glibmm: Glib::IOChannel Class Reference

IOChannel aims to provide portable I/O support for files, pipes and sockets, and to integrate them with the GLib main event loop. More...

#include <glibmm/iochannel.h>

Inheritance diagram for Glib::IOChannel:

[legend]

Public Member Functions
virtual	~IOChannel ()

IOStatus	read (gunichar &thechar)
	Read a single UCS-4 character.

IOStatus	read (char *buf, gsize count, gsize &bytes_read)
	Read a character sequence into memory.

IOStatus	read (Glib::ustring & str, gsize count)
	Read a maximum of count bytes into str.

IOStatus	read_line (Glib::ustring &line)
	Read a whole line.

IOStatus	read_to_end (Glib::ustring & str)
	Reads all the remaining data from the file.

IOStatus	write (const Glib::ustring & str)
	Write a string to the I/O channel.

IOStatus	write (const char *buf, gssize count, gsize &bytes_written)
	Write a memory area of count bytes to the I/O channel.

IOStatus	write (gunichar unichar)
	Write a single UCS-4 character to the I/O channel.

IOStatus	seek (gint64 offset, SeekType type=SeekType::SET)
	Seek the I/O channel to a specific position.

IOStatus	flush ()
	Flush the buffers of the I/O channel.

IOStatus	close (bool flush_pending=true)
	Close the I/O channel.

gsize	get_buffer_size () const
	Get the IOChannel internal buffer size.

void	set_buffer_size (gsize size)
	Set the internal IOChannel buffer size.

IOFlags	get_flags () const
	Get the current flags for a IOChannel, including read-only flags such as Glib::IOFlags::IS_READABLE.

IOStatus	set_flags (IOFlags flags)
	Set flags on the IOChannel.

void	set_buffered (bool buffered)
	Set the buffering status of the I/O channel.

bool	get_buffered () const
	Get the buffering status of the I/O channel.

IOCondition	get_buffer_condition () const
	Returns an IOCondition depending on whether there is data to be read/space to write data in the internal buffers in the I/O channel.

bool	get_close_on_unref () const
	Returns whether the file/socket/whatever associated with the I/O channel will be closed when the channel receives its final unref and is destroyed.

void	set_close_on_unref (bool do_close)
	Setting this flag to `true` for a channel you have already closed can cause problems.

IOStatus	set_encoding (const std::string &encoding={})
	Sets the encoding for the input/output of the channel.

std::string	get_encoding () const
	Get the encoding of the I/O channel.

void	set_line_term (const std::string &term={})

std::string	get_line_term () const

Glib::RefPtr< IOSource >	create_watch (IOCondition condition)
	Creates an IOSource object.

virtual void	reference () const

virtual void	unreference () const

GIOChannel *	gobj ()

const GIOChannel *	gobj () const

Static Public Member Functions
static Glib::RefPtr< IOChannel >	create_from_file (const std::string &filename, const std::string &mode)
	Open a file filename as an I/O channel using mode mode.

static Glib::RefPtr< IOChannel >	create_from_fd (int fd)
	Creates an I/O channel from a file descriptor.

static Glib::RefPtr< IOChannel >	create_from_win32_fd (int fd)
	Create an I/O channel for C runtime (emulated Unix-like) file descriptors.

static Glib::RefPtr< IOChannel >	create_from_win32_socket (int socket)
	Create an I/O channel for a winsock socket.

Protected Attributes
GIOChannel *	gobject_

Detailed Description

IOChannel aims to provide portable I/O support for files, pipes and sockets, and to integrate them with the GLib main event loop.

Note that IOChannels implement an automatic implicit character set conversion to the data stream, and usually will not pass by default binary data unchanged. To set the encoding of the channel, use e.g. set_encoding("ISO-8859-15"). To set the channel to no encoding, use set_encoding() without any arguments.

You can create an IOChannel with one of the static create methods.

Constructor & Destructor Documentation

◆ ~IOChannel()

virtual Glib::IOChannel::~IOChannel ( )

virtual

Member Function Documentation

◆ close()

IOStatus Glib::IOChannel::close ( bool flush_pending = true )

Close the I/O channel.

