manpagez: man pages & more
html files: gio
Home | html | info | man

GOutputStream

GOutputStream — Base class for implementing streaming output

Types and Values

Object Hierarchy

    GObject
    ╰── GOutputStream
        ├── GFilterOutputStream
        ├── GFileOutputStream
        ├── GMemoryOutputStream
        ╰── GUnixOutputStream

Known Derived Interfaces

GOutputStream is required by GPollableOutputStream.

Includes

#include <gio/gio.h>

Description

GOutputStream has functions to write to a stream (g_output_stream_write()), to close a stream (g_output_stream_close()) and to flush pending writes (g_output_stream_flush()).

To copy the content of an input stream to an output stream without manually handling the reads and writes, use g_output_stream_splice().

See the documentation for GIOStream for details of thread safety of streaming APIs.

All of these functions have async variants too.

Functions

g_output_stream_write ()

gssize
g_output_stream_write (GOutputStream *stream,
                       const void *buffer,
                       gsize count,
                       GCancellable *cancellable,
                       GError **error);

Tries to write count bytes from buffer into the stream. Will block during the operation.

If count is 0, returns 0 and does nothing. A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, the number of bytes written to the stream is returned. It is not an error if this is not the same as the requested size, as it can happen e.g. on a partial I/O error, or if there is not enough storage in the stream. All writes block until at least one byte is written or an error occurs; 0 is never returned (unless count is 0).

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.

On error -1 is returned and error is set accordingly.

Virtual: write_fn

Parameters

stream

a GOutputStream.

 

buffer

the buffer containing the data to write.

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

count

the number of bytes to write

 

cancellable

optional cancellable object.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

Number of bytes written, or -1 on error


g_output_stream_write_all ()

gboolean
g_output_stream_write_all (GOutputStream *stream,
                           const void *buffer,
                           gsize count,
                           gsize *bytes_written,
                           GCancellable *cancellable,
                           GError **error);

Tries to write count bytes from buffer into the stream. Will block during the operation.

This function is similar to g_output_stream_write(), except it tries to write as many bytes as requested, only stopping on an error.

On a successful write of count bytes, TRUE is returned, and bytes_written is set to count .

If there is an error during the operation FALSE is returned and error is set to indicate the error status.

As a special exception to the normal conventions for functions that use GError, if this function returns FALSE (and sets error ) then bytes_written will be set to the number of bytes that were successfully written before the error was encountered. This functionality is only available from C. If you need it from another language then you must write your own loop around g_output_stream_write().

Parameters

stream

a GOutputStream.

 

buffer

the buffer containing the data to write.

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

count

the number of bytes to write

 

bytes_written

location to store the number of bytes that was written to the stream.

[out]

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

TRUE on success, FALSE if there was an error


g_output_stream_write_all_async ()

void
g_output_stream_write_all_async (GOutputStream *stream,
                                 const void *buffer,
                                 gsize count,
                                 int io_priority,
                                 GCancellable *cancellable,
                                 GAsyncReadyCallback callback,
                                 gpointer user_data);

Request an asynchronous write of count bytes from buffer into the stream. When the operation is finished callback will be called. You can then call g_output_stream_write_all_finish() to get the result of the operation.

This is the asynchronous version of g_output_stream_write_all().

Call g_output_stream_write_all_finish() to collect the result.

Any outstanding I/O request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is G_PRIORITY_DEFAULT.

Note that no copy of buffer will be made, so it must stay valid until callback is called.

Parameters

stream

A GOutputStream

 

buffer

the buffer containing the data to write.

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

count

the number of bytes to write

 

io_priority

the io priority of the request

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

Since: 2.44


g_output_stream_write_all_finish ()

gboolean
g_output_stream_write_all_finish (GOutputStream *stream,
                                  GAsyncResult *result,
                                  gsize *bytes_written,
                                  GError **error);

Finishes an asynchronous stream write operation started with g_output_stream_write_all_async().

As a special exception to the normal conventions for functions that use GError, if this function returns FALSE (and sets error ) then bytes_written will be set to the number of bytes that were successfully written before the error was encountered. This functionality is only available from C. If you need it from another language then you must write your own loop around g_output_stream_write_async().

Parameters

stream

a GOutputStream

 

result

a GAsyncResult

 

bytes_written

location to store the number of bytes that was written to the stream.

