\r') {
                    --readSoFar;
                    data[readSoFar - 1] = '\n';
                }
            }
            data[readSoFar] = '\0';
            return readSoFar;
        }
    }

    if (d->pos != d->devicePos && !sequential && !seek(d->pos))
        return qint64(-1);
    d->baseReadLineDataCalled = false;
    qint64 readBytes = readLineData(data + readSoFar, maxSize - readSoFar);
#if defined QIODEVICE_DEBUG
    printf("%p \tread from readLineData: %d bytes, readSoFar = %d bytes\n", this,
           int(readBytes), int(readSoFar));
    if (readBytes > 0) {
        debugBinaryString(data, int(readSoFar + readBytes));
    }
#endif
    if (readBytes < 0) {
        data[readSoFar] = '\0';
        return readSoFar ? readSoFar : -1;
    }
    readSoFar += readBytes;
    if (!d->baseReadLineDataCalled && !sequential) {
        d->pos += readBytes;
        // If the base implementation was not called, then we must
        // assume the device position is invalid and force a seek.
        d->devicePos = qint64(-1);
    }
    data[readSoFar] = '\0';

    if (d->openMode & Text) {
#if defined(Q_OS_SYMBIAN)
        // Open C fgets strips '\r' but readSoFar gets returned as if it was still there
        if (readSoFar > 1 && data[readSoFar - 1] == '\0' && data[readSoFar - 2] == '\n') {
            --readSoFar;
        }
#endif
        if (readSoFar > 1 && data[readSoFar - 1] == '\n' && data[readSoFar - 2] == '\r') {
            data[readSoFar - 2] = '\n';
            data[readSoFar - 1] = '\0';
            --readSoFar;
        }
    }

#if defined QIODEVICE_DEBUG
    printf("%p \treturning %d, d->pos = %d, d->buffer.size() = %d, size() = %d\n",
           this, int(readSoFar), int(d->pos), d->buffer.size(), int(size()));
    debugBinaryString(data, int(readSoFar));
#endif
    return readSoFar;
}

readLine() [2/2]

QByteArray QIODevice::readLine

(

qint64

maxSize = 0

)

Reads a line from the device, but no more than maxSize characters, and returns the result as a QByteArray.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

This function has no way of reporting errors; returning an empty QByteArray() can mean either that no data was currently available for reading, or that an error occurred.

Definition at line 1220 of file qiodevice.cpp.

{
    Q_D(QIODevice);
    QByteArray result;

    CHECK_MAXLEN(readLine, result);

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::readLine(%d), d->pos = %d, d->buffer.size() = %d\n",
           this, int(maxSize), int(d->pos), int(d->buffer.size()));
#else
    Q_UNUSED(d);
#endif

    if (maxSize > INT_MAX) {
        qWarning("QIODevice::read: maxSize argument exceeds QByteArray size limit");
        maxSize = INT_MAX;
    }

    result.resize(int(maxSize));
    qint64 readBytes = 0;
    if (!result.size()) {
        // If resize fails or maxSize == 0, read incrementally
        if (maxSize == 0)
            maxSize = INT_MAX;

        // The first iteration needs to leave an extra byte for the terminating null
        result.resize(1);

        qint64 readResult;
        do {
            result.resize(int(qMin(maxSize, result.size() + QIODEVICE_BUFFERSIZE)));
            readResult = readLine(result.data() + readBytes, result.size() - readBytes);
            if (readResult > 0 || readBytes == 0)
                readBytes += readResult;
        } while (readResult == QIODEVICE_BUFFERSIZE
                && result[int(readBytes - 1)] != '\n');
    } else
        readBytes = readLine(result.data(), result.size());

    if (readBytes <= 0)
        result.clear();
    else
        result.resize(readBytes);

    return result;
}

readLineData()

qint64 QIODevice::readLineData ( char *  data, qint64  maxSize  )

protectedvirtual

Reads up to maxSize characters into data and returns the number of characters read.

This function is called by readLine(), and provides its base implementation, using getChar(). Buffered devices can improve the performance of readLine() by reimplementing this function.

readLine() appends a '\0' byte to data; readLineData() does not need to do this.

