/* GIO - GLib Input, Output and Streaming Library

 * 

 * Copyright (C) 2006-2007 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

 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Author: Alexander Larsson <alexl@redhat.com>

 */

#include "config.h"

#include "gseekable.h"

#include "glibintl.h"

/**

 * SECTION:gseekable

 * @short_description: Stream seeking interface

 * @include: gio/gio.h

 * @see_also: #GInputStream, #GOutputStream

 *

 * #GSeekable is implemented by streams (implementations of

 * #GInputStream or #GOutputStream) that support seeking.

 *

 * Seekable streams largely fall into two categories: resizable and

 * fixed-size.

 *

 * #GSeekable on fixed-sized streams is approximately the same as POSIX

 * lseek() on a block device (for example: attmepting to seek past the

 * end of the device is an error).  Fixed streams typically cannot be

 * truncated.

 *

 * #GSeekable on resizable streams is approximately the same as POSIX

 * lseek() on a normal file.  Seeking past the end and writing data will

 * usually cause the stream to resize by introducing zero bytes.

 **/

typedef GSeekableIface GSeekableInterface;

G_DEFINE_INTERFACE (GSeekable, g_seekable, G_TYPE_OBJECT)

static void

g_seekable_default_init (GSeekableInterface *iface)

{

}

/**

 * g_seekable_tell:

 * @seekable: a #GSeekable.

 * 

 * Tells the current position within the stream.

 * 

 * Returns: the offset from the beginning of the buffer.

 **/

goffset

g_seekable_tell (GSeekable *seekable)

{

  GSeekableIface *iface;

  g_return_val_if_fail (G_IS_SEEKABLE (seekable), 0);

  iface = G_SEEKABLE_GET_IFACE (seekable);

  return (* iface->tell) (seekable);

}

/**

 * g_seekable_can_seek:

 * @seekable: a #GSeekable.

 * 

 * Tests if the stream supports the #GSeekableIface.

 * 

 * Returns: %TRUE if @seekable can be seeked. %FALSE otherwise.

 **/

gboolean

g_seekable_can_seek (GSeekable *seekable)

{

  GSeekableIface *iface;

  g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);

  iface = G_SEEKABLE_GET_IFACE (seekable);

  return (* iface->can_seek) (seekable);

}

/**

 * g_seekable_seek:

 * @seekable: a #GSeekable.

 * @offset: a #goffset.

 * @type: a #GSeekType.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: a #GError location to store the error occurring, or %NULL to

 * ignore.

 *

 * Seeks in the stream by the given @offset, modified by @type.

 *

 * Attempting to seek past the end of the stream will have different

 * results depending on if the stream is fixed-sized or resizable.  If

 * the stream is resizable then seeking past the end and then writing

 * will result in zeros filling the empty space.  Seeking past the end

 * of a resizable stream and reading will result in EOF.  Seeking past

 * the end of a fixed-sized stream will fail.

 *

 * Any operation that would result in a negative offset will fail.

 *

 * 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. 

 * 

 * Returns: %TRUE if successful. If an error

 *     has occurred, this function will return %FALSE and set @error

 *     appropriately if present.

 **/

gboolean

g_seekable_seek (GSeekable     *seekable,

		 goffset        offset,

		 GSeekType      type,

		 GCancellable  *cancellable,

		 GError       **error)

{

  GSeekableIface *iface;

  g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);

  iface = G_SEEKABLE_GET_IFACE (seekable);

  return (* iface->seek) (seekable, offset, type, cancellable, error);

}

/**

 * g_seekable_can_truncate:

 * @seekable: a #GSeekable.

 * 

 * Tests if the length of the stream can be adjusted with

 * g_seekable_truncate().

 * 

 * Returns: %TRUE if the stream can be truncated, %FALSE otherwise.

 **/

gboolean

g_seekable_can_truncate (GSeekable *seekable)

{

  GSeekableIface *iface;

  g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);

  iface = G_SEEKABLE_GET_IFACE (seekable);

  return (* iface->can_truncate) (seekable);

}

/**

 * g_seekable_truncate: (virtual truncate_fn)

 * @seekable: a #GSeekable.

 * @offset: new length for @seekable, in bytes.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore. 

 * @error: a #GError location to store the error occurring, or %NULL to 

 * ignore.

 * 

 * Sets the length of the stream to @offset. If the stream was previously

 * larger than @offset, the extra data is discarded. If the stream was

 * previouly shorter than @offset, it is extended with NUL ('\0') bytes.

 * 

 * 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. If an

 * operation was partially finished when the operation was cancelled the

 * partial result will be returned, without an error.

 *

 * Returns: %TRUE if successful. If an error

 *     has occurred, this function will return %FALSE and set @error

 *     appropriately if present. 

 **/

gboolean

g_seekable_truncate (GSeekable     *seekable,

		     goffset        offset,

		     GCancellable  *cancellable,

		     GError       **error)

{

  GSeekableIface *iface;

  g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);

  iface = G_SEEKABLE_GET_IFACE (seekable);

  return (* iface->truncate_fn) (seekable, offset, cancellable, error);

}