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GObject ╰── GIOStream ├── GFileIOStream ├── GSimpleIOStream ├── GSocketConnection ╰── GTlsConnection
GIOStream represents an object that has both read and write streams. Generally the two streams act as separate input and output streams, but they share some common resources and state. For instance, for seekable streams, both streams may use the same position.
Examples of GIOStream objects are GSocketConnection, which represents a two-way network connection; and GFileIOStream, which represents a file handle opened in read-write mode.
To do the actual reading and writing you need to get the substreams
with g_io_stream_get_input_stream() and g_io_stream_get_output_stream().
The GIOStream object owns the input and the output streams, not the other
way around, so keeping the substreams alive will not keep the GIOStream
object alive. If the GIOStream object is freed it will be closed, thus
closing the substreams, so even if the substreams stay alive they will
always return G_IO_ERROR_CLOSED for all operations.
To close a stream use g_io_stream_close() which will close the common
stream object and also the individual substreams. You can also close
the substreams themselves. In most cases this only marks the
substream as closed, so further I/O on it fails but common state in the
GIOStream may still be open. However, some streams may support
"half-closed" states where one direction of the stream is actually shut down.
Operations on GIOStreams cannot be started while another operation on the GIOStream or its substreams is in progress. Specifically, an application can read from the GInputStream and write to the GOutputStream simultaneously (either in separate threads, or as asynchronous operations in the same thread), but an application cannot start any GIOStream operation while there is a GIOStream, GInputStream or GOutputStream operation in progress, and an application can’t start any GInputStream or GOutputStream operation while there is a GIOStream operation in progress.
This is a product of individual stream operations being associated with a given GMainContext (the thread-default context at the time the operation was started), rather than entire streams being associated with a single GMainContext.
GIO may run operations on GIOStreams from other (worker) threads, and this may be exposed to application code in the behaviour of wrapper streams, such as GBufferedInputStream or GTlsConnection. With such wrapper APIs, application code may only run operations on the base (wrapped) stream when the wrapper stream is idle. Note that the semantics of such operations may not be well-defined due to the state the wrapper stream leaves the base stream in (though they are guaranteed not to crash).
GInputStream *
g_io_stream_get_input_stream (GIOStream *stream);
Gets the input stream for this object. This is used for reading.
Since: 2.22
GOutputStream *
g_io_stream_get_output_stream (GIOStream *stream);
Gets the output stream for this object. This is used for writing.
Since: 2.22
void g_io_stream_splice_async (GIOStream *stream1,GIOStream *stream2,GIOStreamSpliceFlags flags,int io_priority,GCancellable *cancellable,GAsyncReadyCallback callback,gpointer user_data);
Asyncronously splice the output stream of stream1
to the input stream of
stream2
, and splice the output stream of stream2
to the input stream of
stream1
.
When the operation is finished callback
will be called.
You can then call g_io_stream_splice_finish() to get the
result of the operation.
stream1 |
a GIOStream. |
|
stream2 |
a GIOStream. |
|
flags |
a set of GIOStreamSpliceFlags. |
|
io_priority |
the io priority of the request. |
|
cancellable |
optional GCancellable object, |
[allow-none] |
callback |
[scope async] | |
user_data |
user data passed to |
[closure] |
Since: 2.28
gboolean g_io_stream_splice_finish (GAsyncResult *result,GError **error);
Finishes an asynchronous io stream splice operation.
result |
a GAsyncResult. |
|
error |
a GError location to store the error occurring, or |
Since: 2.28
gboolean g_io_stream_close (GIOStream *stream,GCancellable *cancellable,GError **error);
Closes the stream, releasing resources related to it. This will also close the individual input and output streams, if they are not already closed.
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 some streams
can use a faster close that doesn't block to e.g. check errors.
The default implementation of this method just calls close on the individual input/output streams.
stream |
||
cancellable |
optional GCancellable object, |
[allow-none] |
error |
location to store the error occurring, or |
Since: 2.22
void g_io_stream_close_async (GIOStream *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_io_stream_close_finish() to get
the result of the operation.
For behaviour details see g_io_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.
stream |
||
io_priority |
the io priority of the request |
|
cancellable |
optional cancellable object. |
[allow-none] |
callback |
callback to call when the request is satisfied. |
[scope async] |
user_data |
the data to pass to callback function. |
[closure] |
Since: 2.22
gboolean g_io_stream_close_finish (GIOStream *stream,GAsyncResult *result,GError **error);
Closes a stream.
Since: 2.22
gboolean
g_io_stream_is_closed (GIOStream *stream);
Checks if a stream is closed.
Since: 2.22
gboolean
g_io_stream_has_pending (GIOStream *stream);
Checks if a stream has pending actions.
Since: 2.22
gboolean g_io_stream_set_pending (GIOStream *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
.
Since: 2.22
GIOStreamSpliceFlags determine how streams should be spliced.
|
Do not close either stream. |
||
|
Close the first stream after the splice. |
||
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Close the second stream after the splice. |
||
|
Wait for both splice operations to finish before calling the callback. |
Since: 2.28
“input-stream” property“input-stream” GInputStream *
The GInputStream to read from.
Flags: Read
“output-stream” property“output-stream” GOutputStream *
The GOutputStream to write to.
Flags: Read