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IO Channels

IO Channels — portable support for using files, pipes and sockets

Functions

GIOChannel * g_io_channel_unix_new ()
gint g_io_channel_unix_get_fd ()
GIOChannel * g_io_channel_win32_new_fd ()
GIOChannel * g_io_channel_win32_new_socket ()
GIOChannel * g_io_channel_win32_new_messages ()
void g_io_channel_init ()
GIOChannel * g_io_channel_new_file ()
GIOStatus g_io_channel_read_chars ()
GIOStatus g_io_channel_read_unichar ()
GIOStatus g_io_channel_read_line ()
GIOStatus g_io_channel_read_line_string ()
GIOStatus g_io_channel_read_to_end ()
GIOStatus g_io_channel_write_chars ()
GIOStatus g_io_channel_write_unichar ()
GIOStatus g_io_channel_flush ()
GIOStatus g_io_channel_seek_position ()
GIOStatus g_io_channel_shutdown ()
GIOChannelError g_io_channel_error_from_errno ()
GIOChannel * g_io_channel_ref ()
void g_io_channel_unref ()
GSource * g_io_create_watch ()
guint g_io_add_watch ()
guint g_io_add_watch_full ()
gboolean (*GIOFunc) ()
gsize g_io_channel_get_buffer_size ()
void g_io_channel_set_buffer_size ()
GIOCondition g_io_channel_get_buffer_condition ()
GIOFlags g_io_channel_get_flags ()
GIOStatus g_io_channel_set_flags ()
const gchar * g_io_channel_get_line_term ()
void g_io_channel_set_line_term ()
gboolean g_io_channel_get_buffered ()
void g_io_channel_set_buffered ()
const gchar * g_io_channel_get_encoding ()
GIOStatus g_io_channel_set_encoding ()
gboolean g_io_channel_get_close_on_unref ()
void g_io_channel_set_close_on_unref ()
GIOError g_io_channel_read ()
GIOError g_io_channel_write ()
GIOError g_io_channel_seek ()
void g_io_channel_close ()

Types and Values

Includes

#include <glib.h>

Description

The GIOChannel data type aims to provide a portable method for using file descriptors, pipes, and sockets, and integrating them into the main event loop. Currently, full support is available on UNIX platforms, support for Windows is only partially complete.

To create a new GIOChannel on UNIX systems use g_io_channel_unix_new(). This works for plain file descriptors, pipes and sockets. Alternatively, a channel can be created for a file in a system independent manner using g_io_channel_new_file().

Once a GIOChannel has been created, it can be used in a generic manner with the functions g_io_channel_read_chars(), g_io_channel_write_chars(), g_io_channel_seek_position(), and g_io_channel_shutdown().

To add a GIOChannel to the main event loop, use g_io_add_watch() or g_io_add_watch_full(). Here you specify which events you are interested in on the GIOChannel, and provide a function to be called whenever these events occur.

GIOChannel instances are created with an initial reference count of 1. g_io_channel_ref() and g_io_channel_unref() can be used to increment or decrement the reference count respectively. When the reference count falls to 0, the GIOChannel is freed. (Though it isn't closed automatically, unless it was created using g_io_channel_new_file().) Using g_io_add_watch() or g_io_add_watch_full() increments a channel's reference count.

The new functions g_io_channel_read_chars(), g_io_channel_read_line(), g_io_channel_read_line_string(), g_io_channel_read_to_end(), g_io_channel_write_chars(), g_io_channel_seek_position(), and g_io_channel_flush() should not be mixed with the deprecated functions g_io_channel_read(), g_io_channel_write(), and g_io_channel_seek() on the same channel.

Functions

g_io_channel_unix_new ()

GIOChannel *
g_io_channel_unix_new (int fd);

Creates a new GIOChannel given a file descriptor. On UNIX systems this works for plain files, pipes, and sockets.

The returned GIOChannel has a reference count of 1.

