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/* SPDX-License-Identifier: GPL-3.0-or-later */
#ifndef META_WRITER_H
#define META_WRITER_H
#include "compress.h"
#include "squashfs.h"
/**
* @struct meta_writer_t
*
* @brief Abstracts away I/O on SquashFS meta data
*/
typedef struct {
/**
* @brief A byte offset into the uncompressed data of the current block
*/
size_t offset;
/**
* @brief The location of the current block in the file
*/
size_t block_offset;
/**
* @brief The underlying file descriptor to write to
*/
int outfd;
/**
* @brief A pointer to the compressor to use for compressing the data
*/
compressor_t *cmp;
/**
* @brief The raw data chunk that data is appended to
*/
uint8_t data[SQFS_META_BLOCK_SIZE + 2];
/**
* @brief Scratch buffer for compressing data
*/
uint8_t scratch[SQFS_META_BLOCK_SIZE + 2];
} meta_writer_t;
/**
* @brief Create a meta data writer
*
* @memberof meta_writer_t
*
* @note This function internally prints error message to stderr on failure
*
* @param fd The underlying file descriptor to write from
* @param cmp A pointer to a compressor to use for compressing the data
*
* @return A pointer to a meta data writer, NULL on failure
*/
meta_writer_t *meta_writer_create(int fd, compressor_t *cmp);
/**
* @brief Destroy a meta data writer and free all memory used by it
*
* @memberof meta_writer_t
*
* @param m A pointer to a meta data reader
*/
void meta_writer_destroy(meta_writer_t *m);
/**
* @brief Flush the currently unfinished meta data block to disk
*
* @memberof meta_writer_t
*
* @note This function internally prints error message to stderr on failure
*
* If data has been collected in the block buffer but it is not complete yet,
* this function tries to compress it and write it out anyway and reset the
* internal counters.
*
* @param m A pointer to a meta data reader
*
* @return Zero on success, -1 on failure
*/
int meta_writer_flush(meta_writer_t *m);
/**
* @brief Append data to the current meta data block
*
* @memberof meta_writer_t
*
* @note This function internally prints error message to stderr on failure
*
* This function appends the input data to an internal meta data buffer. If
* the internal buffer is full, it is compressed and written to disk using
* @ref meta_writer flush, i.e. the function allows for transparent writing
* across meta data blocks.
*
* @param m A pointer to a meta data reader
* @param data A pointer to the data block to append
* @param size The number of bytes to read from the data blob
*
* @return Zero on success, -1 on failure
*/
int meta_writer_append(meta_writer_t *m, const void *data, size_t size);
#endif /* META_WRITER_H */
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