IO Channels

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

Synopsis


#include <glib.h>


            GIOChannel;

GIOChannel* g_io_channel_unix_new           (int fd);
gint        g_io_channel_unix_get_fd        (GIOChannel *channel);

void        g_io_channel_init               (GIOChannel *channel);

GIOChannel* g_io_channel_new_file           (const gchar *filename,
                                             const gchar *mode,
                                             GError **error);
GIOStatus   g_io_channel_read_chars         (GIOChannel *channel,
                                             gchar *buf,
                                             gsize count,
                                             gsize *bytes_read,
                                             GError **error);
GIOStatus   g_io_channel_read_unichar       (GIOChannel *channel,
                                             gunichar *thechar,
                                             GError **error);
GIOStatus   g_io_channel_read_line          (GIOChannel *channel,
                                             gchar **str_return,
                                             gsize *length,
                                             gsize *terminator_pos,
                                             GError **error);
GIOStatus   g_io_channel_read_line_string   (GIOChannel *channel,
                                             GString *buffer,
                                             gsize *terminator_pos,
                                             GError **error);
GIOStatus   g_io_channel_read_to_end        (GIOChannel *channel,
                                             gchar **str_return,
                                             gsize *length,
                                             GError **error);
GIOStatus   g_io_channel_write_chars        (GIOChannel *channel,
                                             const gchar *buf,
                                             gssize count,
                                             gsize *bytes_written,
                                             GError **error);
GIOStatus   g_io_channel_write_unichar      (GIOChannel *channel,
                                             gunichar thechar,
                                             GError **error);
GIOStatus   g_io_channel_flush              (GIOChannel *channel,
                                             GError **error);
GIOStatus   g_io_channel_seek_position      (GIOChannel *channel,
                                             gint64 offset,
                                             GSeekType type,
                                             GError **error);
enum        GSeekType;
GIOStatus   g_io_channel_shutdown           (GIOChannel *channel,
                                             gboolean flush,
                                             GError **err);

enum        GIOStatus;
enum        GIOChannelError;
#define     G_IO_CHANNEL_ERROR
GIOChannelError g_io_channel_error_from_errno
                                            (gint en);

GIOChannel* g_io_channel_ref                (GIOChannel *channel);
void        g_io_channel_unref              (GIOChannel *channel);

GSource*    g_io_create_watch               (GIOChannel *channel,
                                             GIOCondition condition);
guint       g_io_add_watch                  (GIOChannel *channel,
                                             GIOCondition condition,
                                             GIOFunc func,
                                             gpointer user_data);
guint       g_io_add_watch_full             (GIOChannel *channel,
                                             gint priority,
                                             GIOCondition condition,
                                             GIOFunc func,
                                             gpointer user_data,
                                             GDestroyNotify notify);
enum        GIOCondition;
gboolean    (*GIOFunc)                      (GIOChannel *source,
                                             GIOCondition condition,
                                             gpointer data);

            GIOFuncs;

gsize       g_io_channel_get_buffer_size    (GIOChannel *channel);
void        g_io_channel_set_buffer_size    (GIOChannel *channel,
                                             gsize size);
GIOCondition g_io_channel_get_buffer_condition
                                            (GIOChannel *channel);
GIOFlags    g_io_channel_get_flags          (GIOChannel *channel);
GIOStatus   g_io_channel_set_flags          (GIOChannel *channel,
                                             GIOFlags flags,
                                             GError **error);
enum        GIOFlags;
const gchar* g_io_channel_get_line_term     (GIOChannel *channel,
                                             gint *length);
void        g_io_channel_set_line_term      (GIOChannel *channel,
                                             const gchar *line_term,
                                             gint length);
gboolean    g_io_channel_get_buffered       (GIOChannel *channel);
void        g_io_channel_set_buffered       (GIOChannel *channel,
                                             gboolean buffered);
const gchar* g_io_channel_get_encoding      (GIOChannel *channel);
GIOStatus   g_io_channel_set_encoding       (GIOChannel *channel,
                                             const gchar *encoding,
                                             GError **error);
gboolean    g_io_channel_get_close_on_unref (GIOChannel *channel);
void        g_io_channel_set_close_on_unref (GIOChannel *channel,
                                             gboolean do_close);