The default encoding for GIOChannel is UTF-8. If your application is reading output from a command using via pipe, you may need to set the encoding to the encoding of the current locale (see g_get_charset()) with the g_io_channel_set_encoding() function. By default, the fd passed will not be closed when the final reference to the GIOChannel data structure is dropped.

If you want to read raw binary data without interpretation, then call the g_io_channel_set_encoding() function with NULL for the encoding argument.

This function is available in GLib on Windows, too, but you should avoid using it on Windows. The domain of file descriptors and sockets overlap. There is no way for GLib to know which one you mean in case the argument you pass to this function happens to be both a valid file descriptor and socket. If that happens a warning is issued, and GLib assumes that it is the file descriptor you mean.

Parameters

fd

a file descriptor.

 

Returns

a new GIOChannel.


g_io_channel_unix_get_fd ()

gint
g_io_channel_unix_get_fd (GIOChannel *channel);

Returns the file descriptor of the GIOChannel.

On Windows this function returns the file descriptor or socket of the GIOChannel.

Parameters

channel

a GIOChannel, created with g_io_channel_unix_new().

 

Returns

the file descriptor of the GIOChannel.


g_io_channel_win32_new_fd ()

GIOChannel *
g_io_channel_win32_new_fd (gint fd);

Creates a new GIOChannel given a file descriptor on Windows. This works for file descriptors from the C runtime.

This function works for file descriptors as returned by the open(), creat(), pipe() and fileno() calls in the Microsoft C runtime. In order to meaningfully use this function your code should use the same C runtime as GLib uses, which is msvcrt.dll. Note that in current Microsoft compilers it is near impossible to convince it to build code that would use msvcrt.dll. The last Microsoft compiler version that supported using msvcrt.dll as the C runtime was version

  1. The GNU compiler and toolchain for Windows, also known as Mingw, fully supports msvcrt.dll.

If you have created a GIOChannel for a file descriptor and started watching (polling) it, you shouldn't call read() on the file descriptor. This is because adding polling for a file descriptor is implemented in GLib on Windows 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 g_io_channel_read().

This function is available only in GLib on Windows.

Parameters

fd

a C library file descriptor.

 

Returns

a new GIOChannel.


g_io_channel_win32_new_socket ()

GIOChannel *
g_io_channel_win32_new_socket (gint socket);

Creates a new GIOChannel given a socket on Windows.

This function works for sockets created by Winsock. It's available only in GLib on Windows.

Polling a GSource created to watch a channel for a socket puts the socket in non-blocking mode. This is a side-effect of the implementation and unavoidable.

Parameters

socket

a Winsock socket

 

Returns

a new GIOChannel


g_io_channel_win32_new_messages ()

GIOChannel *
g_io_channel_win32_new_messages (gsize hwnd);

Creates a new GIOChannel given a window handle on Windows.

This function creates a GIOChannel that can be used to poll for Windows messages for the window in question.

Parameters

hwnd

a window handle.

 

Returns

a new GIOChannel.


g_io_channel_init ()

void
g_io_channel_init (GIOChannel *channel);

Initializes a GIOChannel struct.

This is called by each of the above functions when creating a GIOChannel, and so is not often needed by the application programmer (unless you are creating a new type of GIOChannel).

Parameters

channel

a GIOChannel

 

g_io_channel_new_file ()

GIOChannel *
g_io_channel_new_file (const gchar *filename,
                       const gchar *mode,
                       GError **error);

Open a file filename as a GIOChannel using mode mode . This channel will be closed when the last reference to it is dropped, so there is no need to call g_io_channel_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

A string containing the name of a file.

[type filename]

mode

One of "r", "w", "a", "r+", "w+", "a+". These have the same meaning as in fopen()

 

error

A location to return an error of type G_FILE_ERROR

 

Returns

A GIOChannel on success, NULL on failure.


g_io_channel_read_chars ()

GIOStatus
g_io_channel_read_chars (GIOChannel *channel,
                         gchar *buf,
                         gsize count,
                         gsize *bytes_read,
                         GError **error);

Replacement for g_io_channel_read() with the new API.

