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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* dir_writer.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_DIR_WRITER_H
#define SQFS_DIR_WRITER_H
#include "sqfs/predef.h"
/**
* @file dir_writer.h
*
* @brief Contains declarations for the @ref sqfs_dir_writer_t.
*/
/**
* @struct sqfs_dir_writer_t
*
* @brief Abstracts generating of directory entries
*
* SquashFS stores directory entries and inodes seperated from each other. The
* inodes are stored in a series of meta data blocks before another series of
* meta data blocks that contain the directory entries. Directory inodes point
* to meta data block (and offset) where its contents are listed and the
* entries in turn point back to the inodes that represent them.
*
* There are some rules to this. Directory entries have to be written in
* ASCIIbetical ordering. Up to 256 entries are preceeded by a header. The
* entries use delta encoding for inode numbers and block locations relative to
* the header, so every time the inodes cross a meta data block boundary, if
* the difference in inode number gets too large, or if the entry count would
* exceed 256, a new header has to be emitted. Even if the inode pointed to is
* an extended type, the entry in the header still has to indicate the base
* type.
*
* In addtion to that, extended directory inodes can contain an index for
* faster lookup. The index points to each header and requires a new header to
* be emitted if the entries cross a block boundary.
*
* The dir writer takes care of all of this and provides a simple interface for
* adding entries. Internally it fills data into a meta data writer and
* generates an index that it can, on request, write to another meta data
* writer used for inodes.
*/
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Create a directory writer.
*
* @memberof sqfs_dir_writer_t
*
* @param dm A pointer to a meta data writer that the generated directory
* entries should be written to.
*
* @return A pointer to a directory writer on success, NULL on
* allocation failure.
*/
SQFS_API sqfs_dir_writer_t *sqfs_dir_writer_create(sqfs_meta_writer_t *dm);
/**
* @brief Destroy a directory writer and free all its memory.
*
* @memberof sqfs_dir_writer_t
*
* @param writer A pointer to a directory writer object.
*/
SQFS_API void sqfs_dir_writer_destroy(sqfs_dir_writer_t *writer);
/**
* @brief Begin writing a directory, i.e. reset and initialize all internal
* state neccessary.
*
* @memberof sqfs_dir_writer_t
*
* @param writer A pointer to a directory writer object.
* @param flags A currently unused flag field. Must be set to 0.
*
* @return Zero on success, a @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_dir_writer_begin(sqfs_dir_writer_t *writer, sqfs_u32 flags);
/**
* @brief Add add a directory entry.
*
* @memberof sqfs_dir_writer_t
*
* @param writer A pointer to a directory writer object.
* @param name The name of the directory entry.
* @param inode_num The inode number of the entry.
* @param inode_ref A reference to the inode, i.e. the meta data block offset
* is stored in bits 16 to 48 and the lower 16 bit hold an
* offset into the block.
* @param mode A file mode, i.e. type and permission bits from which the entry
* type is derived internally.
*
* @return Zero on success, a @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_dir_writer_add_entry(sqfs_dir_writer_t *writer,
const char *name,
sqfs_u32 inode_num, sqfs_u64 inode_ref,
sqfs_u16 mode);
/**
* @brief Finish writing a directory listing and write everything out to the
* meta data writer.
*
* @memberof sqfs_dir_writer_t
*
* @param writer A pointer to a directory writer object.
*
* @return Zero on success, a @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_dir_writer_end(sqfs_dir_writer_t *writer);
/**
* @brief Get the total, uncompressed size of the last written
* directory in bytes.
*
* @memberof sqfs_dir_writer_t
*
* Call this function after @ref sqfs_dir_writer_end to get the uncompressed
* size of the directory listing that is required for the directory inodes.
* And also to determine which kind of directory inode to create.
*
* @param writer A pointer to a directory writer object.
*
* @return The size of the entire, uncompressed listing in bytes.
*/
SQFS_API size_t sqfs_dir_writer_get_size(const sqfs_dir_writer_t *writer);
/**
* @brief Get the numer of entries written to the last directory.
*
* @memberof sqfs_dir_writer_t
*
* Call this function after @ref sqfs_dir_writer_end to get the total
* number of entries written to the directory.
*
* @param writer A pointer to a directory writer object.
*
* @return The number of entries in the directory.
*/
SQFS_API
size_t sqfs_dir_writer_get_entry_count(const sqfs_dir_writer_t *writer);
/**
* @brief Get the location of the last written directory.
*
* @memberof sqfs_dir_writer_t
*
* Call this function after @ref sqfs_dir_writer_end to get the location of
* the directory listing that is required for the directory inodes.
*
* @param writer A pointer to a directory writer object.
*
* @return A meta data reference, i.e. bits 16 to 48 contain the block start
* and the lower 16 bit an offset into the uncompressed block.
*/
SQFS_API sqfs_u64
sqfs_dir_writer_get_dir_reference(const sqfs_dir_writer_t *writer);
/**
* @brief Get the size of the index of the last written directory.
*
* @memberof sqfs_dir_writer_t
*
* Call this function after @ref sqfs_dir_writer_end to get the size of
* the directory index that is required for extended directory inodes.
*
* @param writer A pointer to a directory writer object.
*
* @return The number of index entries.
*/
SQFS_API size_t sqfs_dir_writer_get_index_size(const sqfs_dir_writer_t *writer);
/**
* @brief Helper function for creating an inode from the last directory.
*
* @memberof sqfs_dir_writer_t
*
* Call this function after @ref sqfs_dir_writer_end to create a bare bones
* inode structure for the directory. The directory information is filled in
* completely and the type is set, the rest of the basic information such as
* permission bits, owner and timestamp is left untouched.
*
* If the generated inode is an extended directory inode, you can use another
* convenience function called @ref sqfs_dir_writer_write_index to write the
* index meta data after writing the inode itself.
*
* @param writer A pointer to a directory writer object.
* @param hlinks The number of hard links pointing to the directory.
* @param xattr If set to something other than 0xFFFFFFFF, an extended
* directory inode is created with xattr index set.
* @param parent_ino The inode number of the parent directory.
*
* @return A generic inode or NULL on allocation failure.
*/
SQFS_API sqfs_inode_generic_t
*sqfs_dir_writer_create_inode(const sqfs_dir_writer_t *writer, size_t hlinks,
sqfs_u32 xattr, sqfs_u32 parent_ino);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_DIR_WRITER_H */
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