| /* |
| * Copyright © 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_TYPE_INFO_H__ |
| #define __G_VARIANT_TYPE_INFO_H__ |
| |
| #include <glib/gvarianttype.h> |
| |
| #define G_VARIANT_TYPE_INFO_CHAR_MAYBE 'm' |
| #define G_VARIANT_TYPE_INFO_CHAR_ARRAY 'a' |
| #define G_VARIANT_TYPE_INFO_CHAR_TUPLE '(' |
| #define G_VARIANT_TYPE_INFO_CHAR_DICT_ENTRY '{' |
| #define G_VARIANT_TYPE_INFO_CHAR_VARIANT 'v' |
| #define g_variant_type_info_get_type_char(info) \ |
| (g_variant_type_info_get_type_string(info)[0]) |
| |
| typedef struct _GVariantTypeInfo GVariantTypeInfo; |
| |
| /* < private > |
| * GVariantMemberInfo: |
| * |
| * This structure describes how to construct a GVariant instance |
| * corresponding to a given child of a tuple or dictionary entry in a |
| * very short constant time. It contains the typeinfo of the child, |
| * along with 4 constants that allow the bounds of the child's |
| * serialized data within the container's serialized data to be found |
| * very efficiently. |
| * |
| * Since dictionary entries are serialized as if they were tuples of 2 |
| * items, the term "tuple" will be used here in the general sense to |
| * refer to tuples and dictionary entries. |
| * |
| * BACKGROUND: |
| * The serialized data for a tuple contains an array of "offsets" at |
| * the end. There is one "offset" in this array for each |
| * variable-sized item in the tuple (except for the last one). The |
| * offset points to the end point of that item's serialized data. The |
| * procedure for finding the start point is described below. An |
| * offset is not needed for the last item because the end point of the |
| * last item is merely the end point of the container itself (after |
| * the offsets array has been accounted for). An offset is not needed |
| * for fixed-sized items (like integers) because, due to their fixed |
| * size, the end point is a constant addition to the start point. |
| * |
| * It is clear that the starting point of a given item in the tuple is |
| * determined by the items that precede it in the tuple. Logically, |
| * the start point of a particular item in a given type of tuple can |
| * be determined entirely by the end point of the nearest |
| * variable-sized item that came before it (or from the start of the |
| * container itself in case there is no preceding variable-sized |
| * item). In the case of "(isis)" for example, in order to find out |
| * the start point of the last string, one must start at the end point |
| * of the first string, align to 4 (for the integer's alignment) and |
| * then add 4 (for storing the integer). That's the point where the |
| * string starts (since no special alignment is required for strings). |
| * |
| * Of course, this process requires iterating over the types in the |
| * tuple up to the item of interest. As it turns out, it is possible |
| * to determine 3 constants 'a', 'b', and 'c' for each item in the |
| * tuple, such that, given the ending offset of the nearest previous |
| * variable-sized item (prev_end), a very simple calculation can be |
| * performed to determine the start of the item of interest. |
| * |
| * The constants in this structure are used as follows: |
| * |
| * First, among the array of offsets contained in the tuple, 'i' is the |
| * index of the offset that refers to the end of the variable-sized item |
| * preceding the item of interest. If no variable-sized items precede |
| * this item, then 'i' will be -1. |
| * |
| * Let 'prev_end' be the end offset of the previous item (or 0 in the |
| * case that there was no such item). The start address of this item |
| * can then be calculate using 'a', 'b', and 'c': |
| * |
| * item_start = ((prev_end + a) & b) | c; |
| * |
| * For details about how 'a', 'b' and 'c' are calculated, see the |
| * comments at the point of the implementation in gvariantypeinfo.c. |
| * |
| * The end address of the item is then determined in one of three ways, |
| * according to the 'end_type' field. |
| * |
| * - FIXED: For fixed sized items, the end address is equal to the |
| * start address plus the fixed size. |
| * |
| * - LAST: For the last variable sized item in the tuple, the end |
| * address is equal to the end address of the tuple, minus the size |
| * of the offset array. |
| * |
| * - OFFSET: For other variable sized items, the next index past 'i' |
| * (ie: 'i + 1') must be consulted to find the end of this item. |
| */ |
| |
| typedef struct |
| { |
| GVariantTypeInfo *type_info; |
| |
| gsize i, a; |
| gint8 b, c; |
| |
| guint8 ending_type; |
| } GVariantMemberInfo; |
| |
| #define G_VARIANT_MEMBER_ENDING_FIXED 0 |
| #define G_VARIANT_MEMBER_ENDING_LAST 1 |
| #define G_VARIANT_MEMBER_ENDING_OFFSET 2 |
| |
| /* query */ |
| GLIB_AVAILABLE_IN_ALL |
| const gchar * g_variant_type_info_get_type_string (GVariantTypeInfo *typeinfo); |
| |
| GLIB_AVAILABLE_IN_ALL |
| void g_variant_type_info_query (GVariantTypeInfo *typeinfo, |
| guint *alignment, |
| gsize *size); |
| GLIB_AVAILABLE_IN_2_60 |
| gsize g_variant_type_info_query_depth (GVariantTypeInfo *typeinfo); |
| |
| /* array */ |
| GLIB_AVAILABLE_IN_ALL |
| GVariantTypeInfo * g_variant_type_info_element (GVariantTypeInfo *typeinfo); |
| GLIB_AVAILABLE_IN_ALL |
| void g_variant_type_info_query_element (GVariantTypeInfo *typeinfo, |
| guint *alignment, |
| gsize *size); |
| |
| /* structure */ |
| GLIB_AVAILABLE_IN_ALL |
| gsize g_variant_type_info_n_members (GVariantTypeInfo *typeinfo); |
| GLIB_AVAILABLE_IN_ALL |
| const GVariantMemberInfo * g_variant_type_info_member_info (GVariantTypeInfo *typeinfo, |
| gsize index); |
| |
| /* new/ref/unref */ |
| GLIB_AVAILABLE_IN_ALL |
| GVariantTypeInfo * g_variant_type_info_get (const GVariantType *type); |
| GLIB_AVAILABLE_IN_ALL |
| GVariantTypeInfo * g_variant_type_info_ref (GVariantTypeInfo *typeinfo); |
| GLIB_AVAILABLE_IN_ALL |
| void g_variant_type_info_unref (GVariantTypeInfo *typeinfo); |
| GLIB_AVAILABLE_IN_ALL |
| void g_variant_type_info_assert_no_infos (void); |
| |
| #endif /* __G_VARIANT_TYPE_INFO_H__ */ |