QIODeviceBase Class

Base class for QIODevice that provides flags describing the mode in which a device is opened. More...

Header:	#include <QIODevice>
CMake:	find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core
Inherited By:	QDataStream, QDebug, QIODevice, and QTextStream

• List of all members, including inherited members

Public Types

flags	OpenMode
enum	OpenModeFlag { NotOpen, ReadOnly, WriteOnly, ReadWrite, Append, …, ExistingOnly }

Detailed Description

Member Type Documentation

enum QIODeviceBase::OpenModeFlagflags QIODeviceBase::OpenMode

This enum is used with QIODevice::open() to describe the mode in which a device is opened. It is also returned by QIODevice::openMode().

Constant	Value	Description
QIODeviceBase::NotOpen	0x0000	The device is not open.
QIODeviceBase::ReadOnly	0x0001	The device is open for reading.
QIODeviceBase::WriteOnly	0x0002	The device is open for writing. Note that, for file-system subclasses (e.g. QFile), this mode implies Truncate unless combined with ReadOnly, Append or NewOnly.
QIODeviceBase::ReadWrite	ReadOnly | WriteOnly	The device is open for reading and writing.
QIODeviceBase::Append	0x0004	The device is opened in append mode so that all data is written to the end of the file.
QIODeviceBase::Truncate	0x0008	If possible, the device is truncated before it is opened. All earlier contents of the device are lost.
QIODeviceBase::Text	0x0010	When reading, the end-of-line terminators are translated to '\n'. When writing, the end-of-line terminators are translated to the local encoding, for example '\r\n' for Win32.
QIODeviceBase::Unbuffered	0x0020	Any buffer in the device is bypassed.
QIODeviceBase::NewOnly	0x0040	Fail if the file to be opened already exists. Create and open the file only if it does not exist. There is a guarantee from the operating system that you are the only one creating and opening the file. Note that this mode implies WriteOnly, and combining it with ReadWrite is allowed. This flag currently only affects QFile. Other classes might use this flag in the future, but until then using this flag with any classes other than QFile may result in undefined behavior. (since Qt 5.11)
QIODeviceBase::ExistingOnly	0x0080	Fail if the file to be opened does not exist. This flag must be specified alongside ReadOnly, WriteOnly, or ReadWrite. Note that using this flag with ReadOnly alone is redundant, as ReadOnly already fails when the file does not exist. This flag currently only affects QFile. Other classes might use this flag in the future, but until then using this flag with any classes other than QFile may result in undefined behavior. (since Qt 5.11)

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.

The OpenMode type is a typedef for QFlags<OpenModeFlag>. It stores an OR combination of OpenModeFlag values.