Any pending data to be written will be flushed if flush is true. The channel will not be freed until the last reference is dropped. Accessing the channel after closing it is considered an error.

Parameters

flush_pending Whether to flush() pending data before closing the channel.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError

◆ create_from_fd()

static Glib::RefPtr< IOChannel > Glib::IOChannel::create_from_fd ( int fd )

static

Creates an I/O channel from a file descriptor.

On Unix, IOChannels created with this function work for any file descriptor or socket.

On Win32, this can be used either for files opened with the MSVCRT (the Microsoft run-time C library) _open() or _pipe(), including file descriptors 0, 1 and 2 (corresponding to stdin, stdout and stderr), or for Winsock SOCKETs. If the parameter is a legal file descriptor, it is assumed to be such, otherwise it should be a SOCKET. This relies on SOCKETs and file descriptors not overlapping. If you want to be certain, call either create_from_win32_fd() or create_from_win32_socket() instead as appropriate.

The term file descriptor as used in the context of Win32 refers to the emulated Unix-like file descriptors MSVCRT provides. The native corresponding concept is file HANDLE. There isn't as of yet a way to get IOChannels for Win32 file HANDLEs.

◆ create_from_file()

static Glib::RefPtr< IOChannel > Glib::IOChannel::create_from_file	(	const std::string &	filename,
		const std::string &	mode
	)

static

Open a file filename as an I/O channel using mode mode.

This channel will be closed when the last reference to it is dropped, so there is no need to call close() (though doing so will not cause problems, as long as no attempt is made to access the channel after it is closed).

Parameters

filename	The name of the file to open.
mode	One of `"r"`, `"w"`, `"a"`, `"r+"`, `"w+"`, `"a+"`. These have the same meaning as in `fopen()`.

Returns: An IOChannel for the opened file.

Exceptions

Glib::FileError

◆ create_from_win32_fd()

static Glib::RefPtr< IOChannel > Glib::IOChannel::create_from_win32_fd ( int fd )

static

Create an I/O channel for C runtime (emulated Unix-like) file descriptors.

After calling add_watch() on a I/O channel returned by this function, you shouldn't call read() on the file descriptor. This is because adding polling for a file descriptor is implemented on Win32 by starting a thread that sits blocked in a read() from the file descriptor most of the time. All reads from the file descriptor should be done by this internal GLib thread. Your code should call only IOChannel::read().

◆ create_from_win32_socket()

static Glib::RefPtr< IOChannel > Glib::IOChannel::create_from_win32_socket ( int socket )

static

Create an I/O channel for a winsock socket.

The parameter should be a SOCKET. Contrary to I/O channels for file descriptors (on Win32), you can use normal recv() or recvfrom() on sockets even if GLib is polling them.

◆ create_watch()

Glib::RefPtr< IOSource > Glib::IOChannel::create_watch ( IOCondition condition )

Creates an IOSource object.

Create a slot from a function to be called when condition is met for the channel with sigc::ptr_fun() or sigc::mem_fun() and pass it into the connect() function of the returned IOSource object. Polling of the channel will start when you attach a MainContext object to the returned IOSource object using its attach() function.

Glib::signal_io().connect() is a simpler interface to the same functionality, for the case where you want to add the source to the default main context.

Parameters

condition The condition to watch for.

Returns: An IOSource object that can be polled from a MainContext's event loop.

◆ flush()

IOStatus Glib::IOChannel::flush ( )

Flush the buffers of the I/O channel.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ get_buffer_condition()

IOCondition Glib::IOChannel::get_buffer_condition ( ) const

Returns an IOCondition depending on whether there is data to be read/space to write data in the internal buffers in the I/O channel.

Only the flags Glib::IOCondition::IO_IN and Glib::IOCondition::IO_OUT may be set.

Returns: Bitwise combination of Glib::IOCondition flags.

◆ get_buffer_size()

gsize Glib::IOChannel::get_buffer_size ( ) const

Get the IOChannel internal buffer size.

Returns: The buffer size.

◆ get_buffered()

bool Glib::IOChannel::get_buffered ( ) const

Get the buffering status of the I/O channel.

Returns: The buffering status of the channel.