If you reimplement this function, be careful to return the correct value: it should return the number of bytes read in this line, including the terminating newline, or 0 if there is no line to be read at this point. If an error occurs, it should return -1 if and only if no bytes were read. Reading past EOF is considered an error.

Reimplemented in QFile, and QAbstractSocket.

Definition at line 1285 of file qiodevice.cpp.

Referenced by readLine(), QAbstractSocket::readLineData(), and QFile::readLineData().

{
    Q_D(QIODevice);
    qint64 readSoFar = 0;
    char c;
    int lastReadReturn = 0;
    d->baseReadLineDataCalled = true;

    while (readSoFar < maxSize && (lastReadReturn = read(&c, 1)) == 1) {
        *data++ = c;
        ++readSoFar;
        if (c == '\n')
            break;
    }

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::readLineData(%p, %d), d->pos = %d, d->buffer.size() = %d, returns %d\n",
           this, data, int(maxSize), int(d->pos), int(d->buffer.size()), int(readSoFar));
#endif
    if (lastReadReturn != 1 && readSoFar == 0)
        return isSequential() ? lastReadReturn : -1;
    return readSoFar;
}

readyRead

QIODevice::readyRead ( )

signal

This signal is emitted once every time new data is available for reading from the device.

It will only be emitted again once new data is available, such as when a new payload of network data has arrived on your network socket, or when a new block of data has been appended to your device.

readyRead() is not emitted recursively; if you reenter the event loop or call waitForReadyRead() inside a slot connected to the readyRead() signal, the signal will not be reemitted (although waitForReadyRead() may still return true).

Note for developers implementing classes derived from QIODevice: you should always emit readyRead() when new data has arrived (do not emit it only because there's data still to be read in your buffers). Do not emit readyRead() in other conditions.

See also

bytesWritten()

Referenced by QAuthDevice::authorizeMessage(), QAuthDevice::QAuthDevice(), QByteDeviceWrappingIoDevice::QByteDeviceWrappingIoDevice(), QPatternist::QIODeviceDelegate::QIODeviceDelegate(), and QUnixSocketPrivate::readActivated().

reset()

bool QIODevice::reset ( )

virtual

Seeks to the start of input for random-access devices.

Returns true on success; otherwise returns false (for example, if the device is not open).

Note that when using a QTextStream on a QFile, calling reset() on the QFile will not have the expected result because QTextStream buffers the file. Use the QTextStream::seek() function instead.

See also

seek()

Reimplemented in QByteDeviceWrappingIoDevice, QHttpMultiPartIODevice, and QPatternist::QIODeviceDelegate.

Definition at line 732 of file qiodevice.cpp.

Referenced by QMacPasteboardMimeVCard::convertFromMime(), QPdf::ByteStream::operator<<(), QPdf::ByteStream::prepareBuffer(), QPatternist::QIODeviceDelegate::reset(), QNonContiguousByteDeviceIoDeviceImpl::reset(), and QPdf::ByteStream::stream().

{
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::reset()\n", this);
#endif
    return seek(0);
}

seek()

bool QIODevice::seek ( qint64  pos )

virtual

For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred.

For sequential devices, the default behavior is to do nothing and return false.

When subclassing QIODevice, you must call QIODevice::seek() at the start of your function to ensure integrity with QIODevice's built-in buffer. The base implementation always returns true.

See also

pos(), isSequential()

Reimplemented in QAuthDevice, QFile, QBuffer, and QPatternist::QIODeviceDelegate.

Definition at line 659 of file qiodevice.cpp.

Referenced by QHttpPrivate::_q_slotConnected(), QZipWriterPrivate::addEntry(), QTiffHandler::canRead(), QXbmHandler::canRead(), ICOReader::canRead(), QZipWriter::close(), createReadHandlerHelper(), QAudioOutputPrivate::deviceReady(), QPicture::exec(), QZipReader::fileData(), QAudioOutputPrivate::freeBlocks(), ICOReader::iconAt(), iod_read_fn(), QPdf::ByteStream::operator<<(), QTiffHandler::option(), QtIcoHandler::option(), QPictureIO::pictureFormat(), QPicture::play(), QPdf::ByteStream::prepareBuffer(), qt_fill_input_buffer(), qt_term_source(), QTgaFile::QTgaFile(), qtiffSeekProc(), read(), read_dib_body(), ICOReader::readBMPHeader(), ICOReader::readIconEntry(), QTgaFile::readImage(), readLine(), reset(), QNonContiguousByteDeviceIoDeviceImpl::reset(), QGIFFormat::scan(), QZipReaderPrivate::scanFiles(), QPatternist::QIODeviceDelegate::seek(), QBuffer::seek(), QFile::seek(), QDataStream::skipRawData(), QFile::symLinkTarget(), and write().

