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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 "backup.h"
#include <cstring>
#include <fstream>
typedef struct {
std::ifstream in_file;
std::ifstream ref_file;
std::ofstream out_file;
std::unique_ptr<char[]> in_buffer;
std::unique_ptr<char[]> ref_buffer;
std::unique_ptr<char[]> out_buffer;
size_t out_buffer_size;
} resources_backup_t;
static void check_files(const OptionsBackup &opts);
static void write_out_buffer(const char *const buffer, size_t size,
std::ofstream &file);
static resources_backup_t
resources_allocate_for_backup(const OptionsBackup &opts)
{
resources_backup_t res;
res.in_file.open(opts.getInFilePath(),
std::ifstream::in | std::ifstream::binary);
if (!res.in_file) {
throw BackupError("cannot open input file");
}
res.ref_file.open(opts.getRefFilePath(),
std::ifstream::in | std::ifstream::binary);
if (!res.ref_file) {
throw BackupError("cannot open reference file");
}
/* When backing up, the output file is truncated to hold the
* new data
*/
res.out_file.open(opts.getOutFilePath(), std::ifstream::out |
std::ifstream::trunc |
std::ifstream::binary);
if (!res.out_file) {
throw BackupError("cannot open output file");
}
/* The output buffer contains also the offsets */
res.out_buffer_size =
((opts.getBufferSize() / opts.getSectorSize()) * sizeof(uint64_t)) +
opts.getBufferSize();
// TODO: separate function
try {
res.in_buffer = std::make_unique<char[]>(opts.getBufferSize());
} catch (const std::bad_alloc &e) {
throw BackupError("cannot allocate buffer for input file data");
}
try {
res.ref_buffer = std::make_unique<char[]>(opts.getBufferSize());
} catch (const std::bad_alloc &e) {
throw BackupError("cannot allocate buffer for reference file data");
}
try {
res.out_buffer = std::make_unique<char[]>(res.out_buffer_size);
} catch (const std::bad_alloc &e) {
throw BackupError("cannot allocate buffer for output file data");
}
return res;
}
static void
check_files(const OptionsBackup &opts)
{
size_t in_size{0};
try {
in_size = std::filesystem::file_size(opts.getInFilePath());
} catch (const std::exception &e) {
throw BackupError("cannot get size of input file: " +
std::string(e.what()));
}
size_t ref_size{0};
try {
ref_size = std::filesystem::file_size(opts.getRefFilePath());
} catch (const std::exception &e) {
throw BackupError("cannot get size of reference file: " +
std::string(e.what()));
}
/* Check sizes of the input file and the reference file */
if (in_size != ref_size) {
throw BackupError("input file and reference file differ in size");
} else if ((in_size % opts.getSectorSize()) != 0) {
throw BackupError(
"size of input file and reference file is not multiple of " +
std::to_string(opts.getSectorSize()));
}
}
static void
write_out_buffer(const char *const buffer, size_t size, std::ofstream &file)
{
file.write(buffer, size);
if (!file) {
throw BackupError("cannot write to output 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 BackupError("cannot read from file");
} else if ((bytes_read % sector_size) != 0) {
throw BackupError(
"data read from input file is not multiple of sector size");
} else {
return (bytes_read / sector_size);
}
}
void
backup(const OptionsBackup &opts)
{
resources_backup_t res{resources_allocate_for_backup(opts)};
check_files(opts);
size_t out_buffer_index = 0;
uint64_t input_file_offset = 0;
for (;;) {
/* Read the sectors from the input and reference files into the buffers
*/
const size_t in_sectors_read =
read_sectors(res.in_file, res.in_buffer.get(), opts.getBufferSize(),
opts.getSectorSize());
const size_t ref_sectors_read =
read_sectors(res.ref_file, res.ref_buffer.get(),
opts.getBufferSize(), opts.getSectorSize());
if ((in_sectors_read == 0) || (ref_sectors_read == 0)) {
break;
} else if (in_sectors_read != ref_sectors_read) {
throw BackupError(
"cannot read equal amount of sectors from the input files");
}
/* Process the sectors in the buffers */
for (size_t sector = 0; sector < in_sectors_read; ++sector) {
const size_t buffer_offset = sector * opts.getSectorSize();
if (memcmp(res.in_buffer.get() + buffer_offset,
res.ref_buffer.get() + buffer_offset,
opts.getSectorSize()) != 0) {
/* Backup the changed sector */
if (out_buffer_index >= res.out_buffer_size) {
/* The output buffer is full. Write it to the output file */
write_out_buffer(res.out_buffer.get(), out_buffer_index,
res.out_file);
out_buffer_index = 0;
}
/* Write the next backup record */
const uint64_t o = htole64(input_file_offset);
memcpy(res.out_buffer.get() + out_buffer_index, (void *)&o,
sizeof(o));
out_buffer_index += sizeof(o);
memcpy(res.out_buffer.get() + out_buffer_index,
res.in_buffer.get() + buffer_offset,
opts.getSectorSize());
out_buffer_index += opts.getSectorSize();
}
input_file_offset += opts.getSectorSize();
}
}
/* Write out the output buffer */
if (out_buffer_index > 0) {
write_out_buffer(res.out_buffer.get(), out_buffer_index, res.out_file);
}
}
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