◆ get_close_on_unref()

bool Glib::IOChannel::get_close_on_unref ( ) const

Returns whether the file/socket/whatever associated with the I/O channel will be closed when the channel receives its final unref and is destroyed.

The default value of this is true for channels created by create_from_file(), and false for all other channels.

Returns: Whether the channel will be closed on the final unref of the IOChannel object.

◆ get_encoding()

std::string Glib::IOChannel::get_encoding ( ) const

Get the encoding of the I/O channel.

Returns: The current encoding of the channel.

◆ get_flags()

IOFlags Glib::IOChannel::get_flags ( ) const

Get the current flags for a IOChannel, including read-only flags such as Glib::IOFlags::IS_READABLE.

The values of the flags Glib::IOFlags::IS_READABLE and Glib::IOFlags::IS_WRITEABLE are cached for internal use by the channel when it is created. If they should change at some later point (e.g. partial shutdown of a socket with the UNIX shutdown() function), the user should immediately call get_flags() to update the internal values of these flags.

Returns: Bitwise combination of the flags set on the channel.

◆ get_line_term()

std::string Glib::IOChannel::get_line_term ( ) const

◆ gobj() [1/2]

GIOChannel * Glib::IOChannel::gobj ( )

inline

◆ gobj() [2/2]

const GIOChannel * Glib::IOChannel::gobj ( ) const

inline

◆ read() [1/3]

IOStatus Glib::IOChannel::read	(	char *	buf,
		gsize	count,
		gsize &	bytes_read
	)

Read a character sequence into memory.

Parameters

	buf	A buffer to read data into.
	count	The size of the buffer in bytes. Note that the buffer may not be complelely filled even if there is data in the buffer if the remaining data is not a complete character.
[out]	bytes_read	The number of bytes read. This may be zero even on success if count < 6 and the channel's encoding is not `""`. This indicates that the next UTF-8 character is too wide for the buffer.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ read() [2/3]

IOStatus Glib::IOChannel::read	(	Glib::ustring &	str,
		gsize	count
	)

Read a maximum of count bytes into str.

Parameters

[out]	str	The characters that have been read.
	count	The maximum number of bytes to read.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ read() [3/3]

IOStatus Glib::IOChannel::read ( gunichar & thechar )

Read a single UCS-4 character.

Parameters

[out] thechar The Unicode character.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ read_line()

IOStatus Glib::IOChannel::read_line ( Glib::ustring & line )

Read a whole line.

Reads until the line separator is found, which is included in the result string.

Parameters

[out] line The line that was read.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ read_to_end()

IOStatus Glib::IOChannel::read_to_end ( Glib::ustring & str )

Reads all the remaining data from the file.

Parameters

[out] str The resulting string.

Returns: Glib::IOStatus::NORMAL on success. This function never returns Glib::IOStatus::ENDOFFILE.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ reference()

virtual void Glib::IOChannel::reference ( ) const

virtual

◆ seek()

IOStatus Glib::IOChannel::seek	(	gint64	offset,
		SeekType	type = `SeekType::SET`
	)

Seek the I/O channel to a specific position.

Parameters

offset	The offset in bytes from the position specified by type.
type	A SeekType. The type Glib::SeekType::CUR is only allowed in those cases where a call to set_encoding() is allowed. See the documentation for set_encoding() for details.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ set_buffer_size()

void Glib::IOChannel::set_buffer_size ( gsize size )

Set the internal IOChannel buffer size.

Parameters

size	The buffer size the IOChannel should use.

◆ set_buffered()

void Glib::IOChannel::set_buffered ( bool buffered )

Set the buffering status of the I/O channel.

The buffering state can only be set if the channel's encoding is "". For any other encoding, the channel must be buffered.

A buffered channel can only be set unbuffered if the channel's internal buffers have been flushed. Newly created channels or channels which have returned Glib::IOStatus::ENDOFFILE not require such a flush. For write-only channels, a call to flush() is sufficient. For all other channels, the buffers may be flushed by a call to seek(). This includes the possibility of seeking with seek type Glib::SeekType::CUR and an offset of zero. Note that this means that socket-based channels cannot be set unbuffered once they have had data read from them.

The default state of the channel is buffered.

