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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* meta_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_META_WRITER_H
#define SQFS_META_WRITER_H
#include "sqfs/predef.h"
/**
* @file meta_writer.h
*
* @brief Contains declarations for the @ref sqfs_meta_writer_t.
*/
/**
* @struct sqfs_meta_writer_t
*
* @brief Abstracts generating of meta data blocks, either in memory or
* directly on disk.
*
* SquashFS stores meta data by dividing it into fixed size (8k) chunks
* that are written to disk with a small header indicating the on-disk
* size and whether it is compressed or not.
*
* Data written to meta data blocks doesn't have to be alligned, i.e.
* SquashFS doesn't care if an object is written across two blocks.
*
* The main task of the meta data writer is to provide a simple append
* function that transparently takes care of chopping data up into blocks,
* compressing the blocks and pre-pending a header.
*/
/**
* @enum E_SQFS_META_WRITER_FLAGS
*
* @brief Possible flags for @ref sqfs_meta_writer_create.
*/
typedef enum {
/**
* @brief If set, keep finished blocks in memory.
*
* To write them to disk, explicitly call
* @ref sqfs_meta_write_write_to_file.
*/
SQFS_META_WRITER_KEEP_IN_MEMORY = 0x01,
SQFS_META_WRITER_ALL_FLAGS = 0x01,
} E_SQFS_META_WRITER_FLAGS;
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Create a meta data writer.
*
* @memberof sqfs_meta_writer_t
*
* @note The meta writer internally keeps references to the pointers passed
* to this function, so don't destroy them before destroying the
* meta writer.
*
* @param file An output file to write the data to.
* @param cmp A compressor to use.
* @param flags A combination of @ref E_SQFS_META_WRITER_FLAGS.
*
* @return A pointer to a meta writer on success, NULL on allocation failure
* or if an unknown flag was set.
*/
SQFS_API sqfs_meta_writer_t *sqfs_meta_writer_create(sqfs_file_t *file,
sqfs_compressor_t *cmp,
int flags);
/**
* @brief Destroy a meta data writer and free all memory used by it.
*
* @memberof sqfs_meta_writer_t
*
* @param m A pointer to a meta data writer.
*/
SQFS_API void sqfs_meta_writer_destroy(sqfs_meta_writer_t *m);
/**
* @brief Finish the current block, even if it isn't full yet.
*
* @memberof sqfs_meta_writer_t
*
* This function forces the meta writer to compress and store the block it
* is currently writing to, even if it isn't full yet, and either write it
* out to disk (or append it to the in memory chain if told to keep blocks
* in memory).
*
* @param m A pointer to a meta data writer.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_meta_writer_flush(sqfs_meta_writer_t *m);
/**
* @brief Finish the current block, even if it isn't full yet.
*
* @memberof sqfs_meta_writer_t
*
* This function forces reads a speicifed number of bytes from a given data
* block and appends it to the meta data block that the writer is currently
* working on. If the block becomes full, it is compressed, written to disk
* and a new block is started that the remaining data is written to.
*
* @param m A pointer to a meta data writer.
* @param data A pointer to a chunk of data to append to the writer.
* @param size The number of data bytes to append.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_meta_writer_append(sqfs_meta_writer_t *m, const void *data,
size_t size);
/**
* @brief Query the current block start position and offset within the block
*
* @memberof sqfs_meta_writer_t
*
* Get the byte offset relative to the first block that the current block will
* start at once it is written to disk and get the byte offset within this
* block that the next call to @ref sqfs_meta_writer_append will start writing
* data at.
*
* @param m A pointer to a meta data writer.
* @param block_start Returns the offset of the current block from the first.
* @param offset Returns an offset into the current block where the next write
* starts.
*/
SQFS_API void sqfs_meta_writer_get_position(const sqfs_meta_writer_t *m,
uint64_t *block_start,
uint32_t *offset);
/**
* @brief Reset all internal state, including the current block start position.
*
* @memberof sqfs_meta_writer_t
*
* This functions forces the meta data writer to forget everything that
* happened since it was created, so it can be recycled.
*
* The data written is not lost, unless it was kept in memory and never written
* out to disk.
*/
SQFS_API void sqfs_meta_writer_reset(sqfs_meta_writer_t *m);
/**
* @brief Write all blocks collected in memory to disk
*
* @memberof sqfs_meta_writer_t
*
* If the meta writer was created with the flag set to store blocks in
* memory instead of writing them to disk, calling this function forces
* the meta writer to write out all blocks it collected so far.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_meta_write_write_to_file(sqfs_meta_writer_t *m);
/**
* @brief A convenience function for encoding and writing an inode
*
* @memberof sqfs_meta_writer_t
*
* The SquashFS inode table is essentially a series of meta data blocks
* containing variable sized inodes. This function takes a generic inode
* structure, encodes it and writes the result to a meta data writer
* using @ref sqfs_meta_writer_append internally.
*
* @param iw A pointer to a meta data writer.
* @param n A pointer to an inode.
*
* @return Zero on success, an @ref E_SQFS_ERROR value on failure.
*/
SQFS_API int sqfs_meta_writer_write_inode(sqfs_meta_writer_t *iw,
const sqfs_inode_generic_t *n);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_META_WRITER_H */
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