The QDBusUnixFileDescriptor class holds one Unix file descriptor. More...

#include <qdbusunixfiledescriptor.h>

Public Functions
int	fileDescriptor () const
	Returns the Unix file descriptor contained by this QDBusUnixFileDescriptor object. More...

void	giveFileDescriptor (int fileDescriptor)
	Sets the Unix file descriptor to fileDescriptor without copying. More...

bool	isValid () const
	Returns true if this Unix file descriptor is valid. More...

QDBusUnixFileDescriptor &	operator= (const QDBusUnixFileDescriptor &other)
	Copies the Unix file descriptor from the other QDBusUnixFileDescriptor object. More...

	QDBusUnixFileDescriptor ()
	Constructs a QDBusUnixFileDescriptor without a wrapped file descriptor. More...

	QDBusUnixFileDescriptor (int fileDescriptor)
	Constructs a QDBusUnixFileDescriptor object by copying the fileDescriptor parameter. More...

	QDBusUnixFileDescriptor (const QDBusUnixFileDescriptor &other)
	Constructs a QDBusUnixFileDescriptor object by copying other. More...

void	setFileDescriptor (int fileDescriptor)
	Sets the file descriptor that this QDBusUnixFileDescriptor object holds to a copy of fileDescriptor. More...

int	takeFileDescriptor ()
	Extracts the Unix file descriptor from the QDBusUnixFileDescriptor object and transfers ownership. More...

	~QDBusUnixFileDescriptor ()
	Destroys this QDBusUnixFileDescriptor object and disposes of the Unix file descriptor that it contained. More...

Static Public Functions
static bool	isSupported ()
	Returns true if Unix file descriptors are supported on this platform. More...

Protected Types
typedef QExplicitlySharedDataPointer< QDBusUnixFileDescriptorPrivate >	Data

Protected Variables
Data	d

Detailed Description

The QDBusUnixFileDescriptor class holds one Unix file descriptor.

Attention: Module: QtDBus

Since: 4.8

The QDBusUnixFileDescriptor class is used to hold one Unix file descriptor for use with the QtDBus module. This allows applications to send and receive Unix file descriptors over the D-Bus connection, mapping automatically to the D-Bus type 'h'.

Objects of type QDBusUnixFileDescriptors can be used also as parameters in signals and slots that get exported to D-Bus by registering with QDBusConnection::registerObject.

QDBusUnixFileDescriptor does not take ownership of the file descriptor. Instead, it will use the Unix system call dup(2) to make a copy of the file descriptor. This file descriptor belongs to the QDBusUnixFileDescriptor object and should not be stored or closed by the user. Instead, you should make your own copy if you need that.

Availability

Unix file descriptor passing is not available in all D-Bus connections. This feature is present with D-Bus library and bus daemon version 1.4 and upwards on Unix systems. QtDBus automatically enables the feature if such a version was found at compile-time and run-time.

To verify that your connection does support passing file descriptors, check if the QDBusConnection::UnixFileDescriptorPassing capability is set with QDBusConnection::connectionCapabilities(). If the flag is not active, then you will not be able to make calls to methods that have QDBusUnixFileDescriptor as arguments or even embed such a type in a variant. You will also not receive calls containing that type.

Note also that remote applications may not have support for Unix file descriptor passing. If you make a D-Bus to a remote application that cannot receive such a type, you will receive an error reply. If you try to send a signal containing a D-Bus file descriptor or return one from a method call, the message will be silently dropped.

Even if the feature is not available, QDBusUnixFileDescriptor will continue to operate, so code need not have compile-time checks for the availability of this feature.

On non-Unix systems, QDBusUnixFileDescriptor will always report an invalid state and QDBusUnixFileDescriptor::isSupported() will return false.

See also: QDBusConnection::ConnectionCapabilities, QDBusConnection::connectionCapabilities()

Definition at line 64 of file qdbusunixfiledescriptor.h.

Typedefs

◆ Data

QDBusUnixFileDescriptor::Data

protected

Warning: This function is not part of the public interface.

Definition at line 91 of file qdbusunixfiledescriptor.h.

Constructors and Destructors

◆ QDBusUnixFileDescriptor() [1/3]

QDBusUnixFileDescriptor::QDBusUnixFileDescriptor ( )

Constructs a QDBusUnixFileDescriptor without a wrapped file descriptor.

This is equivalent to constructing the object with an invalid file descriptor (like -1).

See also: fileDescriptor(), isValid()

Definition at line 140 of file qdbusunixfiledescriptor.cpp.

     : d(0)
 {
 }

◆ QDBusUnixFileDescriptor() [2/3]

QDBusUnixFileDescriptor::QDBusUnixFileDescriptor ( int fileDescriptor )

explicit

Constructs a QDBusUnixFileDescriptor object by copying the fileDescriptor parameter.

The original file descriptor is not touched and must be closed by the user.

Note that the value returned by fileDescriptor() will be different from the fileDescriptor parameter passed.

If the fileDescriptor parameter is not valid, isValid() will return false and fileDescriptor() will return -1.

See also: setFileDescriptor(), fileDescriptor()

Definition at line 158 of file qdbusunixfiledescriptor.cpp.