{
    Q_D(QIODevice);
    if (d->openMode == NotOpen) {
        qWarning("QIODevice::seek: The device is not open");
        return false;
    }
    if (pos < 0) {
        qWarning("QIODevice::seek: Invalid pos: %d", int(pos));
        return false;
    }

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::seek(%d), before: d->pos = %d, d->buffer.size() = %d\n",
           this, int(pos), int(d->pos), d->buffer.size());
#endif

    qint64 offset = pos - d->pos;
    if (!d->isSequential()) {
        d->pos = pos;
        d->devicePos = pos;
    }

    if (offset < 0
            || offset >= qint64(d->buffer.size()))
        // When seeking backwards, an operation that is only allowed for
        // random-access devices, the buffer is cleared. The next read
        // operation will then refill the buffer. We can optimize this, if we
        // find that seeking backwards becomes a significant performance hit.
        d->buffer.clear();
    else if (!d->buffer.isEmpty())
        d->buffer.skip(int(offset));

#if defined QIODEVICE_DEBUG
    printf("%p \tafter: d->pos == %d, d->buffer.size() == %d\n", this, int(d->pos),
           d->buffer.size());
#endif
    return true;
}

setErrorString()

void QIODevice::setErrorString ( const QString &  str )

protected

Sets the human readable description of the last device error that occurred to str.

See also

errorString()

Definition at line 1660 of file qiodevice.cpp.

Referenced by QUdpSocket::bind(), QAbstractSocket::connectToHostImplementation(), QPatternist::QIODeviceDelegate::networkTimeout(), QOstDevice::open(), QAbstractSocket::readData(), QUdpSocket::readDatagram(), QNetworkReply::setError(), QAbstractSocket::setSocketDescriptor(), QProcess::start(), QAbstractSocket::waitForBytesWritten(), QAbstractSocket::waitForConnected(), QAbstractSocket::waitForDisconnected(), QAbstractSocket::waitForReadyRead(), QOstDevice::writeData(), QAbstractSocket::writeData(), QProcess::writeData(), and QUdpSocket::writeDatagram().

{
    d_func()->errorString = str;
}

setOpenMode()

void QIODevice::setOpenMode ( OpenMode  openMode )

protected

Sets the OpenMode of the device to openMode.

Call this function to set the open mode if the flags change after the device has been opened.

See also

openMode() OpenMode

Definition at line 477 of file qiodevice.cpp.

Referenced by QUnixSocket::abort(), QUnixSocket::connect(), QPatternist::QIODeviceDelegate::open(), QTemporaryFile::open(), QPatternist::QIODeviceDelegate::QIODeviceDelegate(), QUnixSocket::QUnixSocket(), and QUnixSocket::setSocketDescriptor().

{
    Q_D(QIODevice);
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::setOpenMode(0x%x)\n", this, int(openMode));
#endif
    d->openMode = openMode;
    d->accessMode = QIODevicePrivate::Unset;
    d->firstRead = true;
    if (!isReadable())
        d->buffer.clear();
}

setTextModeEnabled()

void QIODevice::setTextModeEnabled

(

bool

enabled

)

If enabled is true, this function sets the Text flag on the device; otherwise the Text flag is removed.

This feature is useful for classes that provide custom end-of-line handling on a QIODevice.

The IO device should be opened before calling this function.

See also

open(), setOpenMode()

Definition at line 499 of file qiodevice.cpp.

Referenced by QTextStreamPrivate::fillReadBuffer(), and QTextStreamPrivate::flushWriteBuffer().

