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Diffstat (limited to 'glib/glib/gvarianttypeinfo.h')
| -rw-r--r-- | glib/glib/gvarianttypeinfo.h | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/glib/glib/gvarianttypeinfo.h b/glib/glib/gvarianttypeinfo.h new file mode 100644 index 0000000..aaf14f4 --- /dev/null +++ b/glib/glib/gvarianttypeinfo.h @@ -0,0 +1,151 @@ +/* + * Copyright © 2008 Ryan Lortie + * Copyright © 2010 Codethink Limited + * + * 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 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, write to the + * Free Software Foundation, Inc., 59 Temple Place - Suite 330, + * Boston, MA 02111-1307, USA. + * + * 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 + * serialised data within the container's serialised data to be found + * very efficiently. + * + * Since dictionary entries are serialised 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 serialised 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 serialised 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 offets 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 */ +const gchar * g_variant_type_info_get_type_string (GVariantTypeInfo *typeinfo); + +void g_variant_type_info_query (GVariantTypeInfo *typeinfo, + guint *alignment, + gsize *size); + +/* array */ +GVariantTypeInfo * g_variant_type_info_element (GVariantTypeInfo *typeinfo); +void g_variant_type_info_query_element (GVariantTypeInfo *typeinfo, + guint *alignment, + gsize *size); + +/* structure */ +gsize g_variant_type_info_n_members (GVariantTypeInfo *typeinfo); +const GVariantMemberInfo * g_variant_type_info_member_info (GVariantTypeInfo *typeinfo, + gsize index); + +/* new/ref/unref */ +GVariantTypeInfo * g_variant_type_info_get (const GVariantType *type); +GVariantTypeInfo * g_variant_type_info_ref (GVariantTypeInfo *typeinfo); +void g_variant_type_info_unref (GVariantTypeInfo *typeinfo); +void g_variant_type_info_assert_no_infos (void); + +#endif /* __G_VARIANT_TYPE_INFO_H__ */ |