     : d(0)
 {
     if (fileDescriptor != -1)
         setFileDescriptor(fileDescriptor);
 }

◆ QDBusUnixFileDescriptor() [3/3]

QDBusUnixFileDescriptor::QDBusUnixFileDescriptor ( const QDBusUnixFileDescriptor & other )

Constructs a QDBusUnixFileDescriptor object by copying other.

Definition at line 168 of file qdbusunixfiledescriptor.cpp.

     : d(other.d)
 {
 }

◆ ~QDBusUnixFileDescriptor()

QDBusUnixFileDescriptor::~QDBusUnixFileDescriptor ( )

Destroys this QDBusUnixFileDescriptor object and disposes of the Unix file descriptor that it contained.

Definition at line 188 of file qdbusunixfiledescriptor.cpp.

189 {

190 }

Functions

◆ fileDescriptor()

int QDBusUnixFileDescriptor::fileDescriptor ( ) const

Returns the Unix file descriptor contained by this QDBusUnixFileDescriptor object.

An invalid file descriptor is represented by the value -1.

Note that the file descriptor returned by this function is owned by the QDBusUnixFileDescriptor object and must not be stored past the lifetime of this object. It is ok to use it while this object is valid, but if one wants to store it for longer use, the file descriptor should be cloned using the Unix dup(2), dup2(2) or dup3(2) functions.

See also: isValid()

Definition at line 216 of file qdbusunixfiledescriptor.cpp.

Referenced by QDBusMarshaller::append(), and giveFileDescriptor().

 {
     return d ? d->fd.operator int() : -1;
 }

◆ giveFileDescriptor()

void QDBusUnixFileDescriptor::giveFileDescriptor ( int fileDescriptor )

Sets the Unix file descriptor to fileDescriptor without copying.

Warning: This function is not part of the public interface.

See also: setFileDescriptor()

Definition at line 269 of file qdbusunixfiledescriptor.cpp.

Referenced by setFileDescriptor(), QDBusDemarshaller::toUnixFileDescriptor(), and QDBusUnixFileDescriptorPrivate::~QDBusUnixFileDescriptorPrivate().

 {
     // if we are the sole ref, d remains unchanged
     // if detaching happens, d->fd will be -1
     if (d)
         d.detach();
     else
         d = new QDBusUnixFileDescriptorPrivate;
 
     if (d->fd != -1)
         qt_safe_close(d->fd);
 
     if (fileDescriptor != -1)
         d->fd = fileDescriptor;
 }

◆ isSupported()

bool QDBusUnixFileDescriptor::isSupported ( )

static

Returns true if Unix file descriptors are supported on this platform.

In other words, this function returns true if this is a Unix platform.

Note that QDBusUnixFileDescriptor continues to operate even if this function returns false. The only difference is that the QDBusUnixFileDescriptor objects will always be in the isValid() == false state and fileDescriptor() will always return -1. The class will not consume any operating system resources.

Definition at line 236 of file qdbusunixfiledescriptor.cpp.

Referenced by QDBusUnixFileDescriptorPrivate::~QDBusUnixFileDescriptorPrivate().

 {
     return true;
 }

◆ isValid()

bool QDBusUnixFileDescriptor::isValid ( ) const

Returns true if this Unix file descriptor is valid.

A valid Unix file descriptor is not -1.

See also: fileDescriptor()

Definition at line 198 of file qdbusunixfiledescriptor.cpp.

 {
     return d ? d->fd != -1 : false;
 }

◆ operator=()

QDBusUnixFileDescriptor & QDBusUnixFileDescriptor::operator= ( const QDBusUnixFileDescriptor & other )

Copies the Unix file descriptor from the other QDBusUnixFileDescriptor object.

If the current object contained a file descriptor, it will be properly disposed of before.

Definition at line 178 of file qdbusunixfiledescriptor.cpp.

 {
     if (this != &other)
         d.operator=(other.d);
     return *this;
 }

◆ setFileDescriptor()

void QDBusUnixFileDescriptor::setFileDescriptor ( int fileDescriptor )

Sets the file descriptor that this QDBusUnixFileDescriptor object holds to a copy of fileDescriptor.

The original file descriptor is not touched and must be closed by the user.

Note that the value returned by fileDescriptor() will be different from the fileDescriptor parameter passed.

If the fileDescriptor parameter is not valid, isValid() will return false and fileDescriptor() will return -1.

See also: isValid(), fileDescriptor()

Definition at line 254 of file qdbusunixfiledescriptor.cpp.

Referenced by QDBusUnixFileDescriptor(), and QDBusUnixFileDescriptorPrivate::~QDBusUnixFileDescriptorPrivate().

 {
     if (fileDescriptor != -1)
         giveFileDescriptor(qt_safe_dup(fileDescriptor));
 }

◆ takeFileDescriptor()

int QDBusUnixFileDescriptor::takeFileDescriptor ( )

Extracts the Unix file descriptor from the QDBusUnixFileDescriptor object and transfers ownership.

Warning: This function is not part of the public interface.

Note: since QDBusUnixFileDescriptor is implicitly shared, this function is inherently racy and should be avoided.

Definition at line 296 of file qdbusunixfiledescriptor.cpp.

Referenced by QDBusUnixFileDescriptorPrivate::~QDBusUnixFileDescriptorPrivate().

 {
     if (!d)
         return -1;
 
     return d->fd.fetchAndStoreRelaxed(-1);
 }

Properties

◆ d

QDBusUnixFileDescriptor::d