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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 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);
};
/**
* @struct sqfs_block_writer_stats_t
*
* @brief Collects run time statistics of the @ref sqfs_block_writer_t
*/
struct sqfs_block_writer_stats_t {
/**
* @brief Holds the size of the structure.
*
* If a later version of libsquashfs expands this structure, the value
* of this field can be used to check at runtime whether the newer
* fields are avaialable or not.
*/
size_t size;
/**
* @brief Total number of bytes submitted, including blocks that were
* removed by deduplication and not counting any padding.
*/
sqfs_u64 bytes_submitted;
/**
* @brief Actual number of bytes written to disk, excluding deduplicated
* blocks and including padding.
*/
sqfs_u64 bytes_written;
/**
* @brief Total number of submitted blocks, including ones later
* removed by deduplication.
*/
sqfs_u64 blocks_submitted;
/**
* @brief Total number of blocks actually written, excluding
* deduplicated blocks.
*/
sqfs_u64 blocks_written;
};
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Create a block writer object.
*
* @memberof sqfs_block_writer_t
*
* @param file A pointer to a file object that data should be appended to.
* @param devblksz The underlying device block size if output data
* should be aligned.
* @param flags Currently must be set to 0 or creation will fail.
*
* @return A pointer to a new block writer on success, NULL on failure.
*/
SQFS_API sqfs_block_writer_t *sqfs_block_writer_create(sqfs_file_t *file,
size_t devblksz,
sqfs_u32 flags);
/**
* @brief Register a set of callbacks with a block writer.
*
* @memberof sqfs_block_writer_t
*
* @param wr A pointer to a block writer object.
* @param user_ptr A user data pointer that should be passed to the callbacks.
* @param hooks A structure holding various callbacks.
*
* @return Zero on success, an @ref E_SQFS_ERROR on failure.
*/
SQFS_API int sqfs_block_writer_set_hooks(sqfs_block_writer_t *wr,
void *user_ptr,
const sqfs_block_hooks_t *hooks);
/**
* @brief Destroy a block writer object.
*
* @memberof sqfs_block_writer_t
*
* @param wr A pointer to a block writer object.
*/
SQFS_API void sqfs_block_writer_destroy(sqfs_block_writer_t *wr);
/**
* @brief Submit a data block to a blokc writer.
*
* @memberof sqfs_block_writer_t
*
* If the @ref SQFS_BLK_FIRST_BLOCK flag is set, the data block writer
* memorizes the starting location and block index of the block. If the
* @ref SQFS_BLK_LAST_BLOCK flag is set, it uses those stored locations
* to do block deduplication.
*
* If the flag @ref SQFS_BLK_ALIGN is set in combination with the
* @ref SQFS_BLK_FIRST_BLOCK, the file size is padded to a multiple of the
* device block size before writing. If it is set together with the
* @ref SQFS_BLK_LAST_BLOCK flag, the padding is added afterwards.
*
* @param wr A pointer to a block writer.
* @param block The block to write to disk next.
* @param location Returns the location where the block has been written.
* If the @ref SQFS_BLK_LAST_BLOCK flag was set, deduplication
* is performed and this returns the (new) location of the
* first block instead.
*
* @return Zero on success, an @ref E_SQFS_ERROR error on failure.
*/
SQFS_API int sqfs_block_writer_write(sqfs_block_writer_t *wr,
sqfs_block_t *block,
sqfs_u64 *location);
/**
* @brief Get access to a block writers run time statistics.
*
* @memberof sqfs_block_writer_t
*
* @param wr A pointer to a block writer.
*
* @return A pointer to the internal statistics counters.
*/
SQFS_API const sqfs_block_writer_stats_t
*sqfs_block_writer_get_stats(const sqfs_block_writer_t *wr);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_BLOCK_WRITER_H */
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