[out]

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

TRUE on success, FALSE if there was an error

Since: 2.44


g_output_stream_splice ()

gssize
g_output_stream_splice (GOutputStream *stream,
                        GInputStream *source,
                        GOutputStreamSpliceFlags flags,
                        GCancellable *cancellable,
                        GError **error);

Splices an input stream into an output stream.

Parameters

stream

a GOutputStream.

 

source

a GInputStream.

 

flags

a set of GOutputStreamSpliceFlags.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

a gssize containing the size of the data spliced, or -1 if an error occurred. Note that if the number of bytes spliced is greater than G_MAXSSIZE, then that will be returned, and there is no way to determine the actual number of bytes spliced.


g_output_stream_flush ()

gboolean
g_output_stream_flush (GOutputStream *stream,
                       GCancellable *cancellable,
                       GError **error);

Forces a write of all user-space buffered data for the given stream . Will block during the operation. Closing the stream will implicitly cause a flush.

This function is optional for inherited classes.

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned.

Parameters

stream

a GOutputStream.

 

cancellable

optional cancellable object.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

TRUE on success, FALSE on error


g_output_stream_close ()

gboolean
g_output_stream_close (GOutputStream *stream,
                       GCancellable *cancellable,
                       GError **error);

Closes the stream, releasing resources related to it.

Once the stream is closed, all other operations will return G_IO_ERROR_CLOSED. Closing a stream multiple times will not return an error.

Closing a stream will automatically flush any outstanding buffers in the stream.

Streams will be automatically closed when the last reference is dropped, but you might want to call this function to make sure resources are released as early as possible.

Some streams might keep the backing store of the stream (e.g. a file descriptor) open after the stream is closed. See the documentation for the individual stream for details.

On failure the first error that happened will be reported, but the close operation will finish as much as possible. A stream that failed to close will still return G_IO_ERROR_CLOSED for all operations. Still, it is important to check and report the error to the user, otherwise there might be a loss of data as all data might not be written.

If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. Cancelling a close will still leave the stream closed, but there some streams can use a faster close that doesn't block to e.g. check errors. On cancellation (as with any error) there is no guarantee that all written data will reach the target.

Parameters

stream

A GOutputStream.

 

cancellable

optional cancellable object.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

TRUE on success, FALSE on failure


g_output_stream_write_async ()

void
g_output_stream_write_async (GOutputStream *stream,
                             const void *buffer,
                             gsize count,
                             int io_priority,
                             GCancellable *cancellable,
                             GAsyncReadyCallback callback,
                             gpointer user_data);

Request an asynchronous write of count bytes from buffer into the stream. When the operation is finished callback will be called. You can then call g_output_stream_write_finish() to get the result of the operation.

During an async request no other sync and async calls are allowed, and will result in G_IO_ERROR_PENDING errors.

A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.

On success, the number of bytes written will be passed to the callback . It is not an error if this is not the same as the requested size, as it can happen e.g. on a partial I/O error, but generally we try to write as many bytes as requested.

You are guaranteed that this method will never fail with G_IO_ERROR_WOULD_BLOCK - if stream can't accept more data, the method will just wait until this changes.

Any outstanding I/O request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is G_PRIORITY_DEFAULT.

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

For the synchronous, blocking version of this function, see g_output_stream_write().

Note that no copy of buffer will be made, so it must stay valid until callback is called. See g_output_stream_write_bytes_async() for a GBytes version that will automatically hold a reference to the contents (without copying) for the duration of the call.

Parameters

stream

A GOutputStream.

 

buffer

the buffer containing the data to write.

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

count

the number of bytes to write

 

io_priority

the io priority of the request.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_output_stream_write_finish ()

gssize
g_output_stream_write_finish (GOutputStream *stream,
                              GAsyncResult *result,
                              GError **error);

Finishes a stream write operation.

Parameters

stream

a GOutputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

a gssize containing the number of bytes written to the stream.


g_output_stream_splice_async ()

void
g_output_stream_splice_async (GOutputStream *stream,
                              GInputStream *source,
                              GOutputStreamSpliceFlags flags,
                              int io_priority,
                              GCancellable *cancellable,
                              GAsyncReadyCallback callback,
                              gpointer user_data);

Splices a stream asynchronously. When the operation is finished callback will be called. You can then call g_output_stream_splice_finish() to get the result of the operation.

