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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* id_table.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_ID_TABLE_H
#define SQFS_ID_TABLE_H
#include "sqfs/predef.h"
/**
* @file id_table.h
*
* @brief Contains declarations for the @ref sqfs_id_table_t data structure.
*/
/**
* @struct sqfs_id_table_t
*
* @implements sqfs_object_t
*
* @brief A simple data structure that encapsulates ID to index mapping for
* user and group IDs.
*
* SquashFS does not store user and group IDs in inodes directly. Instead, it
* collects the unique 32 bit IDs in a table with at most 64k entries and
* stores a 16 bit index into the inode. This allows SquashFS to only have 16
* bit UID/GID entries in the inodes but actually have 32 bit UIDs/GIDs under
* the hood (at least 64k selected ones).
*/
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Create an ID table object.
*
* @memberof sqfs_id_table_t
*
* @param flags Currently must be set to 0 or creating the table fails.
*
* @return A pointer to an ID table object, NULL on allocation failure.
*/
SQFS_API sqfs_id_table_t *sqfs_id_table_create(sqfs_u32 flags);
/**
* @brief Resolve a 32 bit ID to a unique 16 bit index.
*
* @memberof sqfs_id_table_t
*
* @param tbl A pointer to an ID table object.
* @param id The ID to resolve.
* @param out Returns the unique table index.
*
* @return Zero on success, an @ref SQFS_ERROR on failure.
*/
SQFS_API int sqfs_id_table_id_to_index(sqfs_id_table_t *tbl, sqfs_u32 id,
sqfs_u16 *out);
/**
* @brief Write an ID table to disk.
*
* @memberof sqfs_id_table_t
*
* @param tbl A pointer to an ID table object.
* @param file The underlying file to append the table to.
* @param super A pointer to a super block in which to store the ID table
* start location.
* @param cmp A compressor to use to compress the ID table.
*
* @return Zero on success, an @ref SQFS_ERROR on failure.
*/
SQFS_API int sqfs_id_table_write(sqfs_id_table_t *tbl, sqfs_file_t *file,
sqfs_super_t *super, sqfs_compressor_t *cmp);
/**
* @brief Read an ID table from disk.
*
* @memberof sqfs_id_table_t
*
* @param tbl A pointer to an ID table object.
* @param file The underlying file to read the table from.
* @param super A pointer to a super block from which to get
* the ID table location.
* @param cmp A compressor to use to extract compressed table blocks.
*
* @return Zero on success, an @ref SQFS_ERROR on failure.
*/
SQFS_API int sqfs_id_table_read(sqfs_id_table_t *tbl, sqfs_file_t *file,
const sqfs_super_t *super,
sqfs_compressor_t *cmp);
/**
* @brief Resolve a 16 bit index to a 32 bit ID.
*
* @memberof sqfs_id_table_t
*
* @param tbl A pointer to an ID table object.
* @param index The table index to resolve.
* @param out Returns the underlying 32 bit ID that the index maps to.
*
* @return Zero on success, an @ref SQFS_ERROR on failure.
*/
SQFS_API int sqfs_id_table_index_to_id(const sqfs_id_table_t *tbl,
sqfs_u16 index, sqfs_u32 *out);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_ID_TABLE_H */
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