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/* Copyright 2021 Ján Sučan <jan@jansucan.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "restore.h"
#include <errno.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <filesystem>
#include <fstream>
#include <iostream>
typedef struct {
std::ifstream in_file;
std::fstream out_file;
std::unique_ptr<char[]> in_buffer;
std::unique_ptr<char[]> out_buffer;
size_t in_sector_size;
size_t in_buffer_size;
} resources_restore_t;
static resources_restore_t
resources_allocate_for_restore(const OptionsRestore &opts)
{
resources_restore_t res;
res.in_file.open(opts.getInFilePath(), std::ios::in | std::ios::binary);
if (!res.in_file) {
throw RestoreError("cannot open input file");
}
/* When restoring, the file must be opened for writing and not
* truncated
*/
res.out_file.open(opts.getOutFilePath(),
std::ios::in | std::ios::out | std::ios::binary);
if (!res.out_file) {
throw RestoreError("cannot open output file");
}
/* Allocate the buffer for data from the input file */
/* The input buffer contains also the offsets */
res.in_sector_size = sizeof(uint64_t) + opts.getSectorSize();
const size_t in_buffer_sector_count =
opts.getBufferSize() / res.in_sector_size;
res.in_buffer_size = in_buffer_sector_count * res.in_sector_size;
try {
res.in_buffer = std::make_unique<char[]>(res.in_buffer_size);
} catch (const std::bad_alloc &e) {
throw RestoreError("cannot allocate buffer for input file data");
}
return res;
}
static void
check_input_file(resources_restore_t &res, const OptionsRestore &opts)
{
size_t in_size{0};
try {
in_size = std::filesystem::file_size(opts.getInFilePath());
} catch (const std::exception &e) {
throw RestoreError("cannot get size of input file: " +
std::string(e.what()));
}
if (in_size == 0) {
throw RestoreError("input file is empty");
} else if ((in_size % (sizeof(uint64_t) + opts.getSectorSize())) != 0) {
/* The input file must hold equally sized sectors and the
* offset of each of them
*/
throw RestoreError(
"input file has size that cannot contain valid diff data");
}
size_t out_size{0};
try {
out_size = std::filesystem::file_size(opts.getOutFilePath());
} catch (const std::exception &e) {
throw RestoreError("cannot get size of output file: " +
std::string(e.what()));
}
uint64_t prev_out_offset = 0;
bool is_first_reading = true;
/* Scan the input file and check */
for (;;) {
uint64_t out_offset;
/* Read the next offset */
res.in_file.read(reinterpret_cast<char *>(&out_offset),
sizeof(out_offset));
if (res.in_file.eof() && res.in_file.fail() && !res.in_file.bad()) {
break;
} else if (!res.in_file.good() && !res.in_file.eof()) {
throw RestoreError("cannot read from file");
}
out_offset = le64toh(out_offset);
if (!is_first_reading && (out_offset <= prev_out_offset)) {
throw RestoreError(
"a sector offset points behind the previous offset");
} else if ((out_offset + opts.getSectorSize()) > out_size) {
throw RestoreError(
"a sector offset points past the end of the output file");
} else if (!res.in_file.seekg(opts.getSectorSize(),
std::ios_base::cur)) {
throw RestoreError("cannot seek in input file");
}
is_first_reading = false;
prev_out_offset = out_offset;
}
/* The input file must be read completely */
char c;
res.in_file.read(&c, 1);
if (res.in_file.gcount() != 0) {
throw RestoreError("input file is not valid");
}
res.in_file.clear();
/* The file must be prepared for the restoring */
if (!res.in_file.seekg(0, std::ios_base::beg)) {
throw RestoreError("cannot seek in input file");
}
}
static size_t
read_sectors(std::ifstream &file, char *const buffer, uint32_t buffer_size,
uint32_t sector_size)
{
file.read(buffer, buffer_size);
const size_t bytes_read = file.gcount();
if (!file.good() && !file.eof()) {
throw RestoreError("cannot read from file");
} else if ((bytes_read % sector_size) != 0) {
throw RestoreError(
"data read from input file is not multiple of sector size");
} else {
return (bytes_read / sector_size);
}
}
void
restore(const OptionsRestore &opts)
{
resources_restore_t res{resources_allocate_for_restore(opts)};
check_input_file(res, opts);
/* Restore data from the differential image */
for (;;) {
/* Read data of the offset and the next sector */
const size_t in_sectors_read =
read_sectors(res.in_file, res.in_buffer.get(), res.in_buffer_size,
res.in_sector_size);
if (in_sectors_read == 0) {
break;
}
char *in_buffer = res.in_buffer.get();
for (size_t s = 0; s < in_sectors_read; ++s) {
const uint64_t out_offset = le64toh(*((uint64_t *)in_buffer));
in_buffer += sizeof(uint64_t);
if (!res.out_file.seekp(out_offset, std::ios_base::beg)) {
throw RestoreError("cannot seek in output file");
}
if (!res.out_file.write(in_buffer, opts.getSectorSize())) {
throw RestoreError("cannot write to output file");
}
in_buffer += opts.getSectorSize();
}
}
/* The input file must be read completely */
char c;
res.in_file.read(&c, 1);
if (res.in_file.gcount() != 0) {
throw RestoreError("input file is not valid");
}
res.in_file.clear();
}
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