Parameters

buffered Whether to set the channel buffered or unbuffered.

◆ set_close_on_unref()

void Glib::IOChannel::set_close_on_unref ( bool do_close )

Setting this flag to true for a channel you have already closed can cause problems.

Parameters

do_close Whether to close the channel on the final unref of the IOChannel object. The default value of this is true for channels created by create_from_file(), and false for all other channels.

◆ set_encoding()

IOStatus Glib::IOChannel::set_encoding ( const std::string & encoding = {} )

Sets the encoding for the input/output of the channel.

The internal encoding is always UTF-8. The default encoding for the external file is UTF-8. The encoding "" is safe to use with binary data.

The encoding can only be set if one of the following conditions is true:

The channel was just created, and has not been written to or read from yet.
The channel is write-only.
The channel is a file, and the file pointer was just repositioned by a call to seek_position(). (This flushes all the internal buffers.)
The current encoding is "" or UTF-8.
One of the read methods has just returned Glib::IOStatus::ENDOFFILE (or, in the case of read_to_end(), Glib::IOStatus::NORMAL).
The read() method has returned Glib::IOStatus::AGAIN or thrown a Glib::Error exception. This may be useful in the case of ConvertError::ILLEGAL_SEQUENCE. Returning one of these statuses from read_line() or read_to_end() does not guarantee that the encoding can be changed.

Channels which do not meet one of the above conditions cannot call seek_position() with a seek type of Glib::SeekType::CUR and, if they are "seekable", cannot call write() after calling one of the API "read" methods.

Parameters

encoding The encoding name, or "" for binary.

Returns: Glib::IOStatus::NORMAL if the encoding was successfully set.

Exceptions

Glib::IOChannelError

◆ set_flags()

IOStatus Glib::IOChannel::set_flags ( IOFlags flags )

Set flags on the IOChannel.

Parameters

flags Bitwise combination of the flags to set.

Returns: The operation result code.

Exceptions

Glib::IOChannelError

◆ set_line_term()

void Glib::IOChannel::set_line_term ( const std::string & term = {} )

◆ unreference()

virtual void Glib::IOChannel::unreference ( ) const

virtual

◆ write() [1/3]

IOStatus Glib::IOChannel::write	(	const char *	buf,
		gssize	count,
		gsize &	bytes_written
	)

Write a memory area of count bytes to the I/O channel.

Parameters

	buf	The start of the memory area.
	count	The number of bytes to write.
[out]	bytes_written	The number of bytes written to the channel.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ write() [2/3]

IOStatus Glib::IOChannel::write ( const Glib::ustring & str )

Write a string to the I/O channel.

Note that this method does not return the number of characters written. If the channel is blocking and the returned value is Glib::IOStatus::NORMAL, the whole string was written.

Parameters

str	the string to write.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

◆ write() [3/3]

IOStatus Glib::IOChannel::write ( gunichar unichar )

Write a single UCS-4 character to the I/O channel.

Parameters

unichar The character to write.

Returns: The status of the operation.

Exceptions

Glib::IOChannelError
Glib::ConvertError

Member Data Documentation

◆ gobject_

GIOChannel* Glib::IOChannel::gobject_

protected

Public Member Functions

Static Public Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ ~IOChannel()

Member Function Documentation

◆ close()

◆ create_from_fd()

◆ create_from_file()

◆ create_from_win32_fd()

◆ create_from_win32_socket()

◆ create_watch()

◆ flush()

◆ get_buffer_condition()

◆ get_buffer_size()

◆ get_buffered()

◆ get_close_on_unref()

◆ get_encoding()

◆ get_flags()

◆ get_line_term()

◆ gobj() [1/2]

◆ gobj() [2/2]

◆ read() [1/3]

◆ read() [2/3]

◆ read() [3/3]

◆ read_line()

◆ read_to_end()

◆ reference()

◆ seek()

◆ set_buffer_size()

◆ set_buffered()

◆ set_close_on_unref()

◆ set_encoding()

◆ set_flags()

◆ set_line_term()

◆ unreference()

◆ write() [1/3]

◆ write() [2/3]

◆ write() [3/3]

Member Data Documentation

◆ gobject_