glib/glib/gvariant-serialiser.h
Philip Withnall d1a293c4e2 gvariant: Track checked and ordered offsets independently
The past few commits introduced the concept of known-good offsets in the
offset table (which is used for variable-width arrays and tuples).
Good offsets are ones which are non-overlapping with all the previous
offsets in the table.

If a bad offset is encountered when indexing into the array or tuple,
the cached known-good offset index will not be increased. In this way,
all child variants at and beyond the first bad offset can be returned as
default values rather than dereferencing potentially invalid data.

In this case, there was no information about the fact that the indexes
between the highest known-good index and the requested one had been
checked already. That could lead to a pathological case where an offset
table with an invalid first offset is repeatedly checked in full when
trying to access higher-indexed children.

Avoid that by storing the index of the highest checked offset in the
table, as well as the index of the highest good/ordered offset.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Helps: #2121
2022-12-13 18:15:19 +00:00

100 lines
4.7 KiB
C

/*
* Copyright © 2007, 2008 Ryan Lortie
* Copyright © 2010 Codethink Limited
*
* 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: Ryan Lortie <desrt@desrt.ca>
*/
#ifndef __G_VARIANT_SERIALISER_H__
#define __G_VARIANT_SERIALISER_H__
#include "gvarianttypeinfo.h"
typedef struct
{
GVariantTypeInfo *type_info;
guchar *data;
gsize size;
gsize depth; /* same semantics as GVariant.depth */
/* If ordered_offsets_up_to == n this means that all the frame offsets up to and
* including the frame offset determining the end of element n are in order.
* This guarantees that the bytes of element n don't overlap with any previous
* element.
*
* This is both read and set by g_variant_serialised_get_child() for arrays of
* non-fixed-width types, and for tuples.
*
* Even when dealing with tuples, @ordered_offsets_up_to is an element index,
* rather than an index into the frame offsets. */
gsize ordered_offsets_up_to;
/* Similar to @ordered_offsets_up_to. This gives the index of the child element
* whose frame offset is the highest in the offset table which has been
* checked so far.
*
* This is always ≥ @ordered_offsets_up_to. It is always an element index.
*
* See documentation in gvariant-core.c for `struct GVariant` for details. */
gsize checked_offsets_up_to;
} GVariantSerialised;
/* deserialization */
GLIB_AVAILABLE_IN_ALL
gsize g_variant_serialised_n_children (GVariantSerialised container);
GLIB_AVAILABLE_IN_ALL
GVariantSerialised g_variant_serialised_get_child (GVariantSerialised container,
gsize index);
/* serialization */
typedef void (*GVariantSerialisedFiller) (GVariantSerialised *serialised,
gpointer data);
GLIB_AVAILABLE_IN_ALL
gsize g_variant_serialiser_needed_size (GVariantTypeInfo *info,
GVariantSerialisedFiller gsv_filler,
const gpointer *children,
gsize n_children);
GLIB_AVAILABLE_IN_ALL
void g_variant_serialiser_serialise (GVariantSerialised container,
GVariantSerialisedFiller gsv_filler,
const gpointer *children,
gsize n_children);
/* misc */
GLIB_AVAILABLE_IN_2_60
gboolean g_variant_serialised_check (GVariantSerialised serialised);
GLIB_AVAILABLE_IN_ALL
gboolean g_variant_serialised_is_normal (GVariantSerialised value);
GLIB_AVAILABLE_IN_ALL
void g_variant_serialised_byteswap (GVariantSerialised value);
/* validation of strings */
GLIB_AVAILABLE_IN_ALL
gboolean g_variant_serialiser_is_string (gconstpointer data,
gsize size);
GLIB_AVAILABLE_IN_ALL
gboolean g_variant_serialiser_is_object_path (gconstpointer data,
gsize size);
GLIB_AVAILABLE_IN_ALL
gboolean g_variant_serialiser_is_signature (gconstpointer data,
gsize size);
#endif /* __G_VARIANT_SERIALISER_H__ */