Parameters

channel

a GIOChannel

 

buf

a buffer to read data into.

[out caller-allocates][array length=count][element-type guint8]

count

the size of the buffer. 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.

[in]

bytes_read

The number of bytes read. This may be zero even on success if count < 6 and the channel's encoding is non-NULL. This indicates that the next UTF-8 character is too wide for the buffer.

[out][optional]

error

a location to return an error of type GConvertError or GIOChannelError.

 

Returns

the status of the operation.


g_io_channel_read_unichar ()

GIOStatus
g_io_channel_read_unichar (GIOChannel *channel,
                           gunichar *thechar,
                           GError **error);

Reads a Unicode character from channel . This function cannot be called on a channel with NULL encoding.

Parameters

channel

a GIOChannel

 

thechar

a location to return a character.

[out]

error

a location to return an error of type GConvertError or GIOChannelError

 

Returns

a GIOStatus


g_io_channel_read_line ()

GIOStatus
g_io_channel_read_line (GIOChannel *channel,
                        gchar **str_return,
                        gsize *length,
                        gsize *terminator_pos,
                        GError **error);

Reads a line, including the terminating character(s), from a GIOChannel into a newly-allocated string. str_return will contain allocated memory if the return is G_IO_STATUS_NORMAL.

Parameters

channel

a GIOChannel

 

str_return

The line read from the GIOChannel, including the line terminator. This data should be freed with g_free() when no longer needed. This is a nul-terminated string. If a length of zero is returned, this will be NULL instead.

[out]

length

location to store length of the read data, or NULL.

[out][optional]

terminator_pos

location to store position of line terminator, or NULL.

[out][optional]

error

A location to return an error of type GConvertError or GIOChannelError

 

Returns

the status of the operation.


g_io_channel_read_line_string ()

GIOStatus
g_io_channel_read_line_string (GIOChannel *channel,
                               GString *buffer,
                               gsize *terminator_pos,
                               GError **error);

Reads a line from a GIOChannel, using a GString as a buffer.

Parameters

channel

a GIOChannel

 

buffer

a GString into which the line will be written. If buffer already contains data, the old data will be overwritten.

 

terminator_pos

location to store position of line terminator, or NULL.

[nullable]

error

a location to store an error of type GConvertError or GIOChannelError

 

Returns

the status of the operation.


g_io_channel_read_to_end ()

GIOStatus
g_io_channel_read_to_end (GIOChannel *channel,
                          gchar **str_return,
                          gsize *length,
                          GError **error);

Reads all the remaining data from the file.

Parameters

channel

a GIOChannel

 

str_return

Location to store a pointer to a string holding the remaining data in the GIOChannel. This data should be freed with g_free() when no longer needed. This data is terminated by an extra nul character, but there may be other nuls in the intervening data.

[out][array length=length][element-type guint8]

length

location to store length of the data.

[out]

error

location to return an error of type GConvertError or GIOChannelError

 

Returns

G_IO_STATUS_NORMAL on success. This function never returns G_IO_STATUS_EOF.


g_io_channel_write_chars ()

GIOStatus
g_io_channel_write_chars (GIOChannel *channel,
                          const gchar *buf,
                          gssize count,
                          gsize *bytes_written,
                          GError **error);

Replacement for g_io_channel_write() with the new API.

On seekable channels with encodings other than NULL or UTF-8, generic mixing of reading and writing is not allowed. A call to g_io_channel_write_chars() may only be made on a channel from which data has been read in the cases described in the documentation for g_io_channel_set_encoding().

Parameters

channel

a GIOChannel

 

buf

a buffer to write data from.

[array][element-type guint8]

count

the size of the buffer. If -1, the buffer is taken to be a nul-terminated string.

