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/* GIO - GLib Input, Output and Streaming Library
*
* Copyright (C) 2006-2007 Red Hat, Inc.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* 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: attempting 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 (positive or zero) offset from the beginning of the
* buffer, zero if the target is not seekable.
**/
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
* previously 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);
}
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