gpollableinputstream.c 7.25 KB
Newer Older
1 2 3 4 5 6 7
/* 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
8
 * version 2.1 of the License, or (at your option) any later version.
9 10 11 12 13 14 15
 *
 * 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
16
 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
 */

#include "config.h"

#include <errno.h>

#include "gpollableinputstream.h"
#include "gasynchelper.h"
#include "glibintl.h"

/**
 * SECTION:gpollableinputstream
 * @short_description: Interface for pollable input streams
 * @include: gio/gio.h
 * @see_also: #GInputStream, #GPollableOutputStream, #GFileDescriptorBased
 *
Matthias Clasen's avatar
Matthias Clasen committed
33
 * #GPollableInputStream is implemented by #GInputStreams that
34
 * can be polled for readiness to read. This can be used when
Matthias Clasen's avatar
Matthias Clasen committed
35 36
 * interfacing with a non-GIO API that expects
 * UNIX-file-descriptor-style asynchronous I/O rather than GIO-style.
37 38 39 40 41 42 43 44 45
 *
 * Since: 2.28
 */

G_DEFINE_INTERFACE (GPollableInputStream, g_pollable_input_stream, G_TYPE_INPUT_STREAM)

static gboolean g_pollable_input_stream_default_can_poll         (GPollableInputStream *stream);
static gssize   g_pollable_input_stream_default_read_nonblocking (GPollableInputStream  *stream,
								  void                  *buffer,
46
								  gsize                  count,
47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114
								  GError               **error);

static void
g_pollable_input_stream_default_init (GPollableInputStreamInterface *iface)
{
  iface->can_poll         = g_pollable_input_stream_default_can_poll;
  iface->read_nonblocking = g_pollable_input_stream_default_read_nonblocking;
}

static gboolean
g_pollable_input_stream_default_can_poll (GPollableInputStream *stream)
{
  return TRUE;
}

/**
 * g_pollable_input_stream_can_poll:
 * @stream: a #GPollableInputStream.
 *
 * Checks if @stream is actually pollable. Some classes may implement
 * #GPollableInputStream but have only certain instances of that class
 * be pollable. If this method returns %FALSE, then the behavior of
 * other #GPollableInputStream 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_input_stream_can_poll (GPollableInputStream *stream)
{
  g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), FALSE);

  return G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->can_poll (stream);
}

/**
 * g_pollable_input_stream_is_readable:
 * @stream: a #GPollableInputStream.
 *
 * Checks if @stream can be read.
 *
 * Note that some stream types may not be able to implement this 100%
 * reliably, and it is possible that a call to g_input_stream_read()
 * after this returns %TRUE would still block. To guarantee
 * non-blocking behavior, you should always use
 * g_pollable_input_stream_read_nonblocking(), which will return a
 * %G_IO_ERROR_WOULD_BLOCK error rather than blocking.
 *
 * Returns: %TRUE if @stream is readable, %FALSE if not. If an error
 *   has occurred on @stream, this will result in
 *   g_pollable_input_stream_is_readable() returning %TRUE, and the
 *   next attempt to read will return the error.
 *
 * Since: 2.28
 */
gboolean
g_pollable_input_stream_is_readable (GPollableInputStream *stream)
{
  g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), FALSE);

  return G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->is_readable (stream);
}

/**
115
 * g_pollable_input_stream_create_source:
116
 * @stream: a #GPollableInputStream.
117
 * @cancellable: (nullable): a #GCancellable, or %NULL
118 119 120 121 122 123 124
 *
 * Creates a #GSource that triggers when @stream can be read, or
 * @cancellable is triggered or an error occurs. The callback on the
 * source is of the #GPollableSourceFunc type.
 *
 * As with g_pollable_input_stream_is_readable(), it is possible that
 * the stream may not actually be readable even after the source
Matthias Clasen's avatar
Matthias Clasen committed
125 126
 * triggers, so you should use g_pollable_input_stream_read_nonblocking()
 * rather than g_input_stream_read() from the callback.
127
 *
128
 * Returns: (transfer full): a new #GSource
129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144
 *
 * Since: 2.28
 */
GSource *
g_pollable_input_stream_create_source (GPollableInputStream *stream,
				       GCancellable         *cancellable)
{
  g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), NULL);

  return G_POLLABLE_INPUT_STREAM_GET_INTERFACE (stream)->
	  create_source (stream, cancellable);
}

static gssize
g_pollable_input_stream_default_read_nonblocking (GPollableInputStream  *stream,
						  void                  *buffer,
145
						  gsize                  count,
146 147 148 149
						  GError               **error)
{
  if (!g_pollable_input_stream_is_readable (stream))
    {
150 151
      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_WOULD_BLOCK,
                           g_strerror (EAGAIN));
152 153 154
      return -1;
    }

155 156
  return G_INPUT_STREAM_GET_CLASS (stream)->
    read_fn (G_INPUT_STREAM (stream), buffer, count, NULL, error);
157 158 159 160 161
}

/**
 * g_pollable_input_stream_read_nonblocking:
 * @stream: a #GPollableInputStream
162 163
 * @buffer: (array length=count) (element-type guint8): a buffer to
 *     read data into (which should be at least @count bytes long).
164
 * @count: the number of bytes you want to read
165
 * @cancellable: (nullable): a #GCancellable, or %NULL
166 167
 * @error: #GError for error reporting, or %NULL to ignore.
 *
168
 * Attempts to read up to @count bytes from @stream into @buffer, as
169 170 171 172 173 174 175 176 177 178 179
 * with g_input_stream_read(). If @stream is not currently readable,
 * this will immediately return %G_IO_ERROR_WOULD_BLOCK, and you can
 * use g_pollable_input_stream_create_source() to create a #GSource
 * that will be triggered when @stream is readable.
 *
 * 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.
 *
180
 * Virtual: read_nonblocking
181
 * Returns: the number of bytes read, or -1 on error (including
182 183 184 185 186
 *   %G_IO_ERROR_WOULD_BLOCK).
 */
gssize
g_pollable_input_stream_read_nonblocking (GPollableInputStream  *stream,
					  void                  *buffer,
187
					  gsize                  count,
188 189 190
					  GCancellable          *cancellable,
					  GError               **error)
{
191 192
  gssize res;

193
  g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stream), -1);
194
  g_return_val_if_fail (buffer != NULL, 0);
195 196 197 198

  if (g_cancellable_set_error_if_cancelled (cancellable, error))
    return -1;

199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218
  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_INPUT_STREAM_GET_INTERFACE (stream)->
    read_nonblocking (stream, buffer, count, error);

  if (cancellable)
    g_cancellable_pop_current (cancellable);

  return res;
219
}