 

bytes_written

The number of bytes written. This can be nonzero even if the return value is not G_IO_STATUS_NORMAL. If the return value is G_IO_STATUS_NORMAL and the channel is blocking, this will always be equal to count if count >= 0.

[out]

error

a location to return an error of type GConvertError or GIOChannelError

 

Returns

the status of the operation.


g_io_channel_write_unichar ()

GIOStatus
g_io_channel_write_unichar (GIOChannel *channel,
                            gunichar thechar,
                            GError **error);

Writes a Unicode character to channel . This function cannot be called on a channel with NULL encoding.

Parameters

channel

a GIOChannel

 

thechar

a character

 

error

location to return an error of type GConvertError or GIOChannelError

 

Returns

a GIOStatus


g_io_channel_flush ()

GIOStatus
g_io_channel_flush (GIOChannel *channel,
                    GError **error);

Flushes the write buffer for the GIOChannel.

Parameters

channel

a GIOChannel

 

error

location to store an error of type GIOChannelError

 

Returns

the status of the operation: One of G_IO_STATUS_NORMAL, G_IO_STATUS_AGAIN, or G_IO_STATUS_ERROR.


g_io_channel_seek_position ()

GIOStatus
g_io_channel_seek_position (GIOChannel *channel,
                            gint64 offset,
                            GSeekType type,
                            GError **error);

Replacement for g_io_channel_seek() with the new API.

Parameters

channel

a GIOChannel

 

offset

The offset in bytes from the position specified by type

 

type

a GSeekType. The type G_SEEK_CUR is only allowed in those cases where a call to g_io_channel_set_encoding() is allowed. See the documentation for g_io_channel_set_encoding() for details.

 

error

A location to return an error of type GIOChannelError

 

Returns

the status of the operation.


g_io_channel_shutdown ()

GIOStatus
g_io_channel_shutdown (GIOChannel *channel,
                       gboolean flush,
                       GError **err);

Close an IO 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 using g_io_channel_unref().

Parameters

channel

a GIOChannel

 

flush

if TRUE, flush pending

 

err

location to store a GIOChannelError

 

Returns

the status of the operation.


g_io_channel_error_from_errno ()

GIOChannelError
g_io_channel_error_from_errno (gint en);

Converts an errno error number to a GIOChannelError.

Parameters

en

an errno error number, e.g. EINVAL

 

Returns

a GIOChannelError error number, e.g. G_IO_CHANNEL_ERROR_INVAL.


g_io_channel_ref ()

GIOChannel *
g_io_channel_ref (GIOChannel *channel);

Increments the reference count of a GIOChannel.

Parameters

channel

a GIOChannel

 

Returns

the channel that was passed in (since 2.6)


g_io_channel_unref ()

void
g_io_channel_unref (GIOChannel *channel);

Decrements the reference count of a GIOChannel.

Parameters

channel

a GIOChannel

 

g_io_create_watch ()

GSource *
g_io_create_watch (GIOChannel *channel,
                   GIOCondition condition);

Creates a GSource that's dispatched when condition is met for the given channel . For example, if condition is G_IO_IN, the source will be dispatched when there's data available for reading.

g_io_add_watch() is a simpler interface to this same functionality, for the case where you want to add the source to the default main loop context at the default priority.

On Windows, polling a GSource created to watch a channel for a socket puts the socket in non-blocking mode. This is a side-effect of the implementation and unavoidable.

Parameters

channel

a GIOChannel to watch

 

condition

conditions to watch for

 

Returns

a new GSource


g_io_add_watch ()

guint
g_io_add_watch (GIOChannel *channel,
                GIOCondition condition,
                GIOFunc func,
                gpointer user_data);

Adds the GIOChannel into the default main loop context with the default priority.

Parameters

channel

a GIOChannel

 

condition

the condition to watch for

 

func

the function to call when the condition is satisfied

 

user_data

user data to pass to func

 

Returns

the event source id


g_io_add_watch_full ()

guint
g_io_add_watch_full (GIOChannel *channel,
                     gint priority,
                     GIOCondition condition,
                     GIOFunc func,
                     gpointer user_data,
                     GDestroyNotify notify);

Adds the GIOChannel into the default main loop context with the given priority.

