1 /* GIO - GLib Input, Output and Streaming Library
3 * Copyright (C) 2010 Red Hat, Inc.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General
16 * Public License along with this library; if not, write to the
17 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
18 * Boston, MA 02111-1307, USA.
25 #include "gpollableinputstream.h"
26 #include "gasynchelper.h"
30 * SECTION:gpollableinputstream
31 * @short_description: Interface for pollable input streams
33 * @see_also: #GInputStream, #GPollableOutputStream, #GFileDescriptorBased
35 * #GPollableInputStream is implemented by #GInputStream<!-- -->s that
36 * can be polled for readiness to read. This can be used when
37 * interfacing with a non-GIO API that expects
38 * UNIX-file-descriptor-style asynchronous I/O rather than GIO-style.
43 G_DEFINE_INTERFACE (GPollableInputStream, g_pollable_input_stream, G_TYPE_INPUT_STREAM)
45 static gboolean g_pollable_input_stream_default_can_poll (GPollableInputStream *stream);
46 static gssize g_pollable_input_stream_default_read_nonblocking (GPollableInputStream *stream,
52 g_pollable_input_stream_default_init (GPollableInputStreamInterface *iface)
54 iface->can_poll = g_pollable_input_stream_default_can_poll;
55 iface->read_nonblocking = g_pollable_input_stream_default_read_nonblocking;
59 g_pollable_input_stream_default_can_poll (GPollableInputStream *stream)
65 * g_pollable_input_stream_can_poll:
66 * @stream: a #GPollableInputStream.
68 * Checks if @stream is actually pollable. Some classes may implement
69 * #GPollableInputStream but have only certain instances of that class
70 * be pollable. If this method returns %FALSE, then the behavior of
71 * other #GPollableInputStream methods is undefined.
73 * For any given stream, the value returned by this method is constant;
74 * a stream cannot switch from pollable to non-pollable or vice versa.
76 * Returns: %TRUE if @stream is pollable, %FALSE if not.
81 g_pollable_input_stream_can_poll (GPollableInputStream *stream)
83 g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), FALSE);
85 return G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->can_poll (stream);
89 * g_pollable_input_stream_is_readable:
90 * @stream: a #GPollableInputStream.
92 * Checks if @stream can be read.
94 * Note that some stream types may not be able to implement this 100%
95 * reliably, and it is possible that a call to g_input_stream_read()
96 * after this returns %TRUE would still block. To guarantee
97 * non-blocking behavior, you should always use
98 * g_pollable_input_stream_read_nonblocking(), which will return a
99 * %G_IO_ERROR_WOULD_BLOCK error rather than blocking.
101 * Returns: %TRUE if @stream is readable, %FALSE if not. If an error
102 * has occurred on @stream, this will result in
103 * g_pollable_input_stream_is_readable() returning %TRUE, and the
104 * next attempt to read will return the error.
109 g_pollable_input_stream_is_readable (GPollableInputStream *stream)
111 g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), FALSE);
113 return G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->is_readable (stream);
117 * g_pollable_input_stream_create_source:
118 * @stream: a #GPollableInputStream.
119 * @cancellable: (allow-none): a #GCancellable, or %NULL
121 * Creates a #GSource that triggers when @stream can be read, or
122 * @cancellable is triggered or an error occurs. The callback on the
123 * source is of the #GPollableSourceFunc type.
125 * As with g_pollable_input_stream_is_readable(), it is possible that
126 * the stream may not actually be readable even after the source
127 * triggers, so you should use g_pollable_input_stream_read_nonblocking()
128 * rather than g_input_stream_read() from the callback.
130 * Returns: (transfer full): a new #GSource
135 g_pollable_input_stream_create_source (GPollableInputStream *stream,
136 GCancellable *cancellable)
138 g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), NULL);
140 return G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->
141 create_source (stream, cancellable);
145 g_pollable_input_stream_default_read_nonblocking (GPollableInputStream *stream,
150 if (!g_pollable_input_stream_is_readable (stream))
152 g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_WOULD_BLOCK,
153 g_strerror (EAGAIN));
157 return G_INPUT_STREAM_GET_CLASS (stream)->
158 read_fn (G_INPUT_STREAM (stream), buffer, count, NULL, error);
162 * g_pollable_input_stream_read_nonblocking:
163 * @stream: a #GPollableInputStream
164 * @buffer: a buffer to read data into (which should be at least @count
166 * @count: the number of bytes you want to read
167 * @cancellable: (allow-none): a #GCancellable, or %NULL
168 * @error: #GError for error reporting, or %NULL to ignore.
170 * Attempts to read up to @count bytes from @stream into @buffer, as
171 * with g_input_stream_read(). If @stream is not currently readable,
172 * this will immediately return %G_IO_ERROR_WOULD_BLOCK, and you can
173 * use g_pollable_input_stream_create_source() to create a #GSource
174 * that will be triggered when @stream is readable.
176 * Note that since this method never blocks, you cannot actually
177 * use @cancellable to cancel it. However, it will return an error
178 * if @cancellable has already been cancelled when you call, which
179 * may happen if you call this method after a source triggers due
180 * to having been cancelled.
182 * Virtual: read_nonblocking
183 * Return value: the number of bytes read, or -1 on error (including
184 * %G_IO_ERROR_WOULD_BLOCK).
187 g_pollable_input_stream_read_nonblocking (GPollableInputStream *stream,
190 GCancellable *cancellable,
195 g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), -1);
196 g_return_val_if_fail (buffer != NULL, 0);
198 if (g_cancellable_set_error_if_cancelled (cancellable, error))
204 if (((gssize) count) < 0)
206 g_set_error (error, G_IO_ERROR, G_IO_ERROR_INVALID_ARGUMENT,
207 _("Too large count value passed to %s"), G_STRFUNC);
212 g_cancellable_push_current (cancellable);
214 res = G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->
215 read_nonblocking (stream, buffer, count, error);
218 g_cancellable_pop_current (cancellable);