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/* SPDX-License-Identifier: GPL-3.0-or-later */
#ifndef META_READER_H
#define META_READER_H
#include "compress.h"
#include "squashfs.h"
/**
* @struct meta_reader_t
*
* @brief Abstracts away I/O on SquashFS meta data
*/
typedef struct {
/**
* @brief The location of the current block in the file
*/
uint64_t block_offset;
/**
* @brief The location of the next block after the current one
*/
uint64_t next_block;
/**
* @brief A byte offset into the uncompressed data of the current block
*/
size_t offset;
/**
* @brief The underlying file descriptor to read from
*/
int fd;
/**
* @brief A pointer to the compressor to use for extracting data
*/
compressor_t *cmp;
/**
* @brief The raw data read from the input file
*/
uint8_t data[SQFS_META_BLOCK_SIZE];
/**
* @brief The uncompressed data read from the input file
*/
uint8_t scratch[SQFS_META_BLOCK_SIZE];
} meta_reader_t;
/**
* @brief Create a meta data reader
*
* @memberof meta_reader_t
*
* @note This function internally prints error message to stderr on failure
*
* @param fd The underlying file descriptor to read from
* @param cmp A pointer to a compressor to use for extracting the data
*
* @return A pointer to a meta data reader, NULL on failure
*/
meta_reader_t *meta_reader_create(int fd, compressor_t *cmp);
/**
* @brief Destroy a meta data reader and free all memory used by it
*
* @memberof meta_reader_t
*
* @param m A pointer to a meta data reader
*/
void meta_reader_destroy(meta_reader_t *m);
/**
* @brief Seek to a specific meta data block and offset
*
* @memberof meta_reader_t
*
* @note This function internally prints error message to stderr on failure
*
* @param m A pointer to a meta data reader
* @param block_start The absolute position of the 16 bit header right before
* the compressed data block
* @param offset A byte offset into the data block
*
* @return Zero on success, -1 on failure
*/
int meta_reader_seek(meta_reader_t *m, uint64_t block_start,
size_t offset);
/**
* @brief Read a chunk of data from a meta data block
*
* @memberof meta_reader_t
*
* @note This function internally prints error message to stderr on failure
*
* If the end of the block is reached, this function transparently tries to
* interpret the data after the current block as a further meta data block,
* i.e. it can transparently read across multiple meta data blocks.
*
* @param m A pointer to a meta data reader
* @param data A pointer to a memory block to write the data to
* @param size The number of bytes to read
*
* @return Zero on success, -1 on failure
*/
int meta_reader_read(meta_reader_t *m, void *data, size_t size);
/**
* @brief Read an inode from a meta data block
*
* @memberof meta_reader_t
*
* @note This function internally prints error message to stderr on failure
*
* This function is a conveniance wrapper around @ref meta_reader_read that
* reads and decodes an entire SquashFS inode. It first reads the common inode
* header, interprets it and reads the additional, type dependend data.
*
* @param ir A pointer to a meta data reader
* @param super A pointer to the SquashFS super block
* @param block_start A byte offset relative to the inode table start where
* the meta data containing the inode starts
* @param offset A byte offset into the uncompressed meta data block
* where the inode is stored
*
* @return A pointer to the decoded inode or NULL on failure. Can be freed
* with a single free call.
*/
sqfs_inode_generic_t *meta_reader_read_inode(meta_reader_t *ir,
sqfs_super_t *super,
uint64_t block_start,
size_t offset);
/**
* @brief Read a directory header from a meta data block
*
* @memberof meta_reader_t
*
* @note This function internally prints error message to stderr on failure
*
* This function is a conveniance wrapper around @ref meta_reader_read that
* reads and decodes a SquashFS directory header.
*
* @param m A pointer to a meta data reader
* @param hdr A pointer to a directory header structure to write the decoded
* data to
*
* @return Zero on success, -1 on failure
*/
int meta_reader_read_dir_header(meta_reader_t *m, sqfs_dir_header_t *hdr);
/**
* @brief Read a directory entry from a meta data block
*
* @memberof meta_reader_t
*
* @note This function internally prints error message to stderr on failure
*
* This function is a conveniance wrapper around @ref meta_reader_read that
* reads and decodes a SquashFS directory entry.
*
* @param m A pointer to a meta data reader
*
* @return A pointer to a directory entry or NULL on failure. Can be freed
* with a single free call.
*/
sqfs_dir_entry_t *meta_reader_read_dir_ent(meta_reader_t *m);
#endif /* META_READER_H */
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