106 lines
3.9 KiB
C
106 lines
3.9 KiB
C
/* struct-group.h - mirrored structure macros.
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*
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* Copyright (C) 2021-2022 Bruno Raoult ("br")
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* Licensed under the GNU General Public License v3.0 or later.
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* Some rights reserved. See COPYING.
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*
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* You should have received a copy of the GNU General Public License along with this
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* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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*
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* Some parts are taken from Linux's kernel <linux/stddef.h> and others, and are :
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* SPDX-License-Identifier: GPL-2.0
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*
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*/
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#ifndef _STRUCT_GROUP_H
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#define _STRUCT_GROUP_H
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/**
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* __struct_group() - Create a mirrored named and anonyomous struct
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*
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* @TAG: The tag name for the named sub-struct (usually empty)
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* @NAME: The identifier name of the mirrored sub-struct
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* @ATTRS: Any struct attributes (usually empty)
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical layout
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* and size: one anonymous and one named. The former's members can be used
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* normally without sub-struct naming, and the latter can be used to
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* reason about the start, end, and size of the group of struct members.
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* The named struct can also be explicitly tagged for layer reuse, as well
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* as both having struct attributes appended.
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*/
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#define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
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union { \
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struct { MEMBERS } ATTRS; \
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struct TAG { MEMBERS } ATTRS NAME; \
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}
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/**
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* DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
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*
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* @TYPE: The type of each flexible array element
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* @NAME: The name of the flexible array member
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*
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* In order to have a flexible array member in a union or alone in a
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* struct, it needs to be wrapped in an anonymous struct with at least 1
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* named member, but that member can be empty.
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*/
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#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
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struct { \
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struct { } __empty_ ## NAME; \
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TYPE NAME[]; \
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}
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/**
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* struct_group() - Wrap a set of declarations in a mirrored struct
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*
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* @NAME: The identifier name of the mirrored sub-struct
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical
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* layout and size: one anonymous and one named. The former can be
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* used normally without sub-struct naming, and the latter can be
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* used to reason about the start, end, and size of the group of
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* struct members.
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*/
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#define struct_group(NAME, MEMBERS...) \
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__struct_group(/* no tag */, NAME, /* no attrs */, MEMBERS)
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/**
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* struct_group_attr() - Create a struct_group() with trailing attributes
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*
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* @NAME: The identifier name of the mirrored sub-struct
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* @ATTRS: Any struct attributes to apply
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical
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* layout and size: one anonymous and one named. The former can be
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* used normally without sub-struct naming, and the latter can be
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* used to reason about the start, end, and size of the group of
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* struct members. Includes structure attributes argument.
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*/
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#define struct_group_attr(NAME, ATTRS, MEMBERS...) \
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__struct_group(/* no tag */, NAME, ATTRS, MEMBERS)
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/**
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* struct_group_tagged() - Create a struct_group with a reusable tag
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*
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* @TAG: The tag name for the named sub-struct
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* @NAME: The identifier name of the mirrored sub-struct
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical
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* layout and size: one anonymous and one named. The former can be
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* used normally without sub-struct naming, and the latter can be
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* used to reason about the start, end, and size of the group of
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* struct members. Includes struct tag argument for the named copy,
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* so the specified layout can be reused later.
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*/
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#define struct_group_tagged(TAG, NAME, MEMBERS...) \
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__struct_group(TAG, NAME, /* no attrs */, MEMBERS)
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#endif /* _STRUCT_GROUP_H */
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