This internally creates a main loop source using g_io_create_watch() and attaches it to the main loop context with g_source_attach(). You can do these steps manually if you need greater control.

[rename-to g_io_add_watch]

Parameters

channel

a GIOChannel

 

priority

the priority of the GIOChannel source

 

condition

the condition to watch for

 

func

the function to call when the condition is satisfied

 

user_data

user data to pass to func

 

notify

the function to call when the source is removed

 

Returns

the event source id


GIOFunc ()

gboolean
(*GIOFunc) (GIOChannel *source,
            GIOCondition condition,
            gpointer data);

Specifies the type of function passed to g_io_add_watch() or g_io_add_watch_full(), which is called when the requested condition on a GIOChannel is satisfied.

Parameters

source

the GIOChannel event source

 

condition

the condition which has been satisfied

 

data

user data set in g_io_add_watch() or g_io_add_watch_full()

 

Returns

the function should return FALSE if the event source should be removed


g_io_channel_get_buffer_size ()

gsize
g_io_channel_get_buffer_size (GIOChannel *channel);

Gets the buffer size.

Parameters

channel

a GIOChannel

 

Returns

the size of the buffer.


g_io_channel_set_buffer_size ()

void
g_io_channel_set_buffer_size (GIOChannel *channel,
                              gsize size);

Sets the buffer size.

Parameters

channel

a GIOChannel

 

size

the size of the buffer, or 0 to let GLib pick a good size

 

g_io_channel_get_buffer_condition ()

GIOCondition
g_io_channel_get_buffer_condition (GIOChannel *channel);

This function returns a GIOCondition depending on whether there is data to be read/space to write data in the internal buffers in the GIOChannel. Only the flags G_IO_IN and G_IO_OUT may be set.

Parameters

channel

A GIOChannel

 

Returns

A GIOCondition


g_io_channel_get_flags ()

GIOFlags
g_io_channel_get_flags (GIOChannel *channel);

Gets the current flags for a GIOChannel, including read-only flags such as G_IO_FLAG_IS_READABLE.

The values of the flags G_IO_FLAG_IS_READABLE and G_IO_FLAG_IS_WRITABLE 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 g_io_channel_get_flags() to update the internal values of these flags.

Parameters

channel

a GIOChannel

 

Returns

the flags which are set on the channel


g_io_channel_set_flags ()

GIOStatus
g_io_channel_set_flags (GIOChannel *channel,
                        GIOFlags flags,
                        GError **error);

Sets the (writeable) flags in channel to (flags & G_IO_FLAG_SET_MASK).

Parameters

channel

a GIOChannel

 

flags

the flags to set on the IO channel

 

error

A location to return an error of type GIOChannelError

 

Returns

the status of the operation.


g_io_channel_get_line_term ()

const gchar *
g_io_channel_get_line_term (GIOChannel *channel,
                            gint *length);

This returns the string that GIOChannel uses to determine where in the file a line break occurs. A value of NULL indicates autodetection.

Parameters

channel

a GIOChannel

 

length

a location to return the length of the line terminator

 

Returns

The line termination string. This value is owned by GLib and must not be freed.


g_io_channel_set_line_term ()

void
g_io_channel_set_line_term (GIOChannel *channel,
                            const gchar *line_term,
                            gint length);

This sets the string that GIOChannel uses to determine where in the file a line break occurs.

Parameters

channel

a GIOChannel

 

line_term

The line termination string. Use NULL for autodetect. Autodetection breaks on "\n", "\r\n", "\r", "\0", and the Unicode paragraph separator. Autodetection should not be used for anything other than file-based channels.

[nullable]

length

The length of the termination string. If -1 is passed, the string is assumed to be nul-terminated. This option allows termination strings with embedded nuls.

 

g_io_channel_get_buffered ()

gboolean
g_io_channel_get_buffered (GIOChannel *channel);

Returns whether channel is buffered.

Parameters

channel

a GIOChannel

 

Returns

TRUE if the channel is buffered.


g_io_channel_set_buffered ()

void
g_io_channel_set_buffered (GIOChannel *channel,
                           gboolean buffered);

The buffering state can only be set if the channel's encoding is NULL. 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 G_IO_STATUS_EOF not require such a flush. For write-only channels, a call to g_io_channel_flush() is sufficient. For all other channels, the buffers may be flushed by a call to g_io_channel_seek_position(). This includes the possibility of seeking with seek type G_SEEK_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.

On unbuffered channels, it is safe to mix read and write calls from the new and old APIs, if this is necessary for maintaining old code.

The default state of the channel is buffered.

Parameters

channel

a GIOChannel

 

buffered

whether to set the channel buffered or unbuffered

 

g_io_channel_get_encoding ()

const gchar *
g_io_channel_get_encoding (GIOChannel *channel);

Gets the encoding for the input/output of the channel. The internal encoding is always UTF-8. The encoding NULL makes the channel safe for binary data.

Parameters

channel

a GIOChannel

 

Returns

A string containing the encoding, this string is owned by GLib and must not be freed.


g_io_channel_set_encoding ()

GIOStatus
g_io_channel_set_encoding (GIOChannel *channel,
                           const gchar *encoding,
                           GError **error);

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 NULL is safe to use with binary data.

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

Channels which do not meet one of the above conditions cannot call g_io_channel_seek_position() with an offset of G_SEEK_CUR, and, if they are "seekable", cannot call g_io_channel_write_chars() after calling one of the API "read" functions.

Parameters

channel

a GIOChannel

 

encoding

the encoding type.

[nullable]

error

location to store an error of type GConvertError

 

Returns

G_IO_STATUS_NORMAL if the encoding was successfully set


g_io_channel_get_close_on_unref ()

gboolean
g_io_channel_get_close_on_unref (GIOChannel *channel);

Returns whether the file/socket/whatever associated with channel will be closed when channel receives its final unref and is destroyed. The default value of this is TRUE for channels created by g_io_channel_new_file(), and FALSE for all other channels.

Parameters

channel

a GIOChannel.

 

Returns

TRUE if the channel will be closed, FALSE otherwise.


g_io_channel_set_close_on_unref ()

void
g_io_channel_set_close_on_unref (GIOChannel *channel,
                                 gboolean do_close);

Whether to close the channel on the final unref of the GIOChannel data structure. The default value of this is TRUE for channels created by g_io_channel_new_file(), and FALSE for all other channels.

Setting this flag to TRUE for a channel you have already closed can cause problems when the final reference to the GIOChannel is dropped.

Parameters

channel

a GIOChannel

 

do_close

Whether to close the channel on the final unref of the GIOChannel data structure.

 

g_io_channel_read ()

GIOError
g_io_channel_read (GIOChannel *channel,
                   gchar *buf,
                   gsize count,
                   gsize *bytes_read);

g_io_channel_read has been deprecated since version 2.2 and should not be used in newly-written code.

Use g_io_channel_read_chars() instead.

Reads data from a GIOChannel.

Parameters

channel

a GIOChannel

 

buf

a buffer to read the data into (which should be at least count bytes long)

 

count

the number of bytes to read from the GIOChannel

 

bytes_read

returns the number of bytes actually read

 

Returns

G_IO_ERROR_NONE if the operation was successful.


g_io_channel_write ()

GIOError
g_io_channel_write (GIOChannel *channel,
                    const gchar *buf,
                    gsize count,
                    gsize *bytes_written);

g_io_channel_write has been deprecated since version 2.2 and should not be used in newly-written code.

Use g_io_channel_write_chars() instead.

Writes data to a GIOChannel.

Parameters

channel

a GIOChannel

 

buf

the buffer containing the data to write

 

count

the number of bytes to write

 

bytes_written

the number of bytes actually written

 

Returns

G_IO_ERROR_NONE if the operation was successful.


g_io_channel_seek ()

GIOError
g_io_channel_seek (GIOChannel *channel,
                   gint64 offset,
                   GSeekType type);

g_io_channel_seek has been deprecated since version 2.2 and should not be used in newly-written code.

Use g_io_channel_seek_position() instead.

Sets the current position in the GIOChannel, similar to the standard library function fseek().

Parameters

channel

a GIOChannel

 

offset

an offset, in bytes, which is added to the position specified by type

 

type

the position in the file, which can be G_SEEK_CUR (the current position), G_SEEK_SET (the start of the file), or G_SEEK_END (the end of the file)

 

Returns

G_IO_ERROR_NONE if the operation was successful.


g_io_channel_close ()

void
g_io_channel_close (GIOChannel *channel);

g_io_channel_close has been deprecated since version 2.2 and should not be used in newly-written code.

Use g_io_channel_shutdown() instead.

Close an IO channel. Any pending data to be written will be flushed, ignoring errors. The channel will not be freed until the last reference is dropped using g_io_channel_unref().

Parameters

channel

A GIOChannel

 

Types and Values

struct GIOChannel

struct GIOChannel {
};

A data structure representing an IO Channel. The fields should be considered private and should only be accessed with the following functions.


enum GSeekType

An enumeration specifying the base position for a g_io_channel_seek_position() operation.

Members

G_SEEK_CUR

the current position in the file.

 

G_SEEK_SET

the start of the file.

 

G_SEEK_END

the end of the file.

 

enum GIOStatus

Stati returned by most of the GIOFuncs functions.

Members

G_IO_STATUS_ERROR

An error occurred.

 

G_IO_STATUS_NORMAL

Success.

 

G_IO_STATUS_EOF

End of file.

 

G_IO_STATUS_AGAIN

Resource temporarily unavailable.

 

enum GIOChannelError

Error codes returned by GIOChannel operations.

Members

G_IO_CHANNEL_ERROR_FBIG

File too large.

 

G_IO_CHANNEL_ERROR_INVAL

Invalid argument.

 

G_IO_CHANNEL_ERROR_IO

IO error.

 

G_IO_CHANNEL_ERROR_ISDIR

File is a directory.

 

G_IO_CHANNEL_ERROR_NOSPC

No space left on device.

 

G_IO_CHANNEL_ERROR_NXIO

No such device or address.

 

G_IO_CHANNEL_ERROR_OVERFLOW

Value too large for defined datatype.

 

G_IO_CHANNEL_ERROR_PIPE

Broken pipe.

 

G_IO_CHANNEL_ERROR_FAILED

Some other error.

 

G_IO_CHANNEL_ERROR

#define G_IO_CHANNEL_ERROR g_io_channel_error_quark()

Error domain for GIOChannel operations. Errors in this domain will be from the GIOChannelError enumeration. See GError for information on error domains.


enum GIOCondition

A bitwise combination representing a condition to watch for on an event source.

Members

G_IO_IN

There is data to read.

 

G_IO_OUT

Data can be written (without blocking).

 

G_IO_PRI

There is urgent data to read.

 

G_IO_ERR

Error condition.

 

G_IO_HUP

Hung up (the connection has been broken, usually for pipes and sockets).

 

G_IO_NVAL

Invalid request. The file descriptor is not open.

 

struct GIOFuncs

struct GIOFuncs {
  GIOStatus (*io_read)           (GIOChannel   *channel, 
			          gchar        *buf, 
				  gsize         count,
				  gsize        *bytes_read,
				  GError      **err);
  GIOStatus (*io_write)          (GIOChannel   *channel, 
				  const gchar  *buf, 
				  gsize         count,
				  gsize        *bytes_written,
				  GError      **err);
  GIOStatus (*io_seek)           (GIOChannel   *channel, 
				  gint64        offset, 
				  GSeekType     type,
				  GError      **err);
  GIOStatus  (*io_close)         (GIOChannel   *channel,
				  GError      **err);
  GSource*   (*io_create_watch)  (GIOChannel   *channel,
				  GIOCondition  condition);
  void       (*io_free)          (GIOChannel   *channel);
  GIOStatus  (*io_set_flags)     (GIOChannel   *channel,
                                  GIOFlags      flags,
				  GError      **err);
  GIOFlags   (*io_get_flags)     (GIOChannel   *channel);
};

A table of functions used to handle different types of GIOChannel in a generic way.

Members

io_read ()

reads raw bytes from the channel. This is called from various functions such as g_io_channel_read_chars() to read raw bytes from the channel. Encoding and buffering issues are dealt with at a higher level.

 

io_write ()

writes raw bytes to the channel. This is called from various functions such as g_io_channel_write_chars() to write raw bytes to the channel. Encoding and buffering issues are dealt with at a higher level.

 

io_seek ()

(optional) seeks the channel. This is called from g_io_channel_seek() on channels that support it.

 

io_close ()

closes the channel. This is called from g_io_channel_close() after flushing the buffers.

 

io_create_watch ()

creates a watch on the channel. This call corresponds directly to g_io_create_watch().

 

io_free ()

called from g_io_channel_unref() when the channel needs to be freed. This function must free the memory associated with the channel, including freeing the GIOChannel structure itself. The channel buffers have been flushed and possibly io_close has been called by the time this function is called.

 

io_set_flags ()

sets the GIOFlags on the channel. This is called from g_io_channel_set_flags() with all flags except for G_IO_FLAG_APPEND and G_IO_FLAG_NONBLOCK masked out.

 

io_get_flags ()

gets the GIOFlags for the channel. This function need only return the G_IO_FLAG_APPEND and G_IO_FLAG_NONBLOCK flags; g_io_channel_get_flags() automatically adds the others as appropriate.

 

enum GIOFlags

Specifies properties of a GIOChannel. Some of the flags can only be read with g_io_channel_get_flags(), but not changed with g_io_channel_set_flags().

Members

G_IO_FLAG_APPEND

turns on append mode, corresponds to O_APPEND (see the documentation of the UNIX open() syscall)

 

G_IO_FLAG_NONBLOCK

turns on nonblocking mode, corresponds to O_NONBLOCK/O_NDELAY (see the documentation of the UNIX open() syscall)

 

G_IO_FLAG_IS_READABLE

indicates that the io channel is readable. This flag cannot be changed.

 

G_IO_FLAG_IS_WRITABLE

indicates that the io channel is writable. This flag cannot be changed.

 

G_IO_FLAG_IS_WRITEABLE

a misspelled version of G_IO_FLAG_IS_WRITABLE that existed before the spelling was fixed in GLib 2.30. It is kept here for compatibility reasons. Deprecated since 2.30

 

G_IO_FLAG_IS_SEEKABLE

indicates that the io channel is seekable, i.e. that g_io_channel_seek_position() can be used on it. This flag cannot be changed.

 

G_IO_FLAG_MASK

the mask that specifies all the valid flags.

 

G_IO_FLAG_GET_MASK

the mask of the flags that are returned from g_io_channel_get_flags()

 

G_IO_FLAG_SET_MASK

the mask of the flags that the user can modify with g_io_channel_set_flags()

 

enum GIOError

GIOError is only used by the deprecated functions g_io_channel_read(), g_io_channel_write(), and g_io_channel_seek().

Members

G_IO_ERROR_NONE

no error

 

G_IO_ERROR_AGAIN

an EAGAIN error occurred

 

G_IO_ERROR_INVAL

an EINVAL error occurred

 

G_IO_ERROR_UNKNOWN

another error occurred

 

See Also

g_io_add_watch(), g_io_add_watch_full(), g_source_remove(), GMainLoop

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