{
    Q_D(QIODevice);
    if (!isOpen()) {
        qWarning("QIODevice::setTextModeEnabled: The device is not open");
        return;
    }
    if (enabled)
        d->openMode |= Text;
    else
        d->openMode &= ~Text;
}

size()

qint64 QIODevice::size ( ) const

virtual

For open random-access devices, this function returns the size of the device.

For open sequential devices, bytesAvailable() is returned.

If the device is closed, the size returned will not reflect the actual size of the device.

See also

isSequential(), pos()

Reimplemented in QByteDeviceWrappingIoDevice, QFile, QHttpMultiPartIODevice, QBuffer, QPatternist::QIODeviceDelegate, QNetworkReplyFileImpl, and QNetworkReplyDataImpl.

Definition at line 642 of file qiodevice.cpp.

Referenced by QHttpPrivate::_q_slotConnected(), QFtpPrivate::_q_startNextCommand(), atEnd(), bytesAvailable(), QProcess::bytesToWrite(), QNetworkAccessManager::createRequest(), QPSPrintEnginePrivate::flushPage(), iod_read_fn(), QDeclarativeDataLoader::load(), open(), QHttpPrivate::postMoreData(), QPdf::ByteStream::prepareBuffer(), QFtp::put(), QTgaFile::QTgaFile(), qtiffSeekProc(), readAll(), QUnixSocket::readData(), readLine(), QZipReaderPrivate::scanFiles(), QNetworkAccessHttpBackend::sendCacheContents(), QNetworkReply::setReadBufferSize(), QAbstractSocket::setReadBufferSize(), QUnixSocket::setReadBufferSize(), QUnixSocket::setRightsBufferSize(), QPatternist::QIODeviceDelegate::size(), QNonContiguousByteDeviceIoDeviceImpl::size(), QDataStream::skipRawData(), QFile::symLinkTarget(), and QAbstractSocket::writeData().

{
    return d_func()->isSequential() ?  bytesAvailable() : qint64(0);
}

ungetChar()

void QIODevice::ungetChar

(

char

c

)

Puts the character c back into the device, and decrements the current position unless the position is 0.

This function is usually called to "undo" a getChar() operation, such as when writing a backtracking parser.

If c was not previously read from the device, the behavior is undefined.

Definition at line 1462 of file qiodevice.cpp.

Referenced by ICOReader::canRead(), QSocks5SocketEnginePrivate::parseRequestMethodReply(), qt_read_xpm_image_or_array(), and read_xpm_body().

{
    Q_D(QIODevice);
    CHECK_READABLE(read, Q_VOID);

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::ungetChar(0x%hhx '%c')\n", this, c, isprint(c) ? c : '?');
#endif

    d->buffer.ungetChar(c);
    if (!d->isSequential())
        --d->pos;
}

waitForBytesWritten()

bool QIODevice::waitForBytesWritten ( int  msecs )

virtual

For buffered devices, this function waits until a payload of buffered written data has been written to the device and the bytesWritten() signal has been emitted, or until msecs milliseconds have passed.

If msecs is -1, this function will not time out. For unbuffered devices, it returns immediately.

Returns true if a payload of data was written to the device; otherwise returns false (i.e. if the operation timed out, or if an error occurred).

This function can operate without an event loop. It is useful when writing non-GUI applications and when performing I/O operations in a non-GUI thread.

If called from within a slot connected to the bytesWritten() signal, bytesWritten() will not be reemitted.

Reimplement this function to provide a blocking API for a custom device. The default implementation does nothing, and returns false.

Warning

Calling this function from the main (GUI) thread might cause your user interface to freeze.

See also

waitForReadyRead()

Reimplemented in QUnixSocket, QAbstractSocket, QProcess, QSslSocket, QLocalSocket, and QPatternist::QIODeviceDelegate.

Definition at line 1648 of file qiodevice.cpp.

Referenced by QUnixSocket::read(), and QPatternist::QIODeviceDelegate::waitForBytesWritten().

{
    Q_UNUSED(msecs);
    return false;
}

waitForReadyRead()

bool QIODevice::waitForReadyRead ( int  msecs )

virtual

Blocks until new data is available for reading and the readyRead() signal has been emitted, or until msecs milliseconds have passed.

If msecs is -1, this function will not time out.