GIOError    g_io_channel_read               (GIOChannel *channel,
                                             gchar *buf,
                                             gsize count,
                                             gsize *bytes_read);
enum        GIOError;
GIOError    g_io_channel_write              (GIOChannel *channel,
                                             const gchar *buf,
                                             gsize count,
                                             gsize *bytes_written);
GIOError    g_io_channel_seek               (GIOChannel *channel,
                                             gint64 offset,
                                             GSeekType type);
void        g_io_channel_close              (GIOChannel *channel);

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_close().

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_from_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.

Details

GIOChannel

typedef struct {
} GIOChannel;

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

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.

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 UNIX GIOChannel.

channel : a GIOChannel, created with g_io_channel_unix_new().
Returns : the file descriptor of the 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).

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).

filename : A string containing the name of a file.
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.

channel : a GIOChannel
buf : a buffer to read data into
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.
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.
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);

This function cannot be called on a channel with NULL encoding.

channel : a GIOChannel
thechar : a location to return a character
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.

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.
length : location to store length of the read data, or NULL
terminator_pos : location to store position of line terminator, or NULL
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.

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
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.

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.
length : Location to store length of the data
error : A 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().

channel : a GIOChannel
buf : a buffer to write data from
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.
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);

This function cannot be called on a channel with NULL encoding.

channel : a GIOChannel
thechar : a character
error : A 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.

channel : a GIOChannel
error : location to store an error of type GIOChannelError
Returns : the status of the operation: One of G_IO_CHANNEL_NORMAL, G_IO_CHANNEL_AGAIN, or G_IO_CHANNEL_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.

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.

enum GSeekType

typedef enum
{
  G_SEEK_CUR,
  G_SEEK_SET,
  G_SEEK_END
} GSeekType;

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

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.

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().

channel : a GIOChannel
flush : if TRUE, flush pending
err : location to store a GIOChannelError
Returns : the status of the operation.

enum GIOStatus

typedef enum
{
  G_IO_STATUS_ERROR,
  G_IO_STATUS_NORMAL,
  G_IO_STATUS_EOF,
  G_IO_STATUS_AGAIN
} GIOStatus;

Stati returned by most of the GIOFuncs functions.

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

typedef enum
{
  /* Derived from errno */
  G_IO_CHANNEL_ERROR_FBIG,
  G_IO_CHANNEL_ERROR_INVAL,
  G_IO_CHANNEL_ERROR_IO,
  G_IO_CHANNEL_ERROR_ISDIR,
  G_IO_CHANNEL_ERROR_NOSPC,
  G_IO_CHANNEL_ERROR_NXIO,
  G_IO_CHANNEL_ERROR_OVERFLOW,
  G_IO_CHANNEL_ERROR_PIPE,
  /* Other */
  G_IO_CHANNEL_ERROR_FAILED
} GIOChannelError;

Error codes returned by GIOChannel operations.

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.


g_io_channel_error_from_errno ()

GIOChannelError g_io_channel_error_from_errno
                                            (gint en);

Converts an errno error number to a GIOChannelError.

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.

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.

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 at the default priority.

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 main event loop with the default priority.

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 main event loop with the given priority.

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.

enum GIOCondition

typedef enum
{
  G_IO_IN	GLIB_SYSDEF_POLLIN,
  G_IO_OUT	GLIB_SYSDEF_POLLOUT,
  G_IO_PRI	GLIB_SYSDEF_POLLPRI,
  G_IO_ERR	GLIB_SYSDEF_POLLERR,
  G_IO_HUP	GLIB_SYSDEF_POLLHUP,
  G_IO_NVAL	GLIB_SYSDEF_POLLNVAL
} GIOCondition;

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

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.

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.

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.

