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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* block_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_BLOCK_WRITER_H
#define SQFS_BLOCK_WRITER_H
#include "sqfs/predef.h"
/**
* @file block_writer.h
*
* @brief Contains declarations for the @ref sqfs_block_writer_t structure.
*/
/**
* @struct sqfs_block_writer_t
*
* @brief Abstracts writing and deduplicating of data and fragment blocks.
*/
/**
* @struct sqfs_block_hooks_t
*
* @brief A set of hooks for tapping into the data writer.
*
* This structure can be registered with an @ref sqfs_block_writer_t and
* contains function pointers that will be called during various stages
* when writing data to disk.
*
* The callbacks can not only be used for accounting but may also write extra
* data to the output file or make modifications to the blocks before they are
* writtien.
*
* The callbacks can be individually set to NULL to disable them.
*/
struct sqfs_block_hooks_t {
/**
* @brief Set this to the size of the struct.
*
* This is required for future expandabillity while maintaining ABI
* compatibillity. At the current time, the implementation of
* @ref sqfs_block_writer_set_hooks rejects any hook struct where
* this isn't the exact size. If new hooks are added in the future,
* the struct grows and the future implementation can tell by the size
* whether the application uses the new version or the old one.
*/
size_t size;
/**
* @brief Gets called before writing a block to disk.
*
* If this is not NULL, it gets called before a block is written to
* disk. If the block has the @ref SQFS_BLK_ALIGN flag set, the
* function is called before padding the file.
*
* The function may modify the block itself or write data to the file.
* which is taken into account when padding the file.
*
* @param user A user pointer.
* @param block The block that is about to be written.
* @param file The file that the block will be written to.
*/
void (*pre_block_write)(void *user, sqfs_block_t *block,
sqfs_file_t *file);
/**
* @brief Gets called after writing a block to disk.
*
* If this is not NULL, it gets called after a block is written to
* disk. If the block has the @ref SQFS_BLK_ALIGN flag set, the
* function is called before padding the file.
*
* Modifying the block is rather pointless, but the function may
* write data to the file which is taken into account when padding
* the file.
*
* @param user A user pointer.
* @param block The block that is about to be written.
* @param file The file that the block was written to.
*/
void (*post_block_write)(void *user, const sqfs_block_t *block,
sqfs_file_t *file);
/**
* @brief Gets called before storing a fragment in a fragment block.
*
* The function can modify the block before it is stored.
*
* @param user A user pointer.
* @param block The data chunk that is about to be merged into the
* fragment block.
*/
void (*pre_fragment_store)(void *user, sqfs_block_t *block);
/**
* @brief Gets called if block deduplication managed to get
* rid of the data blocks of a file.
*
* @param user A user pointer.
* @param count The number of blocks that have been erased.
* @param bytes The number of bytes that have been erased. Includes
* potential padding before and after the end.
*/
void (*notify_blocks_erased)(void *user, size_t count,
sqfs_u64 bytes);
/**
* @brief Gets called before throwing away a fragment that turned out
* to be a duplicate.
*
* @param user A user pointer.
* @param block The data chunk that is about to be merged into the
* fragment block.
*/
void (*notify_fragment_discard)(void *user, const sqfs_block_t *block);
/**
* @brief Gets called before writing a block of padding bytes to disk.
*
* @param user A user pointer.
* @param block The padding bytes that are about to be written.
* @param count The number of padding bytes in the block.
*/
void (*prepare_padding)(void *user, sqfs_u8 *block, size_t count);
};
#ifdef __cplusplus
extern "C" {
#endif
SQFS_API sqfs_block_writer_t *sqfs_block_writer_create(sqfs_file_t *file,
size_t devblksz,
sqfs_u32 flags);
SQFS_API int sqfs_block_writer_set_hooks(sqfs_block_writer_t *wr,
void *user_ptr,
const sqfs_block_hooks_t *hooks);
SQFS_API void sqfs_block_writer_destroy(sqfs_block_writer_t *wr);
SQFS_API int sqfs_block_writer_write(sqfs_block_writer_t *wr,
sqfs_block_t *block,
sqfs_u64 *location);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_BLOCK_WRITER_H */
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