Returns true if new data is available for reading; otherwise returns false (if the operation timed out or if an error occurred).

This function can operate without an event loop. It is useful when writing non-GUI applications and when performing I/O operations in a non-GUI thread.

If called from within a slot connected to the readyRead() signal, readyRead() will not be reemitted.

Reimplement this function to provide a blocking API for a custom device. The default implementation does nothing, and returns false.

Warning

Calling this function from the main (GUI) thread might cause your user interface to freeze.

See also

waitForBytesWritten()

Reimplemented in QUnixSocket, QAbstractSocket, QProcess, QSslSocket, QLocalSocket, QPatternist::QIODeviceDelegate, and QOstDevice.

Definition at line 1616 of file qiodevice.cpp.

Referenced by QXmlInputSource::fetchData(), QUnixSocket::read(), QPacketProtocol::waitForReadyRead(), and QPatternist::QIODeviceDelegate::waitForReadyRead().

{
    Q_UNUSED(msecs);
    return false;
}

write() [1/3]

qint64 QIODevice::write	(	const char *	data,
		qint64	maxSize
	)

Writes at most maxSize bytes of data from data to the device.

Returns the number of bytes that were actually written, or -1 if an error occurred.

See also

read() writeData()

Definition at line 1342 of file qiodevice.cpp.

Referenced by QHttpPrivate::_q_slotConnected(), QHttpPrivate::_q_slotReadyRead(), QFtpPI::abort(), QZipWriterPrivate::addEntry(), QNetworkReplyImplPrivate::appendDownstreamData(), QNetworkReplyImplPrivate::appendDownstreamDataDownloadBuffer(), QSocks5PasswordAuthenticator::beginAuthenticate(), buttonChange(), QVNCCursor::clearClientCursor(), QZipWriter::close(), QTemporaryFile::createLocalFile(), QGraphicsAnchorLayoutPrivate::dumpGraph(), dumpOutput(), QPdfEnginePrivate::embedFont(), QPSPrintEnginePrivate::emitHeader(), QPSPrintEnginePrivate::emitPages(), QtopiaPrintEngine::end(), QZipReader::extractAll(), QTextStreamPrivate::flushWriteBuffer(), QAudioInputPrivate::freeBlocks(), QTestLiteStaticInfoPrivate::initializeSupportedAtoms(), QVNCServer::newConnection(), QPdf::ByteStream::operator<<(), QDataStream::operator<<(), QPatternist::XsdStateMachine< XsdSchemaToken::NodeName >::outputGraph(), QHttpNetworkConnectionChannel::pipelineFlush(), QHttpPrivate::postMoreData(), QPdf::ByteStream::prepareBuffer(), qpiw_write_fn(), qt_empty_output_buffer(), qt_get_net_supported(), qt_get_net_virtual_roots(), qt_term_destination(), qt_write_dib(), qt_write_dibv5(), QVNCDirtyMap::QVNCDirtyMap(), qws_write_command(), qws_write_uint(), QAudioInputPrivate::read(), QUnixSocket::read(), QVNCServer::readClient(), registerFont(), QFile::rename(), QPicture::save(), QBuffer::seek(), QPacketProtocol::send(), QWaylandSelection::send(), QVNCCursor::sendClientCursor(), QHttpNetworkConnectionChannel::sendRequest(), QSocks5SocketEnginePrivate::sendRequestMethod(), QSslSocketBackendPrivate::startHandshake(), QFtpPI::startNextCmd(), QSslSocketBackendPrivate::transmit(), QNetworkDiskCache::updateMetaData(), QNetworkAccessFileBackend::uploadReadyReadSlot(), QPatternist::ColorOutputPrivate::write(), QVNCClientCursor::write(), ICOReader::write(), write(), QRfbRect::write(), QRfbPixelFormat::write(), QUnixSocket::write(), QRfbServerInit::write(), QRfbRawEncoder::write(), QRfbSingleColorHextile< SRC >::write(), QRfbDualColorHextile< SRC >::write(), QRfbMultiColorHextile< SRC >::write(), QRfbHextileEncoder< SRC >::write(), QXmlStreamWriterPrivate::write(), write_pbm_image(), write_xbm_image(), writeBMPInfoHeader(), QFtpDTP::writeData(), QAuthDevice::writeData(), writeIconDir(), writeIconDirEntry(), QConfFileSettingsPrivate::writeIniFile(), and QDataStream::writeRawData().

