glib/gio/gpollableoutputstream.c

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/* GIO - GLib Input, Output and Streaming Library
*
* Copyright (C) 2010 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
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* Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "config.h"
#include <errno.h>
#include "gpollableoutputstream.h"
#include "gasynchelper.h"
#include "gfiledescriptorbased.h"
#include "glibintl.h"
/**
* SECTION:gpollableoutputstream
* @short_description: Interface for pollable output streams
* @include: gio/gio.h
* @see_also: #GOutputStream, #GFileDescriptorBased, #GPollableInputStream
*
* #GPollableOutputStream is implemented by #GOutputStreams that
* can be polled for readiness to write. This can be used when
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* interfacing with a non-GIO API that expects
* UNIX-file-descriptor-style asynchronous I/O rather than GIO-style.
*
* Since: 2.28
*/
G_DEFINE_INTERFACE (GPollableOutputStream, g_pollable_output_stream, G_TYPE_OUTPUT_STREAM)
static gboolean g_pollable_output_stream_default_can_poll (GPollableOutputStream *stream);
static gssize g_pollable_output_stream_default_write_nonblocking (GPollableOutputStream *stream,
const void *buffer,
gsize count,
GError **error);
static void
g_pollable_output_stream_default_init (GPollableOutputStreamInterface *iface)
{
iface->can_poll = g_pollable_output_stream_default_can_poll;
iface->write_nonblocking = g_pollable_output_stream_default_write_nonblocking;
}
static gboolean
g_pollable_output_stream_default_can_poll (GPollableOutputStream *stream)
{
return TRUE;
}
/**
* g_pollable_output_stream_can_poll:
* @stream: a #GPollableOutputStream.
*
* 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.
*
* Returns: %TRUE if @stream is pollable, %FALSE if not.
*
* Since: 2.28
*/
gboolean
g_pollable_output_stream_can_poll (GPollableOutputStream *stream)
{
g_return_val_if_fail (G_IS_POLLABLE_OUTPUT_STREAM (stream), FALSE);
return G_POLLABLE_OUTPUT_STREAM_GET_INTERFACE (stream)->can_poll (stream);
}
/**
* g_pollable_output_stream_is_writable:
* @stream: a #GPollableOutputStream.
*
* 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
*/
gboolean
g_pollable_output_stream_is_writable (GPollableOutputStream *stream)
{
g_return_val_if_fail (G_IS_POLLABLE_OUTPUT_STREAM (stream), FALSE);
return G_POLLABLE_OUTPUT_STREAM_GET_INTERFACE (stream)->is_writable (stream);
}
/**
* g_pollable_output_stream_create_source:
* @stream: a #GPollableOutputStream.
* @cancellable: (nullable): a #GCancellable, or %NULL
*
* 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
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* triggers, so you should use g_pollable_output_stream_write_nonblocking()
* rather than g_output_stream_write() from the callback.
*
* Returns: (transfer full): a new #GSource
*
* Since: 2.28
*/
GSource *
g_pollable_output_stream_create_source (GPollableOutputStream *stream,
GCancellable *cancellable)
{
g_return_val_if_fail (G_IS_POLLABLE_OUTPUT_STREAM (stream), NULL);
return G_POLLABLE_OUTPUT_STREAM_GET_INTERFACE (stream)->
create_source (stream, cancellable);
}
static gssize
g_pollable_output_stream_default_write_nonblocking (GPollableOutputStream *stream,
const void *buffer,
gsize count,
GError **error)
{
if (!g_pollable_output_stream_is_writable (stream))
{
g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_WOULD_BLOCK,
g_strerror (EAGAIN));
return -1;
}
return G_OUTPUT_STREAM_GET_CLASS (stream)->
write_fn (G_OUTPUT_STREAM (stream), buffer, count, NULL, error);
}
/**
* g_pollable_output_stream_write_nonblocking:
* @stream: a #GPollableOutputStream
* @buffer: (array length=count) (element-type guint8): a buffer to write
* data from
* @count: the number of bytes you want to write
* @cancellable: (nullable): a #GCancellable, or %NULL
* @error: #GError for error reporting, or %NULL to ignore.
*
* 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
* Returns: the number of bytes written, or -1 on error (including
* %G_IO_ERROR_WOULD_BLOCK).
*/
gssize
g_pollable_output_stream_write_nonblocking (GPollableOutputStream *stream,
const void *buffer,
gsize count,
GCancellable *cancellable,
GError **error)
{
gssize res;
g_return_val_if_fail (G_IS_POLLABLE_OUTPUT_STREAM (stream), -1);
g_return_val_if_fail (buffer != NULL, 0);
if (g_cancellable_set_error_if_cancelled (cancellable, error))
return -1;
if (count == 0)
return 0;
if (((gssize) count) < 0)
{
g_set_error (error, G_IO_ERROR, G_IO_ERROR_INVALID_ARGUMENT,
_("Too large count value passed to %s"), G_STRFUNC);
return -1;
}
if (cancellable)
g_cancellable_push_current (cancellable);
res = G_POLLABLE_OUTPUT_STREAM_GET_INTERFACE (stream)->
write_nonblocking (stream, buffer, count, error);
if (cancellable)
g_cancellable_pop_current (cancellable);
return res;
}