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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* data_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 SFQS_DATA_WRITER_H
#define SFQS_DATA_WRITER_H
#include "sqfs/predef.h"
/**
* @file data_writer.h
*
* @brief Contains declarations for the data block processor.
*/
/**
* @struct sqfs_data_writer_t
*
* @brief Encapsulates a thread pool based block processor.
*
* The actual implementation may even be non-threaded, depending on the
* operating system and compile configuration.
*
* Either way, the instantiated object processes data blocks that can be
* enqueued through @ref sqfs_data_writer_enqueue. The completed blocks
* (compressed and checksumed) are dequeued in the same order and a callback
* is called for each one.
*/
/**
* @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_data_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 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_ALLIGN 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_ALLIGN 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,
uint64_t 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);
};
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Create a data block writer.
*
* @memberof sqfs_data_writer_t
*
* @param max_block_size The maximum size of a data block. Required for the
* internal scratch buffer used for compressing data.
* @param cmp A pointer to a compressor. If multiple worker threads are used,
* the deep copy function of the compressor is used to create
* several instances that don't interfere with each other.
* @param num_workers The number of worker threads to create.
* @param max_backlog The maximum number of blocks currently in flight. When
* trying to add more, enqueueing blocks until the in-flight
* block count drops below the threshold.
* @param devblksz File can optionally be allgined to device block size. This
* specifies the desired allignment.
* @param file The output file to write the finished blocks to.
*
* @return A pointer to a data writer object on success, NULL on allocation
* failure or on failure to create and initialize the worker threads.
*/
SQFS_API
sqfs_data_writer_t *sqfs_data_writer_create(size_t max_block_size,
sqfs_compressor_t *cmp,
unsigned int num_workers,
size_t max_backlog,
size_t devblksz,
sqfs_file_t *file);
/**
* @brief Destroy a data writer and free all memory used by it.
*
* @memberof sqfs_data_writer_t
*
* @param proc A pointer to a data writer object.
*/
SQFS_API void sqfs_data_writer_destroy(sqfs_data_writer_t *proc);
/**
* @brief Add a block to be processed.
*
* @memberof sqfs_data_writer_t
*
* The function takes over ownership of the submitted block. It is freed after
* processing is done and it is written to disk.
*
* @param proc A pointer to a data writer object.
* @param block A pointer to a block to enqueue.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure. Depending on
* the implementation used, the failure could have been caused by
* processing of a block that was submitted earlier.
*/
SQFS_API int sqfs_data_writer_enqueue(sqfs_data_writer_t *proc,
sqfs_block_t *block);
/**
* @brief Wait for the works to finish and finally flush the current
* fragment block.
*
* @memberof sqfs_data_writer_t
*
* @param proc A pointer to a block processor object.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure. The failure
* return value can either be an error encountered during enqueueing,
* processing or writing to disk.
*/
SQFS_API int sqfs_data_writer_finish(sqfs_data_writer_t *proc);
/**
* @brief Write the completed fragment table to disk.
*
* @memberof sqfs_data_writer_t
*
* Call this after producing the inode and directory table to generate
* the fragment table for the squashfs image.
*
* @param proc A pointer to a data writer object.
* @param super A pointer to a super block to write information about the
* fragment table to.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure.
*/
SQFS_API
int sqfs_data_writer_write_fragment_table(sqfs_data_writer_t *proc,
sqfs_super_t *super);
/**
* @brief Register a set of hooks to be invoked when writing blocks to disk.
*
* @memberof sqfs_data_writer_t
*
* @param proc A pointer to a data writer object.
* @param user_ptr A user pointer to pass to the callbacks.
* @param hooks A structure containing the hooks.
*/
SQFS_API
void sqfs_data_writer_set_hooks(sqfs_data_writer_t *proc, void *user_ptr,
const sqfs_block_hooks_t *hooks);
#ifdef __cplusplus
}
#endif
#endif /* SFQS_DATA_WRITER_H */
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