For the synchronous, blocking version of this function, see g_output_stream_splice().

Parameters

stream

a GOutputStream.

 

source

a GInputStream.

 

flags

a set of GOutputStreamSpliceFlags.

 

io_priority

the io priority of the request.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

a GAsyncReadyCallback.

[scope async]

user_data

user data passed to callback .

[closure]

g_output_stream_splice_finish ()

gssize
g_output_stream_splice_finish (GOutputStream *stream,
                               GAsyncResult *result,
                               GError **error);

Finishes an asynchronous stream splice operation.

Parameters

stream

a GOutputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

a gssize of the number of bytes spliced. Note that if the number of bytes spliced is greater than G_MAXSSIZE, then that will be returned, and there is no way to determine the actual number of bytes spliced.


g_output_stream_flush_async ()

void
g_output_stream_flush_async (GOutputStream *stream,
                             int io_priority,
                             GCancellable *cancellable,
                             GAsyncReadyCallback callback,
                             gpointer user_data);

Forces an asynchronous write of all user-space buffered data for the given stream . For behaviour details see g_output_stream_flush().

When the operation is finished callback will be called. You can then call g_output_stream_flush_finish() to get the result of the operation.

Parameters

stream

a GOutputStream.

 

io_priority

the io priority of the request.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

a GAsyncReadyCallback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_output_stream_flush_finish ()

gboolean
g_output_stream_flush_finish (GOutputStream *stream,
                              GAsyncResult *result,
                              GError **error);

Finishes flushing an output stream.

Parameters

stream

a GOutputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

TRUE if flush operation succeeded, FALSE otherwise.


g_output_stream_close_async ()

void
g_output_stream_close_async (GOutputStream *stream,
                             int io_priority,
                             GCancellable *cancellable,
                             GAsyncReadyCallback callback,
                             gpointer user_data);

Requests an asynchronous close of the stream, releasing resources related to it. When the operation is finished callback will be called. You can then call g_output_stream_close_finish() to get the result of the operation.

For behaviour details see g_output_stream_close().

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

Parameters

stream

A GOutputStream.

 

io_priority

the io priority of the request.

 

cancellable

optional cancellable object.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_output_stream_close_finish ()

gboolean
g_output_stream_close_finish (GOutputStream *stream,
                              GAsyncResult *result,
                              GError **error);

Closes an output stream.

Parameters

stream

a GOutputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

TRUE if stream was successfully closed, FALSE otherwise.


g_output_stream_is_closing ()

gboolean
g_output_stream_is_closing (GOutputStream *stream);

Checks if an output stream is being closed. This can be used inside e.g. a flush implementation to see if the flush (or other i/o operation) is called from within the closing operation.

Parameters

stream

a GOutputStream.

 

Returns

TRUE if stream is being closed. FALSE otherwise.

Since: 2.24


g_output_stream_is_closed ()

gboolean
g_output_stream_is_closed (GOutputStream *stream);

Checks if an output stream has already been closed.

Parameters

stream

a GOutputStream.

 

Returns

TRUE if stream is closed. FALSE otherwise.


g_output_stream_has_pending ()

gboolean
g_output_stream_has_pending (GOutputStream *stream);

Checks if an output stream has pending actions.

Parameters

stream

a GOutputStream.

 

Returns

TRUE if stream has pending actions.


g_output_stream_set_pending ()

gboolean
g_output_stream_set_pending (GOutputStream *stream,
                             GError **error);

Sets stream to have actions pending. If the pending flag is already set or stream is closed, it will return FALSE and set error .

Parameters

stream

a GOutputStream.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

TRUE if pending was previously unset and is now set.


g_output_stream_clear_pending ()

void
g_output_stream_clear_pending (GOutputStream *stream);

Clears the pending flag on stream .

Parameters

stream

output stream

 

g_output_stream_write_bytes ()

gssize
g_output_stream_write_bytes (GOutputStream *stream,
                             GBytes *bytes,
                             GCancellable *cancellable,
                             GError **error);

A wrapper function for g_output_stream_write() which takes a GBytes as input. This can be more convenient for use by language bindings or in other cases where the refcounted nature of GBytes is helpful over a bare pointer interface.

However, note that this function may still perform partial writes, just like g_output_stream_write(). If that occurs, to continue writing, you will need to create a new GBytes containing just the remaining bytes, using g_bytes_new_from_bytes(). Passing the same GBytes instance multiple times potentially can result in duplicated data in the output stream.

