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Known Implementations
GPollableOutputStream is implemented by GConverterOutputStream, GMemoryOutputStream and GUnixOutputStream.
Description
GPollableOutputStream is implemented by GOutputStreams that can be polled for readiness to write. This can be used when interfacing with a non-GIO API that expects UNIX-file-descriptor-style asynchronous I/O rather than GIO-style.
Functions
g_pollable_output_stream_can_poll ()
gboolean
g_pollable_output_stream_can_poll (GPollableOutputStream *stream
);
Checks if stream
is actually pollable. Some classes may implement
GPollableOutputStream but have only certain instances of that
class be pollable. If this method returns FALSE
, then the behavior
of other GPollableOutputStream methods is undefined.
For any given stream, the value returned by this method is constant; a stream cannot switch from pollable to non-pollable or vice versa.
Since: 2.28
g_pollable_output_stream_is_writable ()
gboolean
g_pollable_output_stream_is_writable (GPollableOutputStream *stream
);
Checks if stream
can be written.
Note that some stream types may not be able to implement this 100%
reliably, and it is possible that a call to g_output_stream_write()
after this returns TRUE
would still block. To guarantee
non-blocking behavior, you should always use
g_pollable_output_stream_write_nonblocking()
, which will return a
G_IO_ERROR_WOULD_BLOCK
error rather than blocking.
Returns
TRUE
if stream
is writable, FALSE
if not. If an error
has occurred on stream
, this will result in
g_pollable_output_stream_is_writable()
returning TRUE
, and the
next attempt to write will return the error.
Since: 2.28
g_pollable_output_stream_create_source ()
GSource * g_pollable_output_stream_create_source (GPollableOutputStream *stream
,GCancellable *cancellable
);
Creates a GSource that triggers when stream
can be written, or
cancellable
is triggered or an error occurs. The callback on the
source is of the GPollableSourceFunc type.
As with g_pollable_output_stream_is_writable()
, it is possible that
the stream may not actually be writable even after the source
triggers, so you should use g_pollable_output_stream_write_nonblocking()
rather than g_output_stream_write()
from the callback.
Since: 2.28
g_pollable_output_stream_write_nonblocking ()
gssize g_pollable_output_stream_write_nonblocking (GPollableOutputStream *stream
,const void *buffer
,gsize count
,GCancellable *cancellable
,GError **error
);
Attempts to write up to count
bytes from buffer
to stream
, as
with g_output_stream_write()
. If stream
is not currently writable,
this will immediately return G_IO_ERROR_WOULD_BLOCK
, and you can
use g_pollable_output_stream_create_source()
to create a GSource
that will be triggered when stream
is writable.
Note that since this method never blocks, you cannot actually
use cancellable
to cancel it. However, it will return an error
if cancellable
has already been cancelled when you call, which
may happen if you call this method after a source triggers due
to having been cancelled.
Also note that if G_IO_ERROR_WOULD_BLOCK
is returned some underlying
transports like D/TLS require that you send the same buffer
and count
.
Virtual: write_nonblocking
Parameters
stream |
||
buffer |
a buffer to write data from. |
[array length=count][element-type guint8] |
count |
the number of bytes you want to write |
|
cancellable |
a GCancellable, or |
[nullable] |
error |
Types and Values
GPollableOutputStream
typedef struct _GPollableOutputStream GPollableOutputStream;
An interface for a GOutputStream that can be polled for readability.
Since: 2.28
struct GPollableOutputStreamInterface
struct GPollableOutputStreamInterface { GTypeInterface g_iface; /* Virtual Table */ gboolean (*can_poll) (GPollableOutputStream *stream); gboolean (*is_writable) (GPollableOutputStream *stream); GSource * (*create_source) (GPollableOutputStream *stream, GCancellable *cancellable); gssize (*write_nonblocking) (GPollableOutputStream *stream, const void *buffer, gsize count, GError **error); };
The interface for pollable output streams.
The default implementation of can_poll
always returns TRUE
.
The default implementation of write_nonblocking
calls
g_pollable_output_stream_is_writable()
, and then calls
g_output_stream_write()
if it returns TRUE
. This means you only
need to override it if it is possible that your is_writable
implementation may return TRUE
when the stream is not actually
writable.
Members
Checks if the GPollableOutputStream instance is actually pollable |
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Checks if the stream is writable |
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Creates a GSource to poll the stream |
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Does a non-blocking write or returns
|
Since: 2.28