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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* io.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_IO_H
#define SQFS_IO_H
#include "sqfs/predef.h"
/**
* @file io.h
*
* @brief Contains the @ref sqfs_file_t interface for abstracting file I/O
*/
/**
* @enum E_SQFS_FILE_OPEN_FLAGS
*
* @brief Flags for @ref sqfs_open_file
*/
typedef enum {
/**
* @brief If set, access the file for reading only
*
* If not set, the file is expected to have a zero size after opening
* which can be grown with successive writes to end of the file.
*
* Opening an existing file with this flag cleared results in failure,
* unless the @ref SQFS_FILE_OPEN_OVERWRITE flag is also set.
*/
SQFS_FILE_OPEN_READ_ONLY = 0x01,
/**
* @brief If the read only flag is not set, overwrite any
* existing file.
*
* If the file alrady exists, it is truncated to zero bytes size and
* overwritten.
*/
SQFS_FILE_OPEN_OVERWRITE = 0x02,
SQFS_FILE_OPEN_ALL_FLAGS = 0x03,
} E_SQFS_FILE_OPEN_FLAGS;
/**
* @interface sqfs_file_t
*
* @brief Abstracts file I/O to make it easy to embedd SquashFS.
*/
struct sqfs_file_t {
/**
* @brief Close the file and destroy the interface implementation.
*
* @param file A pointer to the file object.
*/
void (*destroy)(sqfs_file_t *file);
/**
* @brief Read a chunk of data from an absolute position.
*
* @param file A pointer to the file object.
* @param offset An absolute offset to read data from.
* @param buffer A pointer to a buffer to copy the data to.
* @param size The number of bytes to read from the file.
*
* @return Zero on success, an @ref E_SQFS_ERROR identifier on failure
* that the data structures in libsquashfs that use this return
* directly to the caller.
*/
int (*read_at)(sqfs_file_t *file, uint64_t offset,
void *buffer, size_t size);
/**
* @brief Write a chunk of data at an absolute position.
*
* @param file A pointer to the file object.
* @param offset An absolute offset to write data to.
* @param buffer A pointer to a buffer to write to the file.
* @param size The number of bytes to write from the buffer.
*
* @return Zero on success, an @ref E_SQFS_ERROR identifier on failure
* that the data structures in libsquashfs that use this return
* directly to the caller.
*/
int (*write_at)(sqfs_file_t *file, uint64_t offset,
const void *buffer, size_t size);
/**
* @brief Get the number of bytes currently stored in the file.
*
* @param file A pointer to the file object.
*/
uint64_t (*get_size)(const sqfs_file_t *file);
/**
* @brief Extend or shrink a file to a specified size.
*
* @param file A pointer to the file object.
* @param size The new capacity of the file in bytes.
*
* @return Zero on success, an @ref E_SQFS_ERROR identifier on failure
* that the data structures in libsquashfs that use this return
* directly to the caller.
*/
int (*truncate)(sqfs_file_t *file, uint64_t size);
};
/**
* @struct sqfs_sparse_map_t
*
* @brief Describes the layout of a sparse file.
*
* This structure is part of a linked list that indicates where the actual
* data is located in a sparse file.
*/
struct sqfs_sparse_map_t {
sqfs_sparse_map_t *next;
uint64_t offset;
uint64_t count;
};
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Open a file through the operating systems filesystem API
*
* This function internally creates an instance of a reference implementation
* of the @ref sqfs_file_t interface that uses the operating systems native
* API for file I/O.
*
* On Unix-like systems, if the open call fails, this function makes sure to
* preserves the value in errno indicating the underlying problem.
*
* @param filename The name of the file to open.
* @param flags A set of @ref E_SQFS_FILE_OPEN_FLAGS.
*
* @return A pointer to a file object on success, NULL on allocation failure,
* failure to open the file or if an unknown flag was set.
*/
SQFS_API sqfs_file_t *sqfs_open_file(const char *filename, int flags);
/**
* @brief Get a read-only file implementation that represents standard input
*
* This function creates a read-only file that represents STDIN. The file
* supports reading up to a specified number of bytes and only allows
* reading sequentially.
*
* @param size The alleged "size" of the file.
*
* @return A pointer to a file object on success, NULL on allocation failure.
*/
SQFS_API sqfs_file_t *sqfs_get_stdin_file(uint64_t size);
/**
* @brief Read a chunk from a file and turn it into a block that can be
* fed to a block processor.
*
* @member sqfs_file_t
*
* @param file A pointer to a file implementation.
* @param offset A byte offset into the file.
* @param size The number of bytes to read, starting at the given offset.
* @param inode The inode pointer to set for the block.
* @param flags The flags to store in the newly created block.
* @param out Returns a pointer to a block on success.
*
* @return Zero on success, an @ref E_SQFS_ERROR identifier on failure.
*/
SQFS_API int sqfs_file_create_block(sqfs_file_t *file, uint64_t offset,
size_t size, sqfs_inode_generic_t *inode,
uint32_t flags, sqfs_block_t **out);
/**
* @brief Read a chunk from a condensed version of a sparse file and turn it
* into a block that can be fed to a block processor.
*
* @member sqfs_file_t
*
* This function works on condensed sparse files, i.e. a sparse file that had
* its holdes removed. The given mapping describes the original data region
* that are actually packed next to each other. The function emulates the
* orignal sparse file by zero-initializing the block data, then figuring
* out which regions overlap the block, working out their physical location and
* stitching the block together.
*
* @param file A pointer to a file implementation.
* @param offset A byte offset into the file.
* @param size The number of bytes to read, starting at the given offset.
* @param inode The inode pointer to set for the block.
* @param flags The flags to store in the newly created block.
* @param map Describes the data regions of the original sparse file.
* @param out Returns a pointer to a block on success.
*
* @return Zero on success, an @ref E_SQFS_ERROR identifier on failure.
*/
SQFS_API int sqfs_file_create_block_dense(sqfs_file_t *file, uint64_t offset,
size_t size,
sqfs_inode_generic_t *inode,
uint32_t flags,
const sqfs_sparse_map_t *map,
sqfs_block_t **out);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_IO_H */
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