Parameters

stream

a GOutputStream.

 

bytes

the GBytes to write

 

cancellable

optional cancellable object.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

Returns

Number of bytes written, or -1 on error


g_output_stream_write_bytes_async ()

void
g_output_stream_write_bytes_async (GOutputStream *stream,
                                   GBytes *bytes,
                                   int io_priority,
                                   GCancellable *cancellable,
                                   GAsyncReadyCallback callback,
                                   gpointer user_data);

This function is similar to g_output_stream_write_async(), but takes a GBytes as input. Due to the refcounted nature of GBytes, this allows the stream to avoid taking a copy of the data.

However, note that this function may still perform partial writes, just like g_output_stream_write_async(). If that occurs, to continue writing, you will need to create a new GBytes containing just the remaining bytes, using g_bytes_new_from_bytes(). Passing the same GBytes instance multiple times potentially can result in duplicated data in the output stream.

For the synchronous, blocking version of this function, see g_output_stream_write_bytes().

Parameters

stream

A GOutputStream.

 

bytes

The bytes to write

 

io_priority

the io priority of the request.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

callback

callback to call when the request is satisfied.

[scope async]

user_data

the data to pass to callback function.

[closure]

g_output_stream_write_bytes_finish ()

gssize
g_output_stream_write_bytes_finish (GOutputStream *stream,
                                    GAsyncResult *result,
                                    GError **error);

Finishes a stream write-from-GBytes operation.

Parameters

stream

a GOutputStream.

 

result

a GAsyncResult.

 

error

a GError location to store the error occurring, or NULL to ignore.

 

Returns

a gssize containing the number of bytes written to the stream.


g_output_stream_printf ()

gboolean
g_output_stream_printf (GOutputStream *stream,
                        gsize *bytes_written,
                        GCancellable *cancellable,
                        GError **error,
                        const gchar *format,
                        ...);

This is a utility function around g_output_stream_write_all(). It uses g_strdup_vprintf() to turn format and @... into a string that is then written to stream .

See the documentation of g_output_stream_write_all() about the behavior of the actual write operation.

Note that partial writes cannot be properly checked with this function due to the variable length of the written string, if you need precise control over partial write failures, you need to create you own printf()-like wrapper around g_output_stream_write() or g_output_stream_write_all().

Parameters

stream

a GOutputStream.

 

bytes_written

location to store the number of bytes that was written to the stream.

[out]

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

format

the format string. See the printf() documentation

 

...

the parameters to insert into the format string

 

Returns

TRUE on success, FALSE if there was an error

Since: 2.40


g_output_stream_vprintf ()

gboolean
g_output_stream_vprintf (GOutputStream *stream,
                         gsize *bytes_written,
                         GCancellable *cancellable,
                         GError **error,
                         const gchar *format,
                         va_list args);

This is a utility function around g_output_stream_write_all(). It uses g_strdup_vprintf() to turn format and args into a string that is then written to stream .

See the documentation of g_output_stream_write_all() about the behavior of the actual write operation.

Note that partial writes cannot be properly checked with this function due to the variable length of the written string, if you need precise control over partial write failures, you need to create you own printf()-like wrapper around g_output_stream_write() or g_output_stream_write_all().

Parameters

stream

a GOutputStream.

 

bytes_written

location to store the number of bytes that was written to the stream.

[out]

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

error

location to store the error occurring, or NULL to ignore

 

format

the format string. See the printf() documentation

 

args

the parameters to insert into the format string

 

Returns

TRUE on success, FALSE if there was an error

Since: 2.40

Types and Values

enum GOutputStreamSpliceFlags

GOutputStreamSpliceFlags determine how streams should be spliced.

Members

G_OUTPUT_STREAM_SPLICE_NONE

Do not close either stream.

 

G_OUTPUT_STREAM_SPLICE_CLOSE_SOURCE

Close the source stream after the splice.

 

G_OUTPUT_STREAM_SPLICE_CLOSE_TARGET

Close the target stream after the splice.

 

GOutputStream

typedef struct _GOutputStream GOutputStream;

Base class for writing output.

All classes derived from GOutputStream should implement synchronous writing, splicing, flushing and closing streams, but may implement asynchronous versions.

© manpagez.com 2000-2017
Individual documents may contain additional copyright information.