{
    Q_D(QIODevice);
    CHECK_WRITABLE(write, qint64(-1));
    CHECK_MAXLEN(write, qint64(-1));

    const bool sequential = d->isSequential();
    // Make sure the device is positioned correctly.
    if (d->pos != d->devicePos && !sequential && !seek(d->pos))
        return qint64(-1);

#ifdef Q_OS_WIN
    if (d->openMode & Text) {
        const char *endOfData = data + maxSize;
        const char *startOfBlock = data;

        qint64 writtenSoFar = 0;

        forever {
            const char *endOfBlock = startOfBlock;
            while (endOfBlock < endOfData && *endOfBlock != '\n')
                ++endOfBlock;

            qint64 blockSize = endOfBlock - startOfBlock;
            if (blockSize > 0) {
                qint64 ret = writeData(startOfBlock, blockSize);
                if (ret <= 0) {
                    if (writtenSoFar && !sequential)
                        d->buffer.skip(writtenSoFar);
                    return writtenSoFar ? writtenSoFar : ret;
                }
                if (!sequential) {
                    d->pos += ret;
                    d->devicePos += ret;
                }
                writtenSoFar += ret;
            }

            if (endOfBlock == endOfData)
                break;

            qint64 ret = writeData("\r\n", 2);
            if (ret <= 0) {
                if (writtenSoFar && !sequential)
                    d->buffer.skip(writtenSoFar);
                return writtenSoFar ? writtenSoFar : ret;
            }
            if (!sequential) {
                d->pos += ret;
                d->devicePos += ret;
            }
            ++writtenSoFar;

            startOfBlock = endOfBlock + 1;
        }

        if (writtenSoFar && !sequential)
            d->buffer.skip(writtenSoFar);
        return writtenSoFar;
    }
#endif

    qint64 written = writeData(data, maxSize);
    if (written > 0) {
        if (!sequential) {
            d->pos += written;
            d->devicePos += written;
        }
        if (!d->buffer.isEmpty() && !sequential)
            d->buffer.skip(written);
    }
    return written;
}

write() [2/3]

qint64 QIODevice::write

(

const char *

data

)

Writes data from a zero-terminated string of 8-bit characters to the device.

Since

4.5

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns the number of bytes that were actually written, or -1 if an error occurred. This is equivalent to

...
QIODevice::write(data, qstrlen(data));
...

See also

read() writeData()

Definition at line 1435 of file qiodevice.cpp.

{
    return write(data, qstrlen(data));
}

write() [3/3]

qint64 QIODevice::write ( const QByteArray &  byteArray )

inline

Writes the content of byteArray to the device.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns the number of bytes that were actually written, or -1 if an error occurred.

See also

read() writeData()

Definition at line 126 of file qiodevice.h.

    { return write(data.constData(), data.size()); }

writeData()

qint64 QIODevice::writeData ( const char *  data, qint64  maxSize  )

protectedpure virtual

Writes up to maxSize bytes from data to the device.

Returns the number of bytes written, or -1 if an error occurred.

This function is called by QIODevice. Reimplement this function when creating a subclass of QIODevice.

When reimplementing this function it is important that this function writes all the data available before returning. This is required in order for QDataStream to be able to operate on the class. QDataStream assumes all the information was written and therefore does not retry writing if there was a problem.

See also

read() write()

Implemented in QtMultimediaInternal::MacInputDevice, MacOutputDevice, QAuthDevice, QProcess, QFile, QAbstractSocket, QSslSocket, QUnixSocket, QByteDeviceWrappingIoDevice, QNetworkReply, OutputPrivate, InputPrivate, QHttpMultiPartIODevice, InputPrivate, OutputPrivate, QLocalSocket, QBuffer, and QOstDevice.

Referenced by QUnixSocket::read(), and write().

---

The documentation for this class was generated from the following files:

• /src/corelib/io/qiodevice.h
• /src/corelib/io/qiodevice.cpp