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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 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,
} SQFS_FILE_OPEN_FLAGS;
/**
* @interface sqfs_file_t
*
* @extends sqfs_object_t
*
* @brief Abstracts file I/O to make it easy to embedd SquashFS.
*
* Files are only copyable if they are read only, i.e. if a file has been
* opened with write access, @ref sqfs_copy will always return NULL. The
* other data types inside libsquashfs assume this to hold for all
* implementations of this interface.
*/
struct sqfs_file_t {
sqfs_object_t base;
/**
* @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 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, sqfs_u64 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 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, sqfs_u64 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.
*/
sqfs_u64 (*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 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, sqfs_u64 size);
};
#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 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, sqfs_u32 flags);
#ifdef __cplusplus
}
#endif
#endif /* SQFS_IO_H */
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