GIOFuncs

typedef struct {
  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);
} GIOFuncs;

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


g_io_channel_get_buffer_size ()

gsize       g_io_channel_get_buffer_size    (GIOChannel *channel);

Gets the buffer size.

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.

channel : a GIOChannel
size : the size of the buffer. 0 == 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.

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_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 g_io_channel_get_flags() to update the internal values of these flags.

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_CHANNEL_SET_MASK).

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.

enum GIOFlags

typedef enum
{
  G_IO_FLAG_APPEND = 1 << 0,
  G_IO_FLAG_NONBLOCK = 1 << 1,
  G_IO_FLAG_IS_READABLE = 1 << 2,	/* Read only flag */
  G_IO_FLAG_IS_WRITEABLE = 1 << 3,	/* Read only flag */
  G_IO_FLAG_IS_SEEKABLE = 1 << 4,	/* Read only flag */
  G_IO_FLAG_MASK = (1 << 5) - 1,
  G_IO_FLAG_GET_MASK = G_IO_FLAG_MASK,
  G_IO_FLAG_SET_MASK = G_IO_FLAG_APPEND | G_IO_FLAG_NONBLOCK
} 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().

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 can not be changed.
G_IO_FLAG_IS_WRITEABLE indicates that the io channel is writable. This flag can not be changed.
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 can not be changed.
G_IO_FLAG_MASK
G_IO_FLAG_GET_MASK
G_IO_FLAG_SET_MASK

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 auto detection.

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.

channel : a GIOChannel
line_term : The line termination string. Use NULL for auto detect. Auto detection breaks on "\n", "\r\n", "\r", "\0", and the Unicode paragraph separator. Auto detection should not be used for anything other than file-based channels.
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 embeded nuls.

g_io_channel_get_buffered ()

gboolean    g_io_channel_get_buffered       (GIOChannel *channel);

Returns whether channel is buffered.

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.

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.

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:

1. The channel was just created, and has not been written to or read from yet.

2. The channel is write-only.

3. The channel is a file, and the file pointer was just repositioned by a call to g_io_channel_seek_position(). (This flushes all the internal buffers.)

4. The current encoding is NULL or UTF-8.

5. One of the (new API) read functions has just returned G_IO_STATUS_EOF (or, in the case of g_io_channel_read_to_end(), G_IO_STATUS_NORMAL).

6. One of the functions g_io_channel_read_chars() or g_io_channel_read_unichar() has returned G_IO_STATUS_AGAIN or G_IO_STATUS_ERROR. This may be useful in the case of G_CONVERT_ERROR_ILLEGAL_SEQUENCE. Returning one of these statuses from g_io_channel_read_line(), g_io_channel_read_line_string(), or g_io_channel_read_to_end() does not guarantee that the encoding can be changed.

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.

channel : a GIOChannel
encoding : the encoding type
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.

channel : a GIOChannel.
Returns : Whether the channel will be closed on the final unref of the GIOChannel data structure.

g_io_channel_set_close_on_unref ()

void        g_io_channel_set_close_on_unref (GIOChannel *channel,
                                             gboolean do_close);

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

channel : a GIOChannel
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.

g_io_channel_read ()

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

Warning

g_io_channel_read is deprecated and should not be used in newly-written code. Use g_io_channel_read_chars() instead.

Reads data from a GIOChannel.

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.

enum GIOError

typedef enum
{
  G_IO_ERROR_NONE,
  G_IO_ERROR_AGAIN,
  G_IO_ERROR_INVAL,
  G_IO_ERROR_UNKNOWN
} GIOError;

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


g_io_channel_write ()

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

Warning

g_io_channel_write is deprecated and should not be used in newly-written code. Use g_io_channel_write_chars() instead.

Writes data to a GIOChannel.

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);

Warning

g_io_channel_seek is deprecated 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().

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);

Warning

g_io_channel_close is deprecated 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().

channel : A GIOChannel

See Also

gtk_input_add_full(), gtk_input_remove(), gdk_input_add(), gdk_input_add_full(), gdk_input_remove()

Convenience functions for creating GIOChannel instances and adding them to the main event loop.