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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* xattr.h - This file is part of libsquashfs
*
* Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
*
* This program 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef SQFS_XATTR_H
#define SQFS_XATTR_H
#include "sqfs/predef.h"
/**
* @file xattr.h
*
* @brief Contains on-disk data structures for storing extended attributes.
*/
/**
* @enum E_SQFS_XATTR_TYPE
*
* Used by @ref sqfs_xattr_entry_t to encodes the xattr prefix.
*/
typedef enum {
SQFS_XATTR_USER = 0,
SQFS_XATTR_TRUSTED = 1,
SQFS_XATTR_SECURITY = 2,
SQFS_XATTR_FLAG_OOL = 0x100,
SQFS_XATTR_PREFIX_MASK = 0xFF,
} E_SQFS_XATTR_TYPE;
/**
* @struct sqfs_xattr_entry_t
*
* @brief On-disk data structure that holds a single xattr key
*
* See @ref sqfs_xattr_reader_t for an overview how SquashFS stores extended
* attributes on disk.
*/
struct sqfs_xattr_entry_t {
/**
* @brief Encodes the prefix of the key
*
* A @ref E_SQFS_XATTR_TYPE value. If the @ref SQFS_XATTR_FLAG_OOL is
* set, the value that follows is not actually a string but a 64 bit
* reference to the location where the value is actually stored.
*/
sqfs_u16 type;
/**
* @brief The size in bytes of the suffix string that follows
*/
sqfs_u16 size;
sqfs_u8 key[];
};
/**
* @struct sqfs_xattr_value_t
*
* @brief On-disk data structure that holds a single xattr value
*
* See @ref sqfs_xattr_reader_t for an overview how SquashFS stores extended
* attributes on disk.
*/
struct sqfs_xattr_value_t {
/**
* @brief The exact size in bytes of the value that follows
*/
sqfs_u32 size;
sqfs_u8 value[];
};
/**
* @struct sqfs_xattr_id_t
*
* @brief On-disk data structure that describes a set of key-value pairs
*
* See @ref sqfs_xattr_reader_t for an overview how SquashFS stores extended
* attributes on disk.
*/
struct sqfs_xattr_id_t {
/**
* @brief Location of the first key-value pair
*
* This is a reference, i.e. the bits 16 to 48 hold an offset that is
* added to xattr_table_start from @ref sqfs_xattr_id_table_t to get
* the location of a meta data block that contains the first key-value
* pair. The lower 16 bits store an offset into the uncompressed meta
* data block.
*/
sqfs_u64 xattr;
/**
* @brief Number of consecutive key-value pairs
*/
sqfs_u32 count;
/**
* @brief Total size of the uncompressed key-value pairs in bytes,
* including data structures used to encode them.
*/
sqfs_u32 size;
};
/**
* @struct sqfs_xattr_id_table_t
*
* @brief On-disk data structure that the super block points to
*
* Indicates the locations of the xattr key-value pairs and descriptor array.
* See @ref sqfs_xattr_reader_t for an overview how SquashFS stores extended
* attributes on disk.
*/
struct sqfs_xattr_id_table_t {
/**
* @brief The location of the first meta data block holding the key
* value pairs.
*/
sqfs_u64 xattr_table_start;
/**
* @brief The total number of descriptors (@ref sqfs_xattr_id_t)
*/
sqfs_u32 xattr_ids;
/**
* @brief Unused, alwayas set this to 0 when writing!
*/
sqfs_u32 unused;
/**
* @brief Holds the locations of the meta data blocks that contain the
* @ref sqfs_xattr_id_t descriptor array.
*/
sqfs_u64 locations[];
};
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Resolve an xattr identifier to the coresponding prefix
*
* Like many file systems, SquashFS stores xattrs be cutting off the common
* prefix of the key string and storing an enumerator instead to save memory.
*
* This function takes an @ref E_SQFS_XATTR_TYPE identifier and returns the
* coresponding prefix string, including the '.' at the end that seperates
* the prefix from the rest of the key.
*/
SQFS_API const char *sqfs_get_xattr_prefix(E_SQFS_XATTR_TYPE id);
/**
* @brief Resolve an xattr prefix into an identifier
*
* Like many file systems, SquashFS stores xattrs be cutting off the common
* prefix of the key string and storing an enumerator instead to save memory.
*
* This function takes a key and finds the enumerator value that represents
* its prefix. An error value is returned if the given prefix isn't supported.
*
* @return On success an @ref E_SQFS_XATTR_TYPE, -1 if it isn't supported.
*/
SQFS_API int sqfs_get_xattr_prefix_id(const char